Spatial distribution of heavy metals in bottom sediment of Yenshui river, Taiwan

Abstract

Distribution of heavy metals in bottom sediments from heavily polluted section of Yenshui river, located in the southern Taiwan, are presented. Sediment cores of seven sites were separated into several cuts and analyzed with both sequential extraction procedure (SEP) to realize the heavy metal contents (including Cr, Co, Zn, Ni, Pb, Cu and Cd) among binding fractions of different sediment depth and multivariate analysis (MA) to conduct the correlations of heavy metal variation in depth profile. Results show that distribution of heavy metals in depth profile of sediment is not identical among different sites. Levels of Zn, Cr, Cu and Ni were higher than other metals, and within the ranges of 30–200 mg/Kg, 8–160 mg/Kg, 5–130 mg/Kg, 10–100 mg/Kg, respectively. The major binding forms of Zn, Cr and Cu in sediment were ‘bound to carbonates’, ‘bound to Fe oxides’ and ‘bound to organic matter’ respectively. And, the percentages of different heavy metal binding forms were not significantly varied in depth profile. Results of principal component analyses (PCA) demonstrate that Cr, Ni and Cu were clustered, which indicate these metals had similar loadings in sediment profile, and might be discharged from the same pollution source of electroplating industry.