Study On Organohalogens Contaminations In Precipitation In Shijingshan District, Beijing

Due to their outstanding cancinogencity, mutagencity and teratogencity, as well as persistence and bioaccomulation, organohalogens have gained unmost attention as they threaten human heath. Their wet atmospheric deposition was important for investigating the transference and conversion. In this study, precipitation samples in Shijingshan District, Beijing were collected during 2006 and 2008. Neuton activation analysis (NAA) has been used to detect extractable organohalogens(EOX) and persistent extractable organohalogens(EPOX), and gas chromatograph-electron capture detector (GC-ECD) has been used to detect organochlorine contaminations such as: organochlorine pesticides (OCPs), and polychlorinated biphenyles(PCBs). The main results and conclusions are summarized as follow:1 NAA for EOX and GC-ECD for organochlorine contaminations in precipitation. The detection limits of NAA were: Cl: 50ng, Br: 8ng, I: 3.5ng, and the detection limit of GC-ECD were: 0.018ng~1.85ng. Relative standard deviation was in the range: 5%~22%. Recoveries ranged from 62% to 129%, which met requirment of trace organic compounds analysis (recovery range: 100%±40% )of American Environmental Protection Agency(EPA).2 Analysis of extractable organohalogens contamination. Concentrations of EOI, EOBr, EOCl were: 0.13~2.06μg/L, 0.11~1.99μg/L, 9.93~262.73μg/L, respectively. Majority of EOX were acid-liable or acid-soluble. EOCl was more persistent than the other organohalogens contaminations. The major proportion of organohalogens was organochlorine contamination. The known organochlorines account for little proportion of EOCl.3 Analysis of organochlorine contaminations. 6 OCPs and 84 PCBs were detected. DDTs and HCHs were major proportion of OCPs, and their concentrations were:∑HCHs,1.5～69.9 ng/L,∑DDTs,1.5~69.9 ng/L. The concentrations of∑PCBs was in the range: 22.04 ~2159.47 ng/L; There were illegal inputs ofγ-HCH and few"new"inputs of DDT to the environment by analyzing composite of isomers. Low chlorinded PCBs accounted for major porportion. Considering the temporal trend, concentrations of organochlorine contaminations tended to lower; There was negative correlation between concentration and temperature and volume, and volume was more effective. When analysing wet deposition, scanverging of DDTs which were mainly in particles was more effective than HCHs which were mainly in gas, which indicated that particles scanverging was the major way of wet deposition. Fluxes of PCBs, DDTs were decreasing obviously, but there was seasonly trend for HCHs and higher fluxes appeared in July and August every year. Annual fluxes of PCBs was much higher than other districts, which indicated that the pollution of PCBs in Shijingshan District was serious.