Sources and assessment of heavy metal contamination in water-level fluctuation zone of the Three Gorges Reservoir, China

The Three Gorges Reservoir is one of the most important water resources in China. Understanding the degree of soil contamination in the water-level fluctuation zone is critical for water/soil conservation in the region. A total of 68 soil samples were collected at 12 sites in the reservoir region and analyzed before the water level rose to 175 m above mean sea level. The degrees of Cu, Pb, Zn, Cd, Hg, As and Cr contamination were determined via the geo-accumulation index (Igeo) method. The study showed that soils in the reservoir region were severely contaminated with As, Cd and Hg. While there was no Cr contamination in the reservoir region; Pb, Cu and Zn contamination was not significant in about 70% of the region. Further Factor Analysis on sources of heavy metals revealed that Cr, Pb, Cu and Zn contamination in the water-level fluctuation zone were caused by natural factors, and that of Hg, As and Cd by industrial factors. The findings of sources and the evaluation of surface soil heavy metal contamination were critical for sustainable environmental management in especially the water-level fluctuation zone in the Three Gorges Reservoir.