Pollution and potential ecological risk assessment of heavy metals in river sediments of Nantong

Based on sediment samples from five urban channels in Nantong City and analysis of the heavy metal mass ratios in the sediment,the distribution characteristics of heavy metal pollution were revealed and the potential ecological risk was evaluated.The results were as follows:(1) All the heavy metal mass ratios exceeded the background soil value,and the pollution was serious,with Hg pollution being the highest.(2) The vertical distribution of heavy metal pollution was divided into two types.One was normal deposit sediment unaffected by dredging measures,wherein the heavy metal pollution was high in the upper layer and low in the lower layer;the other was abnormal deposit sediment affected by dredging measures,wherein the heavy metal pollution was lower in the upper layer and high in the lower layer.The horizontal distribution of the heavy metal pollution had the characteristics of the heavy metal pollution being high in the river of the central city,lower in surrounding rivers,higher in the upper and middle stream of rivers,and lower downstream.(3) According to the evaluation of the potential ecological risk of heavy metals,the Hao River and Falunsi River were heavily polluted,the Yaogang River was moderately polluted,and the Rengang River and Nanchuan River were lightly polluted.The influence degrees of potential ecological risk of heavy metals were as follows: HgCuZnCrPb.