Characteristics and assessment of heavy metals pollution in the sediments from a small catchment in northern Taihu Basin

In recent decades, more attention has been focused on the sedimentary record, sources and pollution level of heavy metals. In order to identify the sources of heavy metals and assess the environmental quality of the small catchment in northern Taihu Basin, the concentrations of eight heavy metals including Mn, Cr, Zn, Cu, As, Pb, Ni and Co in the profile of sediments were analyzed. A series of methods e.g. principal component analysis, the enrichment factor method and the entropy weight fuzzy model were used to determine the pollution sources, define the heavy metal enrichment degree and evaluate the pollution level of heavy metals in the sediments. Results showed that all of the heavy metals concentrations were high, and the order was Mn>Cr>Zn>Cu>As>Pb>Ni>Co. Among them, the concentration of Mn was the highest (380.06~767.69 μg/g).Traffic emissions, agricultural pollution and coal combustion were the main contributors to heavy metal pollution in the sediments. The enrichment index of As was the largest(2.89~15.61), of which 77.59% of the sedimentary layers were significantly enriched and greatly influenced by human activities. The synthetic fuzzy comprehensive evaluation indicated that Cu (0.483) and As (0.352) had the largest weight value, being the primary pollutant in the sediments. Besides, 65.52% of the sedimentary heavy metals in the profile were in moderate pollution level. © 2020, Editorial Board of China Environmental Science. All right reserved.