Characteristics of soil heavy metals pollution in cultivated land in zones between ipsilateral dams of Liaohe River

The heavy metalszinc (Zn), lead (Pb), copper (Cu) and cadmium (Cd) contents in the 0-5 cm, 5-15 cm and 15-30 cm soil depths of zones between ipsilateral dams in ten sections along Liaohe River were detected and the pollution situation of single heavy metal was evaluated using the geological accumulation index method. The potential degree of ecological damage by heavy metals was comprehensively evaluated using potential ecological risk index. The aims of the study were to evaluate the pollution degree of heavy metals, and explore the agricultural safety in zones between ipsilateral dams of Liaohe River. The results showed that the average contents of Cu, Pb and Zn were 32.42 mg·kg^-1, 38.23 mg·kg^-1 and 47.35 mg·kg^-1, respectively. The contents of heavy metals in different sections and at various soil depths were lower than the GradeⅡstandard of the National Soil Environmental Quality Standard. The average content of Cd was 1.625 mg·kg^-1, which was 1.70 times higher than the Grade Ⅱ standard of the National Soil Environmental Quality Standard. While from Zhuer Mountain to YubaoTai Grand Bridge, the trend of soil Cd content increased, it decreased from Yubaotai Grand Bridge to the estuary. Then using the Liaohe Bridge as the divide, the average content of Cd in the upper stream region was 6.47 times that in the lower reaches. The geological accumulation indexes of Pb, Cu and Zn in each sample section were all lower than 1.0, but the geological accumulation index of Cd obviously reflected a pollution trend in the study area. Strong pollution in excess of Grade V standard mainly occurred in the upper reaches of Liaohe River. From Tongjiang port to Yubaotai Bridge, potential ecological risk index of various heavy metals was very strong. Hudedian, Daniudukou, on to Liaohe Bridge was an area with a strong ecological hazard. Then the dawn bridge area had a medium ecological hazard. Finally, Lengdong Bridge, Zhaoquan River and Liaohe River estuary constituted the area with slight ecological hazard. The contribution of Cd in various sections to potential ecological risk of multi-metal was 78.77%-98.23%, which was positively correlated with the potential ecological risk index. The performance trend of various heavy metals in terms of potential ecological risk index was similar to the distribution trend in geological accumulation index of Cd, with the maximum value in Tongjiang estuary.