Spatial and seasonal variations of organochlorine compounds in air on an urban-rural transect across Tianjin, China

The spatial and seasonal variations of atmospheric organochlorine compounds (OCs) concentrations was investigated at six sites on an urban-rural transect in Tianjin, China from July 2006 to June 2008 using XAD-based passive air samplers. The samplers were deployed for six time periods. Hexachlorocyclohexanes (HCHs) air concentrations were highest at Tanggu and Tuanbowa and decreased dramatically further away from these two sites. The maximum proportion of beta-HCH compared to Sigma HCHs (12.1-32.2%) was found in Hangu, suggesting its persistence. The alpha/gamma-HCH ratio was between 1.26 and 5.79 which signified the combined influence of technical HCHs and lindane. Dichlorodiphenyltrichloroethane related compounds (DDTs) were higher at Hangu compared with other sites which was attributed to its continuing production there. Low p,p'-DDE/p,p'-DDT in Hangu and Tanggu were found. reflecting the fresh input of DDTs while the relatively high o,p'-DDT/p,p'-DDT ratios indicated the agricultural application of dicofol. Polychlorinated biphenyls distribution elucidated that the urban area could be their emission source. Hexachlorobenzene. with the highest concentrations in Tanggu. showed the smallest industrial/urban-rural gradient (similar to 4-9 times) than those of other chemicals (similar to 17-49 for Sigma HCHs, similar to 10-77 for Sigma DDTs), but comparable with PCBs (PCB28 and PCB52) (similar to 3-10). Seasonal variations of OCPs; were featured by higher concentration in spring and summer and lower in winter. This was likely associated with (i) their temperature-driven re-volatilization and (ii) application of dicofol in late spring and summer and DDT-containing antifouling paints for fishing ships in summer. However seasonality of PCBs concentrations was site-specific on the Tianjin scale. (C) 2009 Elsevier Ltd. All rights reserved.