PCDD/Fs and PCBs in sediments of the Liaohe River, China: levels, distribution, and possible sources

The contamination status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in the surface sediments of the middle and lower reaches of the Liaohe River, which is one of the most heavily polluted rivers in China, were investigated. The concentrations of PCDD/Fs and PCBs were in the range of 0.24-27.49 ng WHO-TEQ kg(-1) (average value: 3.01 ng WHO-TEQ kg(-1)) and 0.015-0.99 ng WHO-TEQ kg(-1) (average value: 0.33 WHO-TEQ kg(-1)), respectively. For most sediment samples, the pollution levels of PCDD/Fs and PCBs exceeded the interim sediment quality guidelines (ISQGs) established by the Canadian Council of Ministers of the Environment. The highest level of PCDD/F contamination was found at the Tai'an reach of the Liaohe River, whereas the highest level of PCB contamination was found at the Xinmin reach of the Liaohe River. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to the data set of sediment samples and to source-related samples from the literature. The results suggested that, PCDD/F contamination in most sediments of the middle and lower reaches of the Daliao River should mainly originated from the local combustion processes, including coal burning, agricultural straw open burning, iron ore sintering, cement production and secondary Al and Cu metallurgy. For the PCBs, the major source was identified as the usage of technical PCB products, especially Chinese No. 1 PCB.