No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Environmental NMR: Fast-field-cycling Relaxometry
Abstract
Fast-field-cycling (FFC) NMR relaxometry deals with the variation of the spin–lattice relaxation times (T1) in a complex system, as the strength of the applied magnetic field is changed. Information about molecular dynamics can be achieved. Until now, only model theories for FFC NMR relaxometry have been developed for polymer and material sciences. Just a few applications have been performed in the environmental sciences. These mainly deal with soil porosity, rock permeability, biomass transformations, and natural organic matter dynamics. Further, FFC NMR relaxometry can also be applied to monitor the environmental fate of contaminants, to understand the dynamics of nutrients at the soil–plant interface, and to evaluate reaction mechanisms in heterogeneous catalysis for the development of green reactions. This article summarizes the advances of the technique in environmental investigations and describes the tools used to monitor dynamics of organic and inorganic molecules in environmental compartments.Keywords:fast-field cycling;NMR;relaxometry;environmental field cycling;spin–lattice relaxation
... Thickness of coating varies between~20 and 50 nm and the presence of gold indicates a semi-exposed position in the original biochar particle. g EELS spectra from regions indicated in f showing the peak shift of the C = C 1s-π* transition and the presence of Ca in the region of the bright spot in the outermost region of the biochar and Supplementary Fig. 12), i.e., time needed for protons to recover the longitudinal component after magnetization 31 . The different relaxation times indicate the strengths of interactions of water molecules with biochar pore surface as well as with pore water-dissolved or suspended compounds 30,32 . ...
... Liquid chromatography organic carbon detection (LC-OCD, Supplementary Tables 5-7, Supplementary Fig. 17 and Supplementary Discussion) of aqueous biochar extracts revealed a high content of humic-substance-like organic molecules, that might act as surfactants that facilitate this process. In addition, the organic coating can shrink pore sizes thereby reducing water mobility 31 . This is supported by gas adsorption measurements that showed that co-composting led to~18% reduction in specific surface area (SSA) according to CO 2 adsorption, especially in the pore size range of 0.65-0.85 ...
... The samples were put in the probe of a Stelar SpinMaster FFC-2000 fast field cycling relaxometer (Stelar s.r.l., Mede, PV−Italy) and analyzed at 25°C. The basic theory about FFC NMR relaxometry and the sequence applied for the experiments reported in this study have been already summarized by Conte and Alonzo 31 . In brief, non-polarized (NP) and polarized (PP) sequences were applied. ...
Amending soil with biochar (pyrolized biomass) is suggested as a globally applicable approach to address climate change and soil degradation by carbon sequestration, reducing soil-borne greenhouse-gas emissions and increasing soil nutrient retention. Biochar was shown to promote plant growth, especially when combined with nutrient-rich organic matter, e.g., co-composted biochar. Plant growth promotion was explained by slow release of nutrients, although a mechanistic understanding of nutrient storage in biochar is missing. Here we identify a complex, nutrient-rich organic coating on co-composted biochar that covers the outer and inner (pore) surfaces of biochar particles using high-resolution spectro(micro)scopy and mass spectrometry. Fast field cycling nuclear magnetic resonance, electrochemical analysis and gas adsorption demonstrated that this coating adds hydrophilicity, redox-active moieties, and additional mesoporosity, which strengthens biochar-water interactions and thus enhances nutrient retention. This implies that the functioning of biochar in soil is determined by the formation of an organic coating, rather than biochar surface oxidation, as previously suggested.
... FFC NMR relaxometry has been chosen as analytical technique, because it already showed its power in elucidating molecular dynamics of liquids on biochar surfaces [30]. ...
... relaxation rates R 1 or 1/T 1 vs. magnetic field density) were acquired on a Stelar Smartracer Relaxometer (Stelar s.r.l., Mede, PV -Italy) at the constant temperature of 298 K. The details of the NMRD experiments have been already described in Conte and Alonzo [30]. Here, only the conditions used for the experiments discussed below are reported. ...
... When either TFA or Galden ® interacts with biochar, a polyexponential trend is revealed. For this reason, the stretched exponential function (also known as Kohlrausch-Williams-Watts function) reported in equation (2) has been applied to fit the aforementioned decay/recovery curves [30]. This equation provides the best fitting with the largest coefficients of determination (R 2 > 0.998). ...
Background: Recent studies highlighted that biochar efficiency to improve soil fertility is enhanced after it is blended with fresh organic materials. It was suggested that organic coating of inner-porous biochar surfaces acts as a kind of “glue” for plant-nutrients, thereby allowing their slow release towards plant-roots and/or microorganisms. Objective: The aim of the present study is to improve the understanding of the nature of the interactions between fresh organic matter and a poplar biochar. Method: Two fluorinated organic models were used as target molecules in order to apply heteronuclear (i.e. 19F) fast field cycling (FFC) NMR relaxometry. Results: The results suggest that organic coating can be stabilized by charge transfer interactions (involving electron- rich systems of fresh organic matter and electron-poor sites provided by biochar), water bridging (between biochar surface and fluorinated compounds) and van der Waals interactions (occurring between the biochar aromatic system and the carbon chain of the fluorinated compound). Conclusions: The weak interactions outlined above may be responsible for an induced dipole on the biochar organic- cover. The induced dipole, in turn, can be involved in the adsorption of plant nutrients (which adsorb only marginally on the un-coated biochar), while maintaining their availability for plants.
... Two different techniques have been applied. The high energy moisture characteristic (HEMC) technique was applied in order to investigate changes in aggregate stability through measurement of water retention curve at high matric potential (Collis-George and Figueroa 1984;Crescimanno et al. 1995;Mamedov 2002, Mamedov et al. 2010;Ouyang et al. 2013). 1 H NMR relaxometry with fast field cycling (FFC) setup was applied to monitor pore size distribution through the evaluation of the water dynamics in biochar/sandy-clay soil samples (Conte and Alonzo 2013). Results revealed that increasing amount of biochar added to the sandy-clay soil improved aggregate stability and increased soil porosity, thus improving the amount of water that the biochar amended soil was able to retain. ...
... The samples were immediately analyzed by a Stelar Spinmaster Fast Field Cycling Relaxometry instrument at a constant temperature of 25°C. The bases for the FFC NMR relaxometry have been already reported in De Pasquale et al. (2012) and Conte and Alonzo (2013). For this reason, here, we report only the experimental conditions applied for the present study. ...
... Field switching time was 3 ms, while spectrometer dead time was 15 μs. All the recovery curves were evaluated by the UPEN algorithm (Alma Mater Studiorum, Università di Bologna, Italy) (Conte and Alonzo 2013) with the aim to obtain the longitudinal relaxation time (T 1 ) distributions, and therefore, information on the way water molecules are trapped in each sample (Conte et al. 2013a). ...
Purpose The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). Materials and methods All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. 1H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. Results and discussion The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased as the amount of biochar was raised up. The 1H NMR relaxometry revealed a unimodal T 1 distribution for both the sole sandy-clay soil and the biochar. Conversely, a bimodal T 1 distribution was acquired for all the different f bc samples. Conclusions Improvement in aggregate stability was obtained as biochar was progressively added to the sandy-clay soil. A dual mechanism of water retention has been hypothesized. In particular, intra-aggregate porosity was indicated as the main responsible for molecular water diffusion when f bc comprised between 0 and 0.33. Conversely, inter-aggregate porosity resulted predominant, through swelling processes, when f bc overcame 0.33.
... The 2 mm sieved and dried poplar pyrochar and hydrochar samples have been prepared as slurry for FFC NMR relaxometry investigations according to the procedure reported in Dunn et al. 28 The background theory of FFC NMR relaxometry has been already described in De Pasquale et al. 10 Moreover, more general environmental applications of FFC NMR relaxometry can be found in Conte and Alonzo. 29 1 H NMR dispersion profiles (i.e., relaxation rates R 1 or 1/T 1 vs proton Larmor frequencies) were acquired on a Stelar Spinmaster FFC2000 Relaxometer (Stelar s.r.l., Mede, PV, Italy) at temperatures of 25, 50, and 80°C. The proton spins were polarized at a B POL corresponding to the proton Larmor frequency (ω L ) of 24 MHz for a T POL corresponding to about 5 times the T 1 estimated at this frequency. ...
... The choice of this function was due to the large sample heterogeneity resulting in a multiexponential behavior of the decay/recovery curves. 29,31 This approach has the advantage that it is able to handle a wide range of behaviors within a single model. For this reason, assumptions about the number of exponentials to be used in modeling NMRD data are not necessary. ...
... 36 Temporary adsorption can be achieved by formation of weak unconventional hydrogen bonds on the surface of pyrogenic char systems as already outlined in Conte et al. 26 and Conte and Alonzo. 29 However, as surficial polar groups are present, the weak unconventional H-bonds may turn toward stronger conventional ones, which may hook water molecules more strongly on the char surface. The effectiveness of the aforementioned relaxation sink depends on the ratio between the pore surface and the pore volume as well as on the diffusion rate across the pore. ...
The aim of this paper was to understand the water-surface interactions of two chars obtained by gasification (pyrochar) and hydrothermal carbonization (hydrochar) of a poplar biomass. The two samples revealed different chemical composition as evidenced by solid state 13C NMR spectroscopy. In fact, hydrochar resulted in a lignin-like material still containing oxygenated functionalities. Pyrochar was a polyaromatic system where no hetero-nuclei were detected. After saturating with water, hydrochar and pyrochar were analyzed by fast field cycling (FFC) NMR relaxometry. Results showed that water movement in hydrochar was mainly confined in very small pores. Conversely, water movement in pyrochar led to the conclusion that a larger number of transitional and very large pores were present. These results were confirmed by porosity evaluation derived from gas adsorption. Variable temperature FFC NMR experiments confirmed slow motion regime due to a preferential diffusion of water on the solid surface. Conversely, the larger number of large pores in pyrochar allowed slow movement only up to 50 °C. As temperature was raised to 80 °C, water interactions with the pore surface became weaker, thereby allowing a 3D water exchange with the bulk liquid. This paper has shown that pore size distribution was more important than chemical composition in affecting water movement in two chemically different charred systems.
... The basic theory about FFC NMR relaxometry and the sequence applied for the experiments reported in this study have been already summarized in Conte and Alonzo. 26 In brief, by quickly changing the intensity of an applied magnetic field, it is possible to observe the fluctuation in longitudinal relaxation time values (T 1 ) of the observed nuclei (in this case 1 H). The dispersion of the T 1 values occurs when each frequency in the distribution of magnetic fields (DMF) generated by the motional fluctuations matches the Larmor frequencies (ω L ) of the observed nuclei. ...
... All profiles (Figures 2 and 3) show the classical stretched Lorentzian shapes. 26 In particular, the profiles retrieved for the HP05 sample at the considered temperatures were at faster R 1 values than those acquired for Merck and Sigma-Aldrich ( Figure 2). Furthermore, the profiles retrieved for the HP05 sample show faster R 1 values than for the HP05C one ( Figure 3). ...
... In both cases of study, HP05C and HP05 TiO 2 samples, water is not chemically retained on the surface of the porous medium because of the inverse relationship between the exchange correlation time and the temperature enhancement. 26,31 Merck and Sigma-Aldrich samples show faster relaxation rates so that their water fast motion regimes appear prevalent according to their low SSA values. Figure 4 shows the temperature dependence of τ through the Arrhenius equation graphs in terms of ln(τ) vs 1/T for HP05 and HP05C samples. ...
Titanium dioxide is a very well known photocatalyst which is widely used for environmental remediation. The interactions between TiO2 surface and organic contaminants are still poorly understood. Conceivably, water is an ubiquitous solvent and most of the TiO2 research deals with H2O. We have considered the possibility to apply FFC-NMR relaxometry for a deep understanding of the interactions between titanium dioxide surface and water molecules. Early results suggested the presence of different surface waters according to the chemical nature of the active sites present in the TiO2 system. Acknowledgements A.P. gratefully acknowledges a bilateral Erasmus project between Brno University of Technology and University of Palermo which provided grant sustainment. This work was partially funded by Ce.R.T.A. s.c.r.l. (Centri Regionali per le Tecnologie Alimentari; http://www.certa.it/default.asp).
... Fast field cycling NMR relaxometry has been specifically designed for the measurement of the longitudinal relaxation times (T1) of NMR observable spin nuclei [163,164,191,192]. T1 is a measure of the time needed for the recovery of the longitudinal component of the magnetization along the z-axis [193]. ...
... It is widely recognized that the molecular dynamics investigated by the T1 value measurements of liquid systems, such as water, in biochar pores is affected by the interactions with the porous boundaries [163,164,[191][192][193][194][195][196]. Namely, the smaller the pore size, the more constrained water molecules are. ...
Biochar is a porous material obtained by biomass thermal degradation in oxygen-starved conditions. It is nowadays applied in many fields. For instance, it is used to synthesize new materials for environmental remediation, catalysis, animal feeding, adsorbent for smells, etc. In the last decades, biochar has been applied also to soils due to its beneficial effects on soil structure, pH, soil organic carbon content, and stability, and, therefore, soil fertility. In addition, this carbonaceous material shows high chemical stability. Once applied to soil it maintains its nature for centuries. Consequently, it can be considered a sink to store atmospheric carbon dioxide in soils, thereby mitigating the effects of global climatic changes. The literature contains plenty of papers dealing with biochar’s environmental effects. However, a discrepancy exists between studies dealing with biochar applications and those dealing with the physical-chemistry behind biochar behavior. On the one hand, the impression is that most of the papers where biochar is tested in soils are based on trial-and-error procedures. Sometimes these give positive results, sometimes not. Consequently, it appears that the scientific world is divided into two factions: either supporters or detractors. On the other hand, studies dealing with biochar’s physical-chemistry do not appear helpful in settling the factions’ problem. This review paper aims at collecting all the information on physical-chemistry of biochar and to use it to explain biochar’s role in different fields of application.
... Due to being non-destructive and time-saving, proton nuclear magnetic resonance ( 1 H NMR) relaxometry has been widely used in the description of pore size distributions in geological porous media (Chen et al. 1994;Glaves et al. 1988;Kleinberg 1994;Stallmach and Karger 1999;Conte and Alonzo 2013). A magnetic nucleus such as that of a proton possesses a spin that will be aligned by a static magnetic field. ...
... Compared to bulk liquid, in porous materials the proton relaxation is strongly accelerated by interactions between protons and surfaces (Brownstein and Tarr 1979;Todoruk et al. 2003;Bird et al. 2005;Jaeger et al. 2009). The longitudinal relaxation time (T 1 ) and transverse relaxation time (T 2 ) of protons in a pore are proportional to the size of the pore via surface relaxivity, the proportionality constant between the relaxation time (T 1 or T 2 ) and pore size (Slijkerman and Hofman 1998;Godefroy et al. 2001;Bird et al. 2005;Costabel and Yaramanci 2013;Conte and Alonzo 2013). 1 H NMR relaxometry has a faster speed and a wider range of pore assay compared with X-ray computed tomography scanning (Hinedi et al. 1993;Sleutel et al. 2008). NMR relaxation easily reaches the nanometer range and less and has been used for the study of clay-bound water (Matteson et al. 2000), interlayer water in smectites (Fleury et al. 2013), and wet aggregate stability (Buchmann et al. 2014). ...
Purpose
Determining soil pore size distribution is difficult and time-consuming using traditional methods. Additionally, for swelling and shrinking soil, the specific volume of soil changes with soil moisture conditions. Nuclear magnetic resonance (NMR) relaxometry allows observation of pore size distribution changes during the process of dehydration and soil shrinkage.
Materials and methods
Naturally structured soil cores of a Vertisol with characteristic swelling and shrinking behavior were collected from the Huang-Huai-Hai Plain of China. The samples were saturated with water and dehydrated gradually at room temperature and relaxometry tests conducted at different moisture contents as they air-dried. Then, the soil cores were oven-dried at 105 °C and saturated with n-octane, which prevented clay swelling. The pore size distribution of soil cores at the end of the shrinking process was determined through the description of n-octane-filled pores. The shrinkage characteristic curves were determined as naturally structured soil cores were air-dried from moisture content at full expansion to constant volume, indicating the relationship between the volume of bulk soil and moisture content.
Results and discussion
The transverse relaxation time (T 2) distribution deduced from NMR relaxometry gives a good description of the size distribution of pores filled with protons (contained in water or n-octane). The T 2 distribution curves of soil cores at saturation were trimodal, due to the presence of interlayer, interparticular, and interaggregate pores. Combined with the shrinkage characteristic curves, it was deduced that the structural pores were evacuated during the structural shrinkage period. The normal and residual shrinkage was accompanied by the narrowing and closure of the interlayer spaces. During the residual shrinkage period, the frame structure of the soil particles prevented further shrinkage of the bulk soil. The shrinkage process was accompanied by the closure of interlayer spaces and the formation of large cracks between aggregates.
Conclusions
¹H NMR relaxometry was especially suited to studying the changing pore size distribution of swelling and shrinking soils. When the soil cores began shrinking, almost all remaining water was retained in interlayer spaces. The volume change of the interlayer space was the main cause of swelling and shrinking. The swelling limit could be estimated from the T 2 distributions of soils at full expansion.
... (NMR) Relaxometry. The theory of fast field cycling (FFC) NMR relaxometry has been reported in other papers, such as Conte and Alonzo [21]. For this reason, only the experimental setup used to analyse honey is reported in the present study. ...
... Distributions of longitudinal relaxation times ( 1 ) at a fixed proton Larmor frequency (i.e., 0.1 MHz in the present study) can be related to the motional behavior of protons inside multicomponent systems [21]. Proton longitudinal relaxation time values are affected by the strength of the dipolar interactions between a nucleus and its surroundings [26]. ...
The present study aims at the investigation of the changes in water distribution among the organic components of selected honey samples following honey storage at different temperatures. Results, achieved by application of fast field cycling NMR relaxometry, revealed that the organic constituents were homogeneously distributed within the whole samples stored at room temperature. Conversely, after four months of refrigeration at 4°C, the organic systems were included in persistent clusters, as a consequence of the water release due to the larger stability of the intramolecular interactions over the intermolecular ones. The new conformational arrangements of the honey constituents entailed enhancement of honey moisture content. For this reason, it can be suggested that honey refrigeration prior to storage at room temperature may be detrimental for its long-term storage. In fact, higher risk of fermentation may occur once the sample is warmed after the first refrigeration step.
... Nuclear magnetic relaxation (NMR) is one of the modern instrumental methods of physical chemistry (Kimmich and Anoardo, 2004;Conte and Alonzo, 2013, Xu et al., 2013, Bayer et al., 2013Haber-Pohlmeier et al., 2013) and is a fundamental property of nuclear magnetism, characterizing the dynamics of nuclear spins system in the oil bitumen-polymer systems. ...
... Change in the group composition of bitumen after its modification plays an important role in the study of BPB. NMR method allows determining group composition of bitumen and BPB with an accuracy of 3%, this will allow us to estimate the composition changes, as well as the convergence of the results obtained by other methods (Conte and Alonzo, 2013;Kimmich andAnoardo, 2004, Bayer et al., 2010). ...
View at Publisher| Order Document |
Export
| Download | More...
Modern Applied Science
Volume 8, Issue 5, 2014, Pages 115-120
Structural dynamic study of roof waterproofing materials (Article)
Kemalov, A.F. ,
Kemalov, R.A.,
Valiev, D.Z.,
Abdrafikova, I.M.
Kazan (Volga region) Federal University, 8, Kremlevskaya Street, Kazan, Russian Federation
View references (15)
Abstract
The present research was aimed to develop the scientific applied principles and technologies of composite bituminous materials for civil engineering based on the investigation of the structures of polymer modifier and bitumen-polymer binder (BPB) on its basis with the use of nuclear magnetic resonance (NMR). The method of pulsed NMR was chosen as one of the rapid analysis methods that can be used for the analysis of bitumen-polymer systems, especially when assessing the group chemical composition of residual oil feedstock (ROF), bitumens and composite materials based on them. Using the method of pulsed NMR the regularities of the impact of modifier component composition on the changes of structural-group composition of the original and modified products were specified. Based on the results of research the optimal ratio of bitumen-polymer binder components was investigated, the manufacturability of the process for obtaining of composite bituminous materials for civil engineering with the aim of optimizing the quality of the final products was evaluated. Pulsed NMR - spectroscopy is suggested as input and output quality control of bituminous products. The regularities of redistribution of the phases with different molecular mobility and their relationship with the binder components were investigated. Rapid technique for quantifying the content of polymer in the solvent was developed. © 2014 by the author(s).
... The fundamentals of FFC-NMR relaxometry are reported elsewhere (Conte and Alonzo, 2013;Ferrante and Sykora, 2005;Kimmich and Anoardo, 2004). Briefly, the technique is based on the cycling of the Zeeman magnetic field (B 0 ) through three different values usually indicated as B pol (polarization field), B relax (relaxation field), and B acq (acquisition field). ...
... The recovery curves retrieved by applying the sequence outlined above were elaborated by the UPEN algorithm (Alma Mater Studiorum, Università di Bologna, Italy) (Borgia et al., 1998;Borgia et al., 2000) with the aim to obtain the T 1 distributions and, therefore, information on pore distributions and water interactions (Bayer et al., 2010;Conte and Alonzo, 2013). ...
Lignite and lignite humic acids, which are used as soil amendments sometimes, are supposed to improve soil properties such as water holding capacity. The structure of those materials is composed of various organic molecules stabilized mostly by weak interactions. Therefore, excess of water causes only partial swelling, but most of the physical structure is destabilized. This accelerates the desiccation and hampers their application as natural hydrogel-like substances. In order to stabilize the structure of lignite humic acids and improve the water holding capacity, we applied formaldehyde cross-linking procedure based on covalent coupling of aromatic humic acids moieties. By combining the 1H NMR relaxometry and methods of thermal analysis, the kinetics and degree of hydration, water distribution and moisture uptake were investigated. It was found that cross-linking induced a reduction in moisture sorption capacity at low relative humidity and an increase at higher relative humidity, which was attributed to the separation of functional groups and decreasing of structural compactness after cross-linking. As a result, the cross-linked humic acids, exhibited faster water uptake and approximately three-fold higher water holding capacity in comparison with the parental sample. The distribution of relaxation times of water protons in swollen humic acids revealed the unification of pore size distribution upon cross-linking. Although the improved hydration of cross-linked lignite humic acids already resembles the hydration of some hydrophilic polymers, the water holding capacity is still below the capacity of classical hydrogels. Nevertheless, the low price of lignite, sorption properties and its overall positive affect on soil quality and productivity give a promise in application of this material both in agriculture and remediation technologies.
... Hence, water is better retained in the pores of biochar, making it less mobile, which can explain the retention of water-dissolved nutrients, such as NO 3 − (Hagemann et al., 2017). In addition, the formation of organo-mineral coatings in the pores of the modified biochars can shrink their pore sizes (as seen in Fig. 1), thereby reducing water mobility and improving NO 3 − retention (Conte and Alonzo, 2013). Hence, Ye et al. (2019) posited the suitability of biochar as a carrier for N-containing nutrients due to its substantial adsorption capability for N-containing compounds through pore-filling. ...
Mitigating the loss and negative impacts of reactive N from fertilized soils remains a global environmental challenge. To optimize N retention by biochar, bamboo and pig manure biochars were modified as MgO- and sepiolite-biochar composites and characterized. Novel soil application of the modified biochars and their raw forms were comparatively evaluated for N-retention in a fertilized soil leached for 90 days in a column experiment. Changes in N-cycling-related enzyme and bacterial structure were also reported after 90 days. Results revealed low leaching losses of NH4+, which reduced over time across all the treatments. However, while sole fertilizer (F) increased the initial and cumulative NO3− leached from the soil, the MgO-bamboo biochar (MgOBF) and sepiolite-bamboo biochar (SBF) treatments reduced leachate NO3− by 22.1 % and 10.5 % compared to raw bamboo biochar (BBF) treatment. However, 15.5 % more NO3− was leached from the MgO-pig manure biochar-treated soil (MgOPF) compared to its raw biochar treatment (PMBF) after 90 days. Dissolved organic N leached was reduced by 9.2 % and 0.5 % in MgOBF and SBF, as well as 15.4 % and 40.5 % in MgOPF and SPF compared to their respective raw forms. The total N of the biochars, adjustment of surface charges, cation exchange capacity, surface area, pore filling effects, and the formation of potential Mg-N precipitates on the modified-biochar surfaces regulated N leaching/retention. In addition, the modified biochar treatments reduced the hydrolysis of urea and stimulated some nitrate-reduction-related bacteria crucial for NO3− retention. Hence, unlike the raw biochar and MgOPF treatments, MgOBF, SBF, and SPF hold promise in mitigating inorganic-N losses from fertilized soils while improving the soil's chemical properties.
... 14.4.6 Low Field NMR Low field NMR includes many areas such as mobile NMR (Danieli et al. 2007) and field cycling (Conte and Alonzo 2007). Field cycling NMR makes the graph between relaxation time versus field strength and provides beneficial information on the dynamics of the samples. ...
Pollutants and toxicants in the environment are a major source of concern through around the world; pollutants include heavy metals, pesticides, organic compounds, dye, oil or industrial waste. There have been a slew of reports over last decades on cost effective waste cleanup technologies. Pollutant removal from the ecosystem is problematic due to their longevity, inability to biodegrade and pervasiveness. Environmental pollutant removal through the microbial perspective is apprises eco-friendly as well as a better alternative to conventional approaches. Microbes remove toxins by enzymatic or metabolic reactions such as eradication, immobilization, oxidation or detoxification. Various biotic or abiotic factors may influence the degradation mechanism, but various in situ or ex situ bioremediation techniques are used to degrade toxins all over the planet. Maximum bioremediation processes occurs in aerobic conditions, but for recalcitrant molecules anaerobic conditions are suitable. Microbial aided remediation demonstrates novel strategies for reducing pollutant and toxicant level in environment.
... 14.4.6 Low Field NMR Low field NMR includes many areas such as mobile NMR (Danieli et al. 2007) and field cycling (Conte and Alonzo 2007). Field cycling NMR makes the graph between relaxation time versus field strength and provides beneficial information on the dynamics of the samples. ...
Pollution is an ever-increasing global problem linked with industrialization, urbanization, and population growth. Bioremediation is a sustainable method to curb this threat with minimum adverse effect on the environment. The chapter reviews the recent bioremediation approaches to eliminate the contaminants in water, soil, and air. Genetics and phenotypic properties of extremophiles provide a wealth of knowledge to grey-biotechnology to develop novel biological strategies for bioremediation. From this point of view, novel advances in biotechnology focusses on genetic engineering of organisms and proteins to improve their capabilities in degrading pollutants and restoring natural environment. Genetically modified organisms have been successfully introduced into contaminated sites worldwide. However, special attention is necessary to determine the direct and indirect risks associated with the release of genetically engineered organisms into sensitive environments. This chapter further describes the future strategies to improve the efficiency of bioremediation.
... 14.4.6 Low Field NMR Low field NMR includes many areas such as mobile NMR (Danieli et al. 2007) and field cycling (Conte and Alonzo 2007). Field cycling NMR makes the graph between relaxation time versus field strength and provides beneficial information on the dynamics of the samples. ...
Due to growing pollution concerns over the years, researchers are evaluating various optimization strategies to develop efficient bioremediation alternatives. Bioremediation encompasses numerous process types and each type and pollutant target require a different optimization approach. This chapter intends to provide an overview of knowledge gained from the bioremediation optimization studies performed to treat the most common pollutants. Available literature was classified according to bioremediation types affected by similar processing factors, viz., phytoremediation, bioaugmentation and biostimulation (in-situ bioremediation) and bioreactors, biosorption and enzymatic treatment (ex-situ bioremediation). We discussed and compared the optimization approach followed in each bioremediation type, critical factors affecting the processes, quality targets and process design. This chapter will provide a scientific and technical basis that can assist in the selection of design, process improvement, optimization and implementation of the bioremediation technology.
... Un profil de temps de relaxation longitudinaux T1 correspond à la mesure de ce temps de relaxation, pour un même échantillon, après application d'un champ radiofréquence B1 à différentes fréquences et donc différentes intensités. En fonction de la fréquence de résonnance du champ magnétique B1, deux séquences peuvent être employées : une avec pré-polarisation des échantillons (séquence PP, faibles champs / faibles fréquences jusqu'à 4 MHz environ) et une sans polarisation (séquence NP) 314,315 . ...
Cette thèse porte sur le développement de nanoparticules magnétiques hybrides pour la nanomédecine. Un enjeu majeur est de proposer des solutions innovantes dans le traitement et/ou le diagnostic de certaines pathologies, comme les cancers. Les nanoparticules magnétiques possèdent des propriétés extrêmement intéressantes pour la nanomédecine. Elles peuvent servir à guider magnétiquement un vecteur vers une cible ou à chauffer localement cette cible lorsqu’elles sont soumises à un champ magnétique alternatif. Par ailleurs, l’utilisation de polymères à empreintes de protéines peut permettre de cibler des protéines d’intérêt. L’idée ici est donc de coupler des nanoparticules magnétiques et des polymères à empreintes de protéines (PEP) afin de cibler, détecter et traiter des cellules d’intérêt. Les nano-objets γ-Fe2O3@PEP sont synthétisés en polymérisant un polyacrylamide autour de protéines servant de gabarit, telles que la protéine fluorescente verte ou le complexe de différentiation 44. Les objets obtenus sont composés pour 10 à 30% de PEP, selon la méthode de synthèse. Un ciblage efficace de cellules exprimant ces protéines d’intérêt a été mis en œuvre. Sous champ magnétique alternatif, les protéines sont dénaturées mais les nano-objets γ-Fe2O3@PEP ne se détachent pas des cellules, et seront donc à terme internalisés. Une étude approfondie a montré une absence de toxicité aigüe des objets hybrides, et leur métabolisation dans les lysosomes. Les propriétés de ciblage et d’hyperthermie de γ-Fe2O3@PEP en font donc un bon candidat pour détecter et ralentir le développement de métastases cancéreuses.
... FFC NMR relaxometry versatility makes the technique quite useful in many fields. As an example, it has been applied to monitor food quality [25,26], traceability [27][28][29], conservation [30], and transformation [31][32][33][34][35][36][37]; to evaluate the physical chemical characteristics of systems useful for drug delivery [38]; to design new contrast agents to be used in diagnostic imaging techniques [39][40][41]; to explore tumor development [42]; to monitor environmental quality [18,43,44], and many other different applications that can be found elsewhere [45,46]. ...
Nuclear magnetic resonance (NMR) techniques are largely employed in several fields. As an example, NMR spectroscopy is used to provide structural and conformational information on pure systems, while affording quantitative evaluation on the number of nuclei in a given chemical environment. When dealing with relaxation, NMR allows understanding of molecular dynamics, i.e., the time evolution of molecular motions. The analysis of relaxation times conducted on complex liquid–liquid and solid–liquid mixtures is directly related to the nature of the interactions among the components of the mixture. In the present review paper, the peculiarities of low resolution fast field-cycling (FFC) NMR relaxometry in soil science are reported. In particular, the general aspects of the typical FFC NMR relaxometry experiment are firstly provided. Afterwards, a discussion on the main mathematical models to be used to “read” and interpret experimental data on soils is given. Following this, an overview on the main results in soil science is supplied. Finally, new FFC NMR-based hypotheses on nutrient dynamics in soils are described
... On the other hand, especially surface relaxivity is dependent on the surface-to-volume ratio and therefore on the pore size distribution. 48 However, as shown in the BET results (Table 1), N-HTCs show a very small surface area with negligible intraparticle pores that is only weakly synthesis temperature and N content dependent. This would imply that the difference of the water relaxivity in N-HTC could be interpreted as an effect of the presence of N-functional groups, with a minor pore size contribution. ...
Hydrothermal carbon (HTC) derived from biomass is a class of cost-efficient, eco-friendly functional carbon materials with various potential applications. In this work, solid-state nuclear magnetic resonance (NMR), longitudinal (T1) relaxation time and diffusion NMR were employed to investigate the structure and water dynamics for HTC and nitrogen-functionalized hydrothermal carbon (N-HTC) samples ((N)-HTC). Results showed that the presence of N-functional groups influences the water interaction with (N)-HTC more strongly than surface area, pore size distribution or oxygenated functional groups. Furthermore, the degree of water interaction can be tuned by adjusting the synthesis temperature and the precursor ratio. Water motion was more strongly inhibited in N-HTC than in N-free HTC, thereby suggesting the existence of a differently structured hydration shell around N-HTC particles. In addition, the diffusion data of water in the N-HTC material shows two components that do not exchange on the time scale of the experiment (tens of milliseconds), indicating a significant fraction of slow mobile water that exists inside the structure of N-HTC. 1H–2H isotope exchange and cross-polarization NMR results show this internal water only in a near-surface layer of the N-HTC particles. Based on these findings, a model for water interaction with (N)-HTC particles is proposed.
... The same motions could not be effective for a different value of the applied magnetic field. Molecular motions strongly affect dipolar interactions (Conte and Alonzo 2013). The faster the motions are, the lower is the dipolar interaction efficiency, thereby favoring longer T1 values and shorter R1 values. ...
Water plays a very important role in wood and wood products. The molecular motion of water in wood is susceptible to thermal activation. Thermal energy makes water molecules more active and weakens the force between water and wood; therefore, the water molecules dynamic properties are greatly influenced. Molecular dynamics study is important for wood drying; this paper therefore focuses on water molecular dynamics in wood through fast field cycling nuclear magnetic resonance relaxometry techniques. The results show that the spin-lattice relaxation rate decreases with the Larmor frequency. Nuclear magnetic resonance dispersion profiles at different temperatures could separate the relaxation contribution of water in bigger pores and smaller pores. The T1 distribution from wide to narrow at 10 MHz Larmor frequency reflects the shrinkage of pore size with the higher temperature. The dependence of spin-lattice relaxation rate on correlation time for water molecular motion based on BPP (proposed by Bloembergen, Purcell, and Pound) theory shows that water correlation time increases with higher temperature, and its activation energy, calculated using the Arrhenius transformation equation, is 9.06 +/- 0.53 kJ/mol.
Several chemical compounds and contaminants accumulate in our environment and cause pollution. Identification, detection, and disposal of these pollutants require modification of the existing and/or synthesis of the novel chemical compounds through a green approach. The morphological structure of chemicals can be analyzed through myriads spectroscopy techniques. Spectroscopy has proved itself as an important method for qualitative analysis and quantitative detection of pollutants. The role of spectroscopic techniques popularly involves the use of electromagnetic radiation to identify different chemicals and pollutants structures based on the principle of absorption and radiation. Spectroscopic techniques involving UV-Visible, Infra-Red (IR), X-ray, Nuclear magnetic resonance (NMR), and atomic absorption spectroscopy (AAS) are the most popular techniques to identify hazardous chemicals and their derivatives for making the environment clean and safe. In this chapter, we have discussed the important spectroscopy techniques and approaches that are being explored for environmental sustainability.
This chapter describes the fundamentals of electron paramagnetic (spin) magnetic resonance (EPR, ESR), and nuclear magnetic resonance (NMR). The focus is on phenomena whose quantitative parameters are directly used to characterize the molecular structure, polarity and proticity and dynamics of water and ice, namely NMR chemical shift, the dipolar coupling between nuclear spins, fast‐field‐cycling (FFC) NMR effect, the isotropic Fermi contact, the nuclear Overhauser enhancement or effect (NOE), dynamic nuclear spin polarization, electron spin dipole–dipole interaction, free induction decay (FID), nuclear and electron spin–lattice and spin–spin relaxation, nuclear magnetization of chemically exchanging systems. The above physical phenomena form the basis of methods such as electron–electron double resonance (ELDOR) or double electron–electron resonance (DEER) or pulse electron nuclear double resonance (ENDOR) or multifrequency ESR (MF ESR) techniques, two-dimensional ESR (2D ESR), two-dimensional electron–electron double resonance (2D-ELDOR), ENDOR with circularly polarized radio frequency fields (CP-ENDOR), electron nuclear–nuclear resonance (double ENDOR), proton electron double resonance imaging (PEDRI), and electron nuclear–nuclear triple resonance (TRIPLE).
A Fast-Field-Cycling NMR investigation was carried out on a set of polyurethane cyclodextrin nanosponges, in order to gain information on their textural properties, which have been proven to be quite difficult to assess by means of ordinary porosimetric techniques. Experiments were performed on both dry and wet samples, in order to evaluate the behavior of the “non-exchangeable” C-bound 1H nuclei, as well as the one of the mobile protons belonging to the skeletal hydroxyl groups and the water molecules. The results acquired for the wet samples accounted for the molecular mobility of water molecules within the channels of the nanosponge network, leading back to the possible pore size distribution. Ow-ing to the intrinsic difficulties involved in a quantitative assessment of the textural properties, in the present study we alternatively propose an extension to nanosponges of the concept of “connectivity”, which has been already employed to discuss the properties of soils.
The content of glucose, fructose, sucrose, maltose and water were determined for multiflorous honey of Great Poland. The measurements were carried out for different fractions of honey and also for the liquefied honey at 40 °C. Water activity and pH were both determined for all samples. A new method of recognizing liquefied honey is proposed based on the water influence on pH and the monosaccharides and disaccharides contents. The simple function of quadratic polynomial enabled to reveal the different character of the liquefied honey. The electrical conductivity behavior of different dry matter samples of honey are presented in the wide range of temperature. The proton spin-lattice relaxation measurements were recorded for the crystalline fraction in the magnetic field range covering the proton Larmor frequencies from 0.01 to 25 MHz and in the wide range of temperature. Heating the honey at 30 °C results in the irreversible molecular structure changes.
Hydrological connectivity inside the soil (HCS) is related to the spatial patterns inside the soil (i.e. the structural connectivity). This, in turn, is directly associated with the physical and the chemical processes at a molecular level (i.e. the functional connectivity). Nuclear magnetic resonance (NMR) relaxometry can be successfully applied to reveal both structural and functional components of soil hydrological connectivity. In the present study, the low field NMR relaxometry was applied on water suspended soils sampled at the upstream- and downstream-end of three different length plots. Also the sediments collected from the storage tanks at the end of each plot were water suspended and monitored by NMR relaxometry. The results from the NMR investigations were elaborated by using a mathematical approach in order to quantify both the functional and structural connectivity components. In particular, following integration of the T1 distribution curve, a S-shaped curve was obtained. It revealed two plateaus corresponding to the shortest (low component) and the longest (high component) intervals of relaxation times, respectively. According to relaxometry theory, the two T1 intervals, associated to the different plateaus, were attributed to micro and macro soil pores, respectively. The two T1 intervals were used to define a functional connectivity index (FCI), while the central part of the S-shaped distribution was used to define a structural connectivity index (SCI). Here we provide the physical meaning of the our mathematical approach, thereby revealing that FCI increases with plot length, as a result of a selective eroded particle transport. Moreover, the relationship SCI versus plot length resulted quasi-independent of grainsize distribution, while the values of the structural connectivity index for the sediment samples resulted lower than those obtained for the corresponding soils.
NMR spectroscopy is a versatile tool for the study of structure and interactions in environmental media such as air, soil, and water as well as monitoring the metabolic responses of living organisms to an ever changing environment. Part review, part perspective and part tutorial, this feature is aimed at non-specialists who are interested in learning more about the potential and impact of NMR spectroscopy in environmental research.
Recent studies have demonstrated the importance of the nutrient status of biochar and soils prior to its inclusion in particular agricultural systems. Pre-treatment of nutrient-reactive biochar, where nutrients are loaded into pores and onto surfaces, gives improved yield outcomes compared to untreated biochar. In this study we have used a wide selection of spectroscopic and microscopic techniques to investigate the mechanisms of nutrient retention in a high temperature wood biochar, which had negative effects on Chenopodium quinoa above ground biomass yield when applied to the system without prior nutrient loading, but positive effects when applied after composting. We have compared non-composted biochar (BC) with composted biochar (BCC) to elucidate the differences which may have led to these results. The results of our investigation provide evidence for a complex series of reactions during composting, where dissolved nutrients are first taken up into biochar pores along a concentration gradient and through capillary action, followed by surface sorption and retention processes which block biochar pores and result in deposition of a nutrient-rich organomineral (plaque) layer. The lack of such pretreatment in the BC samples would render it reactive towards nutrients in a soil-fertilizer system, making it a competitor for, rather than provider of, nutrients for plant growth.
Infrared and ¹³C solid state nuclear magnetic resonance spectroscopies and benzene polycarboxylic acids (BPCA) analysis were used to characterize the structural changes occurring during slow pyrolysis of corncob and Miscanthus at different temperatures from 235°C to 800°C. In the case of corncob, a char sample obtained from flash carbonization was also investigated. Spectroscopic techniques gave detailed information on the transformations of the different biomass components, whereas BPCA analysis allowed the amount of aromatic structures present in the different chars and the degree of aromatic condensation to be determined. The results showed that above 500°C both corncob and Miscanthus give polyaromatic solid residues with similar degree of aromatic condensation but with differences in the structure. On the other hand, at lower temperatures, char composition was observed to depend on the different cellulose/hemicellulose/lignin ratios in the feedstocks. Flash carbonization was found to mainly affect the degree of aromatic condensation.
Connectivity is a general concept used to represent the processes involving a transfer of matter among the elements of an environmental system. The expression “hydrological connectivity inside the soil” has been used here to indicate how spatial patterns inside the soil (i.e., the structural connectivity) interact with physical and chemical processes (i.e., the functional connectivity) in order to determine the subsurface flow (i.e., the water transfer), thereby explaining how sediment transport due to surface runoff (i.e., the soil particle transfer) can be affected. This paper explores the hydrological connectivity inside the soil (HCS) and its link to sediment delivery processes at the plot scale. Soils sampled at the upstream- and downstream-end of three different length plots were collected together with sediments from the storage tanks at the end of each plot. All the samples were analyzed by traditional soil analyses (i.e., texture, Fourier transform infrared spectroscopy with attenuated total reflectance, C and N elemental contents) and fast-field-cycling (FFC) nuclear magnetic resonance (NMR) relaxometry. Results revealed that selective erosion phenomena and sediment transport are responsible for the particle size homogeneity in the sediment samples as compared to the upstream- and downstream-end soils. Moreover, while structural connectivity is more efficient in the upstream-end soil samples, functional connectivity appeared more efficient in the downstream-end and sediment samples. Further studies are needed in order to quantitatively assess FFC NMR relaxometry for HCS evaluation.
Two commercial (Merck and Sigma-Aldrich) and two home prepared (HP05 and HP05C) powdered TiO2 photocatalysts were investigated by fast field cycling nuclear magnetic resonance experiments in order to explore the nature of the interactions between water and the solid surfaces. The results were related to the activation energies determined at temperatures ranging from 303 to 353 K for the photocatalytic oxidation in water of three model molecules presenting different interactions with the solid surface (catechol, phenol and metylbenzoate). The photoactivity results at different temperatures were comparable to each other because the runs were carried out while keeping constant the concentration of O2 in the suspensions. The study highlights the influence of the adsorbed water on the activation energy of a photocatalytic reaction. In particular, we showed that competition between water and substrate adsorption is a determining factor in the activation energy of a photocatalytic oxidation reaction.
Biodegradable amphiphilic PLGA-PEG-PLGA triblock copolymers end-terminated with itaconic acid (ITA) having reactive double bonds were synthesized by ring opening polymerization. Prepared α,ω-itaconyl-PLGA-PEG-PLGA telechelic macromonomers were additionally covalently crosslinked under inert atmosphere by blue light irradiation without the use of further cross-linker resulting in end-linked polymeric networks. Effects of the ITA amount attached to the α,ω-itaconyl-PLGA-PEG-PLGA copolymers and the crosslinking time on swelling behaviours and hydrolytic stability of prepared well-defined polymeric network were investigated. Physicochemical properties were characterized by proton and carbon nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR), proton nuclear magnetic resonance relaxometry, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). It was found that hydrolytic stability of ITA modified PLGA-PEG-PLGA end-linked hydrogels enhances with both increasing the time of crosslinking and the amount of double bonds attached to α,ω-itaconyl-PLGA-PEG-PLGA polymer chains. In comparison with the original un-crosslinked α,ω-itaconyl-PLGA-PEG-PLGA copolymer, hydrolytic stability of end-linked hydrogels significantly increased. Three kinds of water fractions (unbounded, weakly and strongly bonded) were determined by proton NMR relaxometry in hydrogel containing 63 mol% of ITA crosslinked for 40 minutes. Even for hydrogel surviving 32 days in water the NMR relaxometry showed structural collapse of hydrogel probably due to breaking of end-linked nodes followed by hydrolysis faster than water diffusion after day 15 of immersion . End-linkedα,ω-itaconyl-PLGA-PEG-PLGA hydrogels can be used in medical, biological or tissue engineering applications.
Knowledge of structural dynamics of dissolved organic matter (DOM) is of paramount importance for understanding DOM stability and role in the fate of solubilized organic and inorganic compounds (e.g. nutrients and pollutants) either in soils or aquatic systems. In this study, Fast Field Cycling (FFC) 1H NMR relaxometry was applied to elucidate structural dynamics of terrestrial DOM, represented by two structurally contrasting DOM models such as the Suwanee river (SRFA) and the Pahokee peat (PPFA) fulvic acids purchased by the International Humic Substance Society. Measurement of NMR relaxation rate of water protons in heating-cooling cycles revealed structural hysteresis in both fulvic acids. In particular, structural hysteresis was related to the delay in re-establishing water network around fulvic molecules as a result of temperature fluctuations. The experiments revealed that the structural temperature dependency and hysteresis were more pronounced in SRFA than in PPFA. This was attributed to the larger content of hydrogel-like structure in SRFA stabilized, at a larger extent, by H-bonds between carboxylic and phenolic groups. Moreover, results supported the view that terrestrial DOM consist of a hydrophobic rigid core surrounded by progressively assembling amphiphilic and polar molecules, which form an elastic structure that can mediate reactivity of the whole DOM.
Many soil functions depend on the interaction of water with soil. The affinity of water for soils can be altered by applying soil amendments like stone meal, manure, or biochar (a carbonaceous material obtained by pyrolysis of biomasses). In fact, the addition of hydrophobic biochar to soil may increase soil repellency, reduce water-adsorbing capacity, inhibit microbial activity, alter soil filter, buffer, storage, and transformation functions. For this reason, it is of paramount importance to monitor water affinity for biochar surface (also referred to as ‘wettability’) in order to better address its applications in soil systems. In this study, we propose the use of fast field cycling NMR relaxometry technique with the application of a new mathematical model for data interpretation, as a valid alternative to the traditional contact angle (CA) measurements for biochar wettability evaluation. Either NMR or CA results revealed the same wettability trend for the biochars studied here. The advantage of NMR relaxometry over CA measurements lies in the possibility to obtain at the microscopic level a variety of different information in only one shot. In fact, while CA provides only wettability evaluation, NMR relaxometry also allows achievement of the mechanisms for water molecular dynamics on biochar surface, thereby leading to the possibility to understand better, in future research, the role of biochar in increasing soil quality and plant nutrition. Copyright
Physico-chemical traits of three eggplant genotypes (''Tunisina " , ''Buia " and ''L 305 ") were evaluated before and after two cooking treatments (grilling and boiling). Different genotypes revealed different changes after cooking, with ''Tunisina " showing a better retention of phytochemicals with respect to other two genotypes. The main physical phenomena were water loss during grilling, and dry matter loss after boiling. Chlorogenic acid, the main phenolic in eggplant, resulted higher in grilled samples, while delphinidin glycosides resulted more retained in boiled samples. Glycoalkaloids, thiols and biogenic ami-nes were generally stable, while 5-hydroxy-methyl-furfural was found only in grilled samples. Interestingly, Folin–Ciocalteu index and free radical scavenging capacity, measured with three different assays, were generally increased after cooking, with a greater formation of antioxidant substances in grilled samples. NMR relaxation experiments clarified the hypothesis about the changes of eggplant compounds in terms of decomposition of larger molecules and production of small ones after cooking.
The field cycling NMR relaxometry method (also known as fast field cycling (FFC) when instruments employing fast electrical switching of the magnetic field are used) allows determination of the spin-lattice relaxation time (T1 ) continuously over five decades of Larmor frequency. The method can be exploited to observe the T1 frequency dependence of protons, as well as any other NMR-sensitive nuclei, such as (2) H, (13) C, (31) P, and (19) F in a wide range of substances and materials. The information obtained is directly correlated with the physical/chemical properties of the compound and can be represented as a 'nuclear magnetic resonance dispersion' curve. We present some recent academic and industrial applications showing the relevance of exploiting FFC NMR relaxometry in complex materials to study the molecular dynamics or, simply, for fingerprinting or quality control purposes. The basic nuclear magnetic resonance dispersion features are outlined in representative examples of magnetic resonance imaging (MRI) contrast agents, porous media, proteins, and food stuffs. We will focus on the new directions and perspectives for the FFC technique. For instance, the introduction of the latest Wide Bore FFC NMR relaxometers allows probing, for the first time, of the dynamics of confined surface water contained in the macro-pores of carbonate rock cores. We also evidence the use of the latest field cycling technology with a new cryogen-free variable-field electromagnet, which enhances the range of available frequencies in the 2D T1 -T2 correlation spectrum for separating oil and water in crude oil. Copyright © 2015 John Wiley & Sons, Ltd.
Copyright © 2015 John Wiley & Sons, Ltd.
Biochar is a carbonaceous porous material deliberately applied to soil to improve its fertility. The mechanisms through which biochar acts on fertility are still poorly understood. The effect of biochar texture size on water dynamics was investigated here in order to provide information to address future research on nutrient mobility towards plant roots as biochar is applied as soil amendment. A poplar biochar has been stainless steel fractionated in three different textured fractions (1.0–2.0 mm, 0.3–1.0 mm and <0.3 mm, respectively). Water-saturated fractions were analyzed by fast field cycling (FFC) NMR relaxometry. Results proved that 3D exchange between bound and bulk water predominantly occurred in the coarsest fraction. However, as porosity decreased, water motion was mainly associated to a restricted 2D diffusion among the surface-site pores and the bulk-site ones. The X-ray μ-CT imaging analyses on the dry fractions revealed the lowest surface/volume ratio for the coarsest fraction, thereby corroborating the 3D water exchange mechanism hypothesized by FFC NMR relaxometry. However, multi-micrometer porosity was evidenced in all the samples. The latter finding suggested that the 3D exchange mechanism cannot even be neglected in the finest fraction as previously excluded only on the basis of NMR relaxometry results. X-ray μ-CT imaging showed heterogeneous distribution of inorganic materials inside all the fractions. The mineral components may contribute to the water relaxation mechanisms by FFC NMR relaxometry. Further studies are needed to understand the role of the inorganic particles on water dynamics. Copyright © 2015 John Wiley & Sons, Ltd.
Aqueous salt solutions play an important role in nature because of their effects on environmental biogeochemical processes and on structural properties of biomolecules. Upon dissolution, salts split in ions that are solvated. Water in hydration shells is subjected to molecular motions that can be monitored by 1 H T 1 NMR relaxometry. This technique allowed the evaluation of the nature of the interactions between water and ions via variable temperature experiments. Examination of relaxometry proper-ties of aqueous solutions at variable salt concentrations allowed acknowledgement of the role played by ions in either structuring or destructuring water aggregates. A mathematical model has been applied on six environmentally relevant salts: NaCl, KCl, CaCl 2 , CaCO 3 , NaNO 3 , and NH 4 NO 3 . It was linear only for the concentration dependence of KCl-R 1 . This model accorded with the one reported in literature where it has been considered valid only for diluted solutions. However, in the present study, the range of linearity for KCl was extended up to the saturation point. The model was modified for NaCl, CaCl 2 , and CaCO 3 by using it as an exponential form in order to account for the nonlinearity of the R 1 -versus-concentration curves. Nonlinearity was explained by the nonnegligible ion–ion interactions occurring as concentration was increased. Finally, further modification was needed to account for the asymmetric distribution of water around nitrate (in NaNO 3 and NH 4 NO 3) and ammonium (in NH 4 NO 3). This study is preliminary to the comprehension of the diffusion mechanisms of ions in water solutions at the equilibrium condition with solid surfaces such as soils and biochar-amended soils.
Biomass-derived biochar is considered as a promising heavy metal adsorbent, due to abundance of polar functional groups, such as carboxylic, hydroxyl, and amino groups, which are available for heavy metal removal. The aims of this study were to evaluate the effectiveness of an orchard pruning-derived biochar in removing some heavy metals (through the evaluation of isotherms) and to study water dynamics at the solid-liquid interface as affected by heavy metal adsorption (through an innovative nuclear magnetic resonance (NMR) relaxometry approach). Both isotherms and NMR spectra revealed that Pb and Cr showed a good affinity for the biochar surface (Pb > Cr), while Cu was less affine. Accordingly, higher amounts of Pb and Cr were adsorbed by biochar as compared to those of Cu in the single systems. In binary systems (i.e., when two metals were applied simultaneously), Pb showed the highest inhibition of the adsorption of the other two metals, whereas the opposite was evidenced when Cu was used; the competitive adsorption was also strongly influenced by the metal residence time on biochar surface. In ternary systems (i.e., when all metals were applied simultaneously), even in the presence of high amounts of Pb and Cr, considerable adsorption of Cu occurred, indicating that some biochar adsorption sites were highly specific for a single metal.
We review experimental studies of the time decay of the nonequilibrium magnetization in high-temperature superconductors, a phenomenon known as magnetic relaxation. This effect has its origin in motion of flux lines out of their pinning sites due to thermal activation or quantum tunneling. The combination of relatively weak flux pinning and high temperatures leads to rich properties that are unconventional in the context of low temperature superconductivity and that have been the subject to intense studies. The results are assessed from a purely experimental perspective and discussed in the context of present phenomenological theories. [S0034-6861(96)00403-5]
The shear flow of hyaluronate solutions are studied on well characterized samples from bacterial sources. The dependence of the zero-shear viscosity, eta0, with polymer concentration, molecular weight, and temperature are discussed. The behavior of this semirigid ionic polymer differs, in some way, from that of flexible polymers in solution. In particular, the slope of the plot of log eta0 vs log M at fixed polymer concentration, C, is equal to 4 instead of 3.4 in the more concentrated domain. Nevertheless the concentration dependences of eta0 have been analyzed on the basis of models developed for flexible polymers.and polyelectrolytes. These models seem to apply to wormlike polymers with a presence of a limited semidilute region. The onset of shear thinning is found to be well characterized from the inverse of the longest relaxation time (tau(r)-1) in the solution taking into account C, M, and T dependences. The differences with hyaluronates of animal sources are attributed to the protein content in these samples.
Diverse proteins and polypeptides have been studied by proton field-cycling relaxation spectroscopy and - after deuterium exchange - by solid-state deuteron NMR. These techniques cover very different and partially complementary time scales of molecular motions spread over many orders of magnitude. On the other hand, deuteron NMR is predominantly sensitive to rotational fluctuations, while proton NMR can be affected by translational displacements in addition. The latter type of motion is considered to be connected with the multiple trapping diffusion mechanism of dilating defects in the protein structure. In particular the mean-square displacement of the diffusing defects is expected to obey a nonlinear time dependence ("anomalous diffusion"). This concept enables us to explain simultaneously (a) the small amplitudes of rotational backbone fluctuations as far as can be judged by the diverse deuteron experiments, (b) the existence of translational backbone fluctuations concluded from the proton T1 dispersion measurements, and (c) the peculiar v3/4 frequency dependence evident for the proton spin-lattice relaxation time in the vicinity of room temperature. In the limit far below room temperature, indications of a crossover to a fractal time process appear.
The magnetic field dependence of water-proton relaxation is reported for a simple protein solution, a cross-linked protein solution, and a series of rat tissues, fresh, dried and rehydrated. The shape of the magnetic field dependence associated with water proton relaxation in tissues is accounted for by magnetic dipole-dipole interactions between the mobile water spins and the immobile spin populations of the nonrotating components of the tissue coupling the behavior of the immobilized spin system to that of the mobile water spin system. The effect of this coupling is to impart the field dependence of the relaxation associated with the immobilized spin population to that of the mobile water spins that are observed in most relaxation and imaging experiments. © 1991 Academic Press, Inc.
Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
CONTIN is a portable Fortran IV package for inverting noisy linear operator equations. These problems occur in the analysis of data from a wide variety experiments. They are generally ill-posed problems, which means that errors in an unregularized inversion are unbounded. Instead, CONTIN seeks the optimal solution by incorporating parsimony and any statistical prior knowledge into the regularizor and absolute prior knowledge into equallity and inequality constraints. This can be greatly increase the resolution and accuracyh of the solution. CONTIN is very flexible, consisting of a core of about 50 subprograms plus 13 small “USER” subprograms, which the user can easily modify to specify special-purpose constraints, regularizors, operator equations, simulations, statistical weighting, etc. Specjial collections of USER subprograms are available for photon correlation spectroscopy, multicomponent spectra, and Fourier-Bessel, Fourier and Laplace transforms. Numerically stable algorithms are used throughout CONTIN. A fairly precise definition of information content in terms of degrees of freedom is given. The regularization parameter can be automatically chosen on the basis of an F-test and confidence region. The interpretation of the latter and of error estimates based on the covariance matrix of the constrained regularized solution are discussed. The strategies, methods and options in CONTIN are outlined. The program itself is described in the following paper.
On-line-first. DOI: 10
- Conte
Conte, Environ. Sci. Poll. Res., 2013. On-line-first. DOI: 10.1007/s11356-
012-1445-4.
- M W I Schmidt
- H Knicker
- P G Hatcher
M. W. I. Schmidt, H. Knicker, P. G. Hatcher, and I. K ¨
ogel-Knaber, Eur. J. Soil
Sci., 1997, 48, 319.
- E Fouissac
- M Milas
- M Rinaudo
- M K Cowman
- S Matsuoka
E. Fouissac, M. Milas, and M. Rinaudo, Macromolecules, 1993, 26, 6945.
42. M. K. Cowman and S. Matsuoka, Carbohydr. Res., 2005, 340, 791.
43. Y. L. Wang and P. S. Belton, Chem. Phys. Let., 2000, 325, 33.
- W Provencher
W. Provencher, Comp. Phys. Commun., 1982, 27, 229.
- S V Dvinskikh
S. V. Dvinskikh, Instrum. Exp. Tech., 1996, 39, 709.
- R Kimmich
R. Kimmich, Bull. Magn. Reson., 1980, 1, 195.
- A M Albano
- P A Beckmann
- M E Carrington
- F A Fusco
- A E Neil
- M E Scott
A. M. Albano, P. A. Beckmann, M. E. Carrington, F. A. Fusco, A. E. O'Neil,
and M. E. Scott, J. Phys. C: Solid State Phys., 1983, 16, L979.
- R G Bryant
- D A Mendelson
- C C Lester
R. G. Bryant, D. A. Mendelson, and C. C. Lester, Magn. Reson. Med., 1991,
21, 117.
- D Canet
D. Canet, Progr. Nucl. Magn. Reson. Spectr., 1989, 21, 237.
- W Provencher
W. Provencher, Computer Phys. Commun., 1982, 27, 213.
- A M Albano
- P A Beckmann
- M E Carrington
- F A Fusco
- A E O'neil
- M E Scott
A. M. Albano, P. A. Beckmann, M. E. Carrington, F. A. Fusco, A. E. O'Neil,
and M. E. Scott, J. Phys. C: Solid State Phys., 1983, 16, L979.
- E Fouissac
- M Milas
- M Rinaudo
E. Fouissac, M. Milas, and M. Rinaudo, Macromolecules, 1993, 26, 6945.
42. M. K. Cowman and S. Matsuoka, Carbohydr. Res., 2005, 340, 791.
43. Y. L. Wang and P. S. Belton, Chem. Phys. Let., 2000, 325, 33.
- M W I Schmidt
- H Knicker
- P G Hatcher
- I Kögel-Knaber
M. W. I. Schmidt, H. Knicker, P. G. Hatcher, and I. Kögel-Knaber, Eur. J. Soil
Sci., 1997, 48, 319.
- Y Yeshurun
- A P Malozemoff
- A Shaulov
Y. Yeshurun, A. P. Malozemoff, and A. Shaulov, Rev. Modern Phys., 1996,
68, 911.