Hexabromocyclododecanes in surface sediments from Shanghai, China: Spatial distribution, seasonal variation and diastereoisomer-specific profiles

The concentrations, spatial distribution, diastereoisomer-specific profiles of hexabromocyclododecanes (HBCDs) in surface sediments from three major rivers in Shanghai as well as the seasonal variation of HBCDs were investigated. The concentrations of total HBCD diastereoisomers ranged from 0.05 to 6.87 ng g(-1), dw. Significant spatial distribution of total HBCDs concentrations were observed. The mean concentration of total HBCDs followed the order of Suzhou Creek (2.00 ng g(-1)) > Huangpu River (1.59 ng g(-1)) > Yunzao Creek (0.77 ng g(-1)). The concentration was a relatively low HBCDs level compared to levels measured in domestic and other parts of the world. The proportions of alpha-HBCD in sediment samples were generally higher than that of commercial formulations. This might be due to thermal isomerization from gamma-HBCD to alpha-HBCD and slower degradation rate of alpha-HBCD compared to gamma-HBCD in anaerobic conditions. The concentrations of Sigma HBCD in the summer were significantly higher than those in the winter (paired t test, p < 0.01). This seasonal variation could probably be attributed to a combined effect of temperature and wet deposition. Moreover, a poor and no significant correlation between Sigma HBCD levels and TOC content in sediments was observed, suggesting that the spatial distributions of HBCDs were not constrained by the TOC in sediments of Shanghai. (C) 2014 Elsevier Ltd. All rights reserved.