Levels of Organic Halogen Compounds in the Atmosphere in Northern China

Organic halogens have long been recognized to be severe environmental pollutants, because of their persistence, bioaccumulation and potential hazardous impact on human health. In this study, a large-scale network of 31 passive air sampling sites was used to better understand the atmospheric distributions of organic halogens across China. EOCl, EOBr, EOI, and PCBs in the atmospheric samples were determined by a hybrid NAA method combined with GC-MS. EOCl, EOBr, EOI, and PCBs exhibited a huge urbanrural gradient. The highest values were detected in the areas of high usage and emission, which were linked to the local urbanization with relatively rapid economic development in China. The results clearly indicate that these pollutants mainly come from industrial pollution. Higher EOCl contents in traffic areas state that exhaust emission from vehicle is another main source of organochlorines in air. The relative proportions of the known organochlorines (84 PCB congeners) to total EOCl are less than 1.0%, which implies that most of EOCl measured in air are unknown. PCBs are dominated by di-CB (mean: 41%) and tri-CB (mean: 43%). No systematic distribution differences of PCB congeners in the sampling locations are found, which suggest that atmospheric contamination of PCBs in China are still controlled by primary sources, rather than secondary ones.