Study On Atmospheric Pollution, Source,Long-range Transport Potential And Health Risk Of HCHs In Gansu Province And Its Surrounding Areas

Hexachlorocyclohexanes(HCHs), as one of organochlorine pesticides, is difficult to degrade in environment. Characterized as persistent organic pollutants, HCHs posses the ability to be transported over long distances through air, water etc., and to be accumulated in living tissues through food chain. HCHs also have the properties of high toxicity and potential carcinogenicity. Located in the northwest arid and semi-arid areas, Gansu province and its surrounding areas is a production base of grain crop and commercial crop in Northwest China in which technical HCHs was heavily used. In this study, air samples were seasonally collected using polyurethane foam based passive air samplers for a year in Gansu province and its surrounding areas and determined for HCHs. The atmospheric pollution, seasonal and spatial variation and sources of HCHs were also investigated. Furthermore, The long-range transport potential and overall persistence of HCHs through air and water in Lanzhou were estimated by the TaPL3model. In addition, population exposure to HCHs and health risk of four subgroups in Lanzhou were evaluated by a multi-pathway human exposure model of US EPA. The results shows that:(1) Atmospheric concentrations ofCHs (a-HCH+β-HCH+γ-HCH+d-HCH) were61.09～1365pg·d-1with the average concentration of288.00pg·d-1in Gansu province and its surrounding areas. In the study areas, theCHs concentrations of Hami in Xinjiang, Guazhou, Jiuquan, Wuwei, Chengxian in Gansu and Yinchuan in Ningxia were higher than the other regions. There was no significant difference of the concentrations of a-HCH, but the concentrations of β-HCH in Guazhou and Hami were a little higher, as were the concentrations of γ-HCH in Jiuquan, Zhangye, Jinchang, Wuwei, Baiyin, Dingxi and Tianshui. The urban, rural, and suburban sampling sites of each region didn’t show significant spatial differences, and the seasonal pollution characteristic of ΣHCHs exhibited the higher levels in autumn and winter and the lower levels in spring and summer. Source apportionment indicated HCHs were mainly originated from historical technical-HCHs residues while there still existed recent Lindane usage in some region.(2) The characteristic travel distance(CTD) of HCHs in Lanzhou through air were between242.2km(a-HCH)～4470.2km(β-HCH), the CTDWater were between1759.6km(a-HCH)～ 173069.lkm(y-HCH); The overall persistence(Pov) of HCHs in air were between15.0d(a-HCH)-1161.6d(y-HCH), the PovWater were between39.6d(a-HCH)～1939.6d(y-HCH). There was no direct link between CTD and Pov.(3)The average daily exposure doses to HCHs of four subgroups in Lanzhou were:2.41ng-(kg-d)-1for adults male,2.63ng-(kg-d)-1for adults female,1.021ng-(kg-d)-1for children male and1.016ng·(kg-d)-1for children female, respectively. Food and water ingestion were the most significant exposure routes, accounting for more than96%and1.17%～1.97%, respectively. In addition, to the Lanzhou population, the cancer risks of HCHs exposure were7.61×10-6and8.28×10-6for adults male and female,3.22×10-6and3.20×10-6for children male and female, respectively, which were within the acceptable level defined by US EPA(10"6～10-4). The non-cancer risk of Lanzhou population caused by HCHs exposure were8.36×10-3and9.05×10-3for adults male and female,3.53×10-3and3.51×10-3for children male and female, respectively, which were much less than1and indicated a low potential health risk to human bodies.