Distribution of AVS-SEM, transformation mechanism and risk assessment of heavy metals in the Nanhai Lake in China

Distribution of AVS (acid volatile sulfide)-SEM (simultaneously extracted metals), transformation mechanism and risk assessment of heavy metals in the Nanhai Lake in Baotou City were discussed in this work. The results showed that the content of heavy metals in sediments increased due to the water pumped from the Yellow River, domestic sewage, municipal runoff and yacht waste release. Increasing water depth, domestic sewage influx and hydrophyte booming made the AVS level higher in downstream than upstream. The vertical distribution of AVS is characterized as multiple-peak in the sediment cores from the studied lake. Comparatively, the control abilities of the carbonate and sulfate to the heavy metals were five orders of magnitude lower than the sulfide phase. Therefore, AVS was the key factor controlling the precipitation of heavy metals in the Nanhai Lake. The ratio of SEM/AVS in the sediments, the acute sediment quality criteria and the chronic sediment quality criteria indicated that no acute toxicity for benthic organisms can be expected, and the AVS plays an important role in controlling the bioavailability and toxicity of heavy metals in the Nanhai Lake.