Characterizing the gas-phase organochlorine pesticides in the atmosphere over the Pearl River Delta Region

The organochlorine pesticides (OCPs) in the atmosphere were measured at four sampling sites located in Guangzhou (GZ), Zhaoqing (ZQ) and Hong Kong (HK) over the Pearl River Delta Region (PRDR) in one year duration from August 2006 to August 2007. Total 14 OCP species in the gas phase including 6 DDTs, 2 Chlordanes, 4 HCHs, HCB and heptachlor (HEP) were studied. It was found that Guangzhou had the highest concentration of DDTs and the mean concentrations of OCPs at these sampling sites were higher than those obtained in other rural/urban regions in the world. The concentrations of most OCPs in summer were higher than those in winter excluding TC, HCB and HCH. The ratios of α- to γ-HCH and o,p′- to p,p′-DDT showed that HCHs in GZ and ZQ might come from the current usage of lindane and dicofol, but in HK might be from other sources. The results using 5 days backward air trajectory analysis indicated that the high concentrations of γ-HCH and HCB were mainly related to air mass through the potential source regions through long-range transport and local usage should not be overlooked.