Occurrence, composition, and spatial distribution of dechlorane plus in surface sediments of black-odorous urban rivers across China

China, one of the two dechlorane plus (DP) producers, might have become a major area of DP pollution. The environmental contamination status of DP in sediments across the whole of China has not yet been studied. In the current study, the pollution levels, spatial distribution, and compositions of DP were investigated comprehensively in surface sediments from 173 black-odorous urban rivers across China for the first time. Total DP concentrations varied from not-detected to 39.71 ng/g dw, with an average concentration of 3.20 ± 4.74 ng/g dw, which was polluted by local emission sources and presented significant differences among different sampling cities. Among the seven administrative regions of China, DP concentrations were the highest in South China and showed a decreasing trend from southeastern coastal areas to northwest inland regions. Spearman’s correlation analysis suggested that the gross industrial output, gross domestic product, and daily wastewater treatment capacity were not the principal factors controlling the spatial distribution of DP. The f anti values (the concentration ratios of anti -DP to the sum of anti -DP and syn -DP) varied from 0.19 to 0.88, with those in most sediments falling in the range of DP technical product (0.60 ~ 0.80), suggesting no apparent stereoselective enrichment occurred. Moreover, the anti -Cl 11 -DP was detected in sediments (n.d. ~ 0.40 ng/g dw), which showed significantly and insignificantly positive correlation with the anti -DP levels and f anti , respectively, implying it might mainly originate from the byproduct of DP technical product rather than the dechlorination of anti -DP.