Lead isotopic determination of historical sources of lead to Lake Erie, North America (original) (raw)
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Isotopic record of lead pollution in lake sediments from the northeastern United States
… et Cosmochimica Acta, 1995
Although it is common knowledge that Pb concentrations have increased in lake sediments in the northeastern United States over the last 150 years, the processes responsible have been the subject of debate. In this study, differences in lead isotopic compositions and concentrations in sediment from large lakes (Lake Erie, Ontario, and Michigan) and small ones (Deep Lake and Lake Andrus) are used to infer temporal changes in the source(s) of anthropogenic Pb in the Great Lakes region. A natural (background) component of Pb is present in sediment deposited prior to 1860 in Lake Erie and the other lakes as indicated from low Pb concentrations and uniform lead isotopic compositions.
Whole-lake lead burdens in sediments of lakes in southern Ontario, Canada
Hydrobiologia, 1982
The anthropogenic stable lead content of the sediments of eight softwater Precambrian lakes in southern Ontario was measured at 34-92 sites per lake. Whole-lake anthropogenic lead burdens varied between only 610 and 770 mg m-2. There was no relationship between lead burden and either water replenishment time of the lake (Tw) or the ratio of watershed area to lake area (Ad/Ao), which varied by factors of 4 and 12 respectively. These results can be explained if a) the lead deposition in this region is uniform, and b) the only significant input of lead to the lakes is via deposition from the atmosphere directly on the lakes' surfaces. Therefore spatial differences in anthropogenic lead within a lake represent the redistribution or focusing pattern of the sediments.
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.
Journal of Paleolimnology, 2005
A simple binary mixing model is used to determine the isotopic ratios of lead (Pb) pollution sources to a lake located near a smelter closed because of excessive Pb aerosols (Horseshoe Lake Madison County, Illinois, USA). As a control, we also examine a relatively unpolluted lake in a rural area of Southern Illinois (Horseshoe Lake Alexander County). Sediment cores were taken from both lakes and analyzed for Pb and Pb isotopes by ICP-MS. The mixing model shows that Madison County Horseshoe Lake had 3 different sources of Pb in its history. The first source is sediment from the Mississippi River with an intermediate 206 Pb/ 207 Pb ratio (1.223 ± 0.009) which dominates inputs in pre-settlement times. From 1750 to 1933, the source of pollution Pb has the high 206 Pb/ 207 Pb ratio (1.256 ± 0.005) characteristic of ore from the southeast Missouri Pb mines. The most recently deposited pollution Pb comes from a source with a low 206 Pb/ 207 Pb ratio (1.202 ± 0.005). This source is similar in isotopic composition to pollution Pb found by several other investigators in the Eastern US and probably represents the mixture of ores used in modern industrial processes. It is unclear from the isotopic composition whether this source at Horseshoe Lake is the local Pb smelter or vehicle exhaust. The sediment core from Horseshoe Lake, Alexander County, shows a less variable isotopic composition. The binary mixing model showed a source composition of 1.225 ± 0.003 before 1850 and 1.231 ± 0.003 after this date. The change does not indicate a pollution source, but may be a shift in the sources of natural sediment with slightly different isotopic ratios to the lake. Our results show the value of simple binary mixing models to reconstruct the isotopic composition of Pb sources to lakes.
Lead analysis of sediment cores from seven Connecticut lakes
2001
Lead analyses were performed on sediment cores from seven Connecticut lakes by dilute acid leaching. The absolute concentrations of lead varied from core to core, but the lead profiles were similar in all of the cores, and each depicted a point where the concentration of lead sharply increased above background levels. The background lead concentrations observed in the bottom portions of the cores ranged from 12-54 µg Pb/g sediment with a mean of 30 µg Pb/g, and increased to a mean maximum of 310 µg Pb/g. In six of the lakes significant increases above background levels were not noted until between 1924 and 1952, suggesting that, at least for Connecticut lakes, the point in a lake sediment core where the concentration of lead began to increase was after ca. 1924, and on average about 1930. Lead concentrations declined in the surface sediments of only three of the lakes, mostly since the 1980's, and presumably in response to the phasing out of leaded gasoline. However, significant declines in lead concentrations were not observed in the remaining cores, possibly due to increased motor vehicle use within the airshed of the lakes and/or changes in the export of lead to the lakes from their watersheds.
Historical changes in anthropogenic lead fallout in southern Ontario, Canada
Hydrobiologia, 1982
A quantitative historical record of anthropogenic lead deposition has been determined for the Haliburton region of southern Ontario from a) the relative change in lead concentration in undisturbed sediment cores, and b) the total anthropogenic lead deposition measured in the region. The first parameter was measured on two sediment cores from a meromictic lake. Total lead deposition was assumed to be the average of that measured for eight other lakes in the study area. The validity of this historical record was tested on sediment cores from nearby dimictic lakes. Predicted lead concentration profiles closely resembled observed profiles.
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.
Proceedings of the National Academy of Sciences, 2000
Francisco Bay waters from 1989 to 1998 have brought new insights into the cycling of anthropogenic lead in estuaries. Isotopic compositions of lead in the shallow (<2 m) southern reach were essentially invariant (ϳ90% derived from 1960s-1970s leaded gasoline) during the study period because of limited hydraulic flushing and the remobilization of lead from bottom sediments. In contrast, in the northern reach freshwater flushing from the San Joaquin and Sacramento rivers produced seasonal and decadal variations in lead isotope compositions. The seasonal shifts are attributed to advection of soils containing late 1980s gasoline lead into the bay during winter rains. Mass balance calculations indicate that only a small fraction (1-10%) of this leaded gasoline fallout from the late 1980s has been washed out of the San Joaquin and Sacramento rivers' drainage basin by 1995. Superimposed on this seasonal cycling was a long-term systematic shift in the component of gasoline lead expressed in the river systems, with a small (ϳ5-10%) decrease in the amount of 1960s-1970s gasoline lead in river and North Bay waters. The retention of gasoline lead in the river systems draining into the bay as well as San Francisco Bay sediments indicates that historic gasoline deposits may remain in the combined riparian͞estuarine system for decades. Such a persistence is in contraindication to recent reports of rapid (annual) decreases in lead contamination in other environments, and the link between climate and contaminant transport suggests local or global climate change will have an impact on contaminant distribution and fate.
Environmental Science & Technology, 2018
There has been a considerable reduction in anthropogenic lead (Pb) emission to the atmosphere in recent decades. However, reduction in Pb inputs to many lakes does not match this as Pb stored in catchment upper soil layers, derived from previous deposition, has become an important source although it is difficult to assess quantitatively. This work uses atmospherically deposited 210 Pb as tracer to track Pb movement and so is able, for first time to calculate the relative Pb inputs from direct atmospheric deposition and catchment sources to lakes in the UK directly. Within individual lake sites, ratios of 210 Pb/Pb in the catchment terrestrial mosses were normally an order of magnitude higher than those in the catchment surface soils, trapped lake sediments and the surface sediments in the lake-bottom. Results suggest that the Pb isotope signatures in the mosses are close to or dominated by atmospheric depositions, and it is reasonable to use ratios of 210 Pb/Pb in terrestrial mosses collected from