Size-resolved Pb distribution in the Athabasca River shows snowmelt in the bituminous sands region an insignificant source of dissolved Pb (original) (raw)
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Transport of industrial lead in snow through soil to stream water and groundwater
Chemical Geology, 1990
Determination of isotopic compositions and concentrations of Pb in stream water, groundwater, soil and bed-rock in a subalpine watershed, combined with concentrations of Ca, Na, K, Mg, Fe and Mn and mineralogical data, show that ~ 90% of the industrial Pb in snow is trapped in a subunit of the upper 2 cm of soil. This is composed of humus plus Fe-hydroxides and Mn-oxides, where industrial Pb mixes isotopically with Pb already accumulated there from previous inputs of industrial Pb and natural rock-Pb. The 2°6pb/2°Tpb ratio of Pb in the upper 2-cm soil accumulation reservoir is different from that of industrial Pb added from snow each year, because it is a mixture of natural rock-Pb derived from weathering (~ 20%) which has a 2°6pb/2°7pb ratio different from industrial Pb, and because the 2°6pb/2°7pb ratio of industrial Pb accumulated from atmospheric inputs during the past century (~ 80%) has changed considerably during that time. During spring melt, when streams are fed mostly by surface runoff, Pb in the surface soil accumulation reservoir is released back into the runoff and into streams. At this time the proportion of industrial Pb in mountain stream waters is that in the surface soil accumulation reservoir, ~ 80%. Concentrations and isotopic composition of Pb in soil profiles, and the relation between Pb and organic matter concentration in soil indicate little or no industrial Pb accumulates in the reservoir below 2-cm depths. These data, combined with measured proportions of Ca and Pb and 2°6pb/2°Tpb ratios in groundwater, indicate that most of the Pb in aquifers at depth below 30 cm originates by weathering from natural rock-Pb. Although aquifers are charged by snow-melt, industrial Pb is removed from the water as it percolates downward through the soil accumulation reservoir. Therefore, during times when streams are fed mainly from these aquifers, stream waters contain mainly natural rock-Pb and some industrial Pb in colloids originally contained in snow-melt. Concentrations of Pb in stream waters tend to remain constant both throughout different seasons (when rates of stream discharge change 20-fold), and over the last decade (when Pb inputs from snow decreased 6-fold) because Pb in those waters originates from a fixed reservoir in the soil.
2009
Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20°latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the 206 Pb/ 207 Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot ( 206 Pb/ 207 Pb vs. 208 Pb/ 206 Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.
Atmospheric Environment, 2016
During three winter seasons (2009-2011), Pb concentrations were measured in precipitation at 10 high-elevation sites in the Czech Republic, close to the borders with Austria, Germany, Poland, and Slovakia. Soluble and insoluble Pb forms were quantified in snow (vertical deposition), and rime (horizontal deposition). The objective was to compare Pb input fluxes into ecosystems via vertical and horizontal deposition, and to identify the residual Pb pollution sources in an era of rapidly decreasing industrial pollution. Lead soluble in diluted HNO 3 made up 96 % of total Pb deposition, with the remaining 4 % Pb bound mainly in silicates. Three times higher concentrations of soluble Pb in rime than in snow, and 2.5 times higher concentrations of insoluble Pb in rime than in snow were associated with slightly different Pb isotope ratios. On average, the 206 Pb/ 207 Pb ratios in rime were higher than those in snow. Higher mean 206 Pb/ 207 Pb ratios of insoluble Pb (1.175) than in soluble Pb (1.165) may indicate an increasing role of geogenic Pb in recent atmospheric deposition. A distinct reversal to more radiogenic 206 Pb/ 207 Pb ratios in snow and rime in 2010, compared to literature data from rain-fed Sphagnum peatlands (1800-2000 A.D.), documented a recent decrease in anthropogenic Pb in the atmosphere of Central Europe. Since the early 1980s, Pb concentrations in snow decreased 18 times in the rural south of the Czech Republic, but only twice in the industrial north of the Czech Republic. Isotope signatures indicated that Pb in today's atmospheric deposition is mainly derived from Mesozoic ores mined/processed in Poland and coal combustion in the Czech Republic and Poland. 4 America in that Pb emissions resulting from coal burning exceeded those from traffic (Vile et al., 2000, Novak et al., 2003, Farmer et al., 2016). The former East Germany was the largest, and the Czech Republic the third largest, soft coal producer in the world. The use of alkyl-lead in petrol was banned at the end of 1996 in Germany, 2000 in the Czech Republic, and 2003 in Poland. We hypothesized that, with easing pollution, Pb is well mixed before being deposited in rural locations. This hypothesis can be tested by a comparison of Pb isotope signatures of individual pollution sources with isotope signatures of Pb deposited in the ecosystems. Knowledge of Pb isotope composition of bedrock is needed to distinguish between geogenic and anthropogenic
Lead biogeochemistry in a central Ontario Forested watershed
Biogeochemistry, 2007
To determine the sources and sinks of atmospherically deposited Pb at a forested watershed (Plastic Lake) in central Ontario, Canada, Pb pools and fluxes through upland, wetland and lake compartments were measured during 2002/ 2003 and compared with previous measurements taken between 1989 and 1991. In 2002/2003, annual bulk deposition of Pb was 0.49 mg m À2 compared with 1.90-1.30 mg m À2 in 1989-1991. Annual Pb concentrations in stream water draining the upland part of the catchment were very low (0.04 mg l À1) and were approximately half those measured in 1989-1991 (0.11-0.08 mg l À1). Leaching losses in stream water were small and mass balance estimates indicate almost complete retention (>95%) of atmospherically deposited Pb in upland soils. In contrast, annual Pb concentrations in stream water draining a wetland were between 0.38 and 0.77 mg l À1 , with the highest concentration occurring in 2002/2003 and mass balance calculations indicate that the wetland is a net source of Pb in all measured years. Lead concentrations in the lake outflow were low and the average Pb concentration measured in 2002/2003 (0.09 mg l À1) was approximately half the value recorded in 1989-1991 (0.19 mg l À1 both years). Annual mass balance estimates indicate that the lake retained between 2.47 mg m À2 (1989/1990) and 1.42 mg m À2 (2002/2003) and that in 2002/2003 68% of the Pb input to the lake is derived from the terrestrial catchment. These estimates are higher than sediment core records, which indicate around 18 mg m À2 Pb was retained in sediment during the 1990s. Nevertheless, Pb concentrations decrease with sediment depth and 206 Pb/ 207 Pb concentrations increase with depth, a pattern also observed in mineral soils that reflects the substantial contribution of anthropogenic Pb to the watershed. Lead isotope data from soil and sediment indicate a recent anthropogenic Pb signal (206 Pb/ 207 Pb * 1.185) in upper soils and sediments and an older anthropogenic signal (206 Pb/ 207 Pb * 1.20) in deeper soil and sediment. Lead isotope data in sediment and vegetation indicate that practically all the Pb cycled in the forest at Plastic Lake is anthropogenic in origin.
Environmental Science & Technology, 2010
Can a climate-triggered export of old contaminants from the soil alter the lead (Pb) contaminant burden of subarctic lakes? To address this question, we reconstructed the pollution history of three high latitude lakes situated in a region where a recent climatic shift has occurred. Dated sediment records were used as archives of past Pb inputs to the lakes, where the difference in the 206 Pb/ 207 Pb ratio between atmospheric contaminants ( 206 Pb/ 207 Pb ratio <1.16) and geogenic Pb in the catchment soil ( 206 Pb/ 207 Pb ratio >1.22) were used to trace fluxes of Pb contaminants. Lead contaminants were found in sediments deposited since Roman times. A significant export of Pb from the soil contaminant pool is indicated in two of the lakes surrounded by near-shore permafrost soils. Here, levels of Pb contaminants and 206 Pb/ 207 Pb ratios of sediments deposited after the 1970s appear not to have been strongly affected by the g90% reduction in atmospheric deposition rates and increasing 206 Pb/ 207 Pb ratios of atmospheric Pb since the 1990s. We concluded that soil processes stimulated by the ongoing climate change at high latitudes might work counteractive to efforts to reduce contaminant levels in subarctic lakes.
Isotopic composition of lead in moss and soil of the European Arctic
Geochimica et Cosmochimica Acta, 2004
Moss, O and C horizons of podzols, mainly forming complementary sample triplets, as well as filter residues of molten snow from northern Norway, northern Finland and NW Russia have been analyzed by TIMS for their Pb isotopic composition in order to study the impacts of local geogenic/anthropogenic sources and long range atmospheric transport on the Pb balance in the European Arctic. Samples were taken along two N-S transects covering an area of ϳ188.000 km 2 , including both pristine environments in the W and certain regions towards the E severely contaminated by heavy metal emissions originating from large nickel smelters and processing plants in NW Russia. The lead in moss and O horizon samples clearly reflects atmospheric deposition, as it displays overall uniform isotope ratios and is decoupled from the geogenic background, i.e. the underlying mineral soils in the C horizon. Moss and O horizon samples from the eastern N-S transect are isotopically indistinguishable from those taken along the western transect but their Pb concentrations tend to be ϳ2 times higher. This points to considerable contamination originating from the nearby Russian industrial and urban centers. However, isotopic signals of emissions from individual industrial point sources cannot be unambiguously identified because they lack characteristic isotope signatures. Pb derived from gasoline additives is swamped by Pb from other sources and can also be excluded as a major contributor to the environmental Pb in the European Arctic. Overall, the Pb isotopic signatures of moss and O horizon overlap values recorded in atmospheric lead all over central and southern Europe, more than 2000 km south of the study area. This may be taken as indicating continent-wide mixing of Pb derived from similar sources in the atmosphere or as reflecting economic globalization, or both. O horizon samples, which accumulate lead over 20-30 yr, conform to a distinct Pb isotope reference line in 207 Pb/ 206 Pb vs. 208 Pb/ 206 Pb space ("European Standard Pollution," ESP) defined by atmospheric Pb considered to be representative for the technical civilization in Europe. Conversely, the Arctic moss samples with a lifetime of Ͻ3 yr display a deviating linear trend reflecting a recent change of atmospheric input towards significantly more radiogenic Pb derived from Mississippi Valley-type ores in the U.S., fully compatible with signatures found in epiphytic lichens from Canada, but also in Pb from urban waste incinerators in central Europe. Considering the elevated Pb concentrations in moss collected along the eastern N-S transect, this congruence indicates that the Pb in moss of the European Arctic most probably originates from the nearby Russian centers of urbanization and not from transatlantic transport. We therefore suspect imported industrial goods and their subsequent attrition to be a more plausible explanation for the appearance of MVT lead in Europe.
Geochimica et Cosmochimica Acta, 2010
A peat core from an ombrotrophic bog documents the isotopic evolution of atmospheric Pb in central Ontario since AD 1804 ± 53 ( 210 Pb dating). Despite the introduction of unleaded gasoline in the mid-1970's, the ratio 206 Pb/ 207 Pb in atmospheric deposition has not increased as expected, but rather continues to decline. In fact, snowpack sampling (2005 and 2009) and rainwater samples (2008) show that the isotopic composition of atmospheric Pb today is often far less radiogenic than the gasoline lead that had been used in Canada in the past. The peat, snow, and rainwater data presented here are consistent with the Pb isotope data for aerosols collected in Dorset in 1984 and 1986 which were traced by Sturges and to emissions from the Noranda smelter in northern Quèbec, Canada's largest single source of atmospheric Pb. Understanding atmospheric Pb deposition in central Ontario, therefore, requires not only consideration of natural sources and past contributions from leaded gasoline, but also emissions from metal smelting and refining.
Using isotopic tracers in lake sediments to assess atmospheric transport of lead in Eastern Canada
Water, Air, and Soil Pollution
The isotopm composition of lead pollution in the environment provides information as to the source of emission. The 2°6pb/2°7pb ratio for Canadian industrial emissions (1.1534-0.005) is significantly less than U.S. industrial emissions (1.2134-0.008) making it possible to determine the relative contributions of emissions from both countries within Eastern North America by means of a simple isotopic mixing model. Profundal sediments in lakes chronicle contaminant inputs and are therefore useful monitors of environmental pollution. Surface sediment from 32 sediment cores across Quebec and Ontario, Canada were analyzed for 2°6pb/2°Tpb to ascertain the relative proportions of Pb emission from Canada and the U.S.A. Data show that U.S. contributions to the total lead burden in surficial sediments across much of southern Quebec and Ontario are often in excess of 50%. Local sources were particularly important in the Eastern Township region of Quebec which lies 200 km south east of the city of Montreal. The results are discussed in relation to the major sources of industrial lead emissions in North America.
The relationships between rock-derived lead and iron in natural waters
Geochimica et Cosmochimica Acta, 1992
The relationships between Fe and Pb released to the hydrocycle via rock weathering is examined in terms of field observations and laboratory experiments. Rock, soil, and unpolluted water samples from granodiorite, basalt, and carbonate terrains were analyzed for their Pb, Fe, and other element (Ca, Mg, Na, K, Si, Al, Mn) concentrations. Samples of granodiorite, soil developed on the granodiorite, basalt, and dolomite rocks, as well as biotite and feldspar minerals, were also used for laboratory leaching experiments. Fe/Pb ratios found in granodiorite, basalt, and insoluble residue of carbonate bedrocks are preserved within an order of magnitude in surface and shallow groundwater reservoirs draining these rocks. With the exception of carbonate rocks, leachates of these rocks have Fe/Pb ratios similar to that of the bedrock. Laboratory experiments suggest that Pb is adsorbed and coprecipitates with Fe-rich particles even in the presence of higher concentrations of competing ions (e.g., Mg'+). Complexation of Pb by ethylenediaminetetraacetate (EDTA), however, substantially decreases the amount of Pb bound to surface sites (ligand competition). Based on our results we suggest that in early phases of the weathering cycle, Pb both coprecipitates and is adsorbed on surfaces of Fe-rich particles. Because of complementary transport mechanisms and comparable rates of release from common source rock and soil minerals, the molar ratio of Fe to natural (rock-derived) Pb in the particulate load of rivers (in many cases it includes particles which pass through 0.45 pm pore size filters) is similar to that of the upper continental crustal rock, approximately 6500. This ratio can vary in watersheds which drain rocks with different Fe/Pb ratios than the average upper continental crust, in rivers loaded with dissolved natural organic matter, or in rivers polluted with Pb or with anthropogenic chelators (secondary pollution effect).