Infuence of anthropogenic activity on the lead isotope signature of Thau Lake sediments (southern France): origin and temporal evolution (original) (raw)
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Pb isotopes and Pb concentrations were measured in two sediment cores sampled in Lake Geneva (i) at the center of the basin (central plain) and (ii) in an area which receives the effluents of the wastewater treatment plant of Lausanne as well as runoff inputs. The presence of an anthropogenic contribution is observed over all the sampled period (150 years), even at the center of the lake. At both sites, the maximum contamination of Pb occurred in the late 1970s, and has declined to present. The site close to Lausanne received much more Pb than the one at the center of the lake. Surprisingly, the Pb isotopes show that gasoline-derived Pb has had a minor influence, at least over the last 20 years. Instead, deposition of Pb from industrial (and domestic) activities predominates. This study demonstrates that one of the major limitations of the isotopic method is the poor (or partial) knowledge of how the isotopic compositions of potential sources have evolved through the past. A simple method of sample dissolution, based on HNO3 leaching assisted by microwave, is also presented. We believe that this sample preparation can be extensively used because it provides a reliable estimate of Pb having an anthropogenic origin.
Science of The Total Environment, 2019
Historical mining has a millennial scale history on the globe often leaving a long-lasting imprint on the environment. Previous results on trace metal concentrations in the Pyrenees, where extensive mining (Ag, Fe) occurred from the Antiquity to the 19 th century, suggest that ≥600 tons of anthropogenic lead (Pb) is stored in soils in the Haut-Vicdessos area (France). Yet the potential bioavailability of this legacy contamination to contemporary biota remains unclear. We therefore asked if previously reported high-levels of legacy Pb can be seen in other environmental compartments including aquatic biota, and how these are distributed within the biota. Based on Pbisotopic data, we also assessed if any Pb contamination found in contemporary biota can be linked to local/regional mining. Samples of sphagnum, soil, sediment, biofilm, and fish (Salmo trutta and Phoxinus phoxinus) were collected from three adjacent valleys in the Haut-Vicdessos area. Pb concentrations varied both between sites (i.e. decreasing concentrations with increasing distance from the former mine) and between within-site environmental compartments (i.e. soil > biofilm ≥ sediment > sphagnum > fish) as well as within organisms (i.e. entire organism>liver>muscle). Further, Pb-isotopic ratios (206 Pb/ 207 Pb, 208 Pb/ 207 Pb and 208 Pb/ 206 Pb) measured in soil, biofilm, and fish indicated both natural (weathering bedrock) and anthropogenic (industrial, transportation and/or former mining activities) sources of Pb-deposition to the area. Generally, body Pbconcentrations were within regulatory guidelines, yet contemporary biota in the upper Haut-Vicdessos area, and their prey, still showed a large range of Pb isotopic signatures, of which former mining activities appeared to have a strong influence. Our study showed that mining derived legacy Pb continues to affect onsite biota even if mining activities ceased >100 years ago, thus reflecting the long-lasting impact of human-environment interaction, suggesting that ecosystem conditions may remain impaired centuries after activities have ceased.
Applied Geochemistry, 2009
Editorial handling by Dr. R. Fuge a b s t r a c t Total Pb concentrations and isotopic composition were determined in stream-bed sediments and bedrock from 29 small agricultural or forested catchments in the Gascogne area (SW France). The contribution of Pb from various natural and anthropogenic sources was investigated in this rural area which is very weakly impacted by industrial or urban emissions. Environmental parameters in catchments (importance of forest cover, organic matter and oxide content in sediments) were considered. A combination of geochemical (enrichment calculation, sequential extraction) and isotopic investigations was performed to constrain the origin of Pb and the distribution of anthropogenic Pb in sediments. Most of the sediments have low total Pb content compared to other agricultural regions more impacted by industrial or urban emissions. The results indicated a moderate but significant Pb enrichment, particularly for catchments draining forested areas. This enrichment was positively related to organic C content in sediment and catchment forest cover, whereas in entirely cultivated catchments it was related to Fe-oxide content.
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.
Tracking natural and anthropogenic Pb exposure to its geological source
Evans, J., Pashley, V., Madgwick, R., Neil, S. and Chenery, C. 2018. Tracking natural and anthropogenic Pb exposure to its geological source. Scientific Reports 8(1): 1969.
Human Pb exposure comes from two sources: (i) natural uptake through ingestion of soils and typified by populations that predate mining activity and (ii) anthropogenic exposure caused by the exposure to Pb derived from ore deposits. Currently, the measured concentration of Pb within a sample is used to discriminate between these two exposure routes, with the upper limit for natural exposure in skeletal studies given as 0.5 or 0.7 mg/kg in enamel and 0.5/0.7 μg/dL in blood. This threshold approach to categorising Pb exposure does not distinguish between the geological origins of the exposure types. However, Pb isotopes potentially provide a more definitive means of discriminating between sources. Whereas Pb from soil displays a crustal average 238U/204Pb (μ) value of c 9.7, Pb from ore displays a much wider range of evolution pathways. These characteristics are transferred into tooth enamel, making it possible to characterize human Pb exposure in terms of the primary source of ingested Pb and to relate mining activity to geotectonic domains. We surmise that this ability to discriminate between silicate and sulphide Pb exposure will lead to a better understanding of the evolution of early human mining activity and development of exposure models through the Anthropocene.