Atmospheric Transport and Bulk Deposition of Organochlorine Compounds at Leigongshan Nature Reserve in Southwestern China

摘要

Atmospheric and bulk deposition samples collected at Leigongshan Nature Reserve (LNR) were analyzed to explore the status, transport, and deposition of atmospheric pollution—specifically, organochlorine compounds—in the foggy mountains of southwestern China. Prohibiting and restricting persistent organic pollutants in the surrounding areas has led to a decline in organochlorine pesticides and polychlorinated biphenyls (PCBs), but not hexachlorobenzene (HCB), in the air. Wet deposition is a factor that strongly influences the atmospheric input at LNR. Despite the relatively low atmospheric concentration levels of hexachlorocyclohexanes (HCHs) and HCB, heavy precipitation can increase the deposition of these compounds in summer. The airborne HCHs exhibited a “bimodal” pattern, with higher concentrations in spring and autumn and lower concentrations in summer, the latter of which are results of high surface input into the ground along the transport routes of these compounds from South and Southeast Asia to southwestern China. The HCB at LNR mainly originates in mainland China. The deposition fluxes are influenced by the enhanced washout of atmospheric particles in the rainy season and increased particle-associated content in winter. The potential sources of o,p? -DDT, p,p? -DDT, and PCBs are distributed widely over low-latitude western areas and eastern China. Atmospheric transport and deposition in spring and summer contribute a significant proportion of the total fluxes annually when air masses originating in Southeast Asia arrive, increasing rainfall at LNR. The foggy local weather may also enhance this deposition, eventually leading to the accumulation of pollutants at LNR.