Levels and distribution of Dechlorane Plus and related compounds in surficial sediments of the Qiantang River in eastern China: the results of urbanization and tide

Dechloranes, including Mirex, Dechlorane 602 (Dec 602), Dechlorane 603 (Dec 603), Dechlorane 604 (Dec 604) and Dechlorane Plus (DP), are a class of chlorinated flame retardants. To investigate the effect of urbanization and tide on the distribution of Dechloranes in sediment, we assayed surficial sediments collected from the Qiantang River in eastern China for the presence of these chemicals. The concentrations of Mirex, Dec 602, Dec 603, and DP ranged from below detection limit (BLD) to 0.68 ng/g dry weight (dw), BLD-0.048 ng/g dw, BLD-0.026 ng/g dw, and BLD-1.1 ng/g dw, respectively. Dechloranes 604 was not detected in any sediment samples. It was evident that local urban and industrial activities were the primary source of DP in surficial sediments in the Qiantang River, which was supported by the fact that the average DP concentration of sediment samples in urban sites was approximately three-fold higher than that in rural sites. An extremely high concentration of DP at a reservoir site in a rural area indicated that a dam can block the movement of DP in the Qiantang River by slowing down the river current and making the reservoir the primary sink of DP. Furthermore, the spatial distribution of Dechloranes suggested that concentrations of Dechloranes in sediment in the tide zone were much lower than those in the non-tidal zone, indicating that tide played an important role in transportation and re-distribution of Dechloranes in sediments of the Qiantang River.