Trace elements in the culturally significant plant Sarracenia purpurea in proximity to dust sources in the oil sands region of Alberta, Canada.

Accessible populations of plants are critical to the meaningful exercise of Aboriginal and treaty rights in Canada. In the oil sands region of Alberta, populations of culturally significant plant species overlap with extensive oil and gas development. This has led to a host of questions and concerns related to plant health and integrity from both Indigenous communities and western scientists. Here, we assessed trace element concentrations in the northern pitcher-plant (tsala' t'ile; Sarracenia purpurea L.) with a focus on elements associated with fugitive dust and bitumen. Plant leaves were collected using clean methods and washed prior to analyses in an ultra-clean, metal-free laboratory. Pitcher-plant was an excellent model for assessing the impacts of industrial development on a culturally important, vulnerable species. Although concentrations of trace elements in pitcher-plant were low and not indicative of a toxicological concern, we saw clear dust signatures in plant tissues related to road and surface mine proximity. Elements associated with fugitive dust and bitumen extraction declined exponentially with increasing distance from a surface mine, a well-established regional pattern. However, our analyses also captured localized spikes in trace element concentrations within 300 m of unpaved roads. These local patterns are more poorly quantified at the regional scale but are indicative of the burden to Indigenous harvesters wishing to access plant populations that are not impacted by dust. Further work to directly quantify dust loads on culturally significant plants will help to define the amount of harvesting area lost to Indigenous communities due to dust impacts.

Application of asymmetric flow field-flow fractionation to the study of aquatic systems: Coupled methods, challenges, and future needs.

Aquatic ecosystems are facing multiple direct and indirect stressors from anthropogenic activities. Aquatic colloids, including natural and manufactured nanoparticles, have received global concern owing to their ability to transport metals, nutrients and pollutants, and their potential to pose ecological risks for wildlife and human health. Asymmetric flow-field flow fractionation (AF4) has become one of the most promising and powerful approaches to characterize colloidal particles over the last ten years. This review overviews the advances and applications of AF4 for the study of aquatic systems over the last decade. The analytical challenge of AF4 and known deviation from theoretical assumptions are also critically discussed, such as sample losses, membrane-analyte interactions, and overloading. Future needs for methodological advances are addressed.

Comment on: "A novel approach to peatlands as archives of total cumulative spatial pollution loads from atmospheric deposition of airborne elements complementary to EMEP data: Priority pollutants (Pb, Cd, Hg)" by Ewa Miszczak, Sebastian Stefaniak, Adam Michczynski, Eiliv Steinnes and Irena Twardowska.

A recent paper by Miszczak et al. (2020) examines metal contamination of mires in Poland and Norway. The authors conclude that lead (Pb) records in ombrotrophic peatlands cannot be used to reconstruct the chronological history of anthropogenic activities due to post-depositional mobility of the metal. We contest this general conclusion which stands in contrast with a significant body of literature demonstrating that Pb is largely immobile in the vast majority of ombrotrophic peatlands. Our aim is to reaffirm the crucial contribution that peat records have made to our knowledge of atmospheric Pb contamination. In addition, we reiterate the necessity of following established protocols to produce reliable records of anthropogenic Pb contamination in environmental archives.

Measuring the distribution of trace elements amongst dissolved colloidal species as a fingerprint for the contribution of tributaries to large boreal rivers.

Organic and inorganic colloids play important roles governing the speciation, transport, and bioaccessibility of trace elements in aquatic systems. These carriers are especially important in the boreal zone, where rivers that contain high concentrations of iron and organic matter are prevalent. The distribution of trace elements amongst different colloidal species (or "speciation profile") can therefore be useful as a fingerprint to detect different trace element sources and for tracking colloid transformations, with implications for bioaccessibility. Asymmetrical flow field-flow fractionation coupled to an inductively coupled plasma mass spectrometer was applied to detect the source of trace elements based on their speciation profile along a 125-km stretch of a large river in the Canadian boreal forest. Both the concentration and proportion of bound trace elements were increased by tributary inputs: bound As, Co, Fe, Mn, Pb, U, and Zn increased monotonically from upstream to downstream, increasingly resembling the speciation profile of tributaries. Principal component (PC) analysis also revealed tributary contributions of bound Cu, Ni, Th, V, and Y reflecting their higher concentrations in tributaries, and PC scores also increased monotonically from upstream-downstream. Monotonically decreasing concentrations of mainly ionic and small (i.e.

Isotopic evolution of atmospheric Pb from metallurgical processing in Flin Flon, Manitoba: Retrospective analysis using peat cores from bogs.

Atmospheric Pb deposition was reconstructed using peat cores from bogs in the vicinity of Flin Flon, Manitoba, Canada, home to a zinc refinery and copper smelter. The Sask Lake (SL4-1) core was collected 85 km NW of Flin Flon and Kotyk Lake (KOL) 30 km NE. The distribution of Sr and U show that both profiles are predominantly minerotrophic (ie groundwater-fed), but the Pb concentration profile shows that Pb was received exclusively from the atmosphere. Graphs of 208Pb/206Pb against 206Pb/207Pb document atmospheric Pb contamination dating from the early to mid-1800's, well before the start of metallurgical processing (in 1930) and attributable to long-range atmospheric transport from other regions of North America. Industrial activities at Flin Flon clearly affected the concentrations, enrichment factor (calculated using Sc), and accumulation rates of Pb, but it is the similarity in isotopic composition, and contrast with crustal values (206Pb/207Pb ca. 1.20 to 1.22) which makes the connection to the Flin Flon ores. The KOL samples dating from 1925-1976 CE have a 206Pb/207Pb of 1.032 ± 0.002 (n = 11) which approach the values for the Flin Flon ores (206Pb/207Pb = 1.008). But even at SL4-1, the peat samples dating from 1925-1976 CE have a 206Pb/207Pb of 1.061 ± 0.022 (n = 18) which is well below the corresponding ratio of Canadian leaded gasoline (206Pb/207Pb = ca. 1.15). The SL4-1 site too, therefore, was clearly impacted by Pb from mining and metallurgy, despite the distance (88 km) from Flin Flon and being predominantly upwind. These two bogs not only provide the chronology of atmospheric Pb deposition for the past decades, but suggest that the extent of contamination may have been underestimated by previous studies.

Comparison of mercury and zinc profiles in peat and lake sediment archives with historical changes in emissions from the Flin Flon metal smelter, Manitoba, Canada.

The copper-zinc smelter at Flin Flon, Manitoba, was historically the largest single Hg point-source in Canada, as well as a major source of Zn. Although emissions were reported by industry to have declined significantly since the late 1980s, these reductions have never been independently verified. Here, the histories of Hg and Zn deposition over the past century or more were determined at five lake sediment and three peat study sites in the surrounding region. At sites spanning the range from heavy to minor pollution, lake sediment Hg and Zn concentration and flux profiles increased significantly in the early 1930s after the smelter opened. Two of the three peat archives were wholly or partially compromised by either physical disturbances or biogeochemical transitions which reduced their effectiveness as atmospheric metal deposition recorders. But the remaining peat records, including a detailed recent 20 yr record at a moderately polluted site, appeared to show that substantive reductions in metal levels had occurred after the late 1980s, coincident with the reported emission reductions. However, the lake sediment results, taken at face value, contradicted the peat results in that no major declines in metal concentrations or fluxes occurred over recent decades. Mercury and Zn fluxes have in fact increased substantially since 1988 in most lakes. We suggest that this discrepancy may be explained by catchment soil saturation by historically deposited metals which are now mobilizing and leaching into lakes, as has been reported from other smelter polluted systems in Canada, whereas the upper sections of the peat cores reflected recent declines in atmospheric deposition. However, further research including instrumented wet and dry deposition measurements and catchment/lake mass balance studies is recommended to test this hypothesis, and to provide definitive data on current atmospheric metal deposition rates in the area.

Atmospheric Pb and Ti accumulation rates from Sphagnum moss: dependence upon plant productivity.

The accumulation rates of atmospheric Pb and Ti were obtained using the production rates of Sphagnum mosses collected in four ombrotrophic bogs from two regions of southern Germany: Upper Bavaria (Oberbayern, OB) and the Northern Black Forest (Nordschwarzwald, NBF). Surfaces of Sphagnum carpets were marked with plastic mesh and one year later the production of plant matter was harvested. Metal concentrations were determined in acid digests using sector field ICP-MS employing well established analytical procedures. Up to 12 samples (40 x 40 cm) were collected per site, and 6-10 sites were investigated per bog. Variations within a given sampling site were in the range 2.3-4x for Pb concentrations, 1.8-2.5x for Ti concentrations, 3-8.3x for Pb/Ti, 5.6-7.8x for Pb accumulation rates, and 2.3-6.4x for Ti accumulation rates. However, the median values of these parameters for the sites (6-10 per bog) were quite consistent. The mosses from the bogs in NBF exhibited significantly greater productivity (187-202 g m(-2) a(-1)) compared to the OB peat bogs (71-91 g m(-2) a(-1)), and these differences had a pronounced effect on the Pb and Ti accumulation rates. Highly productive mosses showed no indication of a "dilution effect" of Pb or Ti concentrations, suggesting that more productive plants were simply able to accumulate more particles from the air. The median rates of net Pb accumulation by the mosses are in excellent agreement with the fluxes obtained by direct atmospheric measurements at nearby monitoring stations in both regions (EMEP and MAPESI data).

Use of Br and Se in peat to reconstruct the natural and anthropogenic fluxes of atmospheric Hg: A 10000-year record from Caribou Bog, Maine.

Using Br and Se as reference elements, the natural and anthropogenic fluxes of atmospheric Hg were reconstructed for the past 10,000 years using peat cores from Caribou Bog, ME. In the ombrotrophic peat layers, the average background Hg accumulation rate (AR) was 1.7 +/- 1.3 microg m(-2) year(-1) which is comparable with the natural rate of atmospheric Hg accumulation reported in other retrospective studies. The average Hg AR determined using all peat samples dating from preindustrial times, including minerotrophic peat, was slightly greater (3.1 +/- 2.3 microg m(-2) year(-1)) which may reflect differences in canopy interception due to the changes in plant communities, aquatic inputs, or possibly climatic factors. The maximum Hg AR (32 microg m(-2) year(-1)) occurred ca. 1961 A.D. In samples predating the settlement by Europeans, there is a linear correlation between the AR of Hg and those of Br and Se; this relationship allows both Br and Se to be used to calculate the natural AR of Hg (Hgnat). The difference between Hg AR and Hg(nat) is the Hg AR in excess of background (Hg(ex)). Because Hg(ex) was positive only after ca. 1840 A.D., it is assumed to represent the anthropogenic Hg component. By the late 19th century, Hg(ex) deposition was equal to the natural flux. At the peak in Hg deposition in 1961 A.D., Hgex made up >90% of total atmospheric Hg deposition. The AR in the uppermost peat decreased to 25% of peak values by 2000 A.D.

An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies.

An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g(-1) level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g(-1) levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.

Development of an ombrotrophic peat bog (low ash) reference material for the determination of elemental concentrations.

Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail.

New peat bog record of atmospheric lead pollution in Switzerland: Pb concentrations, enrichment factors, isotopic composition, and organolead species.

A peat core collected at Etang de la Gruère, an ombrotrophic bog in the Jura Mountains of Switzerland, was analyzed for organolead species (DEL, TEL, DML, and TML) using GC-MIP AES, Pb isotopes using TIMS, and total Pb using XRF and age-dated using 210Pb. The earliest occurrence of quantifiable alkyllead is found at a depth of 24 cm, which is dated at AD 1946 +/- 3; this finding is consistent with the introduction of leaded gasoline in Switzerland in 1947. The maximum concentration of alkyllead (2.89 ng/g) is found at 5 cm, which is dated at AD 1988 +/- 2. This same sample yielded 206Pb/207Pb = 1.1254, which is the least radiogenic value in the entire 2K core and comparable to the isotopic composition of Pb in leaded gasoline. The highest concentrations of DML (906 ng/g) and DEL (1906 ng/g) also were found in this sample. Total alkyllead never accounts for more than 0.02% of total Pb in any given sample. The spatial and temporal variations in organolead species is matched by the changes in the isotopic composition of Pb over the same interval. Despite this, the decline in anthropogenic Pb pre-dates the maximum in total alkyllead and minimum 206Pb/207Pb, indicating that atmospheric Pb emissions had already begun their decline prior to the introduction of unleaded gasoline. In fact the decline in anthropogenic Pb was probably in response to the introduction of legislation, first in Germany and later in the European Union, establishing a maximum allowable concentration of Pb in gasoline.

An analytical protocol for the determination of total mercury concentrations in solid peat samples.

Traditional peat sample preparation methods such as drying at high temperatures and milling may be unsuitable for Hg concentration determination in peats due to the possible presence of volatile Hg species, which could be lost during drying. Here, the effects of sample preparation and natural variation on measured Hg concentrations are investigated. Slight increases in mercury concentrations were observed in samples dried at room temperature and at 30 degrees C (6.7 and 2.48 ng kg(-1) h(-1), respectively), and slight decreases were observed in samples dried at 60, 90 and 105 degrees C (2.36, 3.12 and 8.52 ng kg(-1) h(-1), respectively). Fertilising the peat slightly increased Hg loss (3.08 ng kg(-1) h(-1) in NPK-fertilised peat compared to 0.28 ng kg(-1) h(-1) in unfertilised peat, when averaged over all temperatures used). Homogenising samples by grinding in a machine also caused a loss of Hg. A comparison of two Hg profiles from an Arctic peat core, measured in frozen samples and in air-dried samples, revealed that no Hg losses occurred upon air-drying. A comparison of Hg concentrations in several plant species that make up peat, showed that some species (Pinus mugo, Sphagnum recurvum and Pseudevernia furfuracea) are particularly efficient Hg retainers. The disproportionally high Hg concentrations in these species can cause considerable variation in Hg concentrations within a peat slice. The variation of water content (1.6% throughout 17-cm core, 0.97% in a 10 x 10 cm slice), bulk density (40% throughout 17-cm core, 15.6% in a 10 x 10 cm slice) and Hg concentration (20% in a 10 x 10 cm slice) in ombrotrophic peat were quantified in order to determine their relative importance as sources of analytical error. Experiments were carried out to determine a suitable peat analysis program using the Leco AMA 254, capable of determining mercury concentrations in solid samples. Finally, an analytical protocol for the determination of Hg concentrations in solid peat samples is proposed. This method allows correction for variation in factors such as vegetation type, bulk density, water content and Hg concentration in individual peat slices. Several subsamples from each peat slice are air dried, combined and measured for Hg using the AMA254, using a program of 30 s (drying), 125 s (decomposition) and 45 s (waiting). Bulk density and water content measurements are performed on every slice using separate subsamples.

The chronology of anthropogenic, atmospheric Pb deposition recorded by peat cores in three minerogenic peat deposits from Switzerland.

Peat cores were collected from three minerogenic peatlands in Switzerland: La Tourbière des Genevez (TGE), in Canton Jura; Gola di Lago (GDL), in Canton Ticino; and Mauntschas (MAU), in Canton Grisons. Chemical analyses of the pore waters and the peats document the increasingly minerogenic character with depth. In particular, the Sr concentration profile in the peats reflects the growing importance of mineral sediment dissolution with increasing distance below the peat surface. Despite this circumstance, Pb concentrations are greatest in the surface layers, and decrease with depth. Thus, dissolution of the basal sediments at these sites appears to be an unimportant source of Pb, compared with atmospheric deposition. Twenty-one new radiocarbon age dates for the three cores provide a chronology of Pb enrichment, and these are consistent with the record of atmospheric Pb deposition recorded by the ombrotrophic peat bog 'Etang de la Gruère' (EGR). Sediment samples from TGE and EGR were reacted at pH 5 with ammonium acetate to dissolve the carbonate fraction, filtered, and the residues analyzed using XRF. These analyses show that much of the Ca, Mg, Sr and Mn is lost when the carbonate fraction is dissolved, but this process does not measurably affect Pb. This finding suggests that carbonate dissolution dominates the weathering of the sediments underlying these peat deposits, but this fraction does not contain significant concentrations of Pb. Minerogenic peat deposits such as those described here, therefore, can serve as reliable archives of atmospheric Pb deposition, provided that mineral dissolution in the underlying sediments does not contribute measurably to the Pb inventory of the peat profile.

Enrichment of Cu, Ni, Zn, Pb and As in an ombrotrophic peat bog near a Cu-Ni smelter in southwest Finland.

The accumulation of selected trace elements (Cu, Ni, Zn, Pb, As) in the surface peat layer of an ombrotrophic bog 2.4 km from a Cu-Ni smelter at Harjavalta, Finland was studied using a peat core. A reference core was taken from an ombrotrophic bog at a background site, Hietajärvi, in eastern Finland. Element concentrations were analysed from 1-cm slices and enrichment factors (EF) were calculated. The enrichment factors of both Cu and Ni in the Harjavalta peat bog are extremely high compared to the Hietajärvi site. However, only the 6-cm surface peat Pb values are higher in Harjavalta compared to Hietajärvi. Precipitation was collected during 1992-1996, in the vicinity of the Harjavalta smelter, in order to estimate the current atmospheric deposition load. Comparison between the precipitation and peat data reveals that at Harjavalta the surface peat is relatively much more polluted than the current precipitation. The variation in EF of the Harjavalta peat core with respect to depth shows two patterns: Cu and Pb are similar, as are Ni, Zn and As. The vertical gradient in Harjavalta Cu EF suggests that Cu supplied to the peat by atmospheric deposition is very well preserved by the bog.

Concentrations and distribution of some polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in an ombrotrophic peat bog profile of Switzerland.

An efficient method was developed for the analysis of selected PCBs and PAHs in dry peat samples. The method includes a shaking extraction using acetone and hexane followed by the purification of the crude extract by gel permeation chromatography (GPC) which turned out to be the key clean-up step. The method was used to determine seven indicator PCBs and 16 EPA-PAHs in individual sections of an ombrotrophic peat core in south-west Switzerland. The maximum concentrations of PCBs (19 microg sigma PCBs/kg dm) were found at a peat depth of 10-15 cm which is estimated to correspond to a time period of 1976-1960 whereas the PAH profile showed a maximum (2853 microg sigma PAHs/kg dm) at a depth of 20-25 cm which represents circa 1951-1930. Compared to these maxima, the concentrations of PAHs in the top layer (1990-1986) are six times lower, but the decline in PCBs is only 38%. The concentration profiles are generally consistent with known changes in contaminant emissions, and suggest that more detailed studies of ombrogenic peat bog profiles could be used for detailed reconstructions of the changing atmospheric fluxes of these and other organic contaminants.

Critical examination of trace element enrichments and depletions in soils: As, Cr, Cu, Ni, Pb, and Zn in Swiss forest soils.

The aim of this study was to obtain an overview of trace element concentrations in Swiss forest soils and to critically assess the measured values with respect to anthropogenic input vs. lithogenic background. Twenty-three sites were selected which represent a broad range of natural forest sites, bedrock material and soil types of Switzerland. At each site, samples were collected from all genetic soil horizons down to a C or B/C horizon. Total concentrations of As, Cr, Cu, Ni, Pb, and Zn in all samples were determined by X-ray fluorescence spectrometry. There were distinct differences in the geological background values estimated from the concentrations measured in the samples from the lowest soil horizon. Background concentrations for Cr and Ni were lowest in granite and gneiss, whereas Pb and Zn were highest in limestone and marl. Enrichment or depletion of the trace elements was assessed using Zr as reference element. Within the same profile, the six trace elements showed completely different enrichment/depletion patterns with depth. The various natural processes and anthropogenic inputs that can lead to these patterns are critically discussed. Based on this critical assessment, pollution of the investigated forest soils was found to be most severe for Pb and Zn and to a somewhat lesser extent for As and Cu, whereas anthropogenic input of Cr and Ni seems to be less important. The data suggest that a critical evaluation of enrichment factors is a better tool to assess soil pollution with trace elements than the use of maximum allowable concentrations (MAC) for topsoil samples. The enrichment factors calculated as described here consider the effects of geological variation on metal abundances whereas the MAC does not. In order to obtain an estimate of soil solution concentrations, water extracts of the samples collected from a subset of 10 soil profiles were analyzed for the same trace elements. Solubility of all elements generally decreased with soil depth. An exception was Cr, Cu, and Ni solubility in the humus layer, which was lower than in the underlying mineral horizon. For all elements, solubility was higher for the collective of soil samples depleted in this element when compared to the samples, in which the element was enriched.

A new approach for quantifying cumulative, anthropogenic, atmospheric lead deposition using peat cores from bogs: Pb in eight Swiss peat bog profiles.

Peat cores taken from eight Swiss peatlands were used to calculate inventories of anthropogenic Pb using either Sc or Zr to quantify Pb derived from rock weathering. The shapes of the Pb/Sc and Pb/Zr profiles suggest that Pb was supplied exclusively by atmospheric deposition at all sites. At one of the sites (Etang de la Gruère), anthropogenic Pb was calculated using both Sc and Zr as the conservative reference element. Lithogenic Pb determined using Sc was twice that obtained using Zr, possibly because Zr resides only in zircons which are dense compared to pyroxene and amphibole which are the main Sc-bearing phases in the earth's crust. However, the inventory of 'natural' Pb (supplied almost entirely by soil dust) is dwarfed by the anthropogenic inventory such that anthropogenic Pb calculated using Sc and Zr agree to within 5%. The total amount of anthropogenic Pb accumulated in the bogs was calculated by simply adding the mass of anthropogenic Pb for each peat slice over the length of each core. Cumulative, anthropogenic Pb calculated in this way ranged from 1.0 to 9.7 g/m2 and showed pronounced regional differences: the site south of the Alps (Gola di Lago in Canton Ticino) with direct exposure to the heavily industrialized region of northern Italy received nearly 10 times more anthropogenic Pb as the sites in more remote alpine regions (Schöpfenwaldmoor in Canton Berne, and Mauntschas in Canton Grisons). The approach used here to calculate cumulative, anthropogenic, atmospheric Pb (CAAPb) is simple and robust, independent of the chronology of Pb deposition, and makes no assumptions about the immobility of Pb within the peat profile. Given the worldwide distribution of peat bogs, it should be possible to undertake continental and global inventories of atmospheric metal deposition, for both the natural and anthropogenic components of most trace metals of environmental interest.

Mercury in a spanish peat bog: archive of climate change and atmospheric metal deposition

A peat core from a bog in northwest Spain provides a record of the net accumulation of atmospheric mercury since 4000 radiocarbon years before the present. It was found that cold climates promoted an enhanced accumulation and the preservation of mercury with low thermal stability, and warm climates were characterized by a lower accumulation and the predominance of mercury with moderate to high thermal stability. This record can be separated into natural and anthropogenic components. The substantial anthropogenic mercury component began approximately 2500 radiocarbon years before the present, which is near the time of the onset of mercury mining in Spain. Anthropogenic mercury has dominated the deposition record since the Islamic period (8th to 11th centuries A.D.). The results shown here have implications for the global mercury cycle and also imply that the thermal lability of the accumulated mercury can be used not only to quantify the effects of human activity, but also as a new tool for quantitative paleotemperature reconstruction.

Interdependence of peat and vegetation in a tropical peat swamp forest.

The visual uniformity of tropical peat swamp forest masks the considerable variation in forest structure that has evolved in response to differences and changes in peat characteristics over many millennia. Details are presented of forest structure and tree composition of the principal peat swamp forest types in the upper catchment of Sungai Sebangau, Central Kalimantan, Indonesia, in relation to thickness and hydrology of the peat. Consideration is given to data on peat geochemistry and age of peat that provide evidence of the ombrotrophic nature of this vast peatland and its mode of formation. The future sustainability of this ecosystem is predicted from information available on climate change and human impact in this region.

History of atmospheric lead deposition since 12,370 (14)C yr BP from a peat bog, jura mountains, switzerland

A continuous record of atmospheric lead since 12,370 carbon-14 years before the present (14C yr BP) is preserved in a Swiss peat bog. Enhanced fluxes caused by climate changes reached their maxima 10, 590 (14)C yr BP (Younger Dryas) and 8230 (14)C yr BP. Soil erosion caused by forest clearing and agricultural tillage increased lead deposition after 5320 (14)C yr BP. Increasing lead/scandium and decreasing lead-206/lead-207 beginning 3000 (14)C yr BP indicate the beginning of lead pollution from mining and smelting, and anthropogenic sources have dominated lead emissions ever since. The greatest lead flux (15.7 milligrams per square meter per year in A.D. 1979) was 1570 times the natural, background value (0.01 milligram per square meter per year from 8030 to 5320 (14)C yr BP).