Distribution and pollution character of heavy metals in the surface sediments of Liao River

The concentrations of 7 heavy metals (Ni, Cu, Cr, Pb, Cd, As, Hg) and organic matters in the surface sediments of Liao River were determined by atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS), and sediments pollution assessment was carried out using geoaccumulation index. Moreover, the sources of heavy metal contamination were estimated with the principal component analysis (PCA). The results demonstrate that the heavy metal concentrations of Liao River are markedly higher than that of Liao River in 1998 and lay at medium level compared with other rivers in China. The average concentrations (mg/kg) obtained were: Ni 26.5 mg x kg(-1), Cu 37.9 mg x kg(-1), Cr 90.3 mg x kg(-1), Pb 32.9 mg x kg(-1), Cd 0.49 mg x kg(-1), As 12.3 mg x kg(-1), Hg 0.14 mg x kg(-1). The results of geoaccumulation index reveal that sediments of Liao River are uncontaminated with Ni, As, lightly contaminated with Cu, Cr, Pb and moderately contaminated with Cd, Hg. The order of the analyzed heavy metals, arranged from the highest to lowest pollution degree, is as follows Cd > Hg > Cu > Cr > Pb > As > Ni. By estimating the sources of heavy metal contamination with the Principal component analysis (PCA), it was found that the first two components account for 58.74% and 17.18% of the total variance, respectively. The industrial and living wastewater, degradation of organic matter atmospheric precipitation and geochemical changes are the main sources of heavy metal contamination.