Occurrence and distribution of chlorobenzenes in the Tonghui river of Beijing, China.

Eleven chlorobenzenes (CBs) in surface water and sediments of Tonghui River, a main urban drainage river of Beijing in China, were determined in October 2003, January 2004, and April 2006. CBs were widely detected and the summation operatorCB concentrations in water ranged from 89.9 to 6638.0 ng/L, with average values of 1902.8 ng/L in 2003, 2084.0 ng/L in 2004, and 1281.2 ng/L in 2006, respectively. The summation operatorCB concentrations in surficial sediments varied from 18.2 to 1827.7 ng/g dry weight (dw), with average values of 897.4 ng/g dw in 2003, 653.4 ng/g dw in 2004, and 562.6 ng/g dw in 2006, respectively. Nonparametric statistical analysis (Mann-Whitney U test) showed that there were no statistically significant changes in summation operatorCB concentrations in either surface water or sediments over the period 2003-2006. The distribution pattern of CBs in the Tonghui River indicates that further effort is warranted in reducing local sources of contaminants. Additionally, the summation operatorCB levels in sediment samples were found to be dependent on total organic carbon contents.