Selected organochlorine pesticides and polychlorinated biphenyls in atmosphere at Ruoergai high altitude prairie in eastern edge of Qinghai-Tibet Plateau and their source identifications

Compared to the low-altitude areas, high-altitude regions have low air temperature and relatively high snow precipitation. These climatological characteristics will affect the environmental behavior of persistent organic pollutants (POPs) in such a special geographical environment, leading to cold-trapping of certain POPs in these areas. Ruoergai highland prairie in the eastern edge of the Qinghai-Tibetan Plateau was selected to study the distribution characteristics of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in aerosols and gas phase samples collected in two seasons of 2011 and measured by isotope dilution-HRGC/HRMS method. OCPs and PCBs in the Ruoergai air were at low levels compared with the adjacent populated areas such as Lanzhou and Chengdu. Higher concentrations of POPs in aerosol and gas phase were observed in winter than in summer, showing the impact of monsoon on the transport of POPs to this region. Northwesterly winds in winter may transport OCPs and PCBs from industrial and agricultural areas in the northwestern China. HCB, α-HCH, and PCB 28 were the predominant compounds found in the air. Soil to air fugacity ratios show that Ruoergai soils behave as a secondary source of the relatively volatile compounds (HCHs, α-endosulfan, PCB 28 and 52) to the atmosphere during summer and behave as a sink of atmospheric DDTs due to the OC-rich soils as well as lower temperatures. Similar 206Pb/207Pb and 208Pb/207Pb ratios in Ruoergai aerosols to those of aerosols of Lanzhou and ores in Qinghai, Xinjiang, Kazakhstan, and Russia may indicate that the aerosol sources were mainly related to air mass passing over the neighboring regions and countries.