The historical residue trends of DDT, hexachlorocyclohexanes and polycyclic aromatic hydrocarbons in an ice core from Mt. Everest, central Himalayas, China

摘要

High mountains may serve as "cold traps" for persistent organic pollutants (POPs) and ice cores can provide long-term records of atmospheric deposition of pollutants. In this study, DDT, hexachlorocyclohexanes (HCHs) and polycyclic aromatic hydrocarbons (PAHs) in an ice core from East Rongbuk Glacier were analyzed and the deposition fluxes of these pollutants were investigated. Concentrations of total DDTs reached maxima of approximately 2 ngl~(-1) in mid-1970s, which is corresponding to the peak of malaria cases in India (in 1976). The decrease of DDT concentration after 1990s was in-line with the ban of DDT in India (in 1989). High level of α-HCH was observed in early 1970s and it showed a decrease to undetectable level at the end of 1990s, which is in agreement with the period when India banned the usage of HCH (in 1997). Concentrations of total PAHs sharply increased after 1990 and the peak (approximately 100ng l~(-1)) was found at the end of 1990s, when India entered the rapid industrialization (urbanization). PAHs in the ice core are dominantly pyrogenic in source, and are mainly from incomplete combustion of coal and biomass burning. Good correlations among concentrations of PAHs, nssSO_4~(2-) and microparticles in snow pit samples showed that the origin of the PAHs and nssSO_4~(2-) is often the same and they may be absorbed by particles and transported to high mountain regions by atmospheric circulation.