Assessment of Heavy Metal Pollution in Chinese Suburban Farmland

A total of 650 arable soil samples were collected from the suburbs of Liaocheng, Shandong Province, China to identify the concentrations and the sources of heavy metals and to assess the environmental quality of soil. Subsequently, the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the samples were analyzed. The investigation revealed that the mean concentrations of As, Cd, Hg, Ni, Hg, and Cd exceeded their corresponding background values. The maximum concentrations of As, Cd, Hg, and Cu are all higher than the allowable values. Each soil sample had a low or slight pollution index (PI) of As, Cr, Cu, Ni, Pb, and Zn, whereas the PI values of Hg and Cd were high; more than 39.7% and 18.6% of the samples were classified as being moderately or heavily contaminated by Hg and Cd, respectively. Using multivariate statistical approaches (cluster analysis and principal component analysis), four factors controlling the heavy metal variability were identified; these accounted for more than 80% of the total variance. The As, Zn, Ni, Cu, and Cr levels were controlled by the parent material in the soils. Cd and Hg levels were controlled mainly by anthropic sources, such as industrial activities, manure, and the burning of coal; however, the parent materials of the soils may partially control the concentrations of Cd and Hg. The abnormally high levels of heavy metals mostly coincided with industrial locations.