Distribution, sources and ecological risk assessment of heavy metals in surface sediments from Lake Taihu, China

The distribution, sources and ecological risk of heavy metals in surface sediments from Lake Taihu were studied. Results showed that the measured heavy metals had varied spatial distribution patterns, indicating that they had complex origins and controlling factors. Pearson's correlation analysis revealed that the total phosphorus and the loss on ignition were positively correlated with the measured metals except Cd. Principal component analysis and cluster analysis demonstrated that Hg, Cu, Cr, Cd and Pb might originate from domestic sewage and industrial wastewater, whereas As predominantly originated from natural processes. Potential ecological risk indices indicated that sediment from Wuli Lake, Gonghu Bay and the Northwest Area suffered high pollution, whereas other areas of Lake Taihu were moderately polluted. A comparison of metal levels with the effects range low (ERL) and effects range median (ERM) showed that metals exceeded their corresponding ERL limit at 13.6-72.3% (72.3% for As, 52.4% for Pb, 27.7% for Cu, 22.8% for Cd, 16.0 for Hg and 13.6% for Cr) of the sites investigated. Moreover, 3.90% and 0.50% of the sites sampled exceeded the ERM thresholds for Hg and Pb, respectively.