Heavy metal pollution and ecological risk assessment of surface sediments covered by emerged and submerged plants in a shallow lake

Surface sediments were collected to investigate the pollution levels and ecological risks of heavy metals (e.g., As, Ni, Pb, Cu, Zn, Cr, Cd, and Mn) in the surface sediments covered by emerged and submerged plants in the main areas of the Baiyangdian Lake. The results showed that Pb and Cd highly exceeded the background values of Hebei Province and had high pollution levels, while other heavy metals exhibited no pollution. With the exception of Mn, there was no significant difference in the concentrations of heavy metals in surface sediments between the emerged-plant and submerged-plant zones. The concentrations of heavy metals in Zaolinzhuang were relatively low, while those in Wangjiazhai, Nanliuzhuang and Shaochedian were relatively high. In the two plant zones, Cd in surface sediments posed a considerable risk at all sampling sites regardless of plant zones, followed by Pb with light pollution level. Correlation analysis and factor analysis results showed that all these heavy metals generally originated from three different sources in both plant zones, of which As, Cu and Zn had two sources in the emerged plant zones. Our findings indicate that Cd and Pb pollution of the Baiyangdian Lake should be given more attention to contribute to the environmental control and ecosystem conservation of the lake.