Speciation of heavy metals in sediments from Xiang River and analysis of their environmental factors
湘江表层沉积物重金属的赋存形态及其环境影响因子分析

BCR three stages sequential extraction procedure was applied to investigate the speciation and contents of four types of heavy metals (Cd, Pb, Cu, Zn) in the surface sediments in Hengyang-to-Yueyang section of Xiang River. The relationship between the speciation of these heavy metals and their environmental factors were described. Morerover, the bioavailability of these four types of heavy metals was also determined preliminarily. The results showed that all of these four types of metals existed mainly in extractable fractions which included weak soluble fraction, reducible fraction and oxidisable fraction, and the bioavailability for four types of metals were in the descending order of Cd>Pb>Zn>Cu. Heavy metals had positive correlation with their contents of extractable fractions. Correlation Analysis showed that organic matter was the most important environmental factor that influenced the contents and speciation of heavy metals deposited on surface sediments of Xiang River. Accumulation and ecological risk of these four types of metals in the middle and lower reaches were higher than that in the upper reaches, peaking at Shuikoushan aera in Hengyang. This phenomenon showed that emissions from industries along the river was the main impact factor of spatial distribution of heavy metals in sediments in Xiang River area.