Risk assessment concerning the heavy metals in sediment around Taihu Lake, China

The present study sought to determine the systematic pollution status of the heavy metals (HMs) found in the sediment around Taihu Lake, China. The concentrations and speciations of the HMs in the sediment were measured. The Ni and Cr concentrations exceeded the probable effect level (PEL), while the concentrations of the other HMs (except Hg) were between the threshold effect level and the PEL. The enrichment factor values for all HMs indicated slight enrichment. The geoaccumulation index revealed that the HMs represented light pollution, while the average contaminant factor value of the HMs indicated moderate pollution. The ecological risk factor value indicated a medium ecological risk, with Cd and Hg being associated with a high and considerable potential ecological risk, respectively. The ecological risk index indicated that the ecological risk posed by the HMs was high. The contamination degree revealed a moderate level of metal pollution, while the pollution load index indicated a heavy pollution level. The extractable proportion of the HMs (except for Cr and As) exceeded 50%. In the case of Cd, the exchangeable proportion was 51.11%, which indicated it to be extremely unstable. PRACTITIONER POINTS: Heavy metals (except for Cr and As) have a high potential ecological risk. All selected heavy metals implying varying degrees of instability. Cd was the most serious pollutant based on the Igeo, Cf and EF analyses.