Article

Monitoring organic matter dynamics in soil profiles by 'Rock-Eval pyrolysis': Bulk characterization and quantification of degradation

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Rock-Eval pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. Nevertheless, this technique can be used for bulk characterization of the immature organic matter in soil samples and recent sediments. We studied 76 samples from seven soil classes and showed that their pyrograms can be described by a combination of four elementary Gaussian components: F1, F2, F3 and F4. These four components are related to major classes of organic constituents differing in origin and their resistance to pyrolysis: labile biological constituents (F1), resistant biological constituents (F2), immature non-biotic constituents (F3) and a mature refractory fraction (F4). We discriminated the relative contributions of these components and used them to derive two indices: (i) to quantify the relative contributions of labile and resistant biological constituents and (ii) to quantify the degradation stage of the soil organic matter. The practical applications are illustrated via the influence of vegetal cover on soil organic matter dynamics and peat development in a Holocene sedimentary sequence, but we suggest that the approach is of much wider application.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The socalled S2 peak integrates the quantity of pyrolyzed emission products between 200 and 650 • C. Utilizing mathematical deconvolution determines individual peaks within the S2 peak. Fractions of OM differing in thermal stability are assignable to the resulting temperature intervals: (A1) 200-340 • C, thermally unstable biological macromolecules, like saccharides; (A2) 340-400 • C, stable biological macromolecules, like cellulose and/or lignin or polypeptides; (A3) 400-460 • C, immature geological macromolecules, like humic substances; (A4) 460-520 • C, re-fractory geological macromolecules; and (A5) 520-650 • C, highly refractory pool (Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016. Investigations of composts using 13 C nuclear magnetic resonance (NMR) showed that the thermal stability separating the mentioned groups also correlates with the chemical stability (Albrecht et al., 2015). ...
... Based on this, Sebag et al. (2006) and Albrecht et al. (2015) developed indices based on the aforementioned temperature intervals, whereby the indices are defined as follows: R index (R is recalcitrant OM) = (A3 + A4 + A5)/100, and I index (I is immature OM) = log 10 ((A1 + A2)/A3). However, Sebag et al. (2016) point out that due to their mathematical derivation, these indices cannot exactly indicate the quantity or identity of the chemical components in the OM, unlike the classic Rock-Eval parameters. We acknowledge that the four different temperature intervals cannot differentiate the entire spectrum of organic compounds and therefore refer to the thermal rather than chemical stability of OM (Sebag et al., 2016). ...
... However, Sebag et al. (2016) point out that due to their mathematical derivation, these indices cannot exactly indicate the quantity or identity of the chemical components in the OM, unlike the classic Rock-Eval parameters. We acknowledge that the four different temperature intervals cannot differentiate the entire spectrum of organic compounds and therefore refer to the thermal rather than chemical stability of OM (Sebag et al., 2016). Nevertheless, this sufficiently reflects the changes in the organic components during their transformation. ...
... Palynofacies analysis, phytoliths, and isotopic techniques are widely applied in studies of palaeoenvironmental reconstruction (vegetation and climate) and also to the understanding of soil genesis (Souza et al., 2007;Horak et al., 2011Horak et al., , 2014Calegari et al., 2013a). The study of palynofacies includes qualitative and quantitative analyses of the different components of particulate organic matter (Tyson, 1995;Sebag et al., 2006aSebag et al., , 2006bGraz et al., 2010). This approach aims to identify the organic components and determine their state of preservation. ...
... The high values of amorphous organic matter that occurred in this range, especially Fig. 6. Ternary diagrams used to discriminate the nature and origin of major organic fractions in soil samples (adapted from Sebag et al., 2006b). E.C.d. ...
... Unlike the previous phase, in which particulate organic matter indicated the presence of more particles of aquatic origin, in this phase, contents derived from the soil were indicated by the palynofacies analysis (Fig. 6). The highest proportion of phytoclasts (fragments of lignocellulosic tissues derived from superior plants) preserved was accompanied by transformed particles, representing biological signatures typical of the genesis of organic horizons (Sebag et al., 2006a(Sebag et al., , 2006b. ...
... The socalled S2 peak integrates the quantity of pyrolyzed emission products between 200 and 650 • C. Utilizing mathematical deconvolution determines individual peaks within the S2 peak. Fractions of OM differing in thermal stability are assignable to the resulting temperature intervals: (A1) 200-340 • C, thermally unstable biological macromolecules, like saccharides; (A2) 340-400 • C, stable biological macromolecules, like cellulose and/or lignin or polypeptides; (A3) 400-460 • C, immature geological macromolecules, like humic substances; (A4) 460-520 • C, re-fractory geological macromolecules; and (A5) 520-650 • C, highly refractory pool (Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016. Investigations of composts using 13 C nuclear magnetic resonance (NMR) showed that the thermal stability separating the mentioned groups also correlates with the chemical stability (Albrecht et al., 2015). ...
... Based on this, Sebag et al. (2006) and Albrecht et al. (2015) developed indices based on the aforementioned temperature intervals, whereby the indices are defined as follows: R index (R is recalcitrant OM) = (A3 + A4 + A5)/100, and I index (I is immature OM) = log 10 ((A1 + A2)/A3). However, Sebag et al. (2016) point out that due to their mathematical derivation, these indices cannot exactly indicate the quantity or identity of the chemical components in the OM, unlike the classic Rock-Eval parameters. We acknowledge that the four different temperature intervals cannot differentiate the entire spectrum of organic compounds and therefore refer to the thermal rather than chemical stability of OM (Sebag et al., 2016). ...
... However, Sebag et al. (2016) point out that due to their mathematical derivation, these indices cannot exactly indicate the quantity or identity of the chemical components in the OM, unlike the classic Rock-Eval parameters. We acknowledge that the four different temperature intervals cannot differentiate the entire spectrum of organic compounds and therefore refer to the thermal rather than chemical stability of OM (Sebag et al., 2016). Nevertheless, this sufficiently reflects the changes in the organic components during their transformation. ...
Article
Sedimentary organic matter (OM) analyses along a 130 km long transect of the Mkhuze River from the Lebombo Mountains to its outlet into Lake St Lucia, Africa's most extensive estuarine system, revealed the present active trapping function of a terminal freshwater wetland. Combining bulk OM analyses, such as Rock-Eval®, and source-specific biomarker analyses of plant-wax n-alkanes and their stable carbon (δ13C) and hydrogen (δD) isotopic composition showed that fluvial sedimentary OM originating from inland areas is mainly deposited in the floodplain and swamp area of the wetland system but not in the downstream lake area. A distinctly less degraded OM signature, i.e., a considerably lower degree of transformation of unstable components (higher I index) and lower contribution of refractory and persistent fractions (lower R index) as well as recognizably higher δD values compared to samples from upstream sub-environments, characterizes surface sediments of Lake St Lucia. The offset in δD indicates that the contributing vegetation, although similar to upstream vegetation inputs in terms of photosynthetic pathway (δ13C) and alkane distribution pattern, experienced different hydrological growth conditions. The results suggest that under current conditions hinterland sedimentary OM is deposited throughout the wetland system up to the Mkhuze Swamps, which ultimately captures the transported OM. Consequently, samples from the downstream located Lake St Lucia show locally derived signals instead of integrated signals encompassing the river catchment. This finding raises important constraints for future environmental studies as the assumption of watershed-integrated signals in sedimentary archives retrieved from downstream lakes or offshore might not hold true in certain settings.
... En effet, le domaine d'application de la Pyrolyse Rock-Eval a été élargi au cours des deux dernières décennies compte tenu de la fiabilité des informations apportées et sa facilité d'utilisation. La pyrolyse aborde, entre autres, l'étude de la MO des sols et des humus (Di- Giovanni et al., 1998 ;Disnar et al., 2003 ;Sebag et al., 2006, des sédiments lacustres et marins (Botz et al., 2007), des tourbières Gogo et al., 2010 ;Delarue et al., 2013). Elle est effectuée sur un appareil Rock-Eval VI. ...
... Utilisée pour étudier la MO sédimentaire (i.e. Giovanni et al., 1999 ;Macaire et al., 2005 ;Copard et al., 2006) elle a montré son intérêt pour analyser la composition de la MOS et des litières (Baudin et al., 2015 ;Carrie et al., 2012 ;Delarue et al., 2013 ;Disnar et al., 2003 ;Obame et al., 2014 ;Saenger et al., 2013 ;Sebag et al. 2006Sebag et al. , 2013aSebag et al. , 2013bVolland-Tuduri, 2005). ...
... La caractérisation de la MO en termes du degré de son évolution globale est établie par le paramètre IH (Delarue et al., 2013 ;Disnar et al., 2003 ;Saenger et al., 2013 ;Sebag et al., 2006). En effet, les valeurs élevées observées de l'IH, comprises entre 300 à 400 mg HC g -1 COT RE6 sont caractéristiques de MO « fraîches » et/ou de litières, ou suppose une forte contribution de composés hydrogénés (i.e. ...
Thesis
Full-text available
En régions arides et semi-arides, la gestion du carbone (C) du sol est inséparable des contraintes thermo-hydriques. Le concept de la séquestration du C pour ces régions est encore trop peu connu ou compris, en raison du manque des données expérimentales.Avant de pouvoir effectuer un bilan C à l’échelle des profils de sols et du paysage interdunaire, l’évaluation du stock de C du sol est nécessaire ainsi que la caractérisation de sa stabilité. L’étude a été conduite sur les sites des polders de Bol, nord-est du lac Tchad. Une chronoséquence par « approche synchronique » a été choisie selon les différents âges de poldérisation et de mise en culture ; les sites sélectionnés t0, t10, t60, t62 et à t65 correspondent à un historique de 0 à 65 ans. Le t0 représente le site de référence de sédiment récent. Les sols étudiés sont chimiquement fertiles ; ils se différencient sur les formations quaternaires anciennes de la cuvette tchadienne. Ce sont des sols d’apports alluviaux, hydromorphes, localement salés, cultivés de manière intensive. Dans ce dispositif, 36 profils pédologiques ont été creusés et décrits, y compris 3 profils dans la zone alluviale t0. Les sols ont été échantillonnés de la surface jusqu’à 1 m de profondeur, par incréments de 0,1 m.Les stocks de C organique (COS) (0-1 m) se différencient selon les traitements: à t0 200 ± 0,8 ; t10 241 ± 0,9 ; t60 183 ± 34 ; t62 174 ± 0,3 et à t65 189 ± 1,1 MgC ha-1 (P=0,004) ; les stocks de C inorganiques (CIS) pour la même profondeur sont négligeables et varient de façon significative entre traitements (P = 0,03) de 1 pour t0 à 6 MgC ha-1 pour t65 représentant environ 5 % de stocks de COS. Pour la couche de sol 0-0,3 m, les stocks de COS exprimés en masse de sol varient en moyenne de 53 à 64 MgC ha-1 entre t65 à t0 avec un taux de perte moyenne annuelle de -0,17 MgC ha-1 an-1. L’analyse par pyrolyse Rock-Eval confirme le caractère hérité de la matière organique de l’écosystème lacustre. Dans la couche de surface des sols (0-0,4 m), le caractère résistant de cette matière organique a également été révélé par des valeurs élevées observées des stocks de carbone résistant (ResC), entre 62,6 ± 13,8 et 79,9 ± 5,8 Mg C ha-1 de t0 à t65 par rapport à celles de carbone labile (LabC), plus faibles. Le compartiment résistant représente de 17 à 23 % du stock total de C. La relation entre l’acquisition des propriétés des sols suite à la poldérisation a été discutée au regard de la caractérisation physique des sols et de la nature de la matière organique. Après plus d’un demi-siècle de mise en poldérisation, les stocks de COS ont présenté un caractère relativement stable et résistant à la biodégradation dans ce contexte semi-aride.
... Among thermal analyses used to characterize SOM, Rock-Eval (RE) analysis has provided promising results showing that SOC thermal stability observed in RE thermograms results can be related to SOC biogeochemical stability (Gregorich et al., 2015;Saenger et al., 2015;Barré et al., 2016;Soucémarianadin et al., 2018a;Poeplau et al., 2019). RE was also shown to provide information on organic matter evolutions in soils at various depth or during composting (Hetényi et al., 2005;Hetényi et al., 2006;Sebag et al., 2006;Albrecht et al., 2015), and it has been specifically applied to characterize litters, bulk soil, organic layers and POM fractions in mineral soils (Disnar et al., 2003;Saenger et al., 2015;Sebag et al., 2016). ...
... Similarly, with depth, HI decreased while T 50_CO2_PYR increased: these opposite trends match what is generally observed for bulk soil OC and organic material (Disnar et al., 2003;Sebag et al., 2016;Soucémarianadin et al., 2018a). These evolutions have been linked to an increased decomposition and a decrease in labile C compounds, resulting in a more thermally and biogeochemically stable OC (Sebag et al., 2006;Albrecht et al., 2015;Barré et al., 2016;Cécillon et al., 2018). Our results for the thermal parameters could thus suggest a more decomposed POM in the deep layers. ...
... There are variations of HI values among plant organs, with "woody" materials tending to have lower HI. For instance, high HI values have been observed for needles or OL horizons of deciduous forest floors (≈ 300; Disnar et al., 2003;Sebag et al., 2006;Carrie et al., 2012), while bark HI was only 140 mg HC·g −1 TOC (Carrie et al., 2012). The observed increase of T 50_CO2_PYR in the POM fraction of the deep layer could also be related to the fact that the deeper POM comes from a different source that is more stable (i.e., woody roots vs. leaves and needles litter). ...
Article
In temperate forests, soils contain a significant part of the ecosystem carbon (C) stock that can be subjected to C losses upon global changes. In forest soils, particulate organic matter (POM) is a major contributor to the labile C pool and its dynamics can significantly influence the overall total soil organic carbon stock. However, POM has been overlooked in forest soils, specifically in deep horizons. We isolated the POM fraction of mineral soil samples collected in 52 French forest sites, using a size-(> 50 μm) and density-(< 1.6 g·cm −3) fractionation scheme. These soil samples presented variability in terms of depth (0-10 cm; 40-80 cm), soil class (dystric Cambisol, eutric Cambisol, entic Podzol) and vegetation type (deciduous, coniferous). First, we determined the POM chemical composition and thermal stability using elemental analysis, mid infrared-attenuated total reflectance spectroscopy and Rock-Eval thermal analysis. Then, we assessed how depth, soil class and vegetation type influenced POM chemistry and thermal stability in these temperate forest soils. Depth, soil class and vegetation type were all important factors influencing POM chemistry and thermal stability. Variations in POM chemistry (higher C/N ratio, lower ether + alcohol and carbonyl + carboxyl ratios and decrease in hydrogen-rich compounds) and increase in thermal stability with depth suggested different POM input sources for the surface and deep soil layers and an increased biogeochemical stability of POM in deep soil layers. Whatever the vegetation, POM in eutric Cambisols had lower aliphatic and higher aromatic ratios than POM in dystric Cambisols. POM in soils under deciduous trees had higher aliphatic and carbonyl + carboxyl ratios and lower aromatic ratio, more hydrogen-rich and less oxygen-rich compounds than POM in soils under coniferous trees, reflecting the difference in litter chemistry between the two vegetation types. POM from deciduous plots was also significantly more thermally stable than from coniferous plots, suggesting a higher bio-geochemical stability for POM in deciduous forest soils. This study highlights the variations in POM chemistry and thermal stability existing within and among soil profiles and the role of depth, soil class and vegetation type in these variations. It appears that if POM can be regarded as a labile carbon fraction in soils, its lability varies depending on the ecosystem (soil, vegetation) and depth considered.
... 40 Rock-Eval pyrolysis is a method of geochemical screening which was originally used for petroleum exploration but has more recently been applied as a technique to characterise soil and peat organic matter. The technique has previously been used to characterise carbon cycling and organic matter transformation within mangrove (Marchand et al., 2008) and marine sediments (Hare et al., 2014), as well as soil organic matter (OM) dynamics with profile depth (Sebag et al., 2006, Sebag et al., 2016, Upton et al., 2018, and the extent of decomposition and humification in northern peats (Delarue et al., 2013, Biester et al., 2014. During analysis, dried bulk soil samples are thermally degraded in an inert atmosphere at 300 °C producing volatile hydrocarbons. ...
... S2 pyrograms were deconvoluted into six Gaussian signals (F1 -F6) based on maximising R 2 coefficient values. F1 -F6 values have previously been attributed to organic compounds of increasing complexity and recalcitrance (Disnar et al., 2003, Sebag et al., 2006 (2013) proposed combining these signals into three pools representing different phases of carbon thermal stability, with C l representing highly labile hydrocarbon compounds (F1 and F2), C i corresponding to the more stabilised carbon pool (F3), and the highly recalcitrant pool, C p (F4 -F6). ...
... Deconvolution of the S2 pyrograms into F1 -F6 fractions has previously been used to assess the thermostability of organic matter through changes in the relative proportions of pools of organic polymers (Saenger et al., 2013), although other indices have been calculated based on integration of areas between temperature nodes (Sebag et al., 2016). Previous comparisons of F1 -F6 with FTIR (Delarue et al., 2013, Biester et al., 2014) and 13 C NMR (Albrecht et al., 2015), indicate only a partial correlation with distinct functional groups as different biomolecules, such as lignin and cellulose, frequently pyrolyse at the same temperature (Sebag et al., 2006). Changes in C l , C i and C p therefore indicate broad scale patterns in thermostability driven by organic matter degradation rather than changes in any one specific functional group (Sebag et al., 2016). ...
Article
Tropical forested peatlands are a major carbon store and are a significant source of global carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions. While the role of environmental variables, including temperature and water table depth have been relatively well studied, uncertainty remains in the extent to which plant roots regulate greenhouse gas (GHG) fluxes and peat biogeochemistry. This study examined the role of roots, and root inputs of carbon and oxygen in regulating fluxes from peat under two dominant plant species, Campnosperma panamensis and Raphia taedigera, a broadleaved evergreen tree and canopy palm, in San San Pond Sak wetland, in Bocas del Toro Province, Panama. A combination of in situ and ex situ experiments were performed between February 2015 and August 2017. Small scale variation in GHG fluxes and peat biogeochemistry was measured at two distances within the rooting zones of C. panamensis and R. taedigera. Peat organic matter properties were assessed using Rock-Eval 6 pyrolysis. Results indicated significant variation in CH4 but not CO2 fluxes at different distances within the rooting zone, with CH4 fluxes subsequently linked to measures of the overall size of the available organic carbon pool (S2). Rock-Eval pyrolysis data was used to construct a three-pool model of organic matter thermostability which indicated significant differences in organic matter composition between peats derived from different botanical origins, in addition to a high level of heterogeneity within the rooting zone. Changes in GHG production and peat biogeochemical properties in response to the addition of root exudate analogues were assessed in an ex situ anoxic incubation experiment. A combination of organic acids and sugars, identified as common forest plant root exudate components, were added over a two week period to peats derived from C. panamensis and R. taedigera. GHG fluxes varied significantly between treatments but not by peat botanical origin, and were associated with significant changes in soil properties including, pH and redox potential, thereby demonstrating a link between plant root carbon inputs, peat properties and GHG fluxes. In situ mesocosms were used to assess the effects of root exclusion on peat biogeochemistry and GHG fluxes. Partial and full root exclusion significantly reduced dissolved oxygen concentrations and was associated with greater root necromass. Full root exclusion increased CH4 fluxes five-six fold compared to partial root exclusion, equivalent to an 86 – 90% reduction in CH4 oxidation, demonstrating the important role of root inputs of oxygen in mitigating CH4 efflux from tropical peat. A 13CO2 pulse labelling experiment was conducted using both R. taedigera, C. panamensis, and Symphonia globulifera, a second broadleaved evergreen tree species, to demonstrate a direct link between plant photosynthesis and CH4 fluxes, and identify aspects of the bacterial and fungal community associated with the turnover of labile carbon. The extent of 13C enrichment of CH4 differed significantly between plant types (palms vs broadleaved evergreen trees), as did the extent of net CH4 efflux. Phospholipid fatty acid (PLFA) biomarker analysis indicated both peat types were dominated by Gram negative bacteria. There was strong 13C enrichment of Gram negative bacteria, supporting their previously proposed role as important decomposers of labile carbon. Collectively, these results demonstrate that root inputs of carbon and oxygen can strongly regulate tropical peatland GHG fluxes, and that the extent of regulation can vary significantly between tropical wetland plant species from contrasting dominant plant types. This is particularly important in understanding regulatory processes in a globally significant carbon store and understanding possible consequences of land use change in the tropics.
... Many methods have been used so far to characterize decomposition, including but not (Steinmann et al. 2006;Sebag et al. 2006;Disnar et al. 2008). As organic material decomposes, humic acid and fulvic acids are formed (Roos- Barraclough et al. 2004). ...
... Rock-Eval analysis was originally established to determine type, quality as well as thermal maturity of organic matter in source rocks for petroleum exploration (Disnar et al. 2003;Sebag et al. 2006). But due to its simplicity, Rock-Eval analysis has later been adapted for use in recent sediments and soils to explore their organic content, especially since isolation of organic components is difficult, expensive and time consuming (Disnar et al. 2003 and references therein). ...
... The oxygen index (OI) corresponds to the amount of CO 2 emanating during pyrolysis below 400 °C divided by the total organic carbon (TOC) content and the hydrogen index A study done by Sebag et al. (2006) also mathematically decomposed the hydrocarbon pyrogram, i.e. S2 curve into individual Gaussian components which could be grouped into 4 groups: F1-F4, similar to Disnar et al. (2003). ...
Thesis
Full-text available
Peat from the temperate regions has been used for paleoenvironmental reconstruction using diverse proxies for over a century now. Peat is rare and severely understudied in the tropics. The montane peat bogs of the Nilgiris, southern India have been found to preserve global climatic signals including the Holocene Optimum and the Last Glacial Maximum (LGM). At Sandynallah, one of the oldest peat accumulations in the world at >40 kyr BP, we had undertaken a high resolution paleoenvironmental reconstruction using multiple proxies which are yet to be evaluated in the tropical context. The study consists of 3 main objectives, i. Establishing an accurate high resolution chronology for the peat profile using radiocarbon dating, ii. Extracting vegetation and climate information from C/N ratio and Rock-Eval indices and iii. Using elemental profiles to establish the utility of inorganic geochemical proxies for processes such as weathering and dust transport. High resolution chronology for the site was built using Accelerator Mass Spectrometry (AMS) radiocarbon dates. To improve accuracy of the age-depth model, we also tested 4 samples for the effects of the AAA (Acid-Alkali-Acid) extraction method, the most common pre-treatment method for peat in the world. We compared ages on bulk samples (acid washed) and AAA treated samples from 4 different depths. We find that for all depths, the ages of the untreated samples do not lie within the internal uncertainty window and differ from the AAA treated sample age by at least an order of magnitude of the internal error, if not more. Based on these results we argue that the internal error should be used in conjunction with a reliable estimate of external error in an age-depth model for more realistic dating of paleoclimatic events. C/N ratios were explored for their paleoclimatic potential in conjunction with Rock-Eval indices and it was found that decomposition in tropical peat, as opposed to temperate peat, may not be sensitive to climatic perturbations. Inorganic geochemical proxies were also evaluated through this study. We see that the major and trace elements, except the lanthanide series do not show many significant trends for paleoenvironmental interpretation. But the lanthanides show some promise for identifying potential sources of dust and weathered material. Our study has addressed the gap in knowledge about the utility of recent geochemical proxies in tropical peat and has attempted to provide a solution to improve reliability in constructing age-depth models.
... In this study, thermal status of SOM was characterized by combining two indexes (denoted R and I) calculated from five subdivided areas of the S2 thermograms related to HC (Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016. Areas were calculated between the following bounds (or nodes): 200−340°C for A1, 340−400°C for A2, 400−460°C for A3, 460−520°C for A4, and 520−650°C for A5. ...
... Areas were calculated between the following bounds (or nodes): 200−340°C for A1, 340−400°C for A2, 400−460°C for A3, 460−520°C for A4, and 520−650°C for A5. The forms of S2 thermograms depend upon the OM cracking temperature, as expressed through five pools corresponding to the sections of the thermograms: highly labile (A1), labile (A2), resistant (A3), refractory (A4) and highly refractory (A5) (Disnar et al., 2003;Sebag et al., 2016Sebag et al., , 2006. ...
... Rock-Eval pyrolysis has previously been used to characterise carbon cycling and organic matter transformation within mangrove (Marchand et al. 2008) and marine sediments (Hare et al. 2014), as well as soil organic matter (SOM) dynamics with profile depth (Disnar et al. 2003;Sebag et al. 2006Sebag et al. , 2016, and the extent of decomposition and humification in northern peats (Delarue et al. 2013;Biester et al. 2014). Parameters from Rock-Eval of particular relevance to peat organic matter include the hydrogen index (HI), indicative of atomic H:C, and the oxygen index (OI), indicative of atomic O:C, in addition to TpkS2, the temperature associated with the highest yield of bound hydrocarbons, and S2, a measure of overall hydrocarbons released on the thermal cracking of organic matter for temperatures up to 650°C. ...
... S2 pyrograms were deconvoluted into six Gaussian signals (F1-F6) based on maximising R 2 coefficient values. F1-F6 values have previously been attributed to organic compounds of increasing thermal stability (Disnar et al. 2003;Sebag et al. 2006). F1 and F2 correspond to thermally labile fresh plant material including simple polysaccharides, and lignin and cellulose derived compounds, respectively. ...
Article
Full-text available
Tropical peatland ecosystems are a significant component of the global carbon cycle and feature a range of distinct vegetation types, but the extent of links between contrasting plant species, peat biogeochemistry and greenhouse gas fluxes remains unclear. Here we assessed how vegetation affects small scale variation of tropical peatland carbon dynamics by quantifying in situ greenhouse gas emissions over 1 month using the closed chamber technique, and peat organic matter properties using Rock-Eval 6 pyrolysis within the rooting zones of canopy palms and broadleaved evergreen trees. Mean methane fluxes ranged from 0.56 to 1.2 mg m⁻² h⁻¹ and were significantly greater closer to plant stems. In addition, pH, ranging from 3.95 to 4.16, was significantly greater closer to stems. A three pool model of organic matter thermal stability (labile, intermediate and passive pools) indicated a large labile pool in surface peat (35–42%), with equivalent carbon stocks of 2236–3065 g m⁻². Methane fluxes were driven by overall substrate availability rather than any specific carbon pool. No peat properties correlated with carbon dioxide fluxes, suggesting a significant role for root respiration, aerobic decomposition and/or methane oxidation. These results demonstrate how vegetation type and inputs, and peat organic matter properties are important determinants of small scale spatial variation of methane fluxes in tropical peatlands that are affected by climate and land use change. Electronic supplementary material The online version of this article (10.1007/s10533-018-0531-1) contains supplementary material, which is available to authorized users.
... Пиролитический анализ Rock-Eval -традиционный метод в нефтяной геологии, используемый для оценки нефтегенерационного потенциала осадочных пород [5][6][7][8]. Тем не менее в настоящее время он все чаще используется и для исследований органической компоненты почв и современных осадков [9][10][11][12][13][14]. В приведенных работах показано, что с помощью пиролитического анализа незрелого органического материала можно получить данные о доле морского и терригенного ОВ и степени его диагенетической преобразованности. ...
... Для сопоставимости полученных результатов с опубликованными исследованиями было решено выделить ключевые параметры в следующем виде: S1=S1 r +S2 a и S2=S2 b [10,18,19]. ...
Article
Full-text available
Актуальность исследования обусловлена необходимостью всестороннего изучения процессов, ответственных за изменения биогеохимического режима арктического региона. Увеличение темпов деградации прибрежной и подводной мерзлоты на Восточно-Сибирском шельфе приводит к вовлечению в современный биогеохимический цикл большого объема ремобилизованного органического углерода. Изучение особенностей его транспорта и преобразования в системе суша–шельф играет важную роль для оценки функционирования крайне хрупкой арктической экосистемы. Цель: изучение геохимических характеристик органического вещества, прослеживаемых по профилю от береговой зоны к континентальному склону моря Лаптевых с применением метода Rock-Eval и оценка их взаимосвязи с литологическими свойствами вмещающих осадков. Объектом исследования явились пробы донных осадков, взятые с поверхностного горизонта (0–2 см). Отбор проб проводился в морских арктических экспедициях 2018–2019 гг. на НИС «Академик Мстислав Келдыш». Результаты. На основе результатов пиролитического анализа дана геохимическая характеристика органического вещества, содержащегося в донных осадках моря Лаптевых. Органическое вещество, экспортируемое с речным стоком и продуктами береговой эрозии, характеризуется относительно низким кислородным (OI) и водородным (HI) индексами в прибрежной зоне и на глубинах до нескольких десятков метров. В районе среднего шельфа существенное влияние на состав органического вещества, по всей видимости, оказывает снос осадочного вещества с Новосибирских островов, где активно действуют термоабразионные процессы (снижение значений HI и увеличение OI). Высказано предположение, что для продуктов, выносимых речным стоком, и продуктов эрозии берегов характерны различные пиролитические параметры, определяемые методом Rock-Eval (в частности, значения HI, OI и Tpeak).
... Both indices are derived from integrated S2 areas between specific bounds (200-400 °C, 400-460 °C, and above 460 °C), usually interpreted as specific thresholds in thermal stability of organic compounds, separating thermally labile, resistant, and refractory C pools (fig. SM1 and SM2;Disnar et al., 2003;Sebag et al., 2006;Saenger et al., 2013Saenger et al., , 2015. Both indices are calculated from S2 thermograms (i.e., hydrocarbon compound released by thermal cracking under pyrolytic conditions) that seem little or not sensitive to interference with mineral matrix and catalytic reactions. ...
... 1-2, Tab. 1) related to decomposition and changes in chemical composition of soil OM. The results are in agreement with previous Rock-Eval ® studies (e.g., Di-Giovanni et al., 1998;Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016Saenger et al., 2013). ...
Article
Soil organic matter (OM) is a complex heterogeneous mixture: resulting from decomposition and organo-mineral interactions, it challenges characterization in terms of composition and biogeochemical stability. From this perspective, the Rock-Eval® method is a rapid and efficient thermal analysis, which combines quantitative and qualitative information on soil OM, including several parameters related to thermal stability. This approach has already been used to monitor changes in OM properties at landscape, cropland, and profile scales. This study aims to assess the stability of soil organic matter pools by characterizing grain-size fractions from forest litters and topsoils using Rock-Eval® thermal analyses. Organic and topsoil samples were selected from a beech forest located in Normandy (France), whose management has been documented for the last 200 years. Fractionation by wet sieving was used to separate large debris (>2000 μm), coarse (200–2000 μm), and fine particulate organic matter (50–200 μm) in organic samples, and coarse (200–2000 μm), medium (50–200 μm), and fine (<50 μm) fractions in topsoils. Rock-Eval® was able to provide thermal parameters sensitive enough to study fine-scale soil processes. In organic layers, quantitative and qualitative changes are all explained by progressive decomposition of labile organic compounds from plant debris to the finest organic particles. On the other hand, the grain size fractions of the topsoil display different characteristics: indeed, the coarse organo-mineral fractions show high C contents, but with a different composition and a higher thermal stability and degree of decomposition than the plant debris forming the organic layers. These results are consistent with previous studies concluding that the microbial activity is more effective in this fraction. The finest fractions of topsoil reveal low C contents and the highest thermal stability, but also a low degree of decomposition, which can be explained by stronger interactions with the mineral matrix. Therefore, it is suggested that the dynamics of OM present in the different size fractions be interpreted in the light of a plant-microbes-soil continuum. Finally, three distinct thermal stability C pools are highlighted through the grain-size heterogeneity of soil OM: free-coarse organic matter (large debris, coarse and fine particles), weakly-protected organic matter in (bio)aggregates (coarse fraction of topsoil), and stabilized organic matter in fine fractions of topsoil, the latter resulting from interactions inside organo-mineral complexes. These results allow Rock-Eval® thermal parameters to be used in order to empirically illustrate the conceptual models emphasizing the role of drivers played by the gradual decomposition and protection of the most thermally labile organic constituents.
... Notre étude se réfère à la méthode développée par Disnar et al. (2003) pour estimer la contribution des pools de constituants organiques définis par leur température de craquage spécifique. Ainsi, selon les travaux d' Albrecht et al. (2015), les courbes S2 ont été décomposées en intervalles (Sebag et al., 2007 ;Albrecht et al., 2015 ;Sebag et al., 2016). I-index représente la contribution de la matière organique immature, tandis que R-index représente celle de la matière organique mature. ...
... 6.12, 6.14), было установлено, что величина температуры Т пик отдельных пиков находится в интервале: для F1 в пределах от 300 до 311 °С, для F2 -от 351 до 362, F3 -от 404 до 454, F4от 469 до 485 °С. В соответствии с работами [Disnar et al., 2003;Sebag et al., 2006], в которых этот метод использован для анализа почв, пик F1 можно соотнести с лабильными органическими составляющими, а также липидами. Пик F2 соответствует более стойким биополимерам, таким как лигнин и целлюлоза, или полипептидам, пиролиз которых заканчивается практически при 400 °С. ...
... Our sample set, restricted to a semi-natural environment, thus contained a significant proportion of samples with a high concentration of fresh OM displaying a thermally labile signature. In the same way, Sebag et al. (2006) observed lower R-indices in soil layers under dense plant cover (large inputs) when compared to sparse vegetation (low inputs). ...
Article
Full-text available
Our understanding of mechanisms governing soil organic matter (OM) stability is evolving. It is gradually becoming accepted that soil OM stability is not primarily regulated by the molecular structure of plant inputs, but instead by the biotic and abiotic properties of the edaphic environment. Moreover, several experimental studies conducted in artificial systems have suggested that mechanisms regulating OM stability may differ with depth in the soil profile. Up to now however, there is very limited field-scale evidence regarding the hierarchy of controls on soil OM dynamics and their changes with soil depth. In this study, we take advantage of the high heterogeneity of ecological conditions occurring in the alpine belt to identify the major determinants of OM dynamics and how their significance varies with depth in the soil profile. Aboveground litter, mineral topsoil, and subsoil samples originating from 46 soil profiles spanning a wide range of soil and vegetation types were analysed. We used Rock-Eval pyrolysis, a technique that investigates the thermal stability of OM, as an indicator of OM dynamics. Our results show a clear divergence in predictors of OM thermal stability in the litter, topsoil, and subsoil layers. The composition of OM correlated with its thermal stability in the litter layer but not in mineral soil horizons, where the supply rate of fresh organic material and the physical and chemical characteristics of the pedogenic environment appeared important instead. This study offers direct confirmation that soil OM dynamics are influenced by different ecosystem properties in each soil layer. This has important implications for our understanding of carbon cycling in soils under a changing climate.
... Recently, Pillot et al. (2014) have proposed identifying and quantifying siderite in sedimentary rocks from a thermogram analysis, i.e. using measurements of effluent amounts released by decomposition of the OM and carbonates, according to the temperature. Comparable approaches are often proposed to analyze Recent OM from soils (Disnar et al., 2003;Sebag et al., 2006;Carrie et al., 2012;Saenger et al., 2013), as well as Recent sediments and suspended matter (Copard et al., 2006;Marchand et al., 2008;Tambach et al., 2009;Baudin et al., 2015). In this study, we propose to analyze a ∼12-m-long lake sediment core collected in the Lake Barombi (Cameroon), which includes siderite deposits. ...
Article
Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for the source (aquatic or terrestrial) of the primary production of organic matter (Hydrogen Index vs Oxygen Index). Although this method usually provides valuable evidence, the common presence of siderite in tropical lake sediments can alter the primary signal of the sedimentary organic matter (SOM). Indeed, the CO2 and CO released by the pyrolysis of siderite are integral to the calculation of the SOM-related standard Rock-Eval parameters. In this study, we analyze sediments from a core collected in the Lake Barombi (southwest Cameroon) and describe the impact of siderite on standard Rock-Eval parameters. We propose a workflow that allows standard Rock-Eval parameters to be corrected, based on the analysis of thermograms. The proposed corrections provide siderite-effect-free parameters, accurately reflecting the changes in sedimentary organic matter composition.
... Sample analyses could include determination of SOM quantity (e.g., elemental analysis of organic C and total nitrogen) and quality (e.g., differential Fourier-transform infrared spectroscopy, pyrolysis gas chromatography mass spectrometry, or thermal analysis such as Rock-Eval pyrolysis 56,57,58 ). When looking at the mineral partner, useful analyses could include particle size analysis, quantification of reactive aluminum and iron phases 59 , X-ray diffraction (XRD) on powdered samples for bulk mineralogy or on oriented slides for clay mineralogy 60 . ...
Article
Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF relies on sequential density separation and sedimentation steps to isolate (1) the free light fraction (uncomplexed organic matter), (2) the occluded light fraction (uncomplexed organic matter trapped in soil aggregates) and (3) a variable number of heavy fractions (soil minerals and their associated organic matter) differing in composition. Provided that the parameters of the CSDF (dispersion energy, density cut-offs, sedimentation time) are properly selected, the method yields heavy fractions of relatively homogeneous mineral composition. Each of these fractions is expected to have a different complexing ability towards organic matter, rendering this a useful method to isolate and study the nature of organo-mineral interactions. Combining density and particle size separation brings an improved resolution compared to simple size or density fractionation methods, allowing the separation of heavy components according to both mineralogy and size (related to surface area) criteria. As is the case for all physical fractionation methods, it may be considered as less disruptive or aggressive than chemically-based extraction methods. However, CSDF is a time-consuming method and furthermore, the quantity of material obtained in some fractions can be limiting for subsequent analysis. Following CSDF, the fractions may be analyzed for mineralogical composition, soil organic carbon concentration and organic matter chemistry. The method provides quantitative information about organic carbon distribution within a soil sample and brings light to the sorptive capacity of the different, naturally-occurring mineral phases, thus providing mechanistic information about the preferential nature of organo-mineral interactions in soils (i.e., which minerals, what type of organic matter).
... -TpkS2 corresponds to the temperature when the maximum amount of hydrocarbons was released during pyrolysis. (Disnar et al., 2003;Sebag et al., 2006). -F1-F2 signals represent high labile fresh plant material including simple polysaccharides, HC compounds are pyrolysed below 360°C. ...
Article
Accurate assessment of tropical peatland carbon dynamics is important to (a) determine the size of the active carbon pool, (b) estimate the scale of transfers of peat-derived greenhouse gases (GHGs) to the atmosphere resulting from land use change, and (c) support carbon emissions reduction policies. To date, information on the quality of tropical peatland organic matter and its sensitivity to increases in global temperatures is limited, particularly in the context of land conversion. The aim of this work is therefore to determine peat quality and temperature response of potential GHG emissions under flooded conditions from tropical peatland sites. Whilst reflecting the process of conversion from forest to oil palm plantation. Four land use types that represent the stages of conversion from peat swamp forest to oil palm were chosen: (i) secondary ‘forest’, (ii) recently ‘drained’ but not cleared forest (iii) cleared and recently planted ‘young oil palm’ plantation and (iv) ‘mature oil palm’ plantation. Overall, surface peat carbon was more labile than deeper peats. The largest labile pool was measured at forest sites. In the later stages of land conversion, the labile carbon had been lost and the relative abundance of recalcitrant organic material increased. Potential GHG fluxes were greatest in surface peats compared to deeper peats and declined as labile carbon was depleted following land conversion. Higher temperatures resulted in higher potential GHG emissions at all stages of conversion, but the magnitude of the temperature response depended on organic matter lability. For CO2 fluxes, the temperature response was most pronounced at forest sites. This reflects the greater peat lability at this land use. In contrast, for CH4 emissions, there were increased emissions both at forest and converted land types with higher temperatures. This suggests that increasing temperatures in response to climate warming may drive higher CH4 emissions from sites dominated by degraded organic matter. Collectively, this study demonstrates that during conversion from peat swamp forest to oil palm plantation, the enhanced decomposition and reduced litter input rates is reflected eventually in reduced potential gross CO2 emissions from peat. Nonetheless higher temperature resulting from climate warming may maintain high GHG emissions at plantation sites.
... Rock-Eval 6 pyrolysis has been used to investigate carbon dynamics within a range of systems e.g. mangrove , marine sediments (Hare et al., 2014), freshwater and saltmarsh peats (Engelhart et al., 2013;Newell et al., 2016;Kemp et al., 2017), as well as trends in SOM dynamics through soil profiles (Sebag et al., 2006;Delarue et al., 2013;Biester et al., 2014;Sebag et al., 2016), providing a powerful tool for rapid assessment of shifts in peat organic geochemistry among vegetation types and depth. ...
Article
Tropical peatlands hold large amounts of carbon but the influence of litter inputs and variation in peat properties with depth on carbon storage are poorly understood. Here we present a stratigraphy of peatland carbon stocks and accumulation through the peat profile in a tropical ombrotrophic wetland and assess shifts in vegetation inputs and organic matter degradation using n-alkane distributions and Rock-Eval 6 pyrolysis. Mixed forest (including canopy palms and tropical hardwood trees) contained the greatest total carbon stock in the soil (1884 Mg C ha⁻¹), followed by Rhizophora mangle (mangrove, 1771 Mg C ha⁻¹), Campnosperma panamensis (hardwood, 1694 Mg C ha⁻¹) and Cyperus (sawgrass) bog plain (1488 Mg C ha⁻¹). The long-term apparent rate of carbon accumulation, determined by ¹⁴C dating of the carbon stored in different layers in the peat profile, decreased from the edge to the interior of the peatland, with the highest accumulation rate in at the Rhizophora site (102.2 g C m⁻² y⁻¹) and the lowest in the deeper peat layers at the Cyperus site (45.6 g C m⁻² y⁻¹). High molecular weight n-alkanes dominated in surface peat in all four phasic communities, while deeper in the peat profile n-alkane profiles differed more among sites, suggesting contrasting litter inputs or decomposition environments. Deeper peat was depleted in carbohydrates and had a relatively larger thermostable C pool. Taken together our findings show (i) that different forest types hold varying C stocks and have different peat accumulation rates, even over relatively small distances, and (ii) progressive depletion of carbohydrates and thermolabile compounds with depth, despite strong variation in litter inputs throughout the peat profile.
... Rock-Eval pyrolysis, a temperature programmed heating process, was designed for determination of the total organic carbon (TOC, wt.%) content of rock samples as well as the thermal maturity level of the sedimentary organic matter [Delvaux, 1990;Behar, 2001] . One can use pyrolysis results in order to calculate the several basic parameters, such as production, oxygen, hydrogen indexes and Tmax in order to define properties of the organic matter [Sebag, 2006]. Moreover, pyrolysis provides useful exploration data of the transformation of organic matter to mobile oil and gas during heating, which can be described by first-order chemical kinetics reactions [Dembicki, 1992]. ...
Conference Paper
Full-text available
More than a half of world's hydrocarbon reserves is presented in carbonate reservoirs. Conventional waterflooding leads to inefficient oil recovery from these reservoirs, because majority of them have mixed or oil-wet wetting properties. It is well documented in literature, that the main reason of oil wetness of carbonate rocks is adsorbed components from crude oil. Although progress has been made in determination of oil components, which have a tendency to react with carbonates, carbonate reservoirs development still remains challenging. Hence, in this study we investigated the distribution of adsorbed oil components on rock surfaces in order to define their influence on fluids flow through porous carbonate samples. This work presents the results for several carbonate core samples taken from the oil zone of an oil reservoir, which mostly consist of calcite with the small impurities of magnesite and quartz. The work provides the standard study of pore structure of samples to assess the solvents influence on pore network of samples using μCT; the method of evaluation of the amount of organic matter adsorbed on calcite using Rock - Eval pyrolysis; the visualization of such matter distribution through samples; and also the results of kinetics experiments in order to evaluate the bond disruption energy between organic matter and surface. Studies have shown that combination of pyrolysis and μCT provides comprehensive and improved data about organic matter.
... shales, coals and other tight-formations (Romero-Sarmiento et al., 2016). Further, in recent years Rock-Eval has also found application for characterization of organic-matter in soils, and other near-surface, geologically recent lacustrine and marine sediments (Di- Giovanni et al., 1998;Disnar et al., 2003;Sebag et al., 2006;Saenger et al., 2013). ...
Chapter
The basic pyrolysis techniques used for source-rock geochemical analysis are generally simple and can be interpreted in a straightforward way. However, some of the data generated can be misleading and lead to confused interpretations if not properly assessed. This chapter discusses the different aspects of source-rock evaluation using the commonly used Rock-Eval technique on a step-by-step basis. Here, the impact for several factors on key Rock-Eval derived measurements, viz. particle crush-size, FID signal, S2 pyrogram shape, FID linearity, S4CO2 oxidation graphics, are addressed. Careful monitoring of these key parameters enables analysts/interpreters to conduct meaningful source-rock assessment. The shape of S2 pyrograms helps to predict the type of kerogen(s) present within a sample and can be indicative of their level of thermal maturity. While type I kerogen bearing JR-1 standard and type II kerogen-mimicking IFP160000 synthetic shale standard, show tighter Gaussian shaped S2 peak shapes in their pyrograms, type III kerogen bearing shales typically show a right-side tailed effect. Further, owing to their extremely high hydrocarbon generation potential, even at lower sample weights, type I kerogens show higher FID signals than other kerogen types. Type III-IV kerogen bearing shales show least FID signals even at higher sample weights owing to their lower petroleum generation potential. For type I kerogen bearing shales FID signals can be very high; if they rise beyond the Rock-Eval equipment’s FID detection limits, the resulting pyrograms are likely to be erroneous. Migrated hydrocarbons in the samples tested are likely to have an impact on the Rock-Eval pyrograms they yield. Particle crush-sizes of the samples analyzed are potentially more significant for organic-rich shales compared to organic-lean shales. Sample weights on S4CO2 oxidation graphics are shown to be potentially significant. For carbonate-free shales, with increasing sample weights, increasing portions of the CO2 from the organic-matter (represented by S4CO2 graphics) tends to be undercounted. This result in an underestimation of the residual carbon (RC) and TOC content, and erroneous estimation of carbonate mineral content. To obtain reliable Rock-Eval results it is necessary to conduct simultaneous monitoring of FID signals, S2 pyrograms shapes, and S4CO2 oxidation graphics. For organic-lean shales, the S2 signals may be too low, below the FID detection limits of the Rock-Eval equipment, generating erroneous thermal maturity data.
... In addition to the previously mentioned indices typifying OM sources, two S2-derived indices; the I-and R-indices (Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016Marchand et al., 2008;Albrecht et al., 2014), have been used to qualitatively characterize OM degradation. The S2 thermograms, which measure the amount of pyrolysed HC, are normalized to 100% and divided into 5 temperature ranges, from the most thermally labile to the most thermally refractory organic fraction (A1: 280-340°C, A2: 341-400°C, A3: 401-460°C, A4: 461-550°C, A5: 551-650°C). ...
Article
Full-text available
Qualitative and quantitative changes of organic and carbonate carbon in sedimentary records are frequently used to reconstruct past environments, paleoproductivity and sediment provenance. Amongst the most commonly used proxies are Total organic carbon (TOC), Mineral carbon (MinC), as well as Hydrogen (HI) and Oxygen Indices (OI) of organic matter (OM). Rock Eval pyrolysis enables the assessment of these quantitative and qualitative parameters with a single analysis. This is achieved through transient pyrolysis of the samples up to 650°C followed by combustion up to 850°C, with hydrocarbons, CO and CO2 measured during the thermal decomposition of both OM and carbonate minerals. Carbonate minerals with low thermal cracking temperatures such as siderite (<400°C) can induce significant matrix effects, which bias the TOC, MinC and OI Rock-Eval parameters. Here we assess the applicability of End-Member Analysis (EMA) as a means to correct Rock-Eval thermograms for siderite matrix effects. For this, we performed Rock-Eval pyrolysis on sideritic sediments of Lake Towuti (Indonesia). New thermal boundaries were constrained in Rock-Eval thermograms using EMA to limit siderite matrix effects and improve TOC, MinC, and OI calculations. Our approach allowed us to: 1) evaluate the influence of siderite matrix effects on Rock-Eval thermograms; 2) properly exploit a Rock-Eval dataset to characterize the type and sources of OM in siderite-rich sediments; and 3) identify the OM behind degradation and mineralization processes. The Rock-Eval dataset revealed sediments with a substantial amount of refractory OM, especially in those where TOC is high and HI characteristic of autochthonous biomass. These results, associated to alternative indices used to assess OM preservation, suggest that refractory OM is residually enriched following strong degradation of labile compounds. Finally, relatively labile and refractory organic fractions may be consumed in the formation of siderite during this sequential process of OM mineralization.
... Despite the fact that the TLHC index, the I index and the R index had originally been proposed as useful qualitative metrics of soil carbon dynamics, reflecting a proportion of thermally resistant or labile hydrocarbons (Disnar et al., 2003;Sebag et al., 2006Sebag et al., , 2016Saenger et al., 2013Saenger et al., , 2015, those parameters were not correlated with the CP SOC proportion. Furthermore, they also had a weak importance in the random forests model predictions of the CP SOC proportion ( Table 2). ...
Article
Full-text available
Changes in global soil carbon stocks have considerable potential to influence the course of future climate change. However, a portion of soil organic carbon (SOC) has a very long residence time ( > 100 years) and may not contribute significantly to terrestrial greenhouse gas emissions during the next century. The size of this persistent SOC reservoir is presumed to be large. Consequently, it is a key parameter required for the initialization of SOC dynamics in ecosystem and Earth system models, but there is considerable uncertainty in the methods used to quantify it. Thermal analysis methods provide cost-effective information on SOC thermal stability that has been shown to be qualitatively related to SOC biogeochemical stability. The objective of this work was to build the first quantitative model of the size of the centennially persistent SOC pool based on thermal analysis. We used a unique set of 118 archived soil samples from four agronomic experiments in northwestern Europe with long-term bare fallow and non-bare fallow treatments (e.g., manure amendment, cropland and grassland) as a sample set for which estimating the size of the centennially persistent SOC pool is relatively straightforward. At each experimental site, we estimated the average concentration of centennially persistent SOC and its uncertainty by applying a Bayesian curve-fitting method to the observed declining SOC concentration over the duration of the long-term bare fallow treatment. Overall, the estimated concentrations of centennially persistent SOC ranged from 5 to 11 g C kg⁻¹ of soil (lowest and highest boundaries of four 95 % confidence intervals). Then, by dividing the site-specific concentrations of persistent SOC by the total SOC concentration, we could estimate the proportion of centennially persistent SOC in the 118 archived soil samples and the associated uncertainty. The proportion of centennially persistent SOC ranged from 0.14 (standard deviation of 0.01) to 1 (standard deviation of 0.15). Samples were subjected to thermal analysis by Rock-Eval 6 that generated a series of 30 parameters reflecting their SOC thermal stability and bulk chemistry. We trained a nonparametric machine-learning algorithm (random forests multivariate regression model) to predict the proportion of centennially persistent SOC in new soils using Rock-Eval 6 thermal parameters as predictors. We evaluated the model predictive performance with two different strategies. We first used a calibration set (n = 88) and a validation set (n = 30) with soils from all sites. Second, to test the sensitivity of the model to pedoclimate, we built a calibration set with soil samples from three out of the four sites (n = 84). The multivariate regression model accurately predicted the proportion of centennially persistent SOC in the validation set composed of soils from all sites (R² = 0.92, RMSEP = 0.07, n = 30). The uncertainty of the model predictions was quantified by a Monte Carlo approach that produced conservative 95 % prediction intervals across the validation set. The predictive performance of the model decreased when predicting the proportion of centennially persistent SOC in soils from one fully independent site with a different pedoclimate, yet the mean error of prediction only slightly increased (R² = 0.53, RMSEP = 0.10, n = 34). This model based on Rock-Eval 6 thermal analysis can thus be used to predict the proportion of centennially persistent SOC with known uncertainty in new soil samples from different pedoclimates, at least for sites that have similar Rock-Eval 6 thermal characteristics to those included in the calibration set. Our study reinforces the evidence that there is a link between the thermal and biogeochemical stability of soil organic matter and demonstrates that Rock-Eval 6 thermal analysis can be used to quantify the size of the centennially persistent organic carbon pool in temperate soils.
... Entre 320 et 390°C, les composés plus complexes tels les polysaccharides, la lignine ou la cellulose sont dégradés. Enfin, de 420 à 470°C les substances humiques sont détectées(Sebag et al., 2006). La matière organique labile du sol HOM est donc dominée par des composés biologiques simples composés de chaînes aliphatiques peu stables. ...
Thesis
Les HAP contaminent de nombreux sols de friches industrielles. Leur dissipation par biodégradation est limitée par leur faible disponibilité. Nous avons étudié les facteurs contrôlant cette disponibilité dans les sols ainsi que les variables rhizosphériques qui la font varier. Nous avons préalablement défini que la disponibilité des HAP pouvait être estimée par une extraction en 30 heures sur une résine adsorbante, le Tenax®. Ce protocole a permis de comparer la disponibilité dans trois sols de friche et de déterminer les facteurs de contrôle de celle-ci. Le premier facteur est le diamètre des particules de black carbon qui sont la matrice porteuse de HAP. Ensuite, l'intensité d'agrégation par l'intermédiaire de ciments carbonatés est le deuxième facteur de contrôle important de la disponibilité des HAP. Des expériences de laboratoire ont montré que la disponibilité des HAP peut être influencée par des variables rhizosphériques. Ainsi, l'acidification d'un sol calcaire permet la dissolution des ciments carbonatés et augmente la disponibilité des HAP du fait de la désagrégation. L'alcalinisation quant à elle, augmente la disponibilité en diminuant les forces de sorption et parfois en décondensant la phase organique porteuse de HAP. En plus de son rôle acidifiant, l'acide citrique par ses propriétés complexantes permet d'augmenter la disponibilité des HAP de 40%. Les paramètres modifiés artificiellement au laboratoire ne sont pas toujours aussi facilement contrôlable in situ. Dans des expériences de terrain, nous avons vu qu'une alcalinisation artificielle du sol entraînait l'accroissement de la vitesse de dissipation des HAP. La culture de lupin blanc connu pour exsuder de l'acide citrique dans sa rhizosphère, a permis l'augmentation significative de la dissipation de l'anthracène, résultat très encourageant compte-tenu de la courte durée de culture et la relative phytotoxicité des sols étudiés
... Released hydrocarbons were monitored by a flame ionisation detector (FID) and graphed as the "S2 thermogram", representing the sum of all released hydrocarbons. The analysis of the S2 thermogram provided information on OM bulk chemistry and thermal stability in soils and sediments (Disnar et al., 2003;Hetényi et al., 2005;Sebag et al., 2006). In this study, the area under the S2 curve was subdivided into to five areas (A1 to A5) with predefined temperature ranges: 200-340°C for A1 (labile biopolymers), 340-400°C for A2 (resistant biopolymers), 400-460°C for A3 (immature geopolymers), and A4 and A5, which stands for refractory geopolymers (> 460°C). ...
Article
Soil structure formation in alluvial soils is a fundamental process in near-natural floodplains. A stable soil structure is essential for many ecosystem services and helps to prevent river bank erosion. Plants and earthworms are successful soil engineering organisms that improve the soil structural stability through the incorporation of mineral and organic matter into soil aggregates. However, the heterogeneous succession of different textured mineral and buried organic matter layers could impede the development of a stable soil structure. Our study aims at improving the current understanding of soil structure formation and organic matter dynamics in near natural alluvial soils. We investigate the effects of soil engineering organisms, the composition, and the superimposition of different alluvial deposits on the structuration patterns, the aggregate stability, and organic matter dynamics in in vitro soil columns, representing sediment deposition processes in alluvial soils. Two successions of three different deposits, silt–buried litter–sand, and the inverse, were set up in mesocosms and allocated to four different treatments, i.e. plants, earthworms, plants + earthworms, and a control. X-ray computed tomography was used to identify structuration patterns generated by ecosystem engineers, i.e. plant root galleries and earthworm tunnels. Organic matter dynamics in macro-aggregates were investigated by Rock-Eval pyrolysis. Plant roots only extended in the top layers, whereas earthworms preferentially selected the buried litter and the silt layers. Soil structural stability measured via water stable aggregates (%WSA) increased in the presence of plants and in aggregates recovered from the buried litter layer. Organic matter dynamics were controlled by a complex interplay between the type of engineer, the composition (silt, sand, buried litter) and the succession of the deposits in the mesocosm. Our results indicate that the progress and efficiency of soil structure formation in alluvial soils strongly depends on the textural sequences of alluvial deposits.
... Due to the increasing demands for rapid and quantitative assessments of soil organic matter quality, ther-mal analysis techniques are a unique means to characterize the complete continuum that comprises soil organic matter. Among the most common thermal techniques, Rock-Eval pyrolysis [60,61] has been increasingly applied to geologically recent sediment and soils [58,[62][63][64][65]. Details of the application of Rock-Eval to soils are provided elsewhere [58,62,64,66,67]. Rock-Eval provides information on quantity and quality of organic matter without sample preparation. ...
Chapter
Full-text available
In strongly weathered tropical soils, humus and humic substances (HSs) appear to play an important role in soil fertility because they represent the dominant reservoir and source of plant nutrients. As the refractory organic carbon form of soil, HSs play a vital role in the atmospheric CO 2 sequestration. Detailed classification of humus forms in tropical ecosystems and the dynamics and function of humus are still poorly understood. Nevertheless, in tropical environment many studies indicated that it is very difficult to differentiate between tropical humus, at least in normally drained soil. Moders, mulls, and Amphimull are the dominant humus forms in the topsoil of tropical environment. Knowing the mechanisms of formation, the dynamics and the methods of characterization of humus in tropical zones are a scientific challenge. This chapter aims to share recent findings from a broad humus in tropical soil and research related to this theme.
... Recent years have seen extended application of Rock-Eval for CBM and shale gas unconventional hydrocarbon reservoir characterization (Jarvie 2012;Carvajal-Ortiz and Gentzis 2015;Romero-Sarmiento et al. 2016). Furthermore, the device has also been extended for characterization of mangrove sediments (Marchand et al. 2005(Marchand et al. , 2008 of soil organic-matter characterization (Meyers and Lallier-Vergès 1999;Disnar et al. 2003;Sebag et al. 2006Sebag et al. , 2013Carrie et al. 2012;Hare et al. 2014) and even black carbon in soil (Poot et al. 2009). Furthermore, Poot et al. (2014) used Rock-Eval to predict PAH partitioning and desorption kinetic parameters of sedimentary organic-matter. ...
Article
The Rock-Eval technique has been conventionally used for source-rock analysis. In this work we document the importance of Rock-Eval S4 oxidation graphics and S4-Tpeak as indicators for coal reactivity and thermal maturity. Two non-coking coals (lower maturity), one coking coal (higher maturity), and one jhama (intrusion-induced metamorphosed coal), were collected and studied in terms of their reactivity and combustion properties. Our results indicate that Rock-Eval S4-Tpeak can be convincingly used to decipher the thermal maturity level of a coal sample. The two non-coking coals owing to their higher reactivity and corresponding lower activation energies, combusted at lower temperatures, almost entirely below 650 °C, and showed lower Rock-Eval S4-Tpeak. The coking coal sample on the other hand due to its higher thermal maturity level and lower reactivity, combusted at higher temperature, showing higher S4-Tpeak. While the S2 Tmax showed higher maturity for the coking coal than the jhama, the S4 oxidation graphics and S4-Tpeak clearly revealed higher thermal maturity of the jhama relative to the other samples. With increasing sample weights, the S4CO2 curves were observed to be broader, and consequently the S4-Tpeak was observed to be higher and erroneous, the errors being more for the more-mature coking coal and jhama. With lowering sample weights, the curves became tighter and the S4-Tpeak became lower and more precise. Parameters calculated using TG-DTG-DSC were observed to complement the data from Rock-Eval oxidation-stage, and revealed higher maturity, less reactivity, higher temperatures of ignition and burn out for the jhama, followed by the coking coal. Our results also indicate the suitability of applying Rock-Eval for combustion-profiling of coals, beyond source-rock characterization and CBM reservoir analysis.
... The described recovery system can be used to characterize a wide range of geological solid and liquid samples, including source and reservoir rocks containing natural petroleum or contaminated with drilling additives and various petroleum products. Although the Rock-Eval Ò device was primarily developed to investigate sedimentary rocks and kerogens from the perspectives of the petroleum industry, this analytical technique has been used increasingly in other geo-applications including: (1) the characterization of organic matter in soils (e.g., Di-Giovanni et al., 2000;Disnar et al., 2003;Hetényi et al., 2005;Sebag et al., 2006;Graz et al., 2012;Saenger et al., 2013;Hétényi and Nyilas, 2014); (2) the study of recent lacustrine sediments (e.g., Campy et al., 1994;Di-Giovanni et al., 1998;Meyers and Lallier-Vergès, 1999;Ariztegui et al., 2001;Steinmann et al., 2003;Jacob et al., 2004;Sanei et al., 2005;Boussafir et al., 2012;Zocatelli et al., 2012;Lavrieux et al., 2013;Sebag et al., 2013); and (3) the evaluation of recent marine sediments (e.g., Peters and Simoneit, 1982;Hussain and Warren, 1991;Calvert et al., 1992;Combourieu-Nebout et al., 1999;Ganeshram et al., 1999;Ozcelik and Altunsoy, 2000;Holtvoeth et al., 2001Holtvoeth et al., , 2003Holtvoeth et al., , 2005Tamburini et al., 2003;Baudin et al., 2007Baudin et al., , 2010Kim et al., 2007;Marchand et al., 2008;Tribovillard et al., 2008Tribovillard et al., , 2009Biscara et al., 2011;Riboulleau et al., 2011;Hare et al., 2014;Hatcher et al., 2014). Additional testing is needed to determine the applica- Table 5 Pure n-alkane recovery through the developed on-line system coupled to Rock-Eval Ò device showing loss and correction factors associated with the evaporation of the investigated pure n-alkanes. ...
Article
The Rock-Eval® device has been widely used to identify the type and the thermal maturity of sedimentary organic matter as well as quantifying the total organic carbon content. Traditionally, it is a screening tool to estimate the petroleum generation potential of source rocks using standardize parameters. More recently, a new Rock-Eval® method (Shale PlayTM) was proposed to investigate the hydrocarbon content in liquid-rich tight rock samples. In this study, we describe a dual vacuum and on-line system that was developed to recover most compounds that are thermally released during a Rock-Eval® Shale PlayTM analysis. Thermally vaporized products are divided so that half is analyzed by the Rock-Eval® flame ionization detector (FID) while the other portion is cryogenically trapped in the on-line recovery system. The trapped products can then be transferred via a vacuum line system into a sample vial for subsequent molecular and/or isotopic composition analyses. The recovery vacuum line volumes were calibrated using known quantities of gas (CH4 and CO2). Sample transfer from without isotopic fractionation was demonstrated for CO2 evolved from Rock-Eval® preparation of pure carbonate standards (siderite, magnesite and azurite). Recovery efficiencies were first measured on C8-C16n-alkane standards and then on produced oil samples. Results indicate a high quantitative recovery and an accurate mass balance of most compounds released during the Shale PlayTM Sh0 thermovaporization step (100-200°C). Thermally vaporized compounds released at higher temperatures Sh1 (200-350°C) are recovered at lower efficiencies but are still suitable for subsequent characterization. The coupled Rock-Eval® and recovery system could have applications beyond petroleum geochemistry.
... An additional informative geochemical method, Rock-Eval (RE) pyrolysis, was traditionally used in petroleum geochemistry to assess the hydrocarbon potential of the source rocks at the exploration stage [21][22][23][24][25][26]. In the recent decades, this method has been increasingly applied to study recent organic matter stored in freshwater and marine surface sediments, peat and soils [27][28][29][30][31][32][33][34]. These studies showed that RE results may significantly contribute to identification of the OM sources, distribution and degradation state. ...
Article
Full-text available
Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.
... Soil organic carbon quality was assessed with the R-index calculated as the relative HC contribution of the most thermally resistant organic fraction (i.e. thermal cracking above 400°C; see Disnar et al., 2003;Sebag et al., 2016Sebag et al., , 2006. The higher the R-index, the more organic fractions are thermally resistant. ...
Article
Full-text available
Rubber tree plantations (Hevea brasiliensis) cover large areas in the tropics. In historical producing regions like South Thailand, rubber has been planted by smallholders for three successive rotations lasting a total of 75 years. Despite possible consequences on topsoil, the long-term impacts of repeated rubber plantations on soil quality remain unknown. This study aims to better understand how various factors linked to long-term rubber land use and land use change affect topsoil physico-chemical properties and soil organic carbon (SOC) thermal stability. We focus on the effects of three factors: i. deforestation (change from forest to first rubber plantation); ii. the age of the rubber stand (immature vs mature); and iii. Long-term rubber cultivation (first, second or third successive rotation) over a chronosequence in farmers plots. Our results show that soil was deeply degraded after deforestation to a rubber plantation. Long-term rubber cultivation is also detrimental for the soil and has a more negative impact on soil physico-chemical properties and carbon dynamics, than the age of the rubber stand (e.g. on average, decrease of 50% of SOC content between forest and third rotation). At the third rotation, after 50 years of rubber cultivation, the quality of the 0–10 cm soil layer was very low, with an increase in SOC thermal stability. At this stage, logging practices upset the sustainability of the system. These impacts could be limited by less destructive practices during planting. This article is protected by copyright. All rights reserved.
... The Rock-Eval® device has also been used and developed for many different matrices to detect and quantify the total organic carbon (TOC) and the mineral carbon (MINC) contents. This analytical technique has been used increasingly in other geoscience applications including: (1) the characterization of organic matter in soils (e.g., Di-Giovanni et al., 2000;Disnar et al., 2003;Hetényi et al., 2005;Sebag et al., 2006;Saenger et al., 2013); (2) the study of recent lacustrine sediments (e.g., Campy et al., 1994;Di-Giovanni et al., 1998;Jacob et al., 2004;Sanei et al., 2005); (3) the evaluation of recent marine sediments (e.g., Peters and Simoneit, 1982;Hussain and Warren, 1991;Calvert et al., 1992;Ganeshram et al., 1999;Tribovillard et al., 2008Tribovillard et al., , 2009); (4) the study of past climate changes and global carbon cycle (e.g. Baudin et al., 2007Baudin et al., , 2010Rohais et al., 2019), and many other applications. ...
Article
In this work, artificial thermal degradation experiments using the Rock-Eval® device were performed on selected polymer microsphere samples (PE, PP, PE100, PA6, PA11, PFA and PET). The main idea of this work is first to create a database of different polymer standard responses using the specific Rock-Eval® FID/IR peak signals. Several specific Rock-Eval® parameters are now defined to characterize each polymer family. For instance, each polymer is characterized by specific quantified parameters like Total HCpolymer, Total COpolymer, TotalCO2polymer, Tpeakpolymer, among others. This study attempts to demonstrate if this quick thermal degradation method can be also used to characterize the plastic contents (detection, type, and quantity) in sedimentary samples. Results indicate that each investigated polymer shows specific Rock-Eval® parameters that can be considered as useful characteristics of polymer families (mainly Tpeakpolymer, TOCpolymer, PCpolymer, RCpolymer, total HCpolymer, total COpolymer and total CO2polymer parameters). Samples containing different mineral matrices (e.g. sand, shale, marl and carbonate) were also mixed with polymers at different concentrations varying between 0.2 and 4.2 wt%. These composite samples were also analyzed in order to evaluate their thermal degradation comparing their specific Rock-Eval® FID/IR signatures. For example, most composite samples show an excellent linear correlation between TOC, PC, RC, total HC, CO and CO2 parameters versus the amount polymer at different concentrations. Although more work is still needed, a methodology is here proposed to distinguish and quantify the presence of plastics in the environment applying the proposed polymer Rock-Eval® database.
... The rock-eval pyrolysis technique is the fundamental geochemical analysis technique of organic matter characterization. Published literature reveal that Barker (1974); Peters and Simoneit (1982); Singh et al., (1993); Sykes and Snowdon (2002); Sebag et al., (2006); David L. LePain and Russell A. Kirkham (2015), mention a few, have used rock-eval pyrolysis technique to generate data on organic matter, type, maturity and interpret source potential. ...
Article
The Oligocene succession of the Tikak Parbat Formation has prominent coal bearing horizons. The formation comprises of medium to coarse grained light coloured sandstone, clay and carbonaceous shale with four workable coal seams. Core samples from two wells has been studied with regards to organic matter content and type. Relatively high total organic carbon (TOC) contents are present (average 72.103 wt %) in coal; the hydrogen index (HI) values reach a maximum of 410 mg HC/g TOC, indicating presence of type III-II kerogen, and the organic matter is thermally immature (Tmax 428°C) in coal. The genetic potential have maximum yield of 246.53 mg/g, so the coal deposits could act as an excellent source rock for hydrocarbons if the burial depth is sufficient. Carbonaceous shale samples are at early mature stage (Tmax 438°C). Kerogen at this maturity level is within oil window and is capable of generating oil and thermogenic gas upon thermal cracking. The study highlights dense accumulation of reactive macerals (vitrinite + liptinite) and low concentration of inertinite. The empirically derived values for coal reveal a high conversion (>90%) and oil yield (>60%).
... As a result, a pyrogram of sample may be approximated by the sum of "simple" pyrograms of separate OM components. The method of deconvolution (factorization) of some experimental OM pyrograms into pyrograms of separate OM components proposed in (Sebag et al., 2006) allows the contribution of each OM component in recent sediments to be estimated quantitatively. ...
Article
—We present results of study of the chemical composition of organic matter (C, H, N, and S) from Holocene sections of lake sapropels with undisturbed stratification penetrated by vibratory drilling of the bottom sediments, down to the underlying rocks, of Lakes Bol’shie Toroki (1.8 m), Minzelinskoe (5 m), Ochki (4.5 m), Dukhovoe (7 m), and Kotokel’ (6 m). We consider methodological approaches to the identification of the sources and genesis of buried organic matter in marine and lacustrine sediments by a number of organogeochemical indicators: data of a biological analysis (biostratification based on layer-by-layer determination of organic relics in bottom sediment sections); hydrocarbon biomarkers (molecular composition of normal aliphatic hydrocarbons (n-alkanes), nitrogen compounds of a protein complex, etc.); and C/N ratio reflecting a difference in the biochemical compositions of bioproducers. The results of biological analysis (biostratification) show that planktonogenic sapropel (phyto- and zooplankton, the autochthonous source of organic matter) in Lake Ochki formed for 10,760 years, and sphagnum and hypnum moss were supplied from the bogged shores (allochthonous source of organic matter). In Lake Minzelinskoe, peaty sapropel formed at the stage of a flooded lowland bog (5905 years ago); since 3980 years ago and till the present, macrophytogenic sapropel has formed. Pyrolytic study (RE pyrolysis and Pyr–GC–MS analysis) of bioproducers and sapropel from Lake Ochki has shown that phytoplankton and zooplankton were the main autochthonous source of OM in the lake, which is confirmed by the identified macromolecules of nitrogen compounds of different compositions. The presence of hopanes indicates the contribution of microorganisms to the formation of OM in the sediments. The organic matter of sapropel has a terrigenous component, which is confirmed by the presence of high-molecular odd-numbered n-alkanes, ketones, and methyl esters of fatty acid. The C/N ratios in the stratified sections of macrophytogenic sapropels of Lakes Bol’shie Toroki and Minzelinskoe fall in the range of values specific to higher aquatic and terrestrial vegetation (C/N = 15–18), whereas the C/N ratios in planktonogenic sapropel of Lake Dukhovoe are typical of marine and lake plankton (C/N = 5.7–8.6).
... Among thermal analysis techniques, Rock-EvalÒ analysis can provide insights into OM quality changes (Disnar et al. 2003;Matteodo et al. 2018;Poeplau et al. 2017). In particular, the I and R Index scores, calculated from the amounts of hydrocarbon compounds released during pyrolysis, have been proposed as an indicator of variations in the OM quality of diverse soils (Sebag et al. 2006;Sebag et al. 2016). In a study covering a range of geochemically diverse soil types across the Swiss Alps, Matteodo et al. (2018) discovered that CaCO 3 -bearing profiles typically had lower R Index scores (lower thermal stability). ...
Article
Full-text available
Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ 13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ 13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ 13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ 13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ 13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ 13C values. Supplementary information: The online version of this article (10.1007/s10533-021-00779-7) contains supplementary material, which is available to authorized users.
... Notre étude se réfère à la méthode développée par Disnar et al. (2003) pour estimer la contribution des pools de constituants organiques définis par leur température de craquage spécifique. Ainsi, selon les travaux d' Albrecht et al. (2015), les courbes S2 ont été décomposées en intervalles (Sebag et al., 2007 ;Albrecht et al., 2015 ;Sebag et al., 2016). I-index représente la contribution de la matière organique immature, tandis que R-index représente celle de la matière organique mature. . ...
... This technique has been recommended for characterizing soil organic matter (Derenne and Quénéa, 2015;Disnar et al., 2003). In this study, soil organic matter dynamics was analyzed through the combination of two indices (I and R) calculated from five areas of the hydrocarbon thermograms, according to predefined temperature thresholds (Disnar et al., 2003;Sebag et al., 2016Sebag et al., , 2006. By construction, the R-index is related to the most thermally refractory fraction of organic matter, while the I-index is related to the most thermally labile one (see Sebag et al. (2016) for details). ...
Article
The assessment of the impacts of land-use and management on soil organic carbon (SOC) dynamics is a major environmental concern, as the soil carbon cycle underpins key ecosystem services. However, assessments based on short-term SOC dynamics face methodological and experimental difficulties. Hurisso et al. (2016) proposed a method to assess SOC dynamics by coupling two methods: Permanganate Oxidizable Carbon (POXC) and Basal Soil Respiration (BSR). This method has been used in laboratory on dried and re-wetted soil samples from temperate regions mainly. In our study, we adapted this method to the field and proposed a cost-effective in-field indicator combining the POXC and in situ Basal Soil Respiration (SituResp® method). We tested the indicator at four study sites (n = 169 points) within various tropical land-use and management contexts based on rubber, soybean and oil palm cropping systems respectively in Thailand, Cambodia and Indonesia. The results demonstrated the relevance, sensitivity and robustness of the POXC-SituResp® indicator to characterize the impact of a gradient of disturbance on SOC dynamics. The results also highlighted the potential of conservation agriculture (no-tillage and crops residues) and compost amendments to accumulate SOC. Rock-Eval® analysis showed that POXC-SituResp® indicator is negatively linked to excess of potentially mineralizable labile carbon. Carbon pools targeted by the POXC were specified by Rock-Eval® pyrolysis measurements to be a rather thermal resistant pool of SOC. Our study confirms that the integrated indicator based on POXC and BSR assess a relative carbon stabilization of SOC pools. This indicator can be measured in the field by a rapid and cost-effective method.
Article
In the present study, shale samples from Rajmahal Basin, India, were analysed in terms of their source rock properties using an open-system programmed pyrolysis instrument (Rock–Eval 6). Comprehensive analysis of the different Rock–Eval graphics was conducted for the samples under consideration. Construction of S2 (mg HC/g rock) vs. total organic carbon (wt%) cross-plot using iso-HI (iso-hydrogen index) lines classified the studied suit of samples into three zones with increasing hydrogen index (Zone A < Zone B < Zone C). Analysis of S2 curves of samples from different zones revealed distinctive features attributed to the variable nature of kerogen present within the sample as well as the levels of S2 and HI. S2 curves of sample with higher Tmax were observed to be asymmetric, broad, and marked by lower flame ionization detector signals. However, for those samples, the S4 Tpeak was observed to be similar to that of the other samples. On the other hand, the higher S2 Tmax of some samples coincided with higher S4 Tpeak indicating the samples to be more mature. Additionally, samples with higher levels of oxygen index (OI), and siderite content, were observed to have S3′ curve marked by pronounced release of CO2 above 400 °C, whereas the samples with higher OI but without any presence of siderite were marked by noisy curves due to low IR CO2 signal. The results reiterated the importance of careful monitoring of the different curves obtained during the pyrolysis and oxidation stage so that erroneous characterization of the samples could be avoided.
Article
The results of the pyrolytic analysis of products of the organic matter of Sphagnum fuscum, fuscum peat, and humic acids separated from peat with the use of pyrolysis–chromatography–mass spectrometry in the Rock-Eval version are presented. It was shown that Sphagnum fuscum and peat differed only slightly in the degrees of chemical transformation. Benzene, phenol, and their alkyl-substituted homologues predominated in the thermal desorption products of humic acids upon pyrolysis to 400°C. Acetic acid, monohydric phenols, syringol, and guaiacol, which are the basic compounds in the high-temperature fraction, were formed on the pyrolysis humic acids to 700°C from the carbohydrate, phenylpropionic, and guaiacylpropane structural fragments.
Article
The Northern coastline, from Kayar to Saint Louis (Senegal) is characterized by a succession of dunes and inter-dunes. Coastal wetlands located in the inter-dunes which bear Organic Matter (OM) rich soil where market garden agriculture is the main activity. These zones locally called “Niayes” are characterized by shallow groundwater table threatened by anthropogenic pressure, climate and environmental impacts. The scientific interest of this research work is to characterize the composition of soil OM to discuss its origin, composition, and diagenetic evolution in this depositional environment of Mboro research site with regard to natural and anthropogenic pressure. Three selected core samples with depth interval of 5 cm aligned in along a slope transect in the Mboro wetland were carried out. Soil OM were analyzed for Particulate OM, C/N, Rock-Eval HI and OI, δ¹³C, δ¹⁵N whereas sediments and water were respectively analyzed for grain size distribution, water contents and redox potential down to 50 cm depth. We have demonstrated through the results a vertical variability in the content, the nature and preservation quality of sedimentary OM with the occurrence of a peat storage zone. The isotopic markers depict a strong contribution of C3 plants, macrophytes and to a lesser extent of algae and microbial organic materials. High concentrations of dissolved nutrients occurring mainly on the surface slope may derive from the use of fertilizers to improve agricultural yields. These results constitute an added value in the scientific knowledge of this sector of the Niaye of Senegal.
Article
This work is devoted to the study of fillings and late Holocene palaeoenvironments of two marshes located in the savannas of the northern part of Lopé National Park in Gabon. Sedimentological and geochemical analyzes associated with 14C dating were performed on the sedimentary deposits of Yao and Vitex marshes. The results obtained were compared with these of the sedimentary core of the Lopé 2 marsh, previously analysed. All of these data show that the active filling of these marshes was carried out synchronously. The small variation observed are linked to specific physical characters to each of the marshes. This filling began between 2300 and 2000 cal years BP in all of the marshes. It started at the beginning of the humid climatic phase which followed the climatic pejoration recognized throughout the area of Atlantic Central Africa between 2500 and 2000 years BP. During this humid climatic phase, the rains were abundant and regular and the depressions were filled with sediments which are very rich coarse detrital elements from the erosion of slopes. The marshes and its banks were covered with sparse vegetation. Subsequently the sediments gradually become depleted in coarse detrital materials and enriched with organic constituents. This evolution would indicate a gradual reduction in erosion linked to the densification of the vegetation cover on the slopes. It is mostly related to the development of vegetation in the marshy basins. This development of the vegetation and the conservation of the organic matter of the marshes are due to the perennial flooding of the palustrine depressions.
Article
A quantitative assessment of historical sediment yields (SY) was performed using sediment budgets from lacustrine records located in the Mont Dore and Cezallier volcanic provinces (French Massif Central). A source-to-sink approach combining hydro-acoustic images, organic geochemistry (Rock-Eval and quantitative organic petrography) and radiocarbon dating of sediment cores has been adopted on three lake-catchment systems, namely Pavin, Chauvet and Montcineyre. SY was estimated from the quantification of red Amorphous Particles (rAP), a terrigenous organic tracer identified in both soils and sediments. Historical SY range between 3 and 320 t km⁻².yr⁻¹, which is comparable to the magnitude reached in other European lake-based SY records in similar geographical and climatic settings. Comparison of recent SY with predicted values of soil erosion rates from the RUSLE2015 model highlights large differences linked to scale differences between the model at plot scale and lake-based SY reflecting erosion export from the catchment to the lake. In this sense, the role of peatlands as sediment traps within two studied catchments must be considered to explain the large differences between modelled soil erosion rates and reconstructed SY data. SY differences between sites can be firstly attributed to morphology, size and lithology of the catchments as well as to vegetation cover whereas fluctuations reconstructed for each record seem to be mainly related to human-induced land use management. Historical SY from Chauvet and Montcineyre synchronously recorded two events in 850 CE and 1450 CE, respectively. The first marked the rise of SY to their maxima following land-use changes in the catchments. Nearby palaeoenvironmental records from Lake Aydat, Chambedaze peatland, and Espinasse marsh suggest this rise was consecutive to intensification of agro-pastoral activities recorded at regional scale. The second event followed a land-use shift characterized by a ten to fifteen-fold decrease in SY values. The driver remains unclear but could be possibly related to historical events causing a demographic decline (i.e., the Black Plague and/or the Hundred Years War) and/or cultural adaption in response to the onset of the Little Ice Age. Overall, both records suggest erosion in the area has been historically more susceptible to human-induced land use change rather than to precipitation and temperature changes induced by climate variability of the past millennium.
Article
The allocation of urban water resources is an important way to deal with the increasingly serious urban water pollution problems. Analyzing urban water resources and scientific research, so that relatively limited water resources can be used for urban economic, social development and ecological environmental protection. Effective and reasonable configuration. On the basis of soft computing, this article discusses the rational distribution of water resources in various countries in the world, combined with the specific conditions of a city in the scientific research area, and conducts scientific research on comprehensive economics. Subsequently, this article also conducted a certain scientific research on the development trend of low-carbon economy. Scientific research on the development trend of China’s low-carbon economy is one of the hotspots of academic concern. Carefully analyze the shortcomings of the whole process of China’s low-carbon economy development trend, deeply explore its development trend management system, examine the continuous impact of the low-carbon economy on the world’s rights and interests from the perspective of game theory, and analyze the interest game among enterprises, the masses, and financial institutions; A more comprehensive scientific research has been conducted on preferential policies under the development trend of low-carbon economy. This paper establishes a framework management system for China’s low-carbon economic development: China must actively explore based on its own basic national conditions, blaze a path of successful low-carbon economic development, and contribute to the global low-carbon environmental development trend. Focusing closely on the core of low-carbon construction, establish technological innovation, carbon emission rights trading, popular concepts, and improve China’s framework system for the development of a low-carbon economy with the current policy management system as the main content. In this paper, through the research on soft computing and its application in urban water resources allocation and low-carbon economic development, it aims to promote its vigorous development.
Article
The amount of CaCO 3 in sediments and/or sedimentary rocks is usually measured by calcimetry while the nature of the carbonates is determined by X-ray diffraction. Recently, a carbonate recognition method based on the results of Rock-Eval pyrolysis was proposed in 2014 by Pillot et al. [1]. Rock-Eval pyrolysis is also widely used for the characterization of recent sediments. However, later in 2015 Baudin et al. [2]noticed that some of the characteristics of recent sediments tended to produce different results from those of more classical Rock-Eval analyses, causing bias in interpretations. In this study, the thermal stability of fossil and recent marine carbonated sediments was analyzed to identify differences in carbonate decomposition and to underline the importance of accounting for them in Rock-Eval analyses. The state of calcite preservation in recent marine sediments and sedimentary rocks at temperatures between 400 °C and 600 °C was characterized using different techniques (calcimetry, XRD, SEM imaging, etc.)for better interpretation of data obtained with Rock-Eval. Our results highlight a clear difference in the range of calcite decomposition temperatures during Rock-Eval analysis: between 550 °C and 775 °C for bulk clayey hemipelagic sediments versus 650 °C–840 °C after the same sediments were rinsed to get rid of the salt. During heating, water and hydroxide anions are released from clay minerals and react with salt crystals to form acid vapor. This acid vapor reacts with carbonates to produce CO 2 . The chemical decomposition of carbonate starts at temperatures that are lower than the typical range of decomposition temperatures, leading to overestimation of mineral carbon content (overestimation of the S5 peak)and to underestimation of organic carbon content (underestimation of the S4CO 2 peak)with the Rock-Eval method. In the absence of clay minerals, such as in recent marine pure carbonate oozes, there is no evidence for this effect. It is therefore essential to prepare and rinse recent clay-rich carbonated sediment samples before Rock-Eval analysis to avoid misinterpretation.
Article
The characterization of organic matter (OM) composition, physico-chemical, geochemical, and mineralogical studies of sedimentary core can help to better understand the paleoclimates and the depositional environments. The purpose of this work is to identify the factors monitoring the mineralogical composition and the sedimentation of sebkha Mhabeul sediments (southeastern Tunisia), during the Holocene. A 100.5 cm core (Mh 1) collected from this sebkha was analyzed for the determination of chemical composition by X-ray fluorescence (XRF), carbonate content by Bernard calcimetry, grain-sized sediments by AFNOR sieves, OM content by Rock-Eval 6 Pyrolysis, and mineralogical composition by X-ray diffraction (XRD), scanning electronic microscope (SEM), and infrared spectroscopy (IR). The sedimentary fillings of this sebkha, constituted by fine fractions, are characterized by the dominance of the detrital minerals (72–96 %) with high quartz percentages (42.2–91.5 %). The mineralogical composition of the studied sediments included detrital minerals (clay minerals, quartz, and feldspars), carbonate minerals (ankerite, dolomite, and calcite), and evaporitic minerals (halite, bassanite). The clay minerals (11–14%) are composed of a mixture of kaolinite, illite and palygorskite. Fourier transform infrared (FTIR) absorption spectra of all sediment samples confirm the mineralogical composition obtained by XRD and the existence of OM, by defining the band assignments for OM and different minerals as quartz, feldspar, clay, and carbonate minerals. The Rock Eval pyrolysis shows that the OM is immature and has a mixed origin (terrestrial and aquatic). The statistical analyses prove the results of geochemical and mineralogical studies. Indeed, the principal component analysis (PCA) of geochemical and mineralogical data and the depth help to prove the relationships between minerals and chemical elements. Moreover, the negative correlation between the Rock Eval Pyrolysis parameters and the depth shows a homogenous statistical group.
Article
Among the different Rock-Eval parameters, the hydrocarbons released under the S 2 peak of Rock-Eval is of significance as it indicates the residual hydrocarbon content of the rock. Further, through its relationship with total organic carbon (TOC)content, it helps in calculating hydrogen indices (HI)which helps in understanding the type of organic matter present in a rock [HI= (S 2 /TOC)*100]. The present study documents the role of sample weight/amount used for analysis on the Rock-Eval S 2 parameter for unconventional source-rock characterization. For the purpose of this study, a vitrain band sample type (manually isolated from a coal), a high-TOC shale sample type, and a carbonaceous shale sample type were analyzed at two different particle sizes (viz. 1 mm-500 μm and 212-75 μm)and different sample weights (5–15 mg for organic matter rich rocks and 30–60 mg for shale)using a Rock-Eval basic cycle (heating rate at 25 °C/min). Although S 2 is reported as mg hydrocarbon (HC)/g rock, with increase in sample weight, an increase in hydrocarbons released under the S 2 peak of Rock-Eval was observed for all three sample types for both the particle sizes. The observations were further validated using a Norwegian geochemical standard (JR-1). Further, all samples were reanalyzed by conducting pyrolysis experiments at a lower heating rate of 5 °C/min. The impact of sample weight on S 2 and HI was observed to be more pronounced for the JR-1 standard (higher hydrocarbon yield)than the Van Krevelen Types III-IV organic matter-bearing rocks. It thus calls for interpreters to be aware of the influence of mass of organic matter on hydrocarbon generation, and to monitor the maximum S 2 values of organic matter-bearing rocks, within the flame ionization detector (FID)detection limits. Further, it is recommended that for Type III organic matter-bearing rocks with TOC content>20 wt %, elemental analysis should be used to derive atomic H/C and O/C ratios for Van Krevelen diagram-based kerogen typing.
Article
In the Majerda delta, the largest wadi in Tunisia, a study is being conducted on the flow of organic matter at the old and new mouths of this wadi (NMM, OMM). This study explores the sources, distribution, evolution, and diagenesis of organic matter in recent sediments by means of Rock–Eval. The pyrolysis results are interpreted in relation to particle size, carbonates, N, Mn, and Fe. Sediments from both cores are predominantly clastic and consist of clay and silt with fragments of higher plants. TOC content varies from 1.13 to 1.59% in the NMM core compared to 1.22 and 2.63 in the OMM core, and C/N ratios range from 9 to 13 for NMM and 11 to 73 for ONM. The C/N ratio < 10 indicates that OM is rapidly decomposed by biomass and mineralized, while a C/N > 10 indicates that OM is preserved. According to the HI vs. OI diagram, there are two distinct OM groups in the delta of Majerda. Temperatures above 300 °C indicate that OM has not been profoundly altered in this delta; however, a high C/N ratio and a low Mn/Fe ratio indicate that OM tends to be lignin rich in the deep sediments of OMM. The low values of HI/OI ratio (0.2 < HI/OI < 0.4) in the new and old Majerda mouths with the lowest C/N and Fe/Mn ratios are due to microbial oxidative diagenesis and reflect a highly oxidizing environment. During OM degradation and progressive oxidation, the labile and lignocellulosic components disappear, leaving stabilized residues.
Article
Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10 %). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values.
Article
Full-text available
Here we present lithological and geochemical characteristics of the core drilled in coastal part of the Laptev Sea (Ivashkina Lagoon, Bykovsky Peninsula). It is shown that for sediments accumulated in specific lagoon conditions the increased content of organic carbon is confined to fine-grained lacustrine and lagoonal sediments in the uppermost layers. Pyrolytic analysis results indicate a sharp variability in the content of total organic carbon and volatile organic compounds across the studied horizons. The distribution of n-alkanes is characterized by the dominance of high molecular weight homologues, which indicates the ubiquitous contribution of higher terrestrial vegetation discharged with river and coastal thermo abrasion fluxes to the organic matter of bottom sediments.
Conference Paper
Full-text available
Valorisation of dredging sediments has gained a lot of attention over the recent years. An application route that has attracted considerable interest is the use of calcined dredged sediments as Supplementary Cementitious Material (SCM) in composite cements to replace clinker. The present study investigates the valorisation potential of sediments dredged from three different inland waterway locations in the Belgian-French cross-border region as part of the Interreg V France-Wallonie-Vlaanderen VALSE project. The objective is to evaluate the optimum calcination temperature of the sediments at which the calcined sediments would be most reactive as SCMs. The mechanically dewatered fine fraction (<63 µm) of the dredged sediments was batch calcined at 500 °C, 600 °C, 700 °C and 800 °C. Physical and chemical characteristics were evaluated as a function of the calcination temperature. The results show that the optimum calcination temperature was at 800 o C for Brussels-Charleroi (BC) and Lens (L), and 700 o C for Ghent-Terneuzen (GT). The optimum calcination resulted in degradation of organic matter, which along with densification of particles and sintering, decreased the specific surface area and increased the particle size; furthermore the optimum calcination resulted in activation of clay minerals, and dissolution of CaCO3. The R 3 test method confirmed the optimum calcination temperature for each sediment to have the highest pozzolanic reactivity in the model system. Furthermore it was seen from the R 3 test that all calcined sediments had comparable or even better reactivity as regular siliceous fly ashes.
Thesis
Full-text available
Ferruginous conditions were a prominent feature of the oceans throughout the Precambrian Eons and thus throughout much of Earth’s history. Organic matter mineralization and diagenesis within the ferruginous sediments that deposited from Earth’s early oceans likely played a key role in global biogeochemical cycling. Knowledge of organic matter mineralization in ferruginous sediments, however, remains almost entirely conceptual, as modern analogue environments are extremely rare and largely unstudied, to date. Lake Towuti on the island of Sulawesi, Indonesia is such an analogue environment and the purpose of this PhD project was to investigate the rates and pathways of organic matter mineralization in its ferruginous sediments. Lake Towuti is the largest tectonic lake in Southeast Asia and is hosted in the mafic and ultramafic rocks of the East Sulawesi Ophiolite. It has a maximum water depth of 203 m and is weakly thermally stratified. A well-oygenated surface layer extends to 70 m depth, while waters below 130 m are persistently anoxic. Intensive weathering of the ultramafic catchment feeds the lake with large amounts of iron(oxy)hydroxides while the runoff contains only little sulfate, leading to sulfate-poor (< 20 µM) lake water and anoxic ferruginous conditions below 130 m. Such conditions are analogous to the ferruginous water columns that persisted throughout much of the Archean and Proterozoic eons. Short (< 35 cm) sediment cores were collected from different water depths corresponding to different bottom water redox conditions. Also, a drilling campaign of the International Continental Scientific Drilling Program (ICDP) retrieved a 114 m long sediment core dedicated for geomicrobiological investigations from a water depth of 153 m, well below the depth of oxygen penetration at the time of sampling. Samples collected from these sediment cores form the fundament of this thesis and were used to perform a suite of biogeochemical and microbiological analyses. Geomirobiological investigations depend on uncontaminated samples. However, exploration of subsurface environments relies on drilling, which requires the use of a drilling fluid. Drilling fluid infiltration during drilling can not be avoided. Thus, in order to trace contamination of the sediment core and to identify uncontaminated samples for further analyses a simple and inexpensive technique for assessing contamination during drilling operations was developed and applied during the ICDP drilling campaign. This approach uses an aqeous fluorescent pigment dispersion commonly used in the paint industry as a particulate tracer. It has the same physical properties as conventionally used particulate tracers. However, the price is nearly four orders of magnitude lower solving the main problem of particulate tracer approaches. The approach requires only a minimum of equipment and allows for a rapid contamination assessment potentially even directly on site, while the senstitivity is in the range of already established approaches. Contaminated samples in the drill core were identified and not included for further geomicrobiological investigations. Biogeochemical analyses of short sediment cores showed that Lake Towutis sediments are strongly depleted in electron acceptors commonly used in microbial organic matter mineralization (i.e. oxygen, nitrate, sulfate). Still, the sediments harbor high microbial cell densities, which are a function of redox conditions of Lake Towuti’s bottom water. In shallow water depths bottom water oxygenation leads to a higher input of labile organic matter and electron acceptors like sulfate and iron, which promotes a higher microbial abundance. Microbial analyses showed that a versatile microbial community with a potential to perform metabolisms related to iron and sulfate reduction, fermentation as well as methanogenesis inhabits Lake Towuti’s surface sediments. Biogeochemical investigations of the upper 12 m of the 114 m sediment core showed that Lake Towuti’s sediment is extremely rich in iron with total concentrations up to 2500 µmol cm-3 (20 wt. %), which makes it the natural sedimentary environment with the highest total iron concentrations studied to date. In the complete or near absence of oxygen, nitrate and sulfate, organic matter mineralization in ferruginous sediments would be expected to proceed anaerobically via the energetically most favorable terminal electron acceptors available - in this case ferric iron. Astonishingly, however, methanogenesis is the dominant (>85 %) organic matter mineralization process in Lake Towuti’s sediment. Reactive ferric iron known to be available for microbial iron reduction is highly abundant throughout the upper 12 m and thus remained stable for at least 60.000 years. The produced methane is not oxidized anaerobically and diffuses out of the sediment into the water column. The proclivity towards methanogenesis, in these very iron-rich modern sediments, implies that methanogenesis may have played a more important role in organic matter mineralization thoughout the Precambrian than previously thought and thus could have been a key contributor to Earth’s early climate dynamics. Over the whole sequence of the 114 m long sediment core siderites were identified and characterized using high-resolution microscopic and spectroscopic imaging together with microchemical and geochemical analyses. The data show early diagenetic growth of siderite crystals as a response to sedimentary organic matter mineralization. Microchemical zoning was identified in all siderite crystals. Siderite thus likely forms during diagenesis through growth on primary existing phases and the mineralogical and chemical features of these siderites are a function of changes in redox conditions of the pore water and sediment over time. Identification of microchemical zoning in ancient siderites deposited in the Precambrian may thus also be used to infer siderite growth histories in ancient sedimentary rocks including sedimentary iron formations.
Article
Full-text available
This review highlights the ubiquity of black carbon (BC) produced by incomplete combustion of plant material and fossil fuels in peats, soils, and lacustrine and marine sediments. We examine various definitions and analytical approaches and seek to provide a common language. BC represents a continuum from partly charred material to graphite and soot particles, with no general agreement on clear-cut boundaries. Formation of BC can occur in two fundamentally different ways. Volatiles recondense to highly graphitized soot-BC, whereas the solid residues form char-BC. Both forms of BC are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport. We summarize, chronologically, the ubiquity of BC in soils and sediments since Devonian times, differentiating between BC from vegetation fires and from fossil fuel combustion. BC has important implications for various biological, geochemical and environmental processes. As examples, BC may represent a significant sink in the global carbon cycle, affect the Earth's radiative heat balance, be a useful tracer for Earth's fire history, build up a significant fraction of carbon buried in soils and sediments, and carry organic pollutants. On land, BC seems to be abundant in dark-colored soils, affected by frequent vegetation burning and fossil fuel combustion, thus probably contributing to the highly stable aromatic components of soil organic matter. We discuss challenges for future research. Despite the great importance of BC, only limited progress has been made in calibrating analytical techniques. Progress in the quantification of BC is likely to come from systematic intercomparison using BCs from different sources and in different natural matrices. BC identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels. The key to estimating BC stocks in soils and sediments is an understanding of the processes involved in BC degradation on a molecular level. A promising approach would be the combination of short-term laboratory experiments and long-term field trials.
Article
Full-text available
Successful petroleum exploration relies on detailed analysis of the petroleum system in a given area. Identification of potential source rocks, their maturity and kinetic parameters, and their regional distribution are best accomplished by rapid screening of rock samples (cores and/or cuttings) using the Rock-Eval apparatus. The technique has been routinely used for about fifteen years and has become a standard tool for hydrocarbon exploration. This paper describes how the new functions of the latest version of Rock-Eval (Rock-Eval 6) have expanded applications of the method in petroleum geoscience. Examples of new applications are illustrated for source rock characterization, reservoir geochemistry, and environmental studies, including quantification and typing of hydrocarbons in contaminated soils.
Article
Full-text available
The particulate organic matter isolated from soils and from underlying geologic formations from Various french watersheds was studied under the light microscope to determine palynofacies composition. The results reveal that modern humus contain notable amounts of ancient organic constituents inherited from the geologic substratum. This ancient contribution varies both qualitatively and quantitatively, mainly as function of the substratum composition. This implies that the cartography of surface formations and the knowledge of their composition is a prerequisite to the evaluation of the soil organic carbon reservoir and to the determination of its turnover. A more immediate conclusion is to remind us that the coaly debris that occur naturally in soils does not always derive from modern biologic production and from pollution.
Article
Full-text available
Sedimentary organic matter has been systematically studied in an eight-metre long core from the centre of the Petit Lac (Annecy, French Alps). The palynofacies composition identifies different terrestrial organic sources including forest floors, soil-horizons and geological substratum. The amount of recycled organic matter derived from the geological substratum is estimated and subtracted from the other contributions from the catchment area. The palynological record indicates that the relative variations in organic sources are directly dependent on human land-use. From ca. 5000 to 1700 BP, the human impact on soil cohesion is very low and organic matter is mainly exported from the surficial forest floor. The Roman invasion (ca. 1700 BP) marks the most important ecological and hydrological change. From 1700 to 900 BP, the clearing of forests released deeper-soil components. This trend is increased after 900 BP with agriculture intensification, which resulted in a higher sedimentation rate. In all the periods, extreme events such as flood or intensive run-off are characterised by notable increases of organic matter from surface (5000 to 1700 BP) and deep (1700 BP to now) soils.
Article
Full-text available
L'étude pétrographique (palynofaciès) et géochimique (pyrolyse Rock Eval) de la matière organique sédimentaire d'une carotte prélevée dans un lac de cratère de Madagascar révèle une sédimentation organique de type tourbeux avant 36 ka, entre ca 28 et 15 ka et entre 6 et 0 ka, mise en place au cours de périodes d'assèchement. Entre ca 36 et 28 ka, elle se caractérise par une sédimentation lacustre (phytoplancton dominant) et des migrations de végétation du bassin versant vers le lac lui-même. Des apports de matière organique allochtone témoignent de l'établissement d'un couvert végétal sur le bassin versant et du lessivage de sols, lors de périodes humides. Les variations d'écosystèmes et de peuplement sont à mettre en relation avec l'évolution du régime hydroclimatique depuis 36 ka, en termes de périodes sèches et humides. (Résumé d'auteur)
Article
This paper is concerned with the impact of carbon black industry on the environment with particular attention to the environmental protection problems. Carbon black manufacturers give high priority in research and development programs to finding solutions to these problems, as well as the conservation of energy sources by improvements in the thermal and material efficiencies of manufacture. The discussion is presented under headings - carbon black industry; decrease in demand; unique form of industrial carbon; evolution of the process; oil furnace carbon black process; need for improving thermal efficiency of carbon black production; the trend to recover the tail gas energy; liquid feedstock and gas requirements; different yields, environmental aspects; and tail gas burning.
Article
Petrographic (palynofacies) and geochemical (Rock Eval pyrolysis) studies of sedimentary organic matter of a core from a crater lake in Madagascar show a peaty sedimentation before 36 ky and between ca 28 and 15 ky, and between 6 and 0 ky. Between 36 and 28 ky, the organic sedimentation is characterized by alternate phytoplanktonic sedimentation and migrations of vegetation from the basin slope to the lake itself. Contributions of oxidized allochthonous organic matter also prove the presence of vegetation on the surrounding basin and soil leaching. The variation of the ecosystems and their development reveal the climatic changes during the last 36 kyrs, in terms of arid and humid periods. -English summary
Book
Production and Accumulation of Organic Matter: A Geological Perspective.- Production and Accumulation of Organic Matter The Organic Carbon Cycle.- Evolution of the Biosphere.- Biological Productivity of Modern Aquatic Environments.- Chemical Composition of the Biomass: Bacteria, Phytoplankton, Zooplankton, Higher Plants.- Sedimentary Processes and the Accumulation of Organic Matter.- The Fate of Organic Matter in Sedimentary Basins: Generation of Oil and Gas.- Diagenesis, Catagenesis and Metagenesis of Organic Matter.- Early Transformation of Organic Matter: The Diagenetic Pathway from Organisms to Geochemical Fossils and Kerogen.- Geochemical Fossils and Their Significance in Petroleum Formation.- Kerogen: Composition and Classification.- From Kerogen to Petroleum.- Formation of Gas.- Formation of Petroleum in Relation to Geological Processes. Timing of Oil and Gas Generation.- Coal and its Relation to Oil and Gas.- Oil Shales: A Kerogen-Rich Sediment with Potential Economic Value.- The Migration and Accumulation of Oil and Gas.- An Introduction to Migration and Accumulation of Oil and Gas.- Physicochemical Aspects of Primary Migration.- Geological and Geochemical Aspects of Primary Migration.- Secondary Migration and Accumulation.- Reservoir Rocks and Traps, the Sites of Oil and Gas Pools.- The Composition and Classification of Crude Oils and the Influence of Geological Factors.- Composition of Crude Oils.- Classification of Crude Oils.- Geochemical Fossils in Crude Oils and Sediments as Indicators of Depositional Environment and Geological History.- Geological Control of Petroleum Type.- Petroleum Alteration.- Heavy Oils and Tar Sands.- Oil and Gas Exploration: Application of the Principles of Petroleum Generation and Migration.- Identification of Source Rocks.- Oil and Source Rock Correlation.- Locating Petroleum Prospects: Application of Principle of Petroleum Generation and Migration - Geological Modeling.- Geochemical Modeling: A Quantitative Approach to the Evaluation of Oil and Gas Prospects.- Habitat of Petroleum.- The Distribution of World Oil and Gas Reserves and Geological-Geochemical Implications.
Article
The Balazuc 1 borehole drilled in the frame of the “Géologie Profonde de la France” programme and the work carried out by various specialists provided the samples and the independent paleotemperature assessment data both needed to check a model aiming to the straightforward determination of maximum paleotemperatures of burial (MPTB) from Rock-Eval® pyrolysis data. Basically, the model supposes that laboratory (e.g., Rock-Eval®) pyrolysis resumes the successive elimination of kerogen moieties of increasing thermal stability where it had stopped during burial diagenesis. Then, the temperature Tmin determined at the onset of the S2 Rock-Eval® pyrolysis peak — supposed to correspond to a peculiar kerogen moiety which was just undergoing cracking when maximum burial depth was reached — might be used to calculate the corresponding MPTB, taking into account the different values of the experimental and natural thermal gradients. The good agreement between calculated MPTB-values and results of fission-track and fluid-inclusion studies carried out on Balazuc 1 borehole samples supports the validity of the model. According to fundamental considerations the application of this approach is limited to samples having at least reached the onset of the metagenetic stage. Other possible limitations and the causes of uncertainty on the obtained results are discussed. A detailed operating procedure is presented.
Article
This review highlights the ubiquity of black carbon (BC) produced by incomplete combustion of plant material and fossil fuels in peats, soils, and lacustrine and marine sediments. We examine various definitions and analytical approaches and seek to provide a common language. BC represents a continuum from partly charred material to graphite and soot particles, with no general agreement on clear-cut boundaries. Formation of BC can occur in two fundamentally different ways. Volatiles recondense to highly graphitized soot-BC, whereas the solid residues form char-BC. Both forms of BC are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport. We summarize, chronologically, the ubiquity of BC in soils and sediments since Devonian times, differentiating between BC from vegetation fires and from fossil fuel combustion. BC has important implications for various biological, geochemical and environmental processes. As examples, BC may represent a significant sink in the global carbon cycle, affect the Earth's radiative heat balance, be a useful tracer for Earth's fire history, build up a significant fraction of carbon buried in soils and sediments, and carry organic pollutants. On land, BC seems to be abundant in dark-colored soils, affected by frequent vegetation burning and fossil fuel combustion, thus probably contributing to the highly stable aromatic components of soil organic matter. We discuss challenges for future research. Despite the great importance of BC, only limited progress has been made in calibrating analytical techniques. Progress in the quantification of BC is likely to come from systematic intercomparison using BCs from different sources and in different natural matrices. BC identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels. The key to estimating BC stocks in soils and sediments is an understanding of the processes involved in BC degradation on a molecular level. A promising approach would be the combination of short-term laboratory experiments and long-term field trials.
Article
A recently developed demineralisation treatment, using 2% hydrofluoric acid, was applied to the <50 mum fraction of a silty loamy soil typical of crop soils from northern France. The material thus isolated was compared with an untreated control through elemental analysis and thermal degradation (Rock-Eval pyrolysis; analysis by combined gas chromatography-mass spectrometry of the pyrolysates obtained by off-line pyrolyses at 300 and 400 degreesC). It appeared that: (i) efficient removal of the minerals was achieved by this treatment while only limited losses of organic carbon occurred; (ii) large retention of the pyrolysis effluents by the mineral matrix took place in the untreated sample; (iii) the extent of this retention, for the different types of pyrolysis products, is controlled by their molecular weight and polarity; (iv) through these off-line pyrolyses information can also be obtained on the origin of the components of Soil organic matter (SOM) pyrolysates (thermovaporized products vs. pyrolysis products formed via cracking reactions; lignin-derived phenolics vs. melanoidin-derived ones); and (%,) pyrolytic studies limited to the untreated sample would have provided highly biased quantitative and qualitative information on SOM so that the presence of some important constituents would have passed unnoticed.
Article
Les études fondamentales réalisées sur les kérogènes à l'aide de diverses méthodes physico-chimiques d'analyse ont permis de mettre au point une méthode et un appareillage adaptés à l'exploration pétrolière. On expose dans cet article la mise au point de cette méthode et on montre, à l'aide des paramètres qu'elle permet d'obtenir, ses applications dans le domaine de l'exploration pétrolière - reconnaissance des différents types de roche mère et de leur potentiel pétrolier; - caractérisation de leur degré d'évolution (zone à huile - zone à gaz). On montre aussi que cette méthode convient particulièrement bien à l'estimation du rendement en huile des roches bitumineuses et à l'étude de la qualité et du rang des charbons. Fundamental research on kerogens by different physico-chemical analysis methods have led to the development of a method and equipment suited for petroleum exploration. This article describes the development of this method and, by means of the parameters it determines, shows how it con be applied in the field of petroleum exploration - exploring different types of source rock and their petroleum potential ; - characterizing their degree of evolution (ail zone/gas zone). This method is also shown ta be particularly suited for estimating the oil yield of cil shales and investigating the quality and classification of cool.
Article
The total organic carbon (TOC) of many recultivated mine soils is composed of a fraction that is lignite-derived as well as a fraction that is derived from recent plant litter. In these soils, precise quantification of the lignite contribution to the TOC content can only be achieved with expensive and time consuming methods. In the present study, we tested diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in combination with multivariate data analysis [partial least squares (PLS)] as a rapid and inexpensive means of quantifying the lignite contribution to the TOC content of soil samples. The conceptual approach included analysis of samples with different lignite content (bulk soil and particle size fractions) by DRIFT-spectroscopy and 14C activity measurements. Afterwards, with both data sets a calibration curve was established by PLS and the lignite content predicted from the DRIFT spectra. A good fit was obtained between this approach and the radiocarbon analysis. Loading factors showed that this prediction was based on structural differences between the two organic matter types. We conclude that DRIFT spectroscopy can be used in combination with multivariate data analysis for the differentiation of carbon derived from lignite and carbon derived from recent organic matter in soils.
Article
Structural information on soil organic matter (SOM) at the molecular level can be obtained on diverse structural units that are amenable to degradation techniques. Chemolytic techniques in combination with colorimetric analyses or GC MS are used to determine amino acids (proteins), sugars (polysaccharides), lipids, or aromatic oxidation products from lignin or charred organic matter. Microbial markers (amino sugars, muramic acid) are analyzed after hydrolysis and gas chromatographic separation. Macromolecular structures can also be subjected to thermochemolytic degradation or pyrolysis and subsequent analysis of the fragments by GC MS. Alternative techniques for the examination of organic matter in heterogeneous macromolecular mixtures are non-destructive spectroscopic methods, such as nuclear magnetic resonance (NMR) spectroscopy. Although this technique can give good results concerning the gross chemical composition, specific compounds are hardly identified. The combination of spectroscopic techniques with thermolytic and chemolytic methods will add substantially to the understanding of the nature of refractory soil organic matter. Physical fractionation prior to analysis provides a means to differentiate between distinct SOM pools that can be further characterized by the methods described above. Studies on SOM structural characteristics have focused mainly on the A horizons of soils under agriculture and litter biodegradation in forest soils and need to be extended to a wider variety of soil types and the subsoil.
Article
Geochemical analysis of sedimentary organic matter in recent lacustrine sediments appears to be a useful tool in providing information concerning past environmental conditions. However, such analysis is often made without knowing the geochemical characteristics of the organic matter derived from the watershed and, more explicitly, its soils. The present work deals with (i) a geochemical investigation (Rock-Eval pyrolysis) of soil organic matter sampled in a lake watershed, and (ii) the study of the sedimentary organic matter trapped in the lake deposits. The research was conducted on Chaillexon Lake which was created by a rock collapse that dammed the palaeovalley of the Doubs River about 12 000 years ago. Since this event, the sediment trap provides a continuous palaeoclimatic record for the Postglacial period.Results obtained lead to two main conclusions. First, the variability of Rock-Eval pyrolysis values observed in soils modifies the common interpretation given to these parameters in the characterization of sedimentary organic matter. Indeed, variations in these parameters point not only to varying proportions of terrestrial and lacustrine organic matter in a lacustrine infilling but also to variations of the terrestrial supply linked with the evolution of vegetal cover in the catchment. The second conclusion is that the story of the Chaillexon lacustrine system is marked by a rather sudden soil and forest development at the Preboreal–Boreal transition (9000 BP). Copyright © 1998 John Wiley & Sons, Ltd.
Article
To study the influence of various metals on the natural (thermal) evolution of organic material, simulation experiments were performed by heating it and organometallic compounds derived from it, to different temperatures.Results of these experiments show that metals delay the onset of decomposition of the organic matrix and that the magnitude of this effect is dependent on the nature of the mental involved (Mn ⩾ Pb > Ni ⩾ Co > Zn ⩾ U > Cu). Furthermore, characterization of the characterization of the carbonaceous residues allows a further insight into the degradation process undergone by the organic matrix. Degradation occurs in steps, each step corresponding to the degradation of a given organic component of the algal matter e.g. glucides undergo degradation before polypeptides). The beginning of these steps is delayed according to the attached metal. Despite this effect, the general evolution of the organic matrix (as revealed in, e.g. H/C vs O/C diagrams) seems to be independent of the metal associated with it, and the step-by-step evolution ends at 300°C, above which temperature the organic matter undergoes general cracking. The metals also affect the S2 peak maximum, during Rock-Eval pyrolysis of the associated organic matrix.
Article
Characterisation of organic matter composition of fossil lake sediments is important in reconstruction of fossil ecosystems and paleoclimates. High time-resolved organic matter analysis is needed to characterize sediments from small lake environments, due to their rapidly changing environmental conditions. A suitable technique for rapid analysis of organic matter in such sediments is Rock Eval pyrolysis. In small lakes, however, routine interpretation of Rock Eval data can be misleading. Lack of tributaries capable of transporting larger woody fragments into small lakes causes a bias towards the input of lipid-rich leaf waxes and cuticles. This hydrogen-rich and oxygen-depleted terrigenous organic matter (HI=250–600 [mg HC/g TOC] and OI=20–40 [mg CO2/g TOC]) can easily be misinterpreted as being of algal origin. Differentiation of terrigenous plant-derived hydrogen-rich organic matter from algal organic matter is readily achieved by including C/N-elemental ratios and lipid biomarker data.
Article
Natural organic materials in soils consist of a complex mixture of different biochemicals exhibiting numerous morphologies and stages of biological oxidation. A continuum of decomposability exists based on chemical structure; however, this continuum can be altered by interactions with minerals within matrices capable of stabilising potentially labile organic matter against biological oxidation. Protection is not considered to equate to a permanent and complete removal of organic C from decomposition, but rather to a reduced decomposition rate relative to similar unprotected materials. The stabilisation of organic materials in soils by the soil matrix is a function of the chemical nature of the soil mineral fraction and the presence of multivalent cations, the presence of mineral surfaces capable of adsorbing organic materials, and the architecture of the soil matrix. The degree and amount of protection offered by each mechanism depends on the chemical and physical properties of the mineral matrix and the morphology and chemical structure of the organic matter. Each mineral matrix will have a unique and finite capacity to stabilise organic matter. Quantifying the protective capacity of a soil requires a careful consideration of all mechanisms of protection and the implications of experimental procedures.
Article
Three types of pathways (degradation–recondensation, natural sulphurization and selective preservation) are commonly considered for the formation of kerogen dispersed in sedimentary rocks. A fourth pathway has been recently put forward, however, from studies on Recent marine sediments, the so-called sorptive protection mechanism. This pathway is based on the adsorption of otherwise labile organic compounds onto minerals, thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen. The main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a Cenomanian kerogen. They provide (i) evidence, on an ancient material, for a crucial role of the mineral matrix both in organic matter (OM) preservation during kerogen formation and in kerogen stability once formed, (ii) indications that the dominant protective process likely involves physical protection by minerals, resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness, rather than OM adsorption as molecular monolayers and (iii) observations of the relatively poor stability of an isolated kerogen, contrary to the inertness commonly assumed for fossil macromolecular organic matter.
Article
This review summarizes advances in soil organic matter (SOM) research obtained by applications of analytical pyrolysis. Conventional pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to investigate a wide range of plant materials and humic substances. Much fewer investigations of whole soils were reported. On the basis of pyrolysis-field ionization mass spectrometry (Py-FIMS) and complementary chemical, physical and biological analyses, progress was achieved in the discovery of relationships between: (1) organic precursors and SOM composition, (2) geographic origin and SOM, and (3) specific SOM constituents and soil functions, e.g. unknown soil N, dissolved organic matter (DOM), particle-size, density and aggregate fractions. Hence it can be concluded that analytical pyrolysis has been developed as a key method for SOM and DOM research and will expand into urgent problems of environmental chemistry with topics such as soil and groundwater contamination, soil amelioration, sustainable agriculture, etc., and, last but not least, the fundamental objectives of soil structure, processes and quality.
Article
Sorption of dissolved organic matter (DOM) is considered to be a major process in the preservation of organic matter (OM) in marine sediments. Evidence for this hypothesis includes the close relationship between sediment surface area (SA) and organic carbon (OC) concentrations and the strongly reduced biological degradability after DOM has sorbed to mineral surfaces. The aim of this study was to discuss the possibility of a similar process in the soil environment. We accomplished this by gathering information from the literature, and by an evaluation of our own studies on DOM sorption and accumulation of OM in soil. We found that in soil a close association of OM with the mineral matrix exists. Both the concentration of soil OM associated with the mineral matrix, and the sorption of DOM are related to reactive mineral phases such as Al and Fe oxyhydroxides. Sorption of DOM derived from the oxidative decomposition of lignocellulose to Al and Fe oxyhydroxides involves strong complexation bondings between surface metals and acidic organic ligands, particularly with those associated with aromatic structures. The strength of the sorption relates to the surface area but more importantly to the surface properties of the sorbing mineral phase. The sorption of a large part of DOM is hardly reversible under conditions similar to those during sorption (hysteresis). Because sorption of the more labile polysaccharide-derived DOM on mineral surfaces is weaker, adsorptive and desorptive processes strongly favour the accumulation of the more recalcitrant lignin-derived DOM. In addition, we found the soil OM in an alluvial B horizon and in the clay fraction of a topsoil strongly resembling lignin-derived DOM from the overlying forest floors. Hence, it seems likely that sorption of DOM contributes considerably to the accumulation and preservation of OM in soil. However, this does not result in a significant relationship between OC concentration and SA. Reasons for that finding may be the ”masking” of mineral surfaces by adsorbed OM, the clustering of OM patches at highly reactive sites of metal hydroxides, and/or the absence of a relationship between SA and the concentration of surface-active Fe and Al oxyhydroxides in some soil types. Overall, we conclude that sorptive preservation of OM in soil is affected by the chemical structure of the sorbing DOM and the surface properties of the mineral matrix. Localisation and conformation of sorbed OM remains unclear and therefore should be subject of further research.
Article
Application of Rock-Eval pyrolysis to soil organic matter (SOM) quantitation and characterization has been explored by the study of about 100 soil samples taken from a variety of soil profiles from different ecosystems at different latitudes. A straightforward illustration of these possibilities can be obtained from a Hydrogen Index (HI in mg hydrocarbons g−1 TOC) vs. Total Organic Carbon (TOC) diagram that effectively allows one to follow simultaneously the main qualitative (SOM hydrogen richness given by HI values) and quantitative (TOC) changes that affect SOM with increasing depth and humification, in the soil profiles. In addition, abnormally high Oxygen Index (OI in mg CO, CO2 or O2 g−1 TOC) values are fully diagnostic of extensive SOM alteration, as frequently observed in podzol B horizons. More detailed information on the heterogeneity of SOM and on its degree of evolution, can be gained from the shape of the pyrolysis S2 peak recorded in the course of programmed pyrolysis in an inert atmosphere (N2) and/or from its maximum temperature "Tpeak". All these parameters and others, all determined rapidly and automatically, are particularly useful to screen major SOM variations within large sets of samples
Article
This edition (second edition) has been expanded by 160 pages over the first edition. The book is divided into five parts: (1) the production and accumulation of organic matter: a geological perspective; (2) the fate of organic matter in sedimentary basins: generation of oil and gas; (3) the migration and accumulation of oil and gas; (4) the composition and classification of crude oils and the influence of geological factors; and (5) oil and gas exploration: application of the principles of petroleum generation and migration.
Article
The Rock-Eval pyrolysis method was designed to meet the needs of petroleum prospection and has now gained widespread use. It quickly provides different data on the organic content of rocks, such as the petroleum potential of series encountered, the nature of kerogens and their state of maturity. Two new versions of this equipment have been developed by Institut Français du Pétrole (IFP) since the appearance of the first Rock-Eval devices in 1977. One is a Rock-Eval II that is completely automated thanks to its microprocessor and is also equipped with a module for determining the organic-carbon content. The other is a Rock-Eval III (Oil Show Analyzer) which is different from the preceding one in that it makes a separate analysis of gas and oil as well as determining the organic-carbon content in place of peak S3. Concerning the interpretation of the method, experience gained both by applications to sedimentary basins and by experimental investigations in the laboratory has provided a better understanding of the parameters used (peaks S1, S2 and S3, pyrolysis temperature Tmax) through their variations and, from this, better insight into the application limits of the method. Concerning the application of the method, the vertical representation of results in the form of geochemical logs leads to an interpretation that is both effective and practical. Reference charts and diagrams are used to characterize source rocks (petroleum potentials, types of organic matter, degree of evolution, weathering, etc. ) as well as migration phenomena. The compiling of geochemical maps on a basin-wide scale then becomes possible. Likewise, the method has left the field of petroleum prospection per se and found applications in the analyzing of coals, bituminous rocks, recent sediments and even techniques of the refining and secondary recovery of crude oils. Conçue pour répondre aux besoins de l'exploration pétrolière, la méthode de pyrolyse Rock-Eval est maintenant largement utilisée. Elle fournit, en effet, et d'une façon rapide, différentes informations sur le contenu organique des roches, telles que le potentiel pétrolier des séries rencontrées, la nature des kérogènes, leur état de maturation. En ce qui concerne le matériel, deux nouvelles versions ont été mises au point à l'Institut Français du Pétrole (IFP) depuis l'apparition en 1977 des premiers appareils Rock-Eval : un Rock-Eval II complètement automatisé grâce à un microprocesseur et doté, en option, d'un module de dosage du carbone organique; un Rock-Eval III (Oil Show Analyzer) qui se distingue du précédent par le fait qu'il analyse séparément le gaz et l'huile et qu'il effectue le dosage du carbone organique à la place du pic S3. En ce qui concerne l'interprétation de la méthode, l'expérience acquise tant par les applications aux bassins sédimentaires que par les études expérimentales menées en laboratoire a permis de mieux connaître les paramètres utilisés (pics S1, S2, S3, température de pyrolyse Tmax) à travers leurs variations et, de là, de mieux discerner les limites d'application de la méthode. En ce qui concerne l'application de la méthode, la représentation verticale des résultats sous forme de logs géochimiques conduit à une interprétation à la fois efficace et pratique. Des abaques et des diagrammes de référence permettent de caractériser les roches mères (potentiels pétroliers, types de matière organique, degré d'évolution, altérations. . . ) ainsi que les phénomènes de migration. L'établissement de cartes géochimiques à l'échelle du bassin devient alors possible. Enfin la méthode est sortie du domaine de l'exploration pétrolière proprement dite pour trouver des applications à l'étude des charbons, des roches bitumineuses, des sédiments récents et même aux techniques du raffinage et de la récupération secondaire des bruts.
Article
The components of soil organic matter (SOM) and their degradation dynamics in forest soils are difficult to study and thus poorly understood, due to time-consuming sample collection, preparation, and difficulty of analyzing and identifying major components. As a result, changes in soil organic matter chemical composition as a function of age, forest type, or disturbance have not been examined. We applied pyrolysis molecular beam mass spectrometry (py-MBMS), which provides rapid characterization of SOM of whole soil samples. to the Tionesta soil samples described by Hoover, C.M., Magrini, K.A., Evans, R.J., 2002. Soil carbon content and character in an old growth forest in northwestern Pennsylvania: a case study introducing molecular beam mass spectrometry (PY-MBMS). Environmental Pollution 116 (Supp. 1), S269-S278. Our goals in this work were to: (1) develop and demonstrate an advanced, rapid analytical method for characterizing SOM components in whole soils, and (2) provide data-based models to predict soil carbon content and residence time from py-MBMS analysis. Using py-MBMS and pattern recognition techniques we were able to statistically distinguish among four Tionesta sites and show an increase in pyrolysis products of more highly decomposed plant materials at increasing sample depth. For example, all four sites showed increasing amounts of older carbon (phenolic and aromatic species) at deeper depths and higher amounts of more recent carbon (carbohydrates and lignin products) at shallower depths. These results indicate that this type of analysis could be used to rapidly characterize SOM for the purpose of developing a model, which could be used in monitoring the effect of forest management practices on carbon uptake and storage.
Compositional variations in sedimentary organic matter in Lake Albano Holocene record: ecosystem reaction to environmental changes In: Palaeoenvironmental Analysis of Italian Crater Lake and Adriatic Sediments
  • D Ariztegui
  • C Chondrogianni
  • E Lafargue
  • J A Mckenzie
Ariztegui, D., Chondrogianni, C., Lafargue, E. & McKenzie, J.A. 1996. Compositional variations in sedimentary organic matter in Lake Albano Holocene record: ecosystem reaction to environmental changes. In: Palaeoenvironmental Analysis of Italian Crater Lake and Adriatic Sediments (eds P. Guilizzoni & F. Oldfield). International Journal of Limnology, 55, 111–117