Past atmospheric Pb deposition in Lake Qinghai,northeastern Tibetan Plateau |
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| Authors: | Zhangdong Jin Yongming Han Li Chen |
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| Institution: | (1) State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, 710075, China;(2) 1st Oil Production Company, Jiangsu Oil Field, SINOPEC, Yangzhou, 225265, China |
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| Abstract: | Two short sediment cores were recovered from sub-basins of Lake Qinghai, China and were analyzed for concentrations of Pb
and 16 other elements to determine historic, regional atmospheric Pb deposition on the Tibetan Plateau. Core chronologies,
dating back to the eighteenth century, were established using activities of 210Pb and 137Cs. The 17 elements were divided into three principal components. Variations in concentrations of PC1 elements (Al, Cr, Cu,
Fe, K, Mn, Ni, and Ti) demonstrate different patterns between the two cores, and are attributed to different sediment sources
in the two sub-basins. PC2 elements (Ba, Ca, Na, and Sr) may be associated with the degree of catchment weathering and/or
water chemistry. Four elements (Pb, Zn, P, and Co) are related to both PC1 and PC2, and reflect a mixture of natural and anthropogenic
sources. The PC3 element is Mg in the north sub-basin, and is perhaps related to aragonite precipitation and/or increased
farming. Elevated Pb concentrations in uppermost sediments of both cores signify a recent regional/global increase in anthropogenic
Pb release into the environment. After subtracting lithogenic Pb, derived from rock weathering and/or dust and normalized
to the background immobile element Ti, results suggest that excess, anthropogenic Pb is transferred to the lake and its sediments
predominantly via the atmosphere. This anthropogenic atmospheric Pb is comparable in magnitude and displays similar variation
patterns in the two cores, reflecting regional atmospheric deposition and local erosion. The average anthropogenic Pb deposition
rate in Lake Qinghai since the 1960s has been ~12.2 ± 3.5 mg/m2/a, comparable with atmospheric Pb fluxes reported for sites elsewhere in the northern hemisphere. |
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