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Distributions, inventories and isotopic composition of lead in 210Pb-dated peat cores from contrasting biogeochemical environments: Implications for lead mobility
Abstract
The use of concentration profiles of lead and other contaminant metals in 210Pb-dated ombrotrophic peat cores for reconstruction of historical trends in atmospheric deposition has become relatively well established. However, uncertainty remains over the validity of the assumption of post-depositional immobility of lead in peats. In particular, a number of studies have suggested that in saturated peat systems, lead is subject to diagenetic remobilisation and redistribution, with the result that 210Pb and lead profiles do not provide a historical record of deposition. Results are presented here for lead concentrations, inventories and stable isotope ratios and for 210Pb activities in two peat cores from locations close to the Glasgow industrial area in west-central Scotland. Contrasting biogeochemical conditions prevailed at the two sampling sites, with one being unsaturated and ombrotrophic while the other was saturated and minerotrophic. The results for the ombrotrophic peat core were compatible with information from other peat and lake sediment core studies, data for archived herbage samples and with known historical trends both in industrial activity and in the use of lead as an additive to petrol, giving a high degree of confidence in the 210Pb chronology and implied record of deposition. This provides strong support for the suggestion that lead is immobile in such systems. In contrast, the lead concentration profile and stable isotope data for the minerotrophic peat provided apparent temporal variations that were inconsistent with other studies and known historical trends, confirming that the saturated peat core did not provide a record of atmospheric deposition. This observation is consistent with the suggestion that lead is subject to diagenetic remobilisation and redistribution in saturated peats.
... Variations in climate (Luque and Julia, 2002), ecology (Twiss and Campbell, 1998), lithology (Allan, 1971;Coker, 1974;Davenport, 1982;Wright et al., 1989;Rogers et al., 1990;Coker et al., 1995;Cook, 2000) and the intermittent nature of sources such as volcanism (Zdanowicz et al., 1999), dust storms (Grousset et al., 2003), and sediment supply (Boyle et al., 1998) cause metals to be heterogeneously distributed in nature. As well, post depositional remobilisation of metals (diagenesis) can obscure the primary depositional signal (Wersin et al., 1991;Rassmussen et al., 1998a;MacKenzie et al., 1998;El Bilali et al., 2002;Telmer et al., 2005). The magnitude and significance of diagenesis is debated (Meili, 1995;Fitzgerald et al., 1998;MacKenzie et al., 1998;Rasmussen et al., 1998b) however, an increasing amount of evidence is illustrating that authigenic minerals and redox conditions are not distributed according to the expected monotonic diagenetic depth profiles (Ferris et al., 1987;van der Zee et al., 2003;George et al., 2004). ...
... As well, post depositional remobilisation of metals (diagenesis) can obscure the primary depositional signal (Wersin et al., 1991;Rassmussen et al., 1998a;MacKenzie et al., 1998;El Bilali et al., 2002;Telmer et al., 2005). The magnitude and significance of diagenesis is debated (Meili, 1995;Fitzgerald et al., 1998;MacKenzie et al., 1998;Rasmussen et al., 1998b) however, an increasing amount of evidence is illustrating that authigenic minerals and redox conditions are not distributed according to the expected monotonic diagenetic depth profiles (Ferris et al., 1987;van der Zee et al., 2003;George et al., 2004). Rather short (seasonal) and long term (Holocene) processes are being recognized as important controls on metals in sediments Telmer et al., 2005b). ...
... Therefore, the mobility of metal elements is a crucial factor. It is determined by the element type, chemical form, sediment type, absorption by plants (MacKenzie et al. 1998), pH variations, and adsorption on oxy-hydroxides (Rausch et al. 2005) etc. Lead is rather immobile in peat (MacKenzie et al. 1997(MacKenzie et al. , 1998Vile et al. 1999, Ali et al. 2008 although some studies have shown that this element can also migrate (Novak & Pacherova 2008). ...
... Therefore, the mobility of metal elements is a crucial factor. It is determined by the element type, chemical form, sediment type, absorption by plants (MacKenzie et al. 1998), pH variations, and adsorption on oxy-hydroxides (Rausch et al. 2005) etc. Lead is rather immobile in peat (MacKenzie et al. 1997(MacKenzie et al. , 1998Vile et al. 1999, Ali et al. 2008 although some studies have shown that this element can also migrate (Novak & Pacherova 2008). ...
Peat Core W3 was taken from the fen in Wolbrom (Silesian-Cracovian Upland, Southern Poland) in September 2015. Previous analyses of Core W3 showed a significant increase in lead concentration during the time of the Roman Empire as well as some changes in peat accumulation conditions. The work reported here investigates its geochemical composition in terms of major and trace elements (Pb, Zn, Na, K, Ca, Fe, Mg, Mn, Cu, Ni, Cr by AAS) as well as Pb isotopic composition, to identify the sources of metal pollution in the Wolbrom peat deposit. The geochemical record spans the period from 4900 BC to modern times, with a likely hiatus corresponding to the period from the Middle Ages to the beginning of the contemporary metallurgical industry. The Pb isotopic composition combined with a cluster analysis allows identification of the primary sources of Pb. In addition, Principal Component Analysis (PCA) helps to decipher the most important factors that affected the chemical composition of sediments at Wolbrom. These factors were linked to chemical denudation and human activity.
... Variations in climate (Luque & Julia 2002), ecology (Twiss & Campbell 1998), lithology (Allan 1971;Coker 1974;Davenport 1982;Wright et al. 1989;Rogers et al. 1990;Coker et al. 1995;Cook 2000) and the intermittent nature of sources such as volcanism (Zdanowicz et al. 1999), dust storms (Grousset et al. 2003) and sediment supply (Boyle et al. 1998) cause metals to be heterogeneously distributed in nature. In addition, post-depositional remobilization of metals (diagenesis) can obscure the primary depositional signal (Wersin et al. 1991;Rassmussen et al. 1998a;MacKenzie et al. 1998;El Bilali et al. 2002;Telmer 2004;Telmer et al. 2005). The magnitude and significance of diagenesis is debated (Meili 1995;Fitzgerald et al. 1998;MacKenzie et al. 1998;Rasmussen et al. 1998b); however, an increasing amount of evidence is illustrating that authigenic minerals and redox conditions are not distributed according to monotonic diagenetic depth profiles (Ferris et al. 1987; Van der Zee et al. 2003;George et al. 2004) and that short-(seasonal) and long-term (Holocene) processes are important controls on metals in lake sediments (Telmer & Desjardins 2004;Telmer et al. 2005). ...
... In addition, post-depositional remobilization of metals (diagenesis) can obscure the primary depositional signal (Wersin et al. 1991;Rassmussen et al. 1998a;MacKenzie et al. 1998;El Bilali et al. 2002;Telmer 2004;Telmer et al. 2005). The magnitude and significance of diagenesis is debated (Meili 1995;Fitzgerald et al. 1998;MacKenzie et al. 1998;Rasmussen et al. 1998b); however, an increasing amount of evidence is illustrating that authigenic minerals and redox conditions are not distributed according to monotonic diagenetic depth profiles (Ferris et al. 1987; Van der Zee et al. 2003;George et al. 2004) and that short-(seasonal) and long-term (Holocene) processes are important controls on metals in lake sediments (Telmer & Desjardins 2004;Telmer et al. 2005). It is becoming clearer, therefore, that understanding (and modelling) the transport and fate of chemicals in lake sediments requires similar methods to those employed for the movement and fate of metals in other porous media such as groundwater aquifers and hydrocarbon reservoirs. ...
Ninety-nine lakes were sampled at varying distances up to 75 km from the Horne smelter at Rouyn-Noranda, Quebec, to study the influence of the smelter versus other factors on metal concentrations in lake sediments. Most of these lakes he within the Abitibi Greenstone Belt, a zone of extensive base metal and gold mineralization and the focus of a mining and smelting economy for almost a century. Lake sediment cores, c. 25 cm long, were collected and sampled at the top (0-2 cm) and the bottom (18-20 cm) to capture sediment that was deposited after the smelter was in operation ('post-industrial') and well before the mining and smelting activity was started ('pre-industrial'). Additionally, nine cores were sampled in 1 cm increments to depths of up to 50 cm to study temporal patterns and potential element remobilization in detail. The cores were analysed for an extensive suite of elements. This paper focuses on those elements that are emitted by the smelter for which there are records of emissions through time, namely As, Cd, Cu, Pb and Zn. A spatial statistical approach - a logistic model of metal content versus distance from the smelter - was used investigate the relationship of sediment chemistry with smelter emissions and other possible influences. Using Cu as a representative proxy for the other emitted metals, this analysis demonstrates that elements are enriched in lake sediments by a factor of about three times around the smelter, that the impact of the smelter is detectable in lakes to a distance of at least 50 km, and that there is no obvious association between sediment Cu concentration and bedrock geology, land-use, lake pH, or lake morphometry Oake area/lake catchment area). The nine lakes studied in detail show enrichment towards the sediment-water interface (SWI) and relatively steady concentrations below depths of c. 10 cm. However, depth profiles do not match changes in the magnitude of smelter emissions through time, nor do they match changes in emission chemistry (element ratios) through time. Element ratios do generally move towards the chemistry of the emissions, suggesting smelter influence, but do not do so predictably. For example, (i) trends in the Cu/Pb ratio continue to the very bottom of cores into material deposited hundreds of years before industrialization, and (ii) proximity to the smelter does not lead to greater similarity between sediment and emission chemistry. These results suggest that significant element remobilization is occurring and that it differs from lake to lake and from element to element. We conclude that lakes within 50 km of the smelter have elevated metal concentrations in their near-surface sediments due to stack emissions but, due to element cycling and mobility, it is difficult to quantitatively determine the magnitude of metal increase attributable to the smelter. We also suggest that due to upward remobilization, the duration of industrial metal enrichments in surface sediments (the residence time) may be increased, thereby making surface enrichments more persistent than would be predicted by the sedimentation rate.
... The mobility of metal and metalloid elements may be due to various factors such as adsorption on oxy-hydroxides and variations in pH (e.g., Rausch et al., 2005a,b), or uptake and recycling by plants (e.g., Damman, 1978;MacKenzie et al., 1998). Numerous studies demonstrated that Pb is an immobile element in ombrotrophic bog based on stable and radioactive Pb isotopes, Pb profiles in porewaters comparison with rain collectors and herbarium samples and transplant experiments (e.g. ...
... Shotyk et al., 2001;Weiss et al., 2002;Farmer et al., 2002;Le Roux et al., 2005;Novak et al., 2011). However, some investigations also demonstrated that Pb can be affected by diagenetic remobilization and redistribution processes in saturated peats (e.g., MacKenzie et al., 1998;Olid et al., 2010). Zinc is often associated to Pb in sulfide minerals (including galena) and coals ). ...
The objective of our study was to determine the trace metal accumulation rates in the Misten bog, Hautes-Fagnes, Belgium, and assess these in relation to established histories of atmospheric emissions from anthropogenic sources. To address these aims we analyzed trace metals and metalloids (Pb, Cu, Ni, As, Sb, Cr, Co, V, Cd and Zn), as well as Pb isotopes, using XRF, Q-ICP-MS and MC-ICP-MS, respectively in two 40-cm peat sections, spanning the last 600 yr. The temporal increase of metal fluxes from the inception of the Industrial Revolution to the present varies by a factor of 5-50, with peak values found between AD 1930 and 1990. A cluster analysis combined with Pb isotopic composition allows the identification of the main sources of Pb and by inference of the other metals, which indicates that coal consumption and metallurgical activities were the predominant sources of pollution during the last 600 years.
... The dominance of local pollutant sources was found in peat records from Atlantic areas, with historical trends in Pb deposition consistent with the mining and coal development during the early XX th century (e.g. Farmer et al., 1997;MacKenzie et al., 1997MacKenzie et al., , 1998Weiss et al., 2002;Cloy et al., 2005Cloy et al., , 2008. Unlike Northern and Central Europe, the history of metal pollution at regional and local scale is not so well-known for Southern Europe. ...
... The reconstruction of recent (last 150 years) atmospheric metal deposition is frequently based on single 210 Pb-dated peat cores (e.g. MacKenzie et al., 1998;Biester et al., 2002;Shotyk et al., 2002). This procedure assumes that ombrotrophic mires are homogeneous collectors of pollutants over short spatial scales and, therefore, single records should adequately represent the atmospheric deposition over the whole region. ...
The natural radionuclide (210)Pb is commonly used to establish accurate and precise chronologies for the recent (past 100-150years) layers of peat deposits. The most widely used (210)Pb-dating model, Constant Rate of Supply (CRS), was applied using data from three peat cores from Chao de Lamoso, an ombrotrophic mire in Galicia (NW Spain). On the basis of the CRS-chronologies, maximum Pb concentrations and enrichment factors (EFs) occurred in the 1960s and late 1970s, consistent with the historical use of Pb. However, maximum Pb fluxes were dated in the 1940s and the late 1960s, 10 to 20 years earlier. Principal component analysis (PCA) showed that, although the (210)Pb distribution was mainly (74%) controlled by radioactive decay, about 20% of the (210)Pb flux variability was associated with atmospheric metal pollution, suggesting an extra (210)Pb supply source and thus invalidating the main assumption of the CRS model. When the CRS-ages were recalculated after correcting for the extra input from the (210)Pb inventory of the uppermost peat layers of each core, Pb flux variations were consistent with the historical atmospheric Pb deposition. Our results not only show the robustness of the CRS model to establish accurate chronologies of recent peat deposits but also provide evidence that there are confounding factors that might influence the calculation of reliable peat accumulation rates (and thus also element accumulation rates/fluxes). This study emphasizes the need to verify the hypotheses of (210)Pb-dating models and the usefulness of a full geochemical interpretation of peat bog records.
... Concerning peatlands, it is generally accepted that the most appropriate media are ombrotrophic peat bogs because their chemistry and hydrology tend to promote the immobility of metals deposited (Lee and Tallis, 1973; Jones and Hao, 1993; Shotyk, 1996a; Norton et al., 1997; Martınez-Cortizas et al., 1997; Shotyk et al., 1998; ´ MacKenzie et al., 1998a ). Evidence of post-depositional lead migrations has already been noticed, at the time scale of the last century, in minerogenic peatlands with ash content less than 10%, making historical interpretation impossible (MacKenzie et al., 1998b). However, at the millennia time scale, coherent lead records have also been reported in marshes featured by high ash content reaching up to 94% (Alfonso et al., 2001). ...
... In all cases, anthropogenic inputs have to dominate over detrital contribution (Weiss et al., 1999), and mineral dissolution of the underlying sediments must not contribute measurably to the lead inventory (Shotyk, 2002 ). Invaluable information on the sources may be obtained by the measurement of lead isotopic compositions (Brannvall et al., 1997; Shotyk et al., 1998; ¨ MacKenzie et al., 1998b; Weiss et al., 1999; Dunlap et al., 1999; Renberg et al., 2000; Alfonso et al., 2001; Aries, 2001; Weiss et al., 2002; ` Martınez-Cortizas et al., 2002; Shotyk et al. ´ 2002a,b; Monna et al., 2004). Regrettably ombrotrophic peat bogs are not available in the High Aldudes Valley, a Basque valley well known for its mineral abundance, so we had to investigate the possible use of geochemical signals archived in high ash minerogenic peatlands to constrain the history of local mining and smelting operations. ...
... Past atmospheric Pb deposition rates can be estimated from ombrotrophic peat bogs, which are supplied with their nutrients, and also pollutants, strictly via the atmosphere (38). There has been debate on the validity of peat deposits for reconstructing atmospheric deposition (39,40), but recent studies have supported the reliability of Pb records in ombrotrophic peat bogs (5,6,7,9,41,42,43,44,45). We calculated the atmospheric flux of Pb by analyses of the three 14 C-dated peat profiles: Store Mosse, Trolls Mosse, and Ö nneby Mosse. ...
... (9,35,46,47,48)) and the British Isles (1.17-1.18 (32,34,45)) rather than of Swedish mineral soils. This indicates that the dominant source of Pb deposited at these sites was from non-Swedish sources. ...
Knowledge of natural, prepollution concentrations of heavy metals in forest soils and temporal trends of soil pollution are essential for understanding present-day pollution (ecotoxicological assessments) and for establishing realistic goals for reductions of atmospheric pollution deposition (critical loads). Soils not exposed to deposition of atmospheric pollution no longer exist and, for example, present lead (Pb) pollution conditions in northern European soils are a consequence of nearly 4,000 years of atmospheric pollution. We use analyses of Pb concentrations and stable Pb isotopes (206Pb/207Pb ratios) of ombrotrophic peat and forest soils from southern Sweden and a model for Pb cycling in forest soils to derive an estimate for the prepollution concentration of Pb in the mor layer of boreal forest soils and to back-calculate Pb concentrations for the last 5,500 years. While the present-day concentra tions of the mor layer are typically 40−100 μg g-1 (0.25−1.0 g m-2), Pb concentrations of pristine forest mor layers in Sweden were quite low, ≤0.1 μg g-1 (≤1 mg m-2). Large-scale atmospheric pollution from the Greek and Roman cultures (ca. 0 AD) increased Pb concentrations to about 1 μg g-1. Lead (Pb) concentrations increased to about 4 μg g-1 following the increase of metal production and atmospheric pollution in Medieval Europe (ca. 1000 AD).
... 210 Pb-derived dates from ombrotrophic peat deposits are always validated by independent evidence such as pollution records or other radioisotopes, including 239+240 Pu, 241 Am (e.g. Appleby et al., 1997;Cwanek et al., 2021;Gallagher et al., 2001;MacKenzie et al., 1998) because decreasing with depth 210 Pb activity provided older than expected data. 210 Pb dating of peat has been suggested to be unreliable in some studies (e.g. ...
The subalpine, atmospherically fed Śnieżka peatland, located in the Polish part of the Sudetes, is one of the nominated candidates for the GSSP of the Anthropocene. Data from two profiles, Sn1 (2012) and Sn0 (2020), from this site are critical for distinguishing the proposed epoch, while an additional core Sn2 is presented to support main evidence. The Sn0 archive contains a wide array of critical markers such as plutonium (Pu), radiocarbon (F ¹⁴ C), fly ash particles, Hg and stable C and N isotopes which are consistent with the previously well documented ²¹⁰ Pb/ ¹⁴ C dated Sn1 profile, which provides a high-resolution and comprehensive database of trace elements and rare earth elements (REE), Pb isotopes, Pu, Cs, pollen and testate amoebae. The 1952 worldwide appearance of Pu, owing to its global synchronicity and repeatability between the cores, is proposed here as a primary marker of the Anthropocene, supported by the prominent upturn of selected chemostratigraphic and biostratigraphic indicators as well as the appearance of technofossils and artificial radionuclides.
... Hence, in applications such as dating of recent deposits using radionuclides as well as radioactive waste disposal management, water resource assessment and remediation of mining environments, it is important to understand and predict the mobility of lead at trace levels (Kelebemang et al., 2017;Lacal et al., 2003;MacKenzie et al., 1998). In natural environments, predicting the concentration of aqueous lead (i.e., Pb(II)) in natural waters and its mobility is challenging due to the many chemical processes in which this element is involved, such as: (i) precipitation or coprecipitation in carbonates and in sulfate-bearing minerals when oxidizing conditions prevail (Fu et al., 2020), (ii) precipitation in sulfide minerals in reducing conditions (Fagbohungbe et al., 2017;Lacal et al., 2003), and (iii) adsorption/ion-exchange on clay minerals (Tabelin et al., 2020;Uddin, 2017) and oxyhydroxides of Fe-Mn (Serpaud et al., 1994). ...
In this study, new experimental data for the adsorption of lead onto a swelling clay mineral with a tetrahedral charge (beidellite) at the ultratrace level (<10⁻¹⁰ mol/L) are presented. The data were interpreted using an ion-exchange multisite model that considers the sorption of major cations (including H⁺), which always compete with trace elements for sorption onto mineral surfaces in natural environments. The ability of the proposed model to predict experimental Kd values under various conditions of ionic strength (fixed by NaCl solutions) and aqueous cation compositions (including Pb²⁺ and PbCl⁺) was tested. The proposed model was applied to experimental data previously published for other types of swelling clay minerals, and the results were compared with the results obtained using previously published models. The preferential adsorption of chloride ion pairs, as well as the effect of the swelling clay crystal chemistry on lead adsorption, were assessed. Finally, the selective adsorption behavior of ²²⁶Ra compared to ²¹⁰Pb was demonstrated, which has implications for the study of many environmental processes using isotope partitioning.
... Vertical profiles of peat sections can be used as an archive of changes in pollution levels only if the studied elements are not mobile; therefore, most often, vertical profiles of peat were used as archives of changes in pollution levels by lead (Novak et al. 2003;Farmer et al. 2006;Le Roux et al. 2004;Shotyk et al. 2016). The mobility of metals, especially in the peat surface layer, is associated with various factors, such as adsorption on oxyhydroxides (Grybos et al. 2007), pH changes (Rausch et al. 2005), and decomposition of organic matter (Biester et al. 2012), as well as uptake and recycling by plants (MacKenzie et al. 1998). ...
This article is devoted to the study of physicochemical parameters and the assessment of the accumulation and distribution of metals in peat deposits from the North European part of Russia (Arkhangelsk region). Peat profiles were selected both in the area with a high anthropogenic load and in a bog remote from industrial pollution. The determination of metals was carried out by using the methods X-ray fluorescence analysis and atomic absorption spectroscopy. It was determined that the studied bogs can be attributed to the low ash type, and the recorded pH and mineralisation values make it possible to attribute these deposits to the acid-oxidising facies of oligotrophic peatlands, characteristic of taiga landscapes. Assessment of metal accumulation showed a high content of titanium, chromium, lead, nickel, vanadium, cobalt, aluminium, silicon, and copper in peat, mainly caused by the burning of fossil fuels and industrial production, as well as the burning of urban and industrial waste. The peat profiles are characterised by significant fluctuations in the content of elements in different horizons. Studies have shown the need to monitor the content of metals in peatlands from the Arkhangelsk region to assess atmospheric pollution from industrial emissions, both at the moment and in the past.
... However, e.g. MacKenzie et al. (1998) and Olid et al. (2010) demonstrated possible diagenetic remobilization and redistribution of Pb in saturated peats. ...
Three peat cores were extracted from the Kovářská Bog in the central Ore Mountains to study anthropogenic pollution generated by mining and metallurgy. The core profiles were14C dated, and concentrations of selected elements were determined by ICP MS and HG-AAS. Principal component analysis indicated that Pb, Cu, As and Ag may be useful elements for the reconstruction of historical atmospheric pollution. Total and anthropogenic accumulation rates (ARs) of Pb, Cu and As estimated for the last ca. 3500years showed similar chronologies, and revealed twelve periods of elevated ARs of Pb, As and Cu related to possible mining and metallurgic activities. In total, four periods of elevated ARs of Pb, Cu and As were detected during the Middle and Late Bronze Ages, including a distinct Late Bronze Age pollution event between 1030BCE and 910BCE. The Iron Age included three episodes of increased ARs of Pb and As; the first and the most distinctive episode, recorded between 730 and 440BCE, was simultaneous with the Bylany culture during the Hallstatt Period. The Roman Age was characterized by one pollution event, two events were detected in the Middle Ages, and the last two during the modern period. Enhanced element ARs in the late 12th and 15th centuries clearly documented the onset of two periods of intense mining in the Ore Mountains. Metal ARs culminated in ca. 1600CE, and subsequently decreased after the beginning of the Thirty Years' War. The last boom of mining between 1700CE and 1830CE represented the last period of important metallurgical operations. Late Medieval and modern period metal ARs are in good agreement with written documents. Earlier pollution peaks suggest that local metal production could have a much longer tradition than commonly believed; however, archaeological or written evidence is scarce or lacking.
... A slight 'flattening' or relative fall in the 210 Pb activity curve near the peat surface, as exhibited in our data, has been observed in many peat profiles in different countries (e.g. Malmer and Holm, 1984;MacKenzie et al., 1998;Olid et al., 2008). Given the high hydraulic conductivity ( The dating results suggest a period of slow, nil or negative accumulation between dates UBA-20285 ...
The peatland pole forests of the Pastaza-Marañón Foreland Basin (PMFB), Peru, are the most carbon-dense ecosystems known in Amazonia once below ground carbon stores are taken into account. Here we present the first multiproxy palaeoenvironmental record including pollen data from one of these peatlands, San Jorge in northern Peru, supported by an age model based on radiocarbon and 210Pb dating. The pollen data indicate that vegetation changes during the early phases of peat initiation resulted from autogenic succession in combination with fluvial influence. The overall pattern of vegetation change is not straightforward: the record does not reflect a process of unidirectional, progressive terrestrialization, but includes a reversal in the succession and vegetation transitions, which omit predicted successional phases. This complexity is similar to that seen in the only other existing pollen record from a PMFB peatland, at Quistococha, but contrasts with peat records from Panama and Southeast Asia where successional patterning appears more predictable. Our dating results provide the first evidence from a PMFB peatland that peat accumulation may have been discontinuous, with evidence for reduced rates of peat accumulation, or a possible hiatus, around 1300–400 cal yr BP. An ecological shift from open lake to palm swamp occurs at this time, possibly driven by climatic change. The pollen data indicate that the present pole forest vegetation at San Jorge began to assemble c. 200–150 cal yr BP. Given this young age, it is likely that the pole forest at this site remains in a state of transition. https://authors.elsevier.com/a/1UEOC73Nzmxnr
... Shotyk et al. (1997a,b) argued that post-depositional Pb migration in bogs is not supported by comparisons of Pb concentrations (total, extractable or in isotopic form) in bogs and lake sediments. Mackenzie et al. (1997Mackenzie et al. ( , 1998 also used Pb isotope ratios in peat cores dated by 210 Pb to argue in favor of the quantitative retention of atmospheric lead in Scottish bogs. By comparing herbarium Sphagnum plant samples and Swiss bog lead isotope ratios with time, Weiss et al. (1999a,b) effectively demonstrated that any post-depositional lead transformation involving redox, pH and dissolved organic matter in the pore waters did not significantly alter the record of atmospheric lead deposition. ...
'In the past two decades there has been considerable work on global climatic change and its effect on the ecosphere, as well as on local and global environmental changes triggered by human activities. From the tropics to the Arctic, peatlands have developed under various geological conditions, and they provide good records of global and local changes since the Late Pleistocene. The objectives of the book are to analyze topics such as geological evolution of major peatlands basins; peatlands as self sustaining ecosystems; chemical environment of peatlands: water and peat chemistry; peatlands as archives of environmental changes; influence of peatlands on atmosphere: circular complex interactions; remote sensing studies of peatlands; peatlands as a resource; peatlands degradation, restoration, plus more.' * Presents an interdisciplinary approach, with an emphasis on Earth Science, and addresses the need for intergration between subdisciplines and the developing of new approaches * Synthesizes the evolutionary, ecological, and chemical characteristics of major peatlands, as well as focuses on the environmental changes, from climate changes to surface ares changes due to human activities * Covers topical studies of worldwide interest and provides examples from many different countries
... Durant une tr entaine d'années , les travau x publiés dans ce domaine , ont été très nombreux et divers ifiés. Out re l'étude des répercussions sur la santé humaine [5][6][7][8][9] et du mode d'action biochimique [2,[10][11][12], les traces de plomb ont été l'objet de différents tests de mesures dans le sol [13,14], les couches glacières de régions polaires (Murozumi , Patterson , 1969, 1971) , l'air [15,[17][18][19][20], ainsi que dans des bio-accumulateurs végétaux [21][22][23][24][25][26], dans différents pays du monde. La contamination des tissus du corps humain par le métal a été relevée par des dosages dans le sang [1,3,27], l'urine [3], les cheveu x, les ongles, et les dents de lait des enfants (Marecek, 1983). ...
Our study on atmospheric pollution aims to define a sampling strategy in order to control the pollution caused by car traffic in Lebanon, and especially in the capital Beirut. The car traffic is the main source, nearly exclusive, of the Beirut's atmospheric pollution by lead. The sampling campaign is made under chosen climatic and seasonal conditions favorable to the stagnation of the pollutants in the over-urbanized areas. The mean level of blood Lead in ail examined policemen in Beirut was 92.47 ± 27.90 µg/l, with a confidence interval (95% CI) of 83.05 to 101.85 µg/l. The mean level of urine Lead was 44.12 ± 16.37 µg/l, with a confidence interval (95% IC) of 38.62-49.62 µg/l). The rate of excretion of lead in urine for the same concentration of lead in blood (Pbu/Pbs) is a function of the age of the policeman and of his degree of exposure ([Pb] Blood, and time of exposure): for a policeman subject to a high level of exposure to lead pollution ([Pb] blood] > 100 µg/l) during continuous periods of time (both workplace and polluted living place), the capacity of lead elimination in urine (Pb u/s) would decrease from year to year as a function of the history of saturnine impregnation.
... Minerotrophic marsh trap TMs brought with water from local sources in adjacent areas as they are topographically supplied, and their water table is controlled by regional underground water resources. Although several studies underline the potential mobility of Pb in water-saturated peat deposits (MacKenzie et al., 1998;Urban et al., 1990), an experimental study (Vile et al., 1999) demonstrates that Pb is nonmobile in 95% of input despite changing redox conditions and drastic fluctuation of the water table. ...
Coring was carried out in a soligenous marsh in the Vosges Mountains in the past mining district of Sainte-Marie-aux-Mines (eastern France). High-resolution palynological, non-pollen-palynomorph, and geochemical analyses were performed along the core. Correlations between the herbal composition of the landscape and trace metals in the core reveal a specific palynological pattern during mining activities. Two main periods of anthropogenic impacts on vegetation and trace metal contamination are shown: during the 16th–17th centuries, for mining and smelting activities, and the beginning of the 20th century, for smelting and the Industrial Revolution. No drastic deforestations occurred near the study site, contrary to historical descriptions and prints of the valley. Controlled forest practices were implemented from the beginning of the record, that is, since cal. AD 1000, so the impact of mining activities seems to be less significant than expected near mining sites. We demonstrate that the minerotrophic characteristics of the record closest to past mining sites allows for (1) the description of the landscape associated with anthropogenic activities and (2) the recording of past trace metal emissions without post-depositional mobility.
... Surveying ombrotrophic bogs in southern England, Jones and Hao (1993) demonstrated an increase in the Cd, Cu, Pb and Zn concentrations with the age of the bogs, and no increase in the level of Fe; they suggested that the history of heavy metals pollution cannot be reconstructed from profiles of bogs under hydrological influences. McKanzie et al. (1998) concluded that ombrotrophic, unsaturated peat bogs where heavy metals are immobilized may reflect the historical level of these elements, while minerotrophic and saturated bogs in which heavy metals are mobile elements cannot be treated as indicators. According to Tyler (1972), the patterns of heavy metals accumulation in ombrotrophic bogs in Sweden do not allow these bogs to be considered sensitive indicators of past changes in the concentrations of heavy metals. ...
We review the use of bryophytes as bioindicators and biomonitors in terrestrial and aquatic habitats in this article. Bryophytes are excellent indicators for a wide range of contaminants. This is in consequence of a series of morphological and physiological properties like the lack of a cuticle or the existence of large cationic exchange properties within the cell wall. Mosses have mainly been used as accumulation indicators especially for heavy metals, radionuclides, and toxic organic compounds. Reviewing a wide range of investigations on this topic, advantages and further needs for research are discussed. Sulfurous and nitrogen depositions can hardly be analysed by methods in the field of accumulation monitoring but by investigating the frequency, distribution, fertility, and vitality of bryophyte species and populations. Similar methods are targeted by global change research, especially for the analysis of climate warming and the influence of land-use intensity on biodiversity.
... However, a peatland is an active system as a result of both accumulation and decomposition processes of organic matter. The mobility of TMs, especially in the peat surface layer (i.e., the acrotelm) is linked to various factors such as adsorption on oxyhydroxides [30], variation in pH [31], decomposition of organic matter [32], and uptake and recycling by plants [33], and thus their behavior is not always well understood, despite the numerous studies undertaken. Lead is by far the most intensively studied heavy metal in peat and is considered by most authors as an immobile element in peat [12,34]. ...
A large number of studies on trace metals and metalloids (TMs) accumulations in peatlands have been reported in Europe and North America. Comparatively little information is available on peat chronological records of atmospheric TMs flux in China. Therefore, the objective of our study was to determine the concentrations and accumulation rates (ARs) of TMs in Motianling peatland from Great Hinggan Mountain, northeast China, and to assess these in relation to establish a historical profile of atmospheric metal emissions from anthropogenic sources. To meet these aims we analyzed 14 TMs (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr, Sb, Tl, and Zn) and Pb isotopes (206Pb, 207Pb, 208Pb) using ICP-AES and ICP-MS, respectively, in three peat sections dated by 210Pb and 137Cs techniques (approximately spanning the last 200 years). There is a general agreement in the elemental concentration profiles which suggests that all investigated elements were conserved in the Motianling bog. Three principal components were discriminated by principal component analysis (PCA) based on Eigen-values >1 and explaining 85% of the total variance of element concentrations: the first component representing Ba, Co, Cr, Mo, Ni, Sr and Tl reflected the lithogenic source; the second component covering As, Cu and Sb, and Cd is associated with an anthropogenic source from ore mining and processing; the third component (Pb isotope, Pb and Zn) is affected by anthropogenic Pb pollution from industrial manufacturing and fossil-fuel combustion. The pre-industrial background of typical pollution elements was estimated as the average concentrations of TMs in peat samples prior to 1830 AD and with a 207Pb/206Pb ratio close to 1.9. ARs and enrichment factors (EFs) of TMs suggested enhanced metal concentrations near the surface of the peatland (in peat layers dated from the 1980s) linked to an increasing trend since the 2000s. This pollution pattern is also fingerprinted by the Pb isotopic composition, even after the ban of leaded gasoline use in China. Emissions from coal and leaded gasoline combustions in northern China are regarded as one of the major sources of anthropogenic Pb input in this region; meanwhile, the long-distance transportation of Pb-bearing aerosols from Mongolia should be also taken into consideration. The reconstructed history of TMs’ pollution over the past ca. 200 years is in agreement with the industrial development in China and clearly illustrates the influence of human activities on local rural environments. This study shows the utility of taking multi-cores to show the heterogeneity in peat accumulation and applying PCA, EF and Pb isotope methods in multi-proxies analyses for establishing a high resolution geochemical metal record from peatland.
... There is also evidence to suggest that 210 Pb-derived dates from ombrotrophic unsaturated peat deposits may be reliable where 210 Pbderived age-depth profiles have been validated by independent evidence such as pollution records, pollen analysis, and other radioisotopes including 241 Am (e.g. Appleby et al. 1997;Mackenzie et al. 1998). However, some controversy surrounds the reliability of 210 Pb-derived dates from ombrotrophic peat deposits, and there are several studies demonstrating that 210 Pb age estimates are too young (e.g. ...
This study compares age estimates of recent peat deposits in 10 European ombrotrophic (precipitation-fed) bogs produced using the ¹⁴C bomb peak, ²¹⁰Pb, ¹³⁷Cs, spheroidal carbonaceous particles (SCPs), and pollen. At 3 sites, the results of the different dating methods agree well. In 5 cores, there is a clear discrepancy between the ¹⁴C bomb peak and ²¹⁰Pb age estimates. In the upper layers of the profiles, the age estimates of ¹⁴C and ²¹⁰Pb are in agreement. However, with increasing depth, the difference between the age estimates appears to become progressively greater. The evidence from the sites featured in the study suggests that, provided aboveground plant material (seeds, leaves) is selected for dating, the ¹⁴C bomb peak is a reliable dating method, and is not significantly affected by the incorporation of old carbon with low ¹⁴C content originating from sources including air pollution deposition or methane produced by peat decomposition. ²¹⁰Pb age estimates that are too old may be explained by the enrichment of ²¹⁰Pb activity in the surface layers of peat resulting from a hypothesized mechanism where rapidly infilling hollows, rich in binding sites, may scavenge ²¹⁰Pb associated with dissolved organic matter passing through the hollow, as part of the surface drainage network. Until further research identifies and resolves the cause of the inaccuracy in ²¹⁰Pb dating, age estimates of peat samples based only on ²¹⁰Pb should be used with caution.
DOI: 10.2458/azu_js_rc.55.16057
... De Vleeschouwer et al. 2007;Rothwell et al. 2007aRothwell et al. , 2010a, mobility of Pb within the peat profile (e.g. Mackenzie et al. 1998;Vile et al. 1999;Novak et al. 2011), release of Pb into the fluvial system (e.g. Tipping et al. 2003;Rothwell et al. 2005Rothwell et al. , 2007bRothwell et al. , 2008Rothwell et al. , 2010bShotbolt et al. 2006;Dawson et al. 2010) and the timing and magnitude of mining and smelting impacts (e.g. ...
Ombrotrophic peatlands are highly sensitive to atmospheric heavy metal deposition. Previous attempts to quantify peatland lead pollution have been undertaken using the inventory approach. However, there can be significant within-site spatial heterogeneity in lead concentrations, highlighting the need for multiple samples to properly quantify lead storage. Field portable x-ray fluorescence (FPXRF) continues to gain acceptance in the study of contaminated soil, but has not thus far been used to assess peatland lead contamination. This study compares lead concentrations in surface peat samples from the South Pennines (UK) derived using (a) FPXRF in the field, (b) FPXRF in the lab on dried samples and (c) ICP-OES analysis. FPXRF field and lab data are directly comparable when field measurements are corrected for water content, both can be easily used to estimate acid extractable lead using regression equations. This study is a successful demonstration of FPXRF as a tool for a time- and cost-effective means of determining the lead content of contaminated peatlands, which will allow rapid landscape scale reconnaissance, core logging, surface surveys and sediment tracing.
... 1850s onwards), peaking in the mid to late-20 th Century, related in part to the rapid expansion in vehicular use and leaded petrol emissions. This is followed by a subsequent decrease in the late 20 th century owing to the decline of heavy industry, improved emissions control and the ban on leaded petrol (Lee and Tallis, 1973;Clymo et al., 1990;Shotyk, 1996;MacKenzie et al., 1998). This trend is clearly replicated in the MTM profile where Pb deposition begins to increase from the 1870s (as does Cu, Zn and Fe) and then quickly increases from the 1960s. ...
Understanding the ecohydrological responses of peatlands to climate change is particularly challenging over the late Holocene owing to the confounding influence of anthropogenic activity. To address this, a core spanning the last ∼2400 years from a raised bog in northern England was analysed using a comprehensive suite of proxy methods in an attempt to elucidate the drivers of change. A testate amoebae-based transfer function was used to quantitatively reconstruct changes in water table depth, supported by humification analysis and a plant macrofossil-derived hydroclimatic index. Pollen and plant macrofossil data were used to examine regional and local vegetation change, and human impacts were inferred from charcoal and geochemistry. Chronological control was achieved through a Bayesian age-depth model based on AMS radiocarbon dates and spheroidal carbonaceous particles, from which peat and carbon accumulation rates were calculated. Phases of both increased and decreased bog surface wetness (inferred effective precipitation) are present, with dry phases at c. AD 320–830, AD 920–1190 and AD 1850–present, and a marked period of increased effective precipitation at c. AD 1460–1850. Coherence with other records from across Northern Europe suggests that these episodes are primarily driven by allogenic climatic change. Periods of high bog surface wetness correspond to the Wolf, Spörer and Maunder sunspot activity minima, suggesting solar forcing was a significant driver of climate change over the last ∼1000 years. Following the intensification of agriculture and industry over the last two centuries, the combined climatic and anthropogenic forcing effects become increasingly difficult to separate due to increases in atmospheric deposition of anthropogenically derived pollutants, fertilising compounds, and additions of wind-blown soil dust. We illustrate the need for multiproxy approaches based on high-resolution palaeoecology and geochemistry to examine the recent trajectories of peatlands.
... To further investigate the dynamics of Pb on the green roof, a simple input/output model was proposed (Fig. 7). Inputs were calculated from atmospheric deposition data (MacKenzie et al., 1998;Fowler et al., 2006;Cloy et al., 2008) and extrapolations from trends in emissions data (MAPAC, 1993;NAEI, 2013) over the lifetime of the green roof. Present day mean soil concentration and soil bulk density were used to estimate the total amount of Pb stored within the green roof as 72 g. ...
Runoff and rainfall quality was compared between an aged intensive green roof and an adjacent conventional roof surface. Nutrient concentrations in the runoff were generally below Environmental Quality Standard (EQS) values and the green roof exhibited [Formula: see text] retention. Cu, Pb and Zn concentrations were in excess of EQS values for the protection of surface water. Green roof runoff was also significantly higher in Fe and Pb than on the bare roof and in rainfall. Input-output fluxes revealed the green roof to be a potential source of Pb. High concentrations of Pb within the green roof soil and bare roof dusts provide a potential source of Pb in runoff. The origin of the Pb is likely from historic urban atmospheric deposition. Aged green roofs may therefore act as a source of legacy metal pollution. This needs to be considered when constructing green roofs with the aim of improving pollution remediation.
... Shotyk et al., 2000; Vile et al., 2000; Mighall et al., 2002; Farmer et al., 2005; Rothwell et al., 2005). Increasingly, the inventory approach has been used as a tool to quantify the store of Pb pollution in peatland environments (e.g. MacKenzie et al., 1998; Novak et al., 2003; Bindler et al., 2004; Rothwell et al., 2007). Accumulating peatland soils act as sinks for large quantities of Pb, but erosion of contaminated peatlands has been highlighted as a potential mechanism for the release of Pb into the fluvial system (e.g. ...
The near-surface layer of peatlands of the Peak District, southern Pennines, UK, is severely contaminated with atmospherically deposited Pb. Contemporary catchment soil Pb inventories at Upper North Grain and Torside Clough reveal that ∼23% and ∼54%, respectively, of the potential store of Pb in each catchment has been lost through erosion of the contaminated near-surface peat layer. Soil Pb inventories and the Pb content of suspended sediments reveal that, in both catchments, the main mechanism for contemporary particulate Pb export is gully erosion. Historical sheet erosion on bare peat flats at Torside Clough has released significant quantities of Pb into the fluvial system, triggered by the exposure of the near-surface peat during an accidental wildfire in 1970. Up to 32% of the total Pb export from the catchment may have been released during a discrete erosion event soon after the wildfire. Accidental wildfires and the subsequent release of highly contaminated peat into the southern Pennine fluvial system may increase under predicted climate change scenarios.
... Surveying ombrotrophic bogs in southern England, Jones and Hao (1993) demonstrated an increase in the Cd, Cu, Pb and Zn concentrations with the age of the bogs, and no increase in the level of Fe; they suggested that the history of heavy metals pollution cannot be reconstructed from profiles of bogs under hydrological influences. McKanzie et al. (1998) concluded that ombrotrophic, unsaturated peat bogs where heavy metals are immobilized may reflect the historical level of these elements, while minerotrophic and saturated bogs in which heavy metals are mobile elements cannot be treated as indicators. According to Tyler (1972), the patterns of heavy metals accumulation in ombrotrophic bogs in Sweden do not allow these bogs to be considered sensitive indicators of past changes in the concentrations of heavy metals. ...
The use of bryophytes as bioindicators and biomonitors in terrestrial and aquatic habitats is reviewed in this article.Bryophytes are excellent indicators for a wide range of contaminants. This is in consequence of a series of morphological and physiological properties like the lack of a cuticle or the existence of large cationic exchange properties within the cell wall. Mosses have mainly been used as accumulation indicators especially for heavy metals, radionucleides and for toxic organic compounds. Reviewing a wide range of investigations on this topic, advantages and further needs for research are discussed. Sulphurous and nitrogen depositions can hardly be analysed by methods in the field of accumulation monitoring but by investigating the frequency, distribution, fertility and vitality of bryophyte species and populations. Similar methods are targeted by global change research, especially for the analysis of climate warming and the influence of land-use intensity on biodiversity.
... Shotyk et al. (1997a,b) argued that post-depositional Pb migration in bogs is not supported by comparisons of Pb concentrations (total, extractable or in isotopic form) in bogs and lake sediments. Mackenzie et al. (1997Mackenzie et al. ( , 1998 also used Pb isotope ratios in peat cores dated by 210 Pb to argue in favor of the quantitative retention of atmospheric lead in Scottish bogs. By comparing herbarium Sphagnum plant samples and Swiss bog lead isotope ratios with time, Weiss et al. (1999a,b) effectively demonstrated that any post-depositional lead transformation involving redox, pH and dissolved organic matter in the pore waters did not significantly alter the record of atmospheric lead deposition. ...
Metal mining landscapes are a palimpsest of human activities, both agricultural and industrial which have interacted in complex ways. Both farmers and metallurgists have helped to create the cultural landscape of today. Paleoenvironmental investigations have chronicled those changes but separating their respective roles and impacts has yet to be fully achieved. Woodland disturbance does, however, coincide with phases of elevated metal concentrations. The reconstruction of atmospheric metal deposition histories close to former metallurgical sites can be useful to test element mobility in bogs. Once immobility of an element has been established, bog archives can be used as an archeological tool to understand the history of a mine or metalworking site.
... The systematic decrease in 206 Pb/ 207 Pb values since the late 1800s at Detour Lake closely matches that observed in the more populated Europe (Mackenzie et al., 1998;Shotyk et al., 1998;Dunlap et al., 1999;Weiss et al., 2002;Bell and Kettles, 2003). This suggests that the remote Canadian site has been affected by anthropogenic activities in part related to past lead-gasoline use and in part due to airborne contaminations from distant smelters. ...
This chapter describes selected basic information about the peatlands of the Hudson Bay Lowland (HBL) gathered in the past four decades or so. The geographic, geological, and climatic settings are presented first. Various aspects of the evolution of the peatlands and peat are described. A brief analysis of the peat stratigraphy reporting the few studies made on the palynology and the organic mineralogy (macerals) is given in the chapter. The chemistry and carbon emission from the vast peatlands are considered, the latter having been analyzed during the 1990 summer by American and Canadian multidisciplinary agencies. A brief note on the main resources of the area is also illustrated.
... In addition, measurements of both the concentrations of individual alkylead species (originating in leaded gasoline) with the isotopic composition of Pb in a peat core dated with 210 Pb lends further support to the view that peat cores from ombrotrophic bogs yield highly reproducible Pb chronologies . Finally, independent investigations by other workers in this field have come to the same conclusion about Pb [Vile et al., 1995[Vile et al., , 1999Bränvall et al., 1997;Farmer et al., 1997;Kempter et al., 1997;Martinez-Cortizas et al., 1997;MacKenzie et al., 1997MacKenzie et al., , 1998Norton et al., 1997]. ...
The lowest concentrations, atmospheric fluxes, and enrichments of Sb in a Swiss bog were found in peat samples dating from 8,020 to 5,320 14C yr BP when Sb inputs were proportional to those of Sc and effectively controlled by deposition of soil dust. For comparison with these ancient samples, modern peat samples from five rural areas of Switzerland and two remote areas of Scotland and Shetland are highly contaminated with Sb, with enrichments of the order of 30 to 80 times. “Lithogenic” Sb concentrations calculated using the Sc concentrations and background Sb/Sc ratio are dwarfed at all sites by “anthropogenic” Sb. The chronology and intensity of the Sb enrichments are in many ways similar to those of Pb which indicates that (1) Sb, like Pb, is well preserved in ombrotrophic peat and (2) the extent of human impacts on the geochemical cycle of Sb is comparable to that of Pb. The similar distribution of Sb and Pb can be explained in terms of their chemical and mineralogical associations, with most lead minerals being rich in Sb. Assuming that the “background” Sb flux (0.35 μg/m2/yr) from the Swiss bog is representative of preanthropogenic deposition rates worldwide, the global flux of natural Sb is estimated at 154 T/a. Using the natural Pb flux published by Patterson and Settle [1987] of 2600 T/a and the “background” Pb/Sb ratio (29) of the preanthropogenic peat samples, the global flux of natural Sb is estimated at 90 T/a. Either way, these values (90 to 154 T/a) are considerably lower than the current estimate of natural Sb to the global atmosphere (2400 T/a) published by Pacyna and Pacyna [2001]. Assuming that the current estimate of anthropogenic Sb to the global atmosphere (1600 T/a) is correct [Pacyna and Pacyna, 2001], the ratio of anthropogenic to natural Sb emissions is on the order of 10 to 18. Taken together, the data from modern and ancient peat samples suggests that the impact of human activities on the global geochemical cycle of Sb may have been underestimated by an order of magnitude. Like Pb, Sb has no known biological function, has a similar toxicity, and is a cumulative poison. The environmental geochemistry of Sb therefore may have a relevance to human and environmental health comparable to that of Pb.
... Shotyk et al. (1997a,b) argued that post-depositional Pb migration in bogs is not supported by comparisons of Pb concentrations (total, extractable or in isotopic form) in bogs and lake sediments. Mackenzie et al. (1997Mackenzie et al. ( , 1998 also used Pb isotope ratios in peat cores dated by 210 Pb to argue in favor of the quantitative retention of atmospheric lead in Scottish bogs. By comparing herbarium Sphagnum plant samples and Swiss bog lead isotope ratios with time, Weiss et al. (1999a,b) effectively demonstrated that any post-depositional lead transformation involving redox, pH and dissolved organic matter in the pore waters did not significantly alter the record of atmospheric lead deposition. ...
This paper presents records of the atmospheric deposition of lead and zinc close to a former metal mining area as recorded by an upland blanket peat that has accumulated on the northern slopes of the Ystwyth valley, Dyfed, mid-Wales, UK. The research objective was to explore the possibility that the peat contained a geochemical record of the pollution generated by mining activity during the last four millennia. Four monoliths were extracted from the blanket peat to reconstruct the pollution history of lead and zinc mining. Three different geochemical measurement techniques were employed, and five lead and zinc profiles have been reconstructed, two of which are radiocarbon-dated. In the radiocarbon-dated monoliths lead enrichment occurs in the peat during the Roman occupation whilst both lead and zinc concentrations increase from the Mediaeval period until the early part of the 20th century. Similar enrichment of lead and zinc is shown in the remaining profiles. Whilst other possible explanations are discussed, it is argued that the high lead concentrations represent evidence of atmospheric pollution caused by mining. Zinc, however, may have suffered from post-depositional mobility. The results of this suggest that lead is largely rendered immobile in blanket peat and can be used to reconstruct atmospheric pollution histories in former lead mining areas.
... Notwithstanding this limitation, several studies have assessed the use of minerotrophic peatlands to reconstruct past changes in atmospheric metal deposition. Whilst Mackenzie et al. (1998) suggest lead mobility through the sediment column means that the historical interpretation of lead is difficult in minerogenic peat with ash content below 10%, Alfonso et al. (2001) were able to reconstruct millennial-scale lead records from sediments with ash contents reaching 94% in coastal marshes. Espi et al. (1997) and Shotyk (2002) successfully produced reliable information regarding atmospheric lead deposition from minerogenic deposits in Bolivia and Switzerland, but showed that other elements may be adversely affected by mineral dissolution. ...
An integrated pollen-analytical and geochemical study is presented from Qinngua Kangilleq, southwest Greenland. This site was formerly one of the largest farms in the Eastern Settlement of Norse Greenland. The study is the first to determine what link, if any, exists between Norse landnám (early settlement), vegetation change, soil erosion, climate change and peat geochemistry. The data suggest that fluxes in lithogenic elements supplied to a peat column by terrestrial sources and atmospheric deposition were coupled to the pattern of local Norse settlement beginning ∼cal. AD 1020. A severe phase of soil erosion is indicated which is coincident with the landnám horizon. This may represent proxy evidence for the stripping of turf for the construction of turf-and-stone buildings at the farm. Radiocarbon dates suggest the presence of a hiatus in the sediment column spanning ∼cal. AD 1380–1950. Following the recommencement of sediment accumulation, the geochemical data indicate a critical change in site conditions which may be consistent with the well-known change in Northern Hemisphere atmospheric circulation that started between c. AD 1400 and 1420. Bromine (Br) and chlorine (Cl) concentrations are demonstrably higher in the sediments dating to the 20th century relative to the pre-15th century deposits. Rising halogen concentrations at Qinngua appear to be correlated with increased levels of Na+(sea salt sodium) precipitation in the GISP2 ice core which earlier studies have interpreted as indicative of increased North Atlantic storminess.
... There is also evidence to suggest that 210 Pb-derived dates from ombrotrophic unsaturated peat deposits may be reliable where 210 Pbderived age-depth profiles have been validated by independent evidence such as pollution records, pollen analysis, and other radioisotopes including 241 Am (e.g. Appleby et al. 1997;Mackenzie et al. 1998). However, some controversy surrounds the reliability of 210 Pb-derived dates from ombrotrophic peat deposits, and there are several studies demonstrating that 210 Pb age estimates are too young (e.g. ...
This study compares age estimates of recent peat deposits in 10 European ombrotrophic (precipitation-fed) bogs produced using the C-14 bomb peak, Pb-210, Cs-137, spheroidal carbonaceous particles (SCPs), and pollen. At 3 sites, the results of the different dating methods agree well. In 5 cores, there is a clear discrepancy between the C-14 bomb peak and Pb-210 age estimates. In the upper layers of the profiles, the age estimates of C-14 and Pb-210 are in agreement. However, with increasing depth, the difference between the age estimates appears to become progressively greater. The evidence from the sites featured in the study suggests that, provided aboveground plant material (seeds, leaves) is selected for dating, the C-14 bomb peak is a reliable dating method, and is not significantly affected by the incorporation of old carbon with low C-14 content originating from sources including air pollution deposition or methane produced by peat decomposition. Pb-210 age estimates that are too old may be explained by the enrichment of Pb-210 activity in the surface layers of peat resulting from a hypothesized mechanism where rapidly infilling hollows, rich in binding sites, may scavenge Pb-210 associated with dissolved organic matter passing through the hollow, as part of the surface drainage network. Until further research identifies and resolves the cause of the inaccuracy in Pb-210 dating, age estimates of peat samples based only on Pb-210 should be used with caution.
... Although there are several studies on the association of trace metals with sulfide minerals (e.g., Huerta-Diaz and Morse, 1992;Larsen and Postma, 1997;Otero et al., 2000), there is little information on the pyritization of Fe and trace metals in areas of marine hydrothermal activity. Post-depositional mobility of redox-sensitive elements in different sedimentary environments has been discussed previously as well as the vertical distributions of these elements in sediments (e.g., John and Zwolsman, 1993;Rosenthal et al., 1995;Gagnon et al., 1997;MacKenzie, 1998). Most of these chemical species have been described under the assumption of steady-state conditions, which implies that rates of diffusion, sedimentation, and biological reaction are constant with time (Mucci and Edenborn, 1992). ...
A core collected in the Guaymas Basin contained an organic-poor, Mn oxide-rich and (relatively) Fe oxide-rich turbidite layer that affected the distribution of Fe, Mn, C, S and trace metals. Results indicate that sediments not influenced by the turbidite layer achieved a 100% degree of pyritization and, by extension, that pyrite production is Fe-limited in these sediments. In contrast, the mud slide layer apparently supplied enough reactive Fe to transfer essentially 98% of the total S present at the base of the turbidite (17–19 cm) to the pyrite reservoir. C/S ratios showed rapid decreases with depth, from a high of 38 close to the sediment-water interface, to minimum values of 2.8 at the lower limit of the turbidite layer, a ratio equal to the average C/S value of normal marine modern sediments, where concentrations of organic C and pyrite supposedly have attained quasi-steady values. A significant part of the reactive Mn was associated with carbonates (41±12%) and, to a much lower degree, with pyrite (2.7±1.2%). The turbidite layer is currently showing a depletion of Mn relative to the host sediment. It is possible that Mn, a major metal constituent in these sediments, was initially present in high concentrations in the mud slide, but was eventually mobilized and transferred either to the water column or to the sediments immediately below the turbidite layer. Metals associated with this element probably followed the same path, affecting their incorporation into pyrite. The turbidite layer apparently affected the distribution of most of the trace metals associated with pyrite, except maybe Cd, Pb and, to a certain, extent Cr. However, Cu, Cr, Zn, Ni and Co were all found to be highly pyritized (>80%) in the sediments of the Guaymas Basin.
... In the peat soils we estimate the Pb store to be slightly higher, 10·03 t km −2 . Pb storage is high in comparison with most peatdominated catchments, which typically have total Pb inventories less than 5 t km −2 (see, e.g., MacKenzie et al., 1998;Shotyk et al., 2000;Yang et al., 2001;Novak et al., 2003). Similarly high Pb levels have, however, been recorded in soils elsewhere in the Peak District (Lee and Tallis, 1973;Livett et al., 1979;Livett, 1988;Rothwell et al., 2007c). ...
A mass balance model of the main Pb stores and fluxes for a typical organic-rich upland catchment in the Peak District, UK, has been produced. The model, based on the Howden reservoir catchment, reveals that the majority of Pb in the catchment is stored within the soil (approximately 8·63 t km−2). Soil Pb levels are extremely high and can only be explained as the result of centuries of atmospheric Pb deposition from surrounding urban–industrial conurbations, and mining and smelting activity within the Peak District National Park. The atmospheric Pb flux onto the Howden catchment is approximately 107 kg a−1. The aquatic Pb flux is estimated at between 29·9 and 71·7 kg a−1; thus, at present, catchment soils are acting as a sink for Pb pollution. The Howden reservoir acts as a secondary store for Pb eroded and leached from catchment soils, with approximately 80% re-deposited in its sediments. It is estimated that 2·3% of the catchment soil Pb pool has been retained in the reservoir sediments over its 91 year lifespan.
Although the catchment is currently acting as a Pb sink, the rate of change in the soil Pb pool is very small. Future change in climate or deposition chemistry could, however, transform catchment soils into a significant source of Pb to the aquatic environment and water supply. Copyright
... Another possible explanation for uniform 210 Pb activity could be post-depositional remobilisation and transport of lead along the sediment column, without physical mixing of the sediment. This phenomenon has been reported in other saturated lake and peat sediments with pH 4-5 (Virkanen et al. 1997;MacKenzie et al. 1998). ...
We inferred the temperature and environmental conditions of Smreczynski Staw Lake in the Tatra Mountains, southern Poland,
from a sediment record covering the last 1,500years. Paleobiological methods (cladocera, chironomid, and diatom analyses)
were used together with sedimentological analysis and dating. These studies provide new information about the timing and character
of climate fluctuations during the Little Ice Age (LIA). The Medieval Warm Period ended in the Tatra region at the beginning
of the thirteenth century, followed by the first episode of the LIA. The LIA was a relatively long but unstable period. The
first part of the LIA was cold in the Tatra Mountains, without evidence of increasing precipitation, while the second part,
after AD 1540, was cold and humid. The LIA terminated in the Tatra Mountains at the beginning of the twentieth century, although
some aspects of its climatic and sedimentological regime continued until the 1920s. We also found some evidence of warming
and acidification during the twentieth century.
KeywordsLittle Ice Age-Dystrophic lake-Cladocera-Diatoms-Chironomids-Tatra Mountains
... Thus the measurement of heavy metals is much easier, a wider array of elements is potentially accessible, and contamination is less problematic. While the possible importance of post-depositional migration remains uncertain for most of the metals of interest (Damman 1978, Damman et al. 1992, recent analyses of the isotopic composition of Pb in dated peat cores indicated little if any vertical downward migration of this element (Shotyk et al. 1996aWeiss 1998;MacKenzie et al. 1997MacKenzie et al. , 1998a. Before using a peat core as archive of atmospheric Pb deposition, however, the ombrotrophic status of the peat bogs must be assessed by geochemical methods (Shotyk 1988(Shotyk , 1996. ...
Environmental archives such as peat bogs, sediments, corals, trees,
polar ice, plant material from herbarium collections, and human tissue
material have greatly helped to assess both ancient and recent
atmospheric lead deposition and its sources on a regional and global
scale. In Europe detectable atmospheric lead pollution began as early as
6000years ago due to enhanced soil dust and agricultural activities, as
studies of peat bogs reveal. Increased lead emissions during ancient
Greek and Roman times have been recorded and identified in many
long-term archives such as lake sediments in Sweden, ice cores in
Greenland, and peat bogs in Spain, Switzerland, the United Kingdom, and
the Netherlands. For the period since the Industrial Revolution, other
archives such as corals, trees, and herbarium collections provide
similar chronologies of atmospheric lead pollution, with periods of
enhanced lead deposition occurring at the turn of the century and since
1950. The main sources have been industry, including coal burning,
ferrous and nonferrous smelting, and open waste incineration until
c.1950 and leaded gasoline use since 1950. The greatest lead emissions
to the atmosphere all over Europe occurred between 1950 and 1980 due to
traffic exhaust. A marked drop in atmospheric lead fluxes found in most
archives since the 1980s has been attributed to the phasing out of
leaded gasoline. The isotope ratios of lead in the various archives show
qualitatively similar temporal changes, for example, the immediate
response to the introduction and phasing out of leaded gasoline. Isotope
studies largely confirm source assessments based on lead emission
inventories and allow the contributions of various anthropogenic sources
to be calculated.
... The data presented here also argue that Pb and Hg are well retained in the peat profile. There is a growing body of information suggesting that Pb is immobile in ombrotrophic peat (Vile et al., 1995; Shotyk et al., 1996; Bränvall et al., 1997; Farmer et al., 1997; Kempter et al., 1997; MacKenzie et al., 1997; Martinez-Cortizas et al., 1997; Norton et al., 1997; Shotyk et al., 1997; MacKenzie et al., 1998; Shotyk et al., 1998; Kempter and Frenzel, 1999; Vile et al., 1999; Weiss et al., 1999a; Weiss et al., 1999b; Kempter and Frenzel, 2000; Vile et al., 2000; Shotyk et al., 2001; Martinez-Cortizas et al., 2002; Nieminen et al., 2002; Renberg et al., 2002; Shotyk, 2002; Shotyk et al., 2002b; Weiss et al., 2002; Givelet et al., 2003; Klaminder et al., 2003; Novak et al., 2003; Givelet et al., 2004; Le Roux et al., 2004 ). Taking Pb to represent an immobile reference element, the coincidence of the Hg (Fig. 7) and Pb (Fig. 8) concentration peaks suggests that Hg also is very well retained by the peat profile. ...
A monolith representing 5420 14C yr of peat accumulation was collected from a blanket bog at Myrarnar, Faroe Islands. The maximum Hg concentration (498 ng/g at a depth of 4.5 cm) coincides with the maximum concentration of anthropogenic Pb (111 μg/g). Age dating of recent peat accumulation using 210Pb (CRS model) shows that the maxima in Hg and Pb concentrations occur at AD 1954 ± 2. These results, combined with the isotopic composition of Pb in that sample (206Pb/207Pb = 1.1720 ± 0.0017), suggest that coal burning was the dominant source of both elements. From the onset of peat accumulation (ca. 4286 BC) until AD 1385, the ratios Hg/Br and Hg/Se were constant (2.2 ± 0.5 × 10-4 and 8.5 ± 1.8 × 10-3, respectively). Since then, Hg/Br and Hg/Se values have increased, also reaching their maxima in AD 1954. The age date of the maximum concentrations of anthropogenic Hg and Pb in the Faroe Islands is consistent with a previous study of peat cores from Greenland and Denmark (dated using the atmospheric bomb pulse curve of 14C), which showed maximum concentrations in AD 1953.
In recent decades, 210Pb has been extensively used as a powerful dating and sedimentation rate-determining tool for sediments deposited over the past ~150 years. However, the conditional assumptions underlying this application have not been explicitly validated, and are always challenged by multiple factors. Here, we synthesize all the possible factors that may limit the accuracy of 210Pb as a geochronometer and bring together related evidence from observations, measurements, and sediment records. It was demonstrated that by affecting the initial 210Pb activity and challenging closed deposition system, particle affinity preference, physical/biological mixing, sedimentation events, and 210Pb post-depositional mobility are the four main contributors to its compromising accuracy. By systematically deepening the knowledge of the 210Pb dating method, this study highlights the necessity of testing the assumption before using it, provides a framework for interpreting non-steady-state accumulation profiles from various sediments, and identifies future research opportunities for chronology improvement and 210Pb application development.
Some 644 individual soil horizons from 169 sites in Scotland were analyzed for Pb concentration and isotopic composition. There were three scenarios: (i) 36 sites where both top and bottom (i.e. lowest sampled) soil horizons were classified as organic in nature, (ii) 67 with an organic top but mineral bottom soil horizon, and (iii) 66 where both top and bottom soil horizons were mineral. Lead concentrations were greater in the top horizon relative to the bottom horizon in all but a few cases. The top horizon (206)Pb/(207)Pb ratio was lesser (outside analytical error) than the corresponding bottom horizon (206)Pb/(207)Pb ratio at (i) 64%, (ii) 94% and (iii) 73% of sites, and greater at only (i) 8%, (ii) 3% and (iii) 8% of sites. A plot of (208)Pb/(207)Pb vs. (208)Pb/(206)Pb ratios showed that the Pb in organic top (i, ii) and bottom (i) horizons was consistent with atmospherically deposited Pb of anthropogenic origin. The (206)Pb/(207)Pb ratio of the organic top horizon in (ii) was unrelated to the (206)Pb/(207)Pb ratio of the mineral bottom horizon as demonstrated by the geographical variation in the negative shift in the ratio, a result of differences in the mineral horizon values arising from the greater influence of radiogenic Pb in the north. In (iii), the lesser values of the (206)Pb/(207)Pb ratio for the mineral top horizon relative to the mineral bottom horizon were consistent with the presence of anthropogenic Pb, in addition to indigenous Pb, in the former. Mean anthropogenic Pb inventories of 1.5 and 4.5gm(-2) were obtained for the northern and southern halves of Scotland, respectively, consistent with long-range atmospheric transport of anthropogenic Pb (mean (206)Pb/(207)Pb ratio~1.16). For cultivated agricultural soils (Ap), this corresponded to about half of the total Pb inventory in the top 30cm of the soil column.
The dynamic changes in selected heavy metal concentrations were analyzed in two ombrotrophic peat bogs from southern Poland: Puścizna Mala (PK) and Puścizna Krauszowska (PM). The highest contents of Pb and Zn occur at the top of profiles examined: 115.36 mg/kg (PM1), 90.61 mg/kg (PM2), 182.40 mg/kg (PK1), 121.68 mg/kg (PK2) and 127.43 mg/kg (PM1), 89.73 mg/kg (PM2), 170 mg/kg (PK1), 130.4 mg/kg (PK2), respectively. Concentrations of copper are similar to those of local soils varying from 9.4 to 12.8 mg/kg. Cadmium strongly varies with depth, which indicates distinct mobility of this element. Two peaks of elevated Fe concentrations are observed at the top and bottom of the Puścizna Mala profile, while the maximum in Puścizna Krauszowska was at the top of the peat bog. The Ti content distinctly varies with depth and correlates with the ash content (R 2 = 0.91-0.99). The strongest and positive correlation is observed between Zn-Pb and Ti-Pb contents. The significant differences of metal concentrations are noted between the profiles, which is probably connected with a rate of peat accumulation and plant composition of the profiles investigated, as well as with their disturbance by human activity.
The use of stable Pb isotope analyses in conjunction with recent (²¹⁰Pb and anthropogenic radionuclide) chronologies has become a well-established method for evaluating historical trends in depositional fluxes and sources of atmospherically deposited Pb using archival records in lake sediment or peat cores. Such studies rely upon (i) simple radioactive disequilibrium between unsupported ²¹⁰Pb and longer-lived members of the ²³⁸U decay series and (ii) well-defined values for the isotopic composition of contaminant Pb and indigenous Pb in the study area. However, areas of high natural radioactivity can present challenging environments for such studies, with potential complications arising from more complex disequilibria in the ²³⁸U decay series and the occurrence, at local or regional level, of anomalous, ill-defined stable isotope ratios due to the presence of elevated levels of radiogenic Pb.
Results are presented here for a study of a sediment core from a freshwater lake, Loch Einich, in the high natural radioactivity area of the Cairngorm Mountains of Scotland. ²³⁸U decay series disequilibria revealed recent diagenetic re-deposition of both U and ²²⁶Ra, the latter resulting in a requirement to use a modified calculation to derive a ²¹⁰Pb chronology for the core. Confidence in the chronology was provided by good agreement with the independent ²⁴¹Am chronology, but the ¹³⁷Cs distribution was affected by significant post-depositional mobility in the organic-rich sediment. The systematics of variations in ²³⁰Th, ²³²Th and stable Pb isotope ratio distributions were used to establish the indigenous Pb characteristics of the sediment. The relatively high radiogenic content of the indigenous Pb resulted in complications in source apportionment, in particular during the 20th century, with multiple natural and anthropogenic sources precluding the use of a simple binary mixing model. Consequently, ²⁰⁶Pb/²⁰⁷Pb ratios in Scottish moss samples from an archive collection were used to provide the input term for atmospheric deposition in order to establish historical trends in indigenous and anthropogenic Pb fluxes.
A test of the accuracy of the derived Pb fluxes was provided by analysis of a core from a nearby blanket peat deposit, Great Moss. Independent atmospheric and basal inputs gave a complex distribution of ²¹⁰Pb in the peat, but this did not affect calculation of a ²¹⁰Pb chronology. Once again, the ²¹⁰Pb chronology was supported by the ²⁴¹Am distribution.
Temporal trends in anthropogenic Pb deposition derived for the Loch Einich sediment core were in generally good agreement with those for the Great Moss peat core, other peat cores and some other lake sediment cores from northern Scotland, providing confidence in the use of the archive moss data to characterise atmospheric deposition. However, sustained input of Pb to Loch Einich sediment at relatively high levels in the late 20th century, after the regional decline in atmospheric Pb deposition, suggested that catchment-derived Pb is now a significant component of the depositional flux for Loch Einich.
A 40 cm peat core was studied from ombrotrophic bog in Western Europe
(Misten bog, Hautes-Fagnes, Belgium). Trace metal and metalloid content
(TM) and Pb isotopes were analysed by Q-ICP-MS and MC-ICP-MS,
respectively. We focused our attention to a selected number of TM
according to their specific enrichment (i.e. Pb, Cu, Ni, As, Sb, Cr, Co,
V, Cd and Zn). Our aims were: 1) to investigate TM mobility; 2) to
determine TM accumulation rates and 3) to link TM accumulation rates
with established histories of anthropogenic atmospheric emission.
According to 210Pb and 14C data the studied peat core section covered
the last two centuries. The general agreement in TM concentration and
flux profiles suggested that all TM (except Zn and Cd), were immobile in
the Misten peat bog. The temporal increase of TM fluxes between the
inception of the Industrial Revolution and the present vary by a factor
of 5 to 50 according to TM. The maximum fluxes of TM were found between
1991 and 1995 AD. The coal consumption and metallurgical activities were
the predominant source of pollution. The historical TM profiles in the
Misten peat profile are in agreement with other European records,
reflecting the influence of regional European pollution.
We have applied a single-bog multi-core approach to reconstruct historical Pb and Hg accumulation in an ombrotrophic bog from NW Spain, Chao de Lamoso (Xistral Mountains). Mercury was determined using a LECO-ALTEC AMA-254 analyzer, Pb with an EMMA-XRF analyzer and stable lead isotopes (four cores) by Quadrupole ICP-MS. Maximum concentrations were 74–122 μg g−1 for Pb and 142–300 ng g−1 for Hg. Higher variability was found for Hg than for Pb (2–3 times and 1.5 times, respectively). The slopes of the relationship between Hg and Pb cumulative inventories also suggested differences in relative accumulation of both elements. This substantial spatial variability indicates that, compared with Pb, a more extended sampling may be needed for an accurate estimation of Hg accumulation in mires.
Knowledge about the natural atmospheric background deposition rate of lead (Pb) prior to anthropogenic pollution is critical in the understanding of present-day pollution and for establishing realistic goals for the reduction of atmospheric Pb. We utilize stable Pb isotopes (206Pb and 207Pb) in radiocarbon-dated peat cores from three ombrotrophic bogs from south Sweden, to calculate fluxes and to survey atmospheric Pb trends prior 3500 BP (the so far known onset of large-scale anthropogenic pollution). The estimated atmospheric Pb deposition rate was between 1 and 10 μg Pb m2 yr−1 between 5900 and 3700 calendar years BP, which is 100 to 1000 times lower than present-day deposition rates. The majority of the samples older than 3500 calendar years BP had 206Pb/207Pb ratios ≤1.20, which is significantly lower than unpolluted Swedish mineral soils (206Pb/207Pb > 1.30), suggesting that even the natural atmospheric deposition of Pb was dominated by long-range transport, rather than local inputs from soil dust. Low 206Pb/207Pb ratios (1.16–1.18) of several samples indicate that this distant transport originated at least partly from early pollution sources. A possible climatic connection with the observed Pb deposition trends is suggested.
The well characterised temporal trend in the 206Pb/207Pb atom ratio of atmospheric lead deposition in Scotland during the 20th century was used to investigate the surface integrity of several cores collected by different methods from Flanders Moss ombrotrophic peat bog, central Scotland, during 1996–2001. Based on 206Pb/207Pb profile comparisons, in conjunction with identified 210Pb radionuclide inventory deficits for two of the cores, it was deduced that 25±7 yrs worth of material was missing from the more seriously affected core. After allowing for an appropriate vertical offset based on 206Pb/207Pb profile matching, the subsequent matching of profiles of titanium, lead, sulfur, arsenic, iron, phosphorus and manganese in three cores for which total concentration data were available was excellent. Without such offset correction, erroneous conclusions could have been drawn concerning the recent historical record of anthropogenic lead and arsenic deposition, the position of the redox boundary, which controls geochemical cycling and enrichment of iron, and the nutrient recycling status of manganese and phosphorus in the near-surface vegetation. Topographic, vegetative and coring (both device and operator) influences may have been responsible, thus endorsing the use of reliable, multiple core sampling and the use of lead isotope ratio profiles, supplemented by appropriate radionuclide data, in both assessing and ensuring the surface integrity of peat cores.
[1] Using two different natural archiving media from remote locations, we have reconstructed the atmospheric deposition of mercury (Hg) over the last 800-1000 years in both hemispheres. This effort was designed (1) to quantify the historical variation and distributional patterns of atmospheric Hg fluxes in the midlatitudes of North America at Nova Scotia (N.S.) and at a comparable midlatitude region in the Southern Hemisphere at New Zealand (N.S.), (2) to identify and quantify the influence of anthropogenic and natural Hg contributions to atmospheric Hg fluxes, (3) to further investigate the suitability and comparability of our two selected media (lake sediments and ombrotrophic peat) for Hg depositional reconstructions, and (4) to assess the relative importance of wet and dry deposition to the study areas. Significant findings from the study include the following: (1) The lake sediments examined appear to faithfully record the contemporary flux of Hg from the atmosphere (e.g., 1997: N.S. Lakes: approximately 8 +/- 3 mug m(-2) yr(-1); N.S. Rain: 8 mug m(-2) yr(-1)). The upper 10 cm (approximately 10 yr) of ombrotrophic peat cores from Nova Scotia were dated using a biological chronometer (Polytrichum) and were also consistent with the flux data provided by current direct sampling of precipitation. These observations place limits on the contribution of dry deposition (40 +/- 50% of wet flux). Unfortunately, the peat samples could not be dated below 10 cm. This was due to the apparent diagenetic mobility of the geochronological tracer (Pb-210). (2) There is no evidence of a significant enhancement in the atmospheric Hg flux as a result of preindustrial (<1900 c.e. (Common Era)) activities such as the extensive Au and Ag mining in the Americas. (3) A factor of 3 and 5x increase in the deposition of Hg to the lake sediment archives was observed since the advent of the industrial revolution in New Zealand and Nova Scotia respectively, suggesting a worldwide increase in the atmospheric deposition of Hg. Furthermore, this increase is synchronous with increases in the release of CO2 from combustion of fossil fuels on a global scale. The magnitude of increase since industrialization appears larger in Nova Scotia than in New Zealand. This may be due to enhanced deposition of Hg as a result of either regional emission of Hg or enhanced regional oxidation of Hg-o.
We examined subfossil Cladocera (crustacean) assemblages and ephippia in a high-resolution sediment core from a small acidified boreal lake, Lake Pieni Majaslampi, in southern Finland, with a focus on community and reproductive responses during a period of environmental disturbances. The results showed a significant community shift ∼1970-1980 AD as planktonic taxon Eubosmina, together with littoral chydorids Acroperus harpae, Alonella excisa, and Alona rustica increased and populations of Alonella nana and Alona affinis declined. In addition, a concurrent and significant change in reproductive patterns occurred, as sexual reproduction of Eubosmina, A. affinis, and A. harpae increased. It appears likely that these ecological shifts were a response to multiple environmental stressors related to severe acidification that took place in this sensitive lake and culminated during the 1980s. Acidification of Lake Pieni Majaslampi resulted in dramatic changes in the food-web structure; perches (Perca fluviatilis) were extirpated and invertebrate predation predominated from the 1980s onwards and after this Eubosmina, which is known to be a desirable prey item for perches in acidic lakes, was apparently favored in the fish-free ecosystem. Furthermore, the observed reproductive shifts were perhaps adaptive responses to either increased invertebrate predation or to increased toxicity of the environment. As the analysis of subfossil ephippia allowed us to detect behavioral shifts in the cladoceran community related to lake acidification, ephippium analysis can provide a powerful tool to integrate ecology and paleoecology, and to enhance our understanding of changes in aquatic ecosystems determined from paleolimnological studies.
Environmental background levels of Pb were measured in ponds, river waters, sediments, suspended sediments, rocks, and air particulates within the Kankakee watershed during the period of 1995 to 1999. Stable isotopic Pb distinguished airborne Pb and its incorporation into riverine wetland sediments from geogenic Pb measured in river sediments. The provenance of the naturally-occurring Pb is from carbonate bedrock and contributes comparable concentrations in riverbank sediments (25.9–30.4 mg kg−1) as Pb found in wetland sediments (18.6–24.8 mg kg−1). Estimates of anthropogenic Pb contributions from airfall into the Kankakee wetlands were found to be near 0.43–0.71 Bq cm−2 yr−1 during 1995 to 1999. While leachable Pb data suggests the uppermost layers of pond sediments were disturbed, 210Pb analyses from undisturbed sedimentation suggests Pb-bearing sediments accumulate approximately 0.46–0.51 cm yr−1 in the ponds within the riparian zones. Transboundary Pb pollution from aerosols of industrial Pb across the Great Lakes occurs, but Pb isotopy indicates that the Pb concentrations are comparable to natural concentrations of Pb in both waters and sediments within the Kankakee watershed.
The Elatia Mires of northern Greece are unique ecosystems of high conservation value. The mires are climatically marginal
and may be sensitive to changing hydroclimate, while northern Greece has experienced a significant increase in aridity since
the late twentieth century. To investigate the impact of recent climatic change on the hydrology of the mires, the palaeoecological
record was investigated from three near-surface monoliths extracted from two sites. Testate amoebae were analysed as sensitive
indicators of hydrology. Results were interpreted using transfer function models to provide quantitative reconstructions of
changing water table depth and pH. AMS radiocarbon dates and 210Pb suggest the peats were deposited within the last c. 50years, but do not allow a secure chronology to be established. Results
from all three profiles show a distinct shift towards a more xerophilic community particularly noted by increases in Euglypha species. Transfer function results infer a distinct lowering of water tables in this period. A hydrological response to recent
climate change is a tenable hypothesis to explain this change; however other possible explanations include selective test
decay, vertical zonation of living amoebae, ombrotrophication and local hydrological change. It is suggested that a peatland
response to climatic change is the most probable hypothesis, showing the sensitivity of marginal peatlands to recent climatic
change.
This study investigates the impact of accidental fires and the record of recent environmental change held within a long peat
core taken on Burbage Moor in the south Pennines (UK). The core has been subjected to mineral magnetic, heavy metal (via inductively
coupled plasma–optical emission spectroscopy) and radiometric analyses. It may be subdivided into three zones reflecting the
infilling of a basin-like depression and reveals pre-industrial conditions and the impact of recent atmospheric particulate
pollution. Peak concentrations of heavy metals are relatively high (e.g., peak Pb concentration is 1,124mg kg−1). However, the mineral magnetic and heavy metal depth profiles may have been affected by post-depositional changes. The core
has been influenced by drainage and a number of moor fires. The area was extensively burnt in 1976, though assessing the impact
of this event is problematic, due to the perturbed nature of the profile and the inability to provide a reliable chronology.
A comparative study has been made of the history of lead and other trace metals that have been deposited on wetlands. A series of sediment cores from the USA, Ireland and the Czech Republic were measured for 210Pb, Pb, other trace metals and the radionuclides 137Cs, 90Sr and 239,240Pu. The 210Pb chronology of the core profiles was established using the CRS method of Appleby and Oldfield and the minimum variance method of Tobin and Schell, i.e., the CRS-MV method. Using the minimum variance of the least-squares fit of the line representing the total core data and propagating the errors, the apparent time error ranges from 2 to 10 years. Cores were taken from Hudson River wetlands, a mountain top bog in the USA, blanket bogs in western and eastern Ireland, and bogs in a highly polluted and a "pristine" zone in the Czech Republic and provided profiles. At the most westward European station in Ireland, the Pb deposition history appears to exceed background levels at dates similar to those in eastern USA, whereas the profiles near Dublin exceed background values at approximately the same date but have maximum deposition values significantly later. Such initiation of the Pb deposition in Ireland could be due to long-range transport across the Atlantic Ocean. In the Czech Republic, the initiation of metal deposition occurs before that in Ireland and the USA, reflecting the earlier development of industrialization and release of metals.
Chemical and physical analyses of dated ombrotrophic peat cores from 8 European regions were undertaken to determine the effect of forest clearances, farming, mining and smelting on the composition of atmospheric aerosols. Elemental concentrations in peat were determined using XRF and the mean concentrations of Ti and Pb in peat as well as Pb enrichment factors (Pb EFs) were calculated for each region and for different time periods (Roman Times, Dark Ages, Middle Ages, modern times). The results show that the concentration of Ti, Pb and the calculated Pb EFs closely follow changes in land use history extending back thousands of years. Concentrations of Ti, for example, reflect changing soil dust inputs in response to forest clearing and agriculture. Lead emissions are characterized by considerable continental-scale variations: elevated concentrations and EFs during the Roman Period at most sites, very high concentrations and EFs in the Harz Mountains during the Medieval period, and elevated to high concentrations and EFs during modern times at all sites. The findings indicate that peat cores from ombrotrophic bogs are useful not only for quantifying temporal changes in metal emissions, but also for identifying spatial variations on scales ranging from regional to global.
Concentrations of Pb, Cd, As, Sb, and Se in peat from 21 ombrotrophic bogs in Norway are discussed with respect to air pollution and compared to other evidence from studies of trace element deposition in Norway. In general the data support conclusions from studies of atmospheric deposition based on moss analysis, and they also confirm specific trends previously observed for the contamination of natural surface soils with these elements. Lead, Cd, As, and Sb all are strongly enriched in the surface peat layers, indicating significant atmospheric input all over the country. In the south the concentrations in the surface peat are about 10 times higher than in the central and northern part of the country, supporting previous evidence of substantial input from source regions in other European countries. For Se there is also a component of anthropogenic input in the south, but this contribution from long range transport is superimposed on a very distinct coast - inland gradient all along the west coast, strongly suggesting atmospheric supply of Se from the marine environment.
Peat cores from ombrotrophic Scandinavian bogs were analyzed for 12 nutrient and trace elements. Nitrogen, Na, K, Mg, and P are removed from the well-drained peat of the hummocks whereas Ca, Al, Fe, Mn, Pb, and Zn are retained. The zone of water table fluctuation shows accumulations of Fe, Al, Zn, and Pb, but all other elements, except possibly Ca, are removed to some extent. Below the permanent water table all elements show real losses. The annual growth of Sphagnum carpets on hummocks contains more K, N, and probably P, than that supplied in the annual precipitation but only 11% of the Na, 28% of the Ca, and 56% of the Mg. Considering the ombrotrophic peat mass as a whole, Na is removed most rapidly, and Mg accumulates to the greatest extent. The study shows that the distribution of elements in ombrotrophic peat is closely tied in with water table location and fluctuation, that K, N, and probably P, are conserved in Sphagnum capitula, and that many elements are removed to a considerable extent before the peat becomes permanently anaerobic. /// В пробах торфа из омброморфных болот Скандинавии определяли 12 элементов питания и редких элементов. Азот, Натрий, калий, магний и фосфор удаля-лись из хорошо пренированных торфяных кочек, а кальций, ал\r=?\иний, железо, марганец и цинк оставались. В зоне колебаний уровня воды происходит ак-кумуляция железа, ал\r=?\миния, цинка и свинца, но все пругие элементы, кроме, очевидно, кальция, в какой-то степени удаляются. Ниже постоянного уровня воды наблюдается заметная потеря всех элементов. Годовой прирост покрова сфагнума на кочках содержит больше калия, азота и вероятно, фосфора, чем их суммарный запас в годовых осадках но нат-рия - лишь 11%, кальция - 2%, магния -56%. В омбротрофной массе торфа в целом натрий удаляется с наибольшей скоростью, а накапливается наиболее интенсивно. Исследования показало, что распрелеление элементов в омбротрофном торфе тесно связано с положением и колебаниями уровия воды, что кадий, азот и вероятно фосфор накапливаются в сфагнуме и что многие элементы удаляют-ся взначительном количестве до того, как торф становится постоянно ан-аэробным.
(1) Analyses of three heavy metals (lead, zinc and copper) in surface peat layers, dated peat profiles and surface vegetation samples from fifteen British sites are discussed in the context of the movement of heavy metals in the peat system, and the present-day and historical patterns of heavy metal accumulation in humified, slow-growing blanket peat. (2) The concentrations of heavy metals in the surface peat samples provide a basis for the division of the fifteen sites into two groups--`low-background' and `high-background' sites--reflecting the current urban/industrial status of the sites. Significant regressions were found of the concentrations of lead and copper in the surface peat layers on the log population of the nearest big town to each site. (3) Dating schemes for five peat profiles were produced by pollen analysis. Generalized linear dating-plots were obtained by correlating individual pollen features with documentary evidence of tree-planting and agrarian or industrial activity. Estimated rates of net peat accumulation varied from 1 cm in 5.5 years to 1 cm in 40 years. (4) Recent rates of heavy metal deposition were calculated for six sites where the rate of peat accumulation had been estimated from pollen analytical/radiocarbon dating. The deposition rates derived from the peat analyses for lead and copper were similar to those obtained by other workers from conventional deposition gauges. The rates for zinc were very much lower than the published figures, suggesting considerable losses by leaching of this metal from the peat surface. (5) Variation in the concentrations of heavy metals was examined in three dated peat profiles. The distribution of lead in a `low-background' profile apparently reflects national trends in production and utilization of lead during the last seven or eight centuries, while well-marked peaks in the lead profiles at two `high-background' sites are shown to correspond well with the documented history of the fortunes of the local lead mines and smelters. The patterns of zinc and copper were less well-defined. (6) In surface samples of present-day blanket bog vegetation consisting of Calluna vulgaris and Eriophorum vaginatum, the concentration of lead was higher in the older, more persistent or decaying plant components, whereas the concentration of zinc was higher in the younger, actively metabolizing organs. In a Sphagnum papillosum sample, the distribution of lead was fairly homogeneous in different age-segments, but the concentration of zinc was higher in the lower, older segments. It is suggested, therefore, that zinc is more mobile within plants and more susceptible to leaching. (7) Two neighbouring peat profiles were analysed for macrofossils. Apparent anomalies in the distribution of zinc were attributed to the differences in the vegetational composition of the profiles. (8) In a laboratory experiment the greater part of the lead and zinc and one-third of the copper in peat blocks was removed by leaching for 24 h with a chelating agent (EDTA). Lead and copper were virtually unaffected by leaching with sulphuric and acetic acids, whereas the zinc was substantially leached by the sulphuric but not by the acetic acid. It is concluded that leaching of lead and copper through peat is unlikely, but that zinc in surface peat is susceptible to leaching, especially in areas where the pH of rainwater is lowered by atmospheric pollution. All three metals may become available to plants by the action of chelating agents. (9) The use of blanket peat deposits as pollution monitors is evaluated.
A brief review of the use of stable lead isotope ratio measurements to identify and apportion sources of lead in human tissue is followed by examples of the use of inductively coupled plasma source mass spectrometry for such studies.
Inductively coupled plasma source mass spectrometry (ICP-MS) has only recently been used for measurements of coupled ratios in body tissues and fluids and in environmental sources of lead. Generally, the inaccuracy of these measurements is about −0.2% and the imprecision less than 0.5%. This analytical performance is sufficient to detect the much larger changes in206Pb:207Pb ratios of −2% or higher, seen in environmental lead exposure and in childhood lead poisoning.
Measurements of lead isotope ratios by ICP-MS have been used to identify specific sources of childhood lead poisoning and to indicate the relative importance of environmental sources, such as drinking water and lead from petrol. Populations in the United Kingdom with low lead uptake usually have206:Pb207Pb ratios in body tissues within the range 1.13 ± 0.01. Significant deviations from this range have been seen in response to increased uptake from lead in: drinking water in parts of Scotland (source ratio ∼1.18 and petrol lead in inner London (source ratio ∼1.07). The dominant source for some Scottish subjects with high concentrations of lead in blood or in teeth was water, which contributed approximately 60% to body lead. Petrol lead was shown to be a significant contributor (30–40%) to the body lead of inner London children.
Knowledge of historical trends in heavy metal deposition can aid the study and impact prediction of contemporary pollution. For this purpose, analysis of ombrotrophic peat cores has proved a valuable complement to other sedimentary analyses. However, doubts still remain concerning the mobility of heavy metals in peat. The debate cannot be resolved until the behaviour of these elements in peat is better understood.Peat cores were collected from hollows and hummocks on Ringinglow Bog in the southern Pennines. The cores were sliced into contiguous 1-cm slices. Samples were analysed for total concentrations of major elements (Al, Ca, K, Mg, Na) and trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) using atomic absorption spectrophotometry. Multivariate statistical analysis was conducted on the data.Preliminary results indicate relatively high concentrations of Cd, Cu, Fe, Pb and Zn reflecting the influence of industrial activities in Sheffield and Manchester. As aluminium, cadmium, copper, lead and zinc exhibit similar profiles they may be suitable surrogates for monitoring historical pollution. However, other elements (e.g. Fe, K, Mn, Na) are clearly influenced by bog hydrology or plant translocation and would be inappropriate monitors.
Lead emitted into the environment, primarily from the combustion of leaded petrol and industrial activities, retains the isotopic signature of the ore(s) from which it is derived. Leaded petrol, atmospheric particulates and street dust sampled in central Edinburgh between February 1989 and December 1991 had mean(206)Pb/(207)Pb ratios of 1.082 ± 0.024, 1.092 ± 0.011 and 1.109 ± 0.016 respectively. These isotope ratios were found to be depleted in(206)Pb compared with a mean of 1.160 ± 0.012 for tap water in contact with lead pipes and %typical ratios of 1.17-1.19 for British lead ore deposits and coal. Paint, with an observed wide range of 20 Pb(207) Pb ratios (1.083-1.183), appears to have significantly influenced house dust and some street dust(206)Pb(207) values. Such overlaps and influences may hinder the quantitative apportionment, via isotope data, of source and route in general population surveys of human exposure to lead.
Peat cores collected from three sites in the Jura region of Switzerland, La Tourbière des Genevez, Etang de la Gruère and Praz Rodet, were analysed for the fallout radionuclides 210Pb, 137Cs, 134Cs and 241Am, and the minerogenic radionuclide 226Ra. Unsupported 210Pb inventories of the cores were all in the range 3900-4784 Bq m-2 and are consistent with their having largely retained the atmospheric flux (ca. 130 Bq m-2y-1). In contrast, comparisons with earlier (1986) cores from these sites suggest that there have been significant losses of fallout 137Cs. Samples from all three sites had low but significant levels of supported 210Pb (226Ra) activity, the origin of which is presumably wind blown soil dust. 210Pb dates calculated using the CRS model were independently validated by 241Am and pollen stratigraphy. The core from La Tourbière des Genevez had a fairly conventional 210Pb activity versus depth profile indicating more or less constant net accumulation during the past 100 years. At the other two sites however the 210Pb profiles contained significant deviations from simple exponential decline that may record episodes in the bog during which there were major variations in the net dry mass accumulation rate. These episodes are dated 1930-50 (Etang de la Gruère) and 1960-80 (Praz Rodet). Although the depths at which total 210Pb reaches equilibrium with the supporting 226Ra range widely, from ca.37 cm in Etang de la Gruére to ca.60 cm in Praz Rodet, mean net dry mass accumulation rates for the past 100 years are remarkably similar, the values for all three sites are in the range 0.023-0.027 g cm-2y-1.
Stable lead isotope data can yield information on the geochemical origins of lead and on its relative contributions from sources such as coal burning, mining, smelting, and car-exhaust emissions. This extremely detailed 206Pb/207Pb profile for dated bottom sediments in Loch Lomond, Scotland, shows the trends clearly related to the varying nature and extent of anthropogenic lead inputs after 1630. In particular, a significant decline in the 206Pb/207Pb ratio of excess lead during 1929−1991 is attributable to the introduction and use of (206Pb-depleted) leaded petrol since the 1920s. This accounts, however, for just 24−53% of the excess lead deposited since 1929 and ≤19% of the total excess lead inventory. Deposition of lead from industrial (and domestic) activities has predominated overall and, on an annual basis, until at least the mid-1950s.
The dominant inorganic anions and cations, and dissolved organic carbon have been measured in the pore waters expressed from peat cores taken from two Sphagnum bogs in the Jura Mountains of Switzerland: Étang de la Gruyère (EGr) consists of > 6 m of peat representing more than 12,000 yr of peat formation while at La Tourbière de Genevez (TGe) ∼ 1.5 m of peat have accumulated over the past 5,000 yr.The pore-water analyses of the core taken at EGr show that the first 100 cm of the core are influenced only by atmospheric inputs. The pH of the pore waters is constant (3.9 ± 0.1) with depth. Relative to the average composition of rainwater in this area, Na+ is enriched throughout the pore-water profile, K+ is neither enriched nor depleted, Mg2+ is significantly depleted in the deeper pore waters and Ca2+ strongly depleted throughout the profile. The dominant process affecting the cations in these waters is ion exchange, with the peats behaving like a simple cation exchanger with ion preference decreasing in the order Ca2+ > Mg2+ > H+ > K+ ⪢ Na+.In contrast, at TGe the pH increases from pH ∼4 at the surface to pH 5 at 80 cm. The Cl− and K+ concentrations are up to 10 times higher than rainwater values because of mixing of the bog pore water with nearby groundwaters. The Mg2+ and Ca2+ concentrations increase with depth to concentrations up to 10 times higher than rainwater values, mainly because of the increasing importance of mineral dissolution within the profile.
Peatlands long have been considered to preserve the record of atmospheric deposition of anthropogenic contaminants such as Pb. In the past two decades, ²¹°Pb has been widely used to data recent strata of peat and to calculate accumulation rates. The assumption that Pb and ²¹°Pb are immobile and not subject to diagenesis in peat has been questioned but not rigorously tested. The authors attempted to determine if Pb is mobile in peatlands and if Pb profiles are altered by diagenic processes by constructing a mass balance for Pb about a small peatland, by comparing inventories, concentrations, and accumulation rates of Pb and ²¹°Pb in peatlands across northeastern North America, and by examining the relationship between concentrations of Pb in bog waters and peat in numerous sites. The results clearly demonstrate that Pb and ²¹°Pb are mobilized by the organic-rich waters of peatlands. Profiles of Pb and ²¹°Pb at depths below the water table do not preserve the record of atmospheric deposition, and inventories of Pb and ²¹°Pb are depleted in peatland hollows. Concentrations of Pb in bog waters are regulated by the concentration of Pb in the peat and the concentration of dissolved organic carbon. The mass balance for one bog indicated that over the specific three-year period of study more than 30% of inputs of Pb were not retained within the peat. As a result of this mobility, dates based on ²¹°Pb can be biased and inaccurate by as much as 30 years. Dates based on ²¹°Pb should be verified by other techniques, especially when the inventory of ²¹°Pb is less than that expected from local rates of deposition.
Rainwater-dependent peatlands retain a record of atmospheric deposition. Unlike lake sediments they record both particulate and soluble influxes, and they are not complicated by processes in the catchment or by mineral particle influx from the catchment. They do, however, have their own difficulties some of which are considered here. The timescale for cores from a suitable peatland in Southwest Scotland was established by a combination of 14C 'wiggle matching', pollen events, 210Pb dating and the 241Am event. Retention of deposited elements varied greatly from less than 1% (Na) to complete retention (N). Hummocks retained more than hollows: the quotient was 1.2-1.8 for elements such as A1 (associated with particles) and up to 5-10 for Mn, Fe and Zn. The vertical scale in profiles should be as cumulative dry mass or, better, as dry mass after reconstructing losses by decay. These give vertical scales that are approximately linear with age. Elements differ greatly in the shape of their concentration profile as a result of varying influx and as a result of relocation in the peat.
Lead isotope analysis, using high-precision thermal ionization mass spectrometry, of herbage samples collected annually since the 1860s has revealed a steady reduction in the 206Pb/207Pb ratio from about 1.170 in 1880 to about 1.098 in the period 1980−1985. The value of 1.170 is very close to that (1.171) found previously in Scottish lake sediments for anthropogenic lead deposited prior to the introduction of leaded petrol. Analysis of the data suggests two dominant components in the lead deposited from the atmosphere over the period of 130 years studied. Prior to the turn of the century, lead of industrial or coal origin had a typical 206Pb/207Pb ratio of 1.170 following which a nonradiogenic component with a lower 206Pb/207Pb ratio (1.09 or less) made an increasingly more significant contribution. The decline in ratio commenced well before the introduction of tetraethyllead in petrol, indicating either changes in the source of lead-containing ores or coal or changes in the relative contributions of different sources. The generally smooth change in the isotopic character of the deposited lead suggests a slow change in the relative proportions of the dominant sources. The trend appears however to have been reversed following the declining use of lead additives in petrol. The deposition, in particular that with the low ratios associated in Britain with petrol additives, has had relatively little effect on the bulk soil. The 206Pb/207Pb ratio in bulk soil samples (to 23 cm) from the site, which had been undisturbed for at least 200 years, decreased from 1.187 in 1876 to 1.180 in 1984 but at no time reached the ratio found in the deposition on herbage. Analysis of sections taken down a soil core showed a steady increase in the 206Pb/207Pb ratio from 1.159 at the surface to 1.181 at 15 cm depth. Recent deposition with low 206Pb/207Pb ratios had a significant but not dominant contribution to the lead in the surface soil, which also contained a substantial proportion of older deposition with higher ratios. The ratios in the sections did not reach however that measured in bulk soil samples collected in 1876, indicating that lower ratio lead had reached a depth of at least 16 cm in the soil. Up to 50% or more of the lead at a depth of 16 cm could be anthropogenic in origin.
We compare lead concentration and stable lead isotope analyses from three peat bog and three lake sediment records in Sweden. Radiocarbon dated stratigraphies give evidence that trends in the concentration of Pb in the peat and sediment cores are very similar, and follow the general outline of historical global Pb production over several thousand years. Due to the large difference in the 206Pb/207Pb ratio between Sweden, about 1.5, and continental Europe (excluding Fennoscandia), 1.2, it is possible to distinguish external sources of Pb to Sweden. In the lake sediments, profiles of 206Pb/207Pb ratio mirror the Pb concentration until 1000 AD; increasing concentration is accompanied by decreasing ratios. After 1000 AD the ratio varies little at about 1.2 in sediments, because of the near total dominance of pollutant Pb. There is a further decline in the Pb ratio to about 1.14 in this century as a result of the addition of alkyl-Pb in petrol. The Pb concentration profiles in the peat match the lakes, but the isotope profiles do not. During the fen-to-bog transition there is a rapid decline in the 206Pb/207Pb ratio from >1.3 to about 1.2, and the ratio continues to decline to the present. We hypothesise that this is because externally-derived Pb from long-range transport of soil dust and atmospheric pollution has always been more important in the ombrotrophic peat than in lakes, which have a greater influx of catchment-derived Pb.
The concentrations, inventories, fluxes and isotopic composition of Pb in four 210Pb-dated cores from the raised Flanders Moss peat bog are compared with corresponding data for two sediment cores from Loch Lomond, also in central Scotland. Although the inventories and fluxes of Pb revealed by the peat record for the past few hundred years are generally lower, the isotopic records are in good agreement, confirming a prevailing 206Pb/207Pb ratio of 1.17 for anthropogenic ("industrial") Pb in the atmosphere prior to the introduction of leaded petrol in the 1920s. The 206Pb-depleted nature of the latter has resulted in a decline of about -0.04 to -0.05 in the 206Pb/207Pb ratio of deposited Pb for both peat and lake sediments. Despite the time-resolution limitations of the peat record, car exhaust emissions of Pb appear to have contributed 35-50% over the past 20 years, 15-30% over the past 75 years, but no more than 27% overall to the peat Pb burden. The finding that 67-85% of anthropogenic Pb in the peat was apparently deposited post-1900 compared with 51% for the Loch Lomond sediments could be due to geographical variations in atmospheric deposition of Pb, other additional inputs to the sediments, or perhaps to some post-depositional loss of Pb from peat, although the integrity of the 206Pb/207Pb record does argue against any significant vertical mobility of Pb in peat.
The bog at Etang de la Grure (Jura Mountains, Switzerland) consists of 420 cm of Sphagnum-dominated bog peat overlying 230 cm of Carex-dominated fen peat. One hundred cm below the bog surface, there is a pronounced peak in lead (Pb) concentration (approx. 10 g/g) which has been dated at 2110 30 BP and can be attributed to Roman Pb mining and smelting.Lead concentrations in peats from deeper, much older layers were measured using ICP-MS and found to be low and relatively constant (0.28 0.04 g/g, n = 17) from 405 cm to 235 cm which corresponds to the period from approx. 8,000 and 5,500 years before present (BP). In this same interval, scandium (Sc) concentrations (measured using INAA) were 0.07 0.02 g/g, yielding an average Pb/Sc ratio of 4.1 1.2. These values are assumed to represent the true "background" Pb and Sc concentrations and Pb/Sc ratios of pre-anthropogenic aerosols. At 205 cm the Pb concentrations began to increase by 2 to 3 times, but these are proportional to the increases in aluminum (Al), titanium (Ti), silicon (Si), and Sc, and reflect an increase in Pb deposition supplied by silicate-derived soil dust. This depth, dated at 5,230 BP, coincides with the development of agriculture and indicates the impact of soil cultivation on metal fluxes to the air. At 115 cm, however, the Pb concentrations increase out of proportion with Sc; this point was dated at 3,000 BP and reflects the beginning of Pb contamination by mining and metallurgy in Europe and the Middle East.There are two pronounced peaks in Pb concentrations centered at 435 cm and 555 cm, corresponding with local maxima in ash and ash-forming major elements at the same depths. These samples have been dated at 8,230 BP and 10,590 BP, respectively, indicating the Vasset/Killian volcanic events (Massif Central, France) and Younger-Dryas cold phase as the most likely explanations.
In the lower part of a raised bog profile from Langegger Filz, southern Bavaria, the Pb and Cd concentrations were comparatively low while considerably higher concentrations of both elements were observed in the upper section of the profile. The peat layers with the highest concentrations of Pb and Cd were found to date from the Iron Age, the Roman Age, and the Middle Ages. The Fagus pollen curve reflects the beginning of a beech decline exactly in those peat layers in which the start of the Pb increase is visible. Therefore it appears that metal smelting caused a local release of heavy metals which were subsequently deposited in the raised bog. Metals could only be smelted when wood was cut and burned, and beech charcoal was preferred as it produces relatively high temperatures. The good agreement between the Pb concentration profile and the pollen analyses suggests that the bog provides an accurate record of atmospheric Pb deposition.
Peat cores were taken from two contrasting Sphagnum bogs in the Jura Mountains of Switzerland. At Etang de la Gruyere (EGr), 6.5 m of peat has accumulated during the past 10,000 years. In the first 100 cm of this profile there are several distinct peaks in ash content, but the values are well within the range for typical ombrotrophic Sphagnum bogs. There is also considerable variation in the concentrations of major and trace lithogenic metals (Al, Ti, Sc, Ca, Mg, Rb, and Sr), but most of this is simply a reflection of the natural variations in the amount of mineral matter in the peats. The Ca/Mg molar ratios in the peats at EGr are comparable to or lower than the average rainwater composition in this area, showing that this section of the peat core is ombrotrophic (i.e. rainwater-fed). In other words, the inorganic constituents in the surface peats at EGr were supplied exclusively by atmospheric deposition. This peat core, therefore, is suitable for studying the historical record of atmospheric metal deposition. Arsenic, Cu, Pb, Sb, and Zn are all more abundant in surface and near surface peat layers compared to deeper parts of the profile. Enrichment factors (EFs) for the profile were calculated conservatively by normalizing the metal/Sc ratios of individual peat samples to the average of the five lowest metal/Sc ratios in this part of the core (69–84 cm); these are tentatively assumed to represent pre-Industrial background values. The maximum EFs are approximately 5 times for Cu, 15 times for As, and 30 to 50 times for Pb, Sb, and Zn.
At La Tourbière des Genevez (TGe), 1.5 m of peat represents 4,800 years of peat formation. At this site, the ash contents are higher and increase progressively with depth to values which are characteristic of minerotrophic fen peats. The concentration profiles of Al, Ti, Sc, Ca, Mg, Rb, Sr show the same general trend. The Ca/Mg molar ratios of these peats are generally twice the rainwater average, showing that this bog is essentially minerotrophic (ie groundwater-fed). Thus, the inorganic cccstituents in these peats were provided by both atmospheric and hydrospheric processes. Despite this, the Cu, Pb, Sb, and Zn concentrations are generally very similar to those at EGr, especially in the uppermost part of the profile, indicating that recent atmospheric inputs also dominate the supply of these metals to this bog. However, the minimum Pb and Sb concentrations in this profile are approximately five times higher than the corresponding values at EGr. The minerotrophic profile at TGT, therefore, could not by itself be used to calculate rates of atmospheric Pb and Sb deposition because it is impossible to distinguish between atmospheric and hydrospheric metal inputs.
At TGe, As concentrations increase continuously with depth, reaching concentrations in the deeper, older peats which are more than 50 times higher than the ‘background’ As values at EGr. At this site the natural supply of As by mineral soil water completely masks the recent, elevated inputs contributed by atmospheric deposition. Thus, the peat core from TGe is also unsuitable for studying atmospheric As deposition.
Stratigraphical (temporal) and physicochemical investigations of different European peat bogs confirm interrelations between increased ash and element concentrations on the one hand and human settlement (found by means of pollen analysis) on the other hand. Phases of enhanced anthropogenic activities (farming, forest clearing, forestry etc.), which can be derived from the corresponding pollen diagrams and by radiocarbon dating, agree well with the increase in soilborne elements (soil dust Pb, Si, Ti) in the peat profiles. The Pb concentrations of the investigated peat layers have been increasing since Roman Times. Changes in the Pb/Ti ratio help to discriminate between soil dust Pb and Pb from ore mining and smelting. Moreover, this approach reveals measurable Pb pollution extending as far back as the Bronze Age (approx. 2nd Millenium B.C.). Some peat bogs show increased Cu concentrations as far back as the Bronze Age.
A core consisting of minerogenic peat and organic-rich mineral sediments was collected at an altitude of 4275 m in the Ovejuyo valley, 100 km NE of La Paz in Bolivia. Age dating with 210Pb showed that the core represents approximately three centuries of sediment accumulation. None of the peats are ombrotrophic. Despite this, the Cd/Al, Cu/Al, Zn/Al, and Pb/Al ratios are all significantly higher in the surface layers, particularly in the top 6 cm: natural, abiological geochemical processes, therefore, cannot account for these elevated heavy metal/Al ratios. There are two possible explanations for the metal enrichments, relative to Al, in the surface layers: bioaccumulation by living plants, and anthropogenic atmospheric metal deposition. While the living plant layer may be responsible for the Cd, Cu, and Zn enrichments, this is an unlikely explanation for the Pb profile. In contrast to the other metals, the concentration of Pb in the first sample (dating from 1985-1994) is less than that of the second sample (dating from 1970-1985). The Pb/Al profile is consistent with the well documented, rapid increase in atmospheric Pb emissions during the present century (which accelerated following the introduction of leaded gasoline), and the decline in Pb pollution during the past 20 years (as a result of the introduction of unleaded gasoline). Thus, the Ovejuyo Valley mire has provided one of the first records of atmospheric Pb pollution in South America.
One metre cores were taken from three peat bogs in the Jura Mountains of Switzerland: Etang de la Gruère (EGr), La Tourbière des Genevez (TGe), and Praz Rodet (PRd). Dried peat samples were analyzed for lead (Pb) using the EMMA XRF and scandium (Sc) using INAA. Enrichment factors (EF) were calculated by normalizing to the background Pb/Sc ratio at EGr. Age dates were obtained using 210Pb (CRS Model) and confirmed using pollen chronostratigraphic markers in replicate cores. The isotopic composition of Pb in selected peat samples from EGr and TGe was determined using TIMS.
Two pronounced peaks in Pb EF occur in the uppermost sections of all three bogs: the upper one corresponds to the late 1960's to late 1970's and the lower one to approximately 1900 to 1920. At EGr, sample 2f5 (11 cm, 86 µg/g Pb, EF = 91, and dated at A.D. 1967 ± 2) has an isotopic composition similar to that of leaded gasoline used in Berne in the 1970's. For comparison, the older peak at EGr (sample 2fl 1 at 29 cm, 84 µg/g Pb, EF = 79 and dated at A.D. 1905 ± 6) is significantly different. In contrast to these two samples, the isotopic composition of sample 2fl 5 (41 cm, 30 µg/g Pb, EF = 13 and pre-dating ca. A.D. 1800) approaches the present day "average terrestrial lead" and is likely to be predominately lithogenic. Therefore, the isotopic data show that the Pb introduced to the bog from leaded gasoline has not penetrated to this depth in the profile. A simple mass balance using the measured Pb concentrations and the isotopic compositions shows that vertical migration of gasoline Pb cannot explain the deeper, older peak in Pb EF. A more likely explanation is that the older peak reflects the rates of atmospheric Pb deposition during the first two decades of the 20th century. Taken together, the Pb concentrations, age dates, and isotopic data suggest that these peat profiles have preserved the record of changing rates of atmospheric Pb deposition. In addition, the results indicate that the isotopic composition of Pb deposited on the surface of the bogs gradually shifted away from lithogenic ratios as long ago as the middle of the 19th century, a change which clearly pre-dates the introduction of leaded gasoline.
The Northwestern Iberian Peninsula is a mid-latitude oceanic region with areas where different types of bogs are frequent or abundant. The ombrotrophic nature of some bogs make them suitable for the study of accumulation patterns of heavy metals. One of these bogs, Penido Vello, was sampled to a depth of 2.5 m and analyzed in detail for its physico-chemical properties and Pb, Zn and Cd concentrations. Ash and organic carbon content, Ca/Mg molar ratios and a number of other characteristics support an ombrotrophic interpretation of the core. Concentrations of Pb, Zn and Cd were measured, showing important variations in the core. While Zn and Cd are concentrated mainly in the upper sections of the core with minor changes with depth, the Pb profile shows significant peaks in the deeper layers suggesting pre-industrial atmospheric pollution. Enrichment factors (EFs) calculated by normalising to Al correlate well with those calculated by normalising to Ti. Maximum EFs are 33, 56 and 52 for Pb, Zn and Cd respectively. While for Pb these values are comparable to those obtained by other authors, maximum Zn EFs are greater than those mentioned in the literature and may be attributed to the emissions of a nearby coal-burning power plant. At least for Pb the accumulation pattern suggests that atmospheric pollution can be dated back some 2800 years, and that pollution increased steadily since the Iron Age to reach considerably elevated levels, up to 5 times the background, during the Roman Empire. Changes in Pb emissions through time are in good accord with the prehistorical and historical record of the Iberian Peninsula.
A peat core from a Swiss bog reveals significant enrichments of As, Sb and Pb extending back to Roman times, indicating that the anthropogenic fluxes of these metals have exceeded the natural fluxes for more than 2000 years. The isotopic composition of Pb provides no evidence of vertical downward Pb migration, suggesting that the bog has faithfully preserved the historical record of atmospheric Pb deposition. Age dating using210Pb (verified independently using pollen markers) provides the chronology of changing metal concentrations during the past 150 years. Present day enrichment factors (relative to the metal/Sc ratios of typical crustal rocks) are of the order of 20 times (As), 70 (Sb), and 130 (Pb). Given the potential toxicity of As and Sb, these new findings suggest that the environmental significance of these, and perhaps other less common trace elements, deserve more attention.
Samples of mosses, peats, lake sediments and clays were collected from 35 Canadian peatlands and analyzed for Cr, Cu, Fe, Mn, Ni, Pb, U, V and Zn. The average composition of the analyzed peats is significantly depleted in Fe and Mn, and enriched in Cu, U, Zn and Pb compared to typical crustal abundance. In contrast, Ni, V and Cr are neither significantly enriched nor depleted, relative to typical crustal abundance.The compositions of the peats vary widely depending on their botanical composition and degree of decomposition, the amount of mineral matter present and depth in the peatland. To summarize the voluminous trace metal chemistry data, a composite Sphagnum bog profile was constructed for each metal from the individual profiles using the peat stratigraphy typical of Sphagnum bogs in eastern Canada. To do this the trace metal concentrations of samples of the same botanical composition and similar degree of decomposition were averaged. After taking into account the differences in mineral matter contents of the sediments, enrichments and depletions through the composite bog profile have been calculated for each stratigraphic layer relative to the average composition of the underlying mineral sediments (clays). These calculations emphasize the dynamic behaviour of Cu, U, Zn and Pb and the conservative behaviour of Ni, V and Cr, through the composite peat profile: Cu, Zn and Pb are enriched in ombrotrophic surface peat layers because of significant anthropogenic atmospheric inputs; Cu and U are enriched in minerotrophic basal peat layers because of natural geochemical processes: Ni, V and Cr are neither significantly enriched nor depleted.We present a summary of the pore water chemistry (pH, SO42−, CH4) of a representative Sphagnum bog which shows that these sediments typically range from being acidic (pH approximately 4) and “oxidizing” at the surface (above the water table) to neutral (pH approximately 7) and “strongly reducing” in the subsurface layers. Predominance area diagrams (log PO2 − pH) based upon equilibrium chemical thermodynamics were constructed and are presented for Cr, Cu, Fe, Mn, Pb, U and Zn. Using the predominance area diagrams, the behaviour of the dynamic metals in peatland environments is explained in terms of the influence of pH and redox potential on the relative stabilities of solid and aqueous species.
Complete porewater profiles from two peat bogs in the Jura Mountains were analysed for major and trace inorganic anions and cations. At La Tourbière des Genevez (TGe) and Etang de la Gruère (EGr), peat formation began approximately 5,000 and 10,000 years bp, respectively. The maximum depths of peat accumulation are 140 cm (TGe) and 650 cm (EGr); previous geochemical studies showed that the ombrogenic sections of the bogs extend to depths of approximately 20 cm (TGe) and 250 cm (EGr). Water samples were obtained using in situ diffusion equilibrium samplers (peepers), which allow filtered (0.2 μm) porewaters to be obtained while preventing degassing and oxidation. These samplers were found to be well suited to bog porewaters and allowed volatile (dissolved CO2, acetate) and redox-sensitive species (HS⁻, Fe²⁺) to be quantified without further sample preparation or treatment. Aqueous species concentrations were determined immediately afterwards using ion chromatography with either conductivity (acetate, HCO3⁻, Cl⁻, Br⁻, NO3⁻, HPO4²⁻, SO4²⁻, Na⁺, NH4⁺, K⁺, Mg²⁺, Ca²⁺), amperometry (HS⁻), or absorbance detection (Fe(III) and Fe(II)). The comprehensive analyses of anions and cations allowed humic substances to be calculated by the difference in electrical charge balance (i.e., the anion deficit).
The reconstruction of historical trends in atmospheric deposition of contaminant metals by use of their concentration profiles in accumulating, ombrotrophic peat deposits, in conjunction with radionuclide-derived chronologies, is subject to uncertainty because of potential post-depositional mobility both of the radionuclides and of the contaminant metals. Results are presented here for a study of the distribution of 210Pb, Pb, stable Pb isotopes and radiocaesium in the unsaturated, surface zone of ombrotrophic peat deposits in three contrasting locations in Scotland. 210Pb chronologies are derived and the implied historical variations in atmospheric depositional fluxes and atom ratios of contaminant Pb are considered, along with total inventories, relative to known historical trends in input and proximity to heavily populated, industrial areas. Similarly, radiocaesium concentration profiles, activity ratios and inventories are considered in the context of the 210Pb chronologies and known inputs. It is concluded that the historical trends in the depositional flux and stable Pb atom ratio of contaminant Pb derived on the basis of the 210Pb chronologies are in good agreement with known temporal variations in these parameters, consistent with post-depositional immobility of Pb under the conditions investigated here. The study confirms that the high degree of mobility of radiocaesium in organic soils renders it of little value in providing chronological information, but suggests that the presence of small amounts of mineral matter may restrict this mobility.
An ombrotrophic peat core from west-central Scotland was subjected to multi-element analysis and 210Pb dating in order to estimate historical trends in atmospheric deposition of contaminants. The inferred depositional flux of ash (total inorganic material) exhibited small, transient increases from as early as the mid 18th century, followed by a larger increase from the mid 19th century to a pronounced maximum approx. 1960. A significant decrease was observed from the peak ash deposition of 29.2 g m−2 year−1 to the contemporary level of 11 g m−2 year−1, although this is still an order of magnitude greater than the pre-industrial value of 1 g m−2 year−1. Depositional fluxes of a wide range of elements (scandium, copper, arsenic, antimony, samarium, cobalt, bromine, lanthanum and lead) also exhibited major increases from the mid 19th century and peak values in the mid 20th century (approx. 1940–1950). Aluminium, cerium and bromine also showed evidence of transiently increased deposition as early as the mid 18th century. Normalisation of the concentrations of individual elements to that of aluminium confirmed that the peak depositional fluxes in the mid 20th century were not due to increased re-deposition of soil minerals from the atmosphere, but were attributable to other sources of contamination including heavy industry, coal burning and vehicle exhaust emission. Nevertheless, re-deposited soil minerals were estimated to constitute an important fraction of the ash, with peak input at the start of the 20th century and subsequent deposition at a relatively constant level, about half that of the maximum flux. Excellent agreement was observed between the inferred trends in contaminant deposition and the known history of industrial development of the area.
Two major periods of increase in atmospheric lead concentrations have been recognized in the Northern Hemisphere-the first resulting from the rapid growth of industry during the eighteenth and nineteenth centuries, the second from the great expansion of motor vehicle traffic since the end of the Second World War1,2. There is clear evidence of lead pollution caused by motor vehicles close to busy roads2-4, and the three-fold increase in lead concentrations in snow from the Greenland ice-cap during the past 20 yr has also been correlated with the emission of lead aerosols from car exhausts1. In Britain many minerals, including lead, have been exploited over a long period of time, but some, including lead, have declined in importance in the past 100 yr after peak extraction levels in the eighteenth and nineteenth centuries. Thus it is probable that in certain areas of Britain heavy metal pollution has been worse in the past than it is now. This communication examines the historical trends in lead pollution in Britain by use of nineteenth century and present-day moss specimens, and by peat profiles-methods used also by other workers to demonstrate historical trends in heavy metal pollution in Scandinavia2,5.
Ash and metal concentrations in peat bogs as indicators of anthropogenic activity Ombrotrophic peat as a medium for histori-cal monitoring of heavy metal pollution
- Gorres M Frenzel
- B355᎐365 Jm Jones
- Hao
Gorres M, Frenzel B. Ash and metal concentrations in peat bogs as indicators of anthropogenic activity. Water Air Soil Pollut 1997;100:355᎐365. Jones JM, Hao J. Ombrotrophic peat as a medium for histori-cal monitoring of heavy metal pollution. Environ Geochem Health 1993;15:67᎐74.
Natural and anthropogenic enrichments of arsenic through three Canadian ombrotrophic sphagnum bog profiles
- W Shotyk
Lead and 206Pb/207Pb profiles in 210Pb dated peat cores from Scotland
- C L Sugden
- J G Farmer
- A B Mackenzie
The measurement of the complexation of heavy metals and radionuclides with natural humic substances
- E M Logan
The midland valley of Scotland
- M Macgregor
- A G Macgregor