Diastereoisomer- and enantiomer-specific profiles of hexabromocyclododecane in the atmosphere of an urban city in South China.

Hexabromocyclododecanes (HBCDs) are ubiquitous contaminants in the environment, but little is known on the occurrence and distribution of HBCDs in the background atmosphere of urban environments. In this study, air samples were collected from four sites in the city of Guangzhou, a typical fast developing metropolitan of South China, for quantifying the concentration levels, diasteroisomer profiles, gas-particle distribution and enantiomeric fractions of HBCDs. The results showed that the measured mean atmospheric HBCD concentrations ranged from 0.69 to 3.09 pg/m3, which were similar to those reported from remote or urban sites of the U.S., but were significantly lower than those of Europe. The analysis on diastereoisomer profiles indicated that alpha-HBCD (59--68%) was the dominant isomer and beta-HBCD was a minor isomer in all air samples, which appeared to be different from commercial products. A large variable percentage of HBCDs (69.1--97.3%) are existed in the particle phase, suggesting that long-range tansport of HBCDs might be occur in some environmental conditions. The results of enantiomeric fractions indicated that beta- and gamma-HBCD were racemic mixtures in the tested air samples and that (--)-alpha-HBCD was slightly enriched in the typical urban site, implying that the HBCDs in these studied sites might be a mixture of emissions from both local sources and soil-air exchange.