Distribution Characteristics and Ecological Risk Assessment of Heavy Metal Pollution in Floodplain Sediments of Xiaojiang River Basin in Dongchuan

Taking the Xiaojiang River floodplain sediments as the research object, 42 samples of floodplain sediments were collected from the upper, middle and lower reaches of the river, and their physical and chemical properties and the contents of 6 heavy metals including Cu, Pb, Mn, Zn, Cr, and Cd were tested. The pollution risk was evaluated by geo-accumulation index method and potential ecological risk method. The results showed that the concentrations of heavy metals Cu, Pb, Mn, Zn, Cr and Cd in the sediments of the Xiaojiang River floodplain were 218.68 mg/kg, 93.48 mg/kg, 1347.97 mg/kg, 414.39 mg/kg, 71.04 mg/kg and 2.47 mg/kg, respectively, except for Cr, the contents of other elements exceeded the environmental background values of heavy metals in Kunming soil(Cu: 69 mg/kg, Pb: 41 mg/kg, Mn: 606 mg/kg, Zn: 90 mg/kg, Cd: 0.27 mg/kg). The contents of other elements were all higher than the environmental background value of heavy metals in Kunming soil. The average contents of Cd and Zn were 9.17 and 4.60 times of the environmental background value, respectively. There were spatial differences in distribution, and the main sources of pollution were human activities; the mean value of potential ecological risk coefficient E_r^i of single heavy metal from large to small was Cd(274.98), Cu(14.67), Zn(4.60), Mn(2.22), Pb(1.79), Cr(1.44), and the mean value of potential ecological risk index RI was 300 to reach the level of strong ecological risk; heavy metals Cu and Zn in sediments of Xiaojiang River floodplain are enriched, while Cd is highly enriched. In summary, heavy metal pollution has occurred in Xiaojiang River basin, and there are potential ecological risks. Appropriate monitoring and corresponding control measures are needed.