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[Assessment of sources, spatial distribution and ecological risk of heavy metals in soils in a typical industry-based city of Shandong Province, Eastern China].

A total of 106 samples were collected from surface soils in Gangcheng District, Laiwu city (a Typical industry-based city of Shandong Province, Eastern China), and the contents of 9 heavy metals including As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn were determined. Multivariate analysis and geostatistics were,applied to examine the sources and spatial distributions of heavy metals in soils; and the assessment on ecological risk of heavy metals was carried out using Hakanson's method. The average concentrations of 9 heavy metals were higher than the background values of Shandong Province; in particular, the mean contents of Cd, Hg, Pb and Zn were 2.42, 4.69, 1.74 and 1.54 times of their respective background values, which indicated there were obvious accumulations of these heavy metals in surface soils. The results from multivariate analysis suggested that all the 9 heavy metals could be classified as 3 Principal Components (PCs). Cd, Pb and Zn, having high loads in PC1, were dominated by industrial, agricultural and traffic sources. PC2 including Co, Cr and Ni came from natural sources, and were controlled by parent materials. As and Hg with high loads in PC3, were originated from coal combustion and smelting. Cu had some loads on different PCs, and was affected by both natural and human sources. Assessment on ecological risk indicated that the study area suffered from a critical level between high and moderate risks. Hg was at the high ecological risk level, and Cd was at the moderate ecological risk level, while other metals had low ecological risk level.