Assessment of heavy metals in surface sediments from Gansu section of Yellow River, China.

The concentrations of Cu, Fe, Mn, Ni, Zn, Cr, Pb, and Cd in 28 samples collected from bottom sediments in the Gansu section of Yellow River, China, were investigated in order to evaluate their distribution and pollution level. The measured metals in the sediments were found to be in the range of Cu 15.52∼57.50 mg/kg, Fe 19593.24∼69963.42 mg/kg, Mn 472.70∼1491.67 mg/kg, Ni 5.10∼74.28 mg/kg, Zn 64.61∼173.83 mg/kg, Cr 57.68∼183.47 mg/kg, Pb 1.21∼28.36 mg/kg, and Cd 0.35∼4.25 mg/kg. The mean values of the heavy metal contents were arranged in the following decreasing order: Fe > Mn > Cr > Zn > Ni > Cu > Pb > Cd. There were significantly positive correlations between Cu, Fe, Mn, and Zn. However, principal component analysis (PCA) extracted two factors with Eigenvalues explaining 62.15 % of the total variance. Cu, Fe, Mn, Zn, and Cr had a natural origin controlled by the first factor. Ni and Pb could originate anthropogenic sources controlled by the second factor. Cd could be affected by natural geological background and human activity. It was attributed principally to anthropogenic activities that the geo-accumulation index, enrichment factor, and pollution load index of Cr were all higher than other measured metals. Zn appears to pose no risk at all of the sites of the system. The pollution class of sediment from the Gansu section in the upstream of Yellow River was 0∼1, from unpolluted to moderately polluted degree.