Chemical Speciation of Trace Metals in Superficial Sediment from Lake Hongfeng, China

Abstract

Heavy metals have been well known to cause numerous adverse effects to humans and ecological systems, and pollution of aquatic systems with heavy metals has aroused a huge public concern. The work reported in this paper deals with the distribution characteristics of trace metals (Pb, Cu, Zn and Ni) in ten surface sediments from Lake Hongfeng, situated in Guizhou Province of southwestern China. Apart from total concentration, the distribution of these metals in four fractions (exchangeable and weak acid soluble fraction (F1), reducible fraction (F2), oxidizable fraction (F3) and residual fraction (F4)) was also studied by means of an analytical procedure involving sequential chemical extraction that was proposed by the Commission of the European Communities Bureau of Reference (BCR). Analysis of total concentration suggested that the mean concentrations of heavy metals under study decreased in the order of Zn>Cu>Pb>Ni, and pollution of all these heavy metals in the North Lake was more serious than that in the South Lake. Study of heavy metals chemical speciation revealed that Pb and Cu were mainly distributed in reducible and residual fractions, and Zn and Ni mainly existed in residual fraction. Therefore, special attention should be paid to Pb and Cu since they presented a large fraction distributed in the exchangeable and weak acid soluble fraction and reducible fraction that were associated with high potential bioavailability. The Pearson correlation analysis between these heavy metals distributed in different fractions and some major elements were also carried out, and the results proved that sulfur (H2S) played an important role in distribution and transformation of heavy metals, especially for Pb, Cu and Zn.