Predominance of industrial Pb in recent snow (1994–2004) and ice (1842–1996) from Devon Island, Arctic Canada (original) (raw)
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Stable lead isotope ratios in arctic aerosols: evidence for the origin of arctic air pollution
Atmospheric Environment (1967)
The isotopic composition of aerosol lead in the polar region potentially contains information on the origin of Arctic pollution which will complement that from meteorological and trace elemental composition studies. Weekly samples of atmospheric aerosols were collected at three locations in the Canadian Arctic from mid-1983 to mid-1984. They were analyzed for elemental composition and stable lead isotope ratios (Pb 206/207). High crustal enrichment factors confirmed that the majority of samples contained lead of anthropogenic origin. Pb 206/207 ratios were very uniform over time and between sites, suggesting a common origin of lead pollution in the Canadian Arctic. The mean isotope ratios at the Alert and Mould Bay stations were 1.160~0.010 and 1.161+0.006, respectively (samples from a third site at Igloolik were eiidently contaminated by local sources). A small nun&r of samples from Spitsbergen, taken durine flow medominantlv out of the northern U.S.S.R.. were found to have a similar mean Pb 206/207 ratio .d 1 of 1.154~0.006. From published lead isotope analyses of Soviet lead-bearing ores, we would ex&t a mean isotope ratio in industrial and vehicular emissions in the U.S.S.R. of around 1.158. Contributions to Arctic lead pollution from the U.S. and western Canadian sources can probably be ruled out, as they have significantly higher Pb 206/207 ratios. Similarly, emissions from northern Canadian and Kola Peninsula smelters can be disregarded, as they appear to have low isotope ratios. Eastern Canadian automotive lead aerosol contained only marginally lower Pb 206/207 ratios than in the Arctic, but meteorological studies argue against this region being a major source area for Arctic pollution. Scant European data suggest that European Pb emissions generally have lower isotope ratios than the Arctic samples. However, more data in Eurasia are needed before apportionments of Arctic Pb between sources within the region can be made.
Geochimica et Cosmochimica Acta, 2000
Elemental concentrations of Al, Ba, Cd, Cu, Mg, Mn, Pb, Rb, Sr, and Zn, as well as Pb and Sr isotopic compositions were determined in samples of snowpack obtained along two main transects from the province of Quebec (Canada); one north-south (between 47°N and 55°N; 1994) and the other within the St. Lawrence Valley (1997). Median enrichment factors (relative to upper crustal abundances) for Cd, Cu, Mn, Pb and Zn for all samples range from Ϸ300 to Ϸ42,000 and are indicative of an anthropogenic origin. Pb isotope ratios for snow samples retrieved in 1994 are highly variable ( 206 Pb/ 207 Pb ϭ 1.148 to 1.193) and are characterized by the most radiogenic Sr isotope values ( 87 Sr/ 86 Sr Ն 0.710). In contrast, the Pb and Sr isotope results for 1997 snow samples collected along the St. Lawrence Valley (below latitude 47°N), yield the most radiogenic Pb isotope ratios ( 206 Pb/ 207 Pb ϭ 1.180 to 1.190) and 87 Sr/ 86 Sr ratios between 0.708 and 0.710. The former indicate that the atmospheric pollution in this region of Quebec is dominated by a mixture of anthropogenic emissions from U.S. ( 206 Pb/ 207 Pb Ϸ 1.20) and Canadian ( 206 Pb/ 207 Pb Ϸ 1.15) sources. Pb isotope ratios ( 206 Pb/ 207 Pb ϭ 1.160 to 1.180) for 1997 samples collected north of latitude 47°N indicate input of an additional anthropogenic component, possibly that of Eurasian pollution being transported over the high Arctic during the winter season.
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.
Temporal variability of Cd, Pb, and Pb isotope deposition in central Greenland snow
Geochemistry, Geophysics, Geosystems, 2000
We present a decade-long (1981-1990) high-resolution (subseasonal) record of Pb and Cd concentrations and Pb isotopic composition in a series of 119 snow samples from a 6-m snow pit at Summit, Greenland. Both metals show order of magnitude seasonal variability, with maxima in spring of every year, coinciding with sulfate peaks. These short-term features complicate attempts to quantify secular decadal-scale trends associated with anthropogenic source changes (e.g., phasing out of leaded gasoline). A small (<50%) decrease during the decade is estimated for Pb, but no significant trend is observed for Cd. Mean concentrations for the snow pit (Pb = 216, Cd = 11 pmol kg À1) are indistinguishable from mean values for nearly continuous samples of the 1-6 m section of a firn core drilled 1 km away, suggesting freedom from contamination artifact. An evaluation of potential sources confirms that Pb and Cd are dominated by anthropogenic inputs. Isotopic ratios (206 Pb/ 207 Pb and 208 Pb/ 207 Pb) determined on a subset of snow pit samples of varying ages within the decade indicate that springtime Pb concentration maxima are consistent with a mixture of eastern European, former Soviet Union, and western European sources, while seasonal Pb minima, especially from the early portion of the decade, plot along a different mixing line, suggesting a mixture of U.S. and European sources. The combination of Pb concentration and isotopic composition are consistent with an estimated decrease in U.S. Pb contributions of about twofold over the decade, which predicts a decadal concentration decrease in the snow of $30%. However, the secular trends in both concentration and isotopes are barely detectable against seasonal and interannual variability. The evidence for seasonally distinct source regions may be useful for interpretation of high-resolution records of other chemical species in Greenland snow and ice. Analyses of two deep core sections dated at 1699-1700 and 1780-1788, compared to the snow pit data, indicate that both Pb and Cd deposition in central Greenland roughly doubled during the eighteenth century, then doubled again by the 1980s.
Journal of Environmental Monitoring, 2005
Adopting recently developed clean laboratory techniques, antimony (Sb) and scandium (Sc) deposition were measured in a 63.72 m-long ice core (1842-1996) and a 5 m deep snow pit (1994-2004) collected on Devon Island, Canadian High Arctic. Antimony concentrations ranged from 0.07 to 108 pg g À1 with a median of 0.98 pg g À1 (N ¼ 510). Scandium, used as a conservative reference element, revealed that dust inputs were effectively constant during the last 160 years. The atmospheric Sb signal preserved in the ice core reflects contamination from industrialisation, the economic boom which followed WWII, as well as the comparatively recent introduction of flue gas filter technologies and emission reduction efforts. Natural contributions to the total Sb inventory are negligible, meaning that anthropogenic emissions have dominated atmospheric Sb deposition throughout the entire period. The seasonal resolution of the snow pit showed that aerosols deposited during the Arctic winter, when air masses are derived mainly from Eurasia, show the greatest Sb concentrations. Deposition during summer, when air masses come mainly from North America, is still enriched in Sb, but less so. Snow and ice provide unambiguous evidence that enrichments of Sb in Arctic air have increased 50% during the past three decades, with two-thirds being deposited during winter. Most Sb is produced in Asia, primarily from Sb sulfides such as stibnite (Sb 2 S 3), but also as a by-product of lead and copper smelting. In addition there is a growing worldwide use of Sb in automobile brake pads, plastics and flame retardants. In contrast to Pb which has gone into decline during the same interval because of the gradual elimination of gasoline lead additives, the enrichments of Sb have been increasing and today clearly exceed those of Pb. Given that the toxicity of Sb is comparable to that of Pb, Sb has now replaced Pb in the rank of potentially toxic trace metals in the Arctic atmosphere. Aim of the investigation Metals are ubiquitous in our modern world, and toxic metals such as Cd and Pb ranking high among major pollutants
Journal of Geophysical Research, 1983
Measurements of A1, Pb, 21øpb, and 21øpo in precipitation and aerosol were used to estimate wet and dry components of the atmospheric flux at a semiremote site in northern Wisconsin. Wet deposition was primarily responsible for removing airborne Pb, 21øpb, and 2•øpo, while dry deposition was also important for A1. Although Pb and 2•øpb both exhibited a wet/total ratio of about 0.8, precipitation washout ratios for Pb and 2•øpb suggested that 2•øpb was washed from the atmosphere with greater efficiency than was Pb. This phenomenon was also illustrated by comparing the weighted mean annual specific activity in precipitation (976 pCi 21øpb mg -• Pb) and in aerosol (476 pCi 21øpb mg -• Pb) at this site between June 1979 and June 1980. By consideration of the apparent differential precipitation washout of Pb and 2•øpb, a reasonable estimate of the atmospheric flux of Pb was obtained by using the mean Pb/2• øPb ratio in aerosol and the 21Opb flux. The atmospheric flux to northern Wisconsin was estimated to be 0.8 #g crn -2 yr -• for Pb and 0.70 pCi cm -2 yr -• for 2•øpb. INTRODUCTION Despite convincing evidence that the atmosphere is the principal source of lead to the oceans [Duce et al., 1976; Patterson et al., 1976; Schaule and Patterson, 1981; Settle and Patterson, 1982] and many freshwater lakes [Winchester and Nifon•?, 1971; Gatz, 1975; Eisenreich, 1980; Talbot, 1981], surprisingly few data have been reported on wet and dry deposition of Pb and the naturally occurring radionuclide 2'øpb (t,/z = 22.3 years) to surface waters. In most cases the atmospheric fluxes of Pb and •"øPb have been inferred from their accumulation rates in sediments. Although this sometimes provides an adequate time-averaged record of lead deposition for chronological and historical input purposes, the specific aspects of the atmospheric input are not revealed. Furthermore, sedimentation regimes and postdepositional processes may redistribute the lead, making such natural repositories unreliable indicators of the actual lead flux. It is therefore highly desirable to conduct atmospheric sampling to estimate atmospheric input to the system. In conjunction with our studies of lead transport within lake systems (R. W. Talbot and A. W. Andren, unpublished manuscript, 1982), it was also of particular interest to us to explore the relationships between Pb and 2•øpb in both precipitation and aerosol over a period of 1 year. These measurements have been used to assess the relative contributions of wet and dry fallout to the total atmospheric deposition of Pb and 2 • Opb ' The specific activity (picocuries of 2• Opb per milligram of Pb) and the ratios Pb/A1 and 2•øPb/A1 have been employed to evaluate the potential for using 2•øpb as a natural geochemical tracer of Pb at sites removed from direct urban influence. SAMPLE COLLECTION Atmospheric sampling was conducted at a site within the Northern Highlands State Forest of north central Wisconsin (Vilas County). The site (46ø3'N, 89ø39'W) is about 80 km southeast of Lake Superior and 190 km west of the northern basin of Lake Michigan. This section of northern Wisconsin is sparsely populated, with the closest major industry being located at Green Bay, Wisconsin, approximately 200 km southeast of the sampling site. The sampling station was located in an open field (area of •,-1 ha) on the grounds of the Wisconsin Department of Natural Resources Forestry Headquarters. The surrounding area is covered by pine forest and a dense population of small lakes. The nearest principal highway is 4.5 km from the sampling site. Total suspended particulate (TSP) samples were collected with a General Metal Works high-volume air sampler. A Sierra model 235 high-volume cascade impactor was employed to collect size-differentiated aerosol samples. Aerosol was collected on Whatman 41 filter paper media. Whatman 41 was used since it exhibits low banks for metals such as lead [Dams et al., 1972; Bate et al., 1976; Sievetinct et al., 1978].
Journal of Geophysical Research, 1990
The concentrations of 7Be and 21øPb were measured in surface air and fresh and aging snow samples from Summit (72o20'N, 38o45•V) and Dye 3 (65 ø10'N, 44ø45'W) Greenland, during June and July 1989. The aerosol concentrations of these radionuclides showed rapid variations at both sites, but were nearly twice as high, on average, at Summit. Concentrations in the 16 fresh snowfall events that were sampled also showed wide variability, but the averages were the same at the two sites. The apparent difference in air-snow fractionation and the lack of coherence in the concentration in air time series between the two sites indicate previously unsuspected complexity in atmospheric dynamics over the ice sheet. Improved understanding of atmospheric processes, and how the results of those processes are recorded in snow and ice, is crucial for full interpretation of the information about past atmospheric chemistry and climate contained in the snow and ice of glaciers around the world.
Peat bogs in northern Alberta, Canada reveal decades of declining atmospheric Pb contamination
Geophysical Research Letters, 2016
Peat cores were collected from six bogs in northern Alberta to reconstruct changes in the atmospheric deposition of Pb, a valuable tracer of human activities. In each profile, the maximum Pb enrichment is found well below the surface. Radiometric age dating using three independent approaches (14 C measurements of plant macrofossils combined with the atmospheric bomb pulse curve, plus 210 Pb confirmed using the fallout radionuclides 137 Cs and 241 Am) showed that Pb contamination has been in decline for decades. Today, the surface layers of these bogs are comparable in composition to the "cleanest" peat samples ever found in the Northern Hemisphere, from a Swiss bog~6000 to 9000 years old. The lack of contemporary Pb contamination in the Alberta bogs is testimony to successful international efforts of the past decades to reduce anthropogenic emissions of this potentially toxic metal to the atmosphere.