High-resolution trace element records of an ice core from the eastern Tien Shan, central Asia, since 1953 AD

High-resolution records of trace elements (Ba, V, Cr, Mn, Co, Ni, Cu, As, Rb, Sr, Mo, Cd, Sn, Sb, Tl, Pb, Bi, Th, and U) quantified in an ice core recovered from the Miaoergou glacier in the eastern Tien Shan, central Asia, spanning the period 1953-2004 AD, provide the first comprehensive time series on characterizing the relative contributions from natural and anthropogenic sources to the deposition of trace elements in central Asia. It is suggested that rock and soil dust is the most important natural source for most of elements investigated. Slight decreases in concentrations (or fallout fluxes) of crustal elements, such as Ba, Mn, Rb, Th, U, and Sr are observed during recent decades, which may be due to decreases in dust emissions from source regions and a decrease of accumulation rate since 1980s. The increasing trends of median concentrations and crustal enrichment factors (EFc) of V, Cr, Co, Ni, Cu, and Mo, during the period 1953-2004 AD, are insignificant in comparison to their respective levels prior to 1953 AD. However, slight enhancements of both concentrations and EFc are observed for Cd, Sb, Pb, Bi, Tl, and Sn since 1950s. Such recent increases are likely to be attributed to enhanced anthropogenic emissions, such as metal smelting, mining, stationary fossil fuel combustion, and combustion of gasoline due to human activities in Eurasia, particularly Xinjiang in northwestern China, Russia, and Kazakhstan. Our study supports evidence that environmental contamination has become a global problem for Pb and Bi and a large-scale phenomenon for Cd, Sb, Tl, and Sn.