Hybrid NAA for study of organic halogens in precipitation in Beijing, China

The rainwater samples were collected from Beijing, China, from May 2006 to November 2007 and measured by a hybrid neutron activation analysis (NAA) method combining with gas chromatography (GC) for the concentrations and distribution of extractable persistent organic halogens (EPOX = EPOCl + EPOBr + EPOI), polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs). The average concentrations of EPOCl, EPOBr and EPOI in all the samples were 102, 0.18, and 0.31 μg/L, respectively. The relative proportions of the known organochlorines (84 PCB congeners + 10 OCPs) to total EPOCl were 0.03–1.44%, which implied that most of EPOCl measured in rainwater were unidentified. Significant correlations between the logarithms of the concentrations of EPOCl and EPOBr (r = 0.65, p < 0.0001) or EPOI (r = 0.72, p < 0.0001) and between the concentrations of EPOBr and EPOI (r = 0.79, p < 0.0001) were observed, which suggested that EPOCl, EPOBr and EPOI in rainwater might mainly come from the similar sources. There were no clear seasonal trends for the concentrations of EPOX. PCBs in rainwater were dominated by tetra-CB and tri-CB. The homologue was consistent with the technical PCB products in China, which indicated that PCBs in the environment mainly came from the historical usage of technical PCB products.