As, Cd, Cr, Hg, Ni and Pb in soil from eastern slope of Mt. Gongga, Eastern Tibet, China

Abstract

Concentrations of As, Cd, Cr, Hg, Ni and Pb were determined in soils from the eastern slope of Mt. Gongga at an altitude of 7,556 m above sea level. Mean concentrations of As, Hg and Pb in top soil were below the tolerance limit (the grade-1 standard) set in China for uncontaminated soils. Nevertheless, Pb was found in topsoil from the eastern slope of Mt. Gongga at mean concentrations of 30.38±7.32 mg/kg dw, which was close to the tolerance limit. At one site in surface layer of the Faber's fir mature forest, concentrations of Pb were all above the tolerance limit (35.7-43.1 mg/kg dw). Mean concentrations of Cd, Cr and Ni did exceed the tolerance limit (the grade-1 standard) set in China. Single-factor contaminant index data were calculated by taking into account the analytical information obtained from topsoil at each sampling site. Among heavy metals determined, the highest degree of topsoil pollution was found for Cd. The single-factor pollutant index values decreased in the order of PCd>PCr>PNi>PPb>PHg>PAs. Evidently, topsoil of the eastern slope of Mt. Gongga accumulated elevated levels of Cd and Cr and Ni. An integrated assessment of topsoil quality for six heavy metals analyzed indicated that the values of index PN for all sites varied between 0.92 and 4.89 and all are considered as 'slight to pronounced impact' by heavy metals. © Maxwell Scientific Organization, 2013.