Distribution of trace elements in sediments from rivers around the northern Taihu Lake and evaluation of the contamination level

There exist the interaction between lake and ambient rivers. This study focuses on the total and bioavailable concentrations of trace elements in river sediments around the northern Taihu Lake. We can recognize the characteristics of trace elements in different sites by comparing the west, north and the east rivers and evaluate the contamination level of sediment. The concentrations of TP and TN in west rivers were higher than those in other rivers. The concentrations of trace elements were highest in sediments from the north rivers. The concentrations of NH₃-N were higher significantly than NO₃-N, denoting the effect of domestic sewage. Sediments of the north rivers showed the elevated bioavailable fractions of Cu, Zn, Pb, indicating input of industrial wastewater. Correlation analyses manifest that there are good correlations between TOC and trace metals, weak correlations between Al₂O₃ and trace metals. No correlation exhibits between CaO, Fe₂O₃ and trace metals. Geoaccumulation index was employed to evaluate the contamination levels of sediment. Zinc shows the moderate contaminated grade, Cu and Mn reveal the slight contaminated grade. The other metals are the uncontaminated level. The west rivers contribute more nutrients to Taihu Lake, and the north rivers contribute more trace metals to Taihu Lake by comparison of trace elements in sediments from the west, north and east regions. Sediments of the east rivers show the low contaminated level.