Heavy metal contamination of agricultural soils and stream sediments near a copper mine in Tongling, Peoples Republic of China.

摘要

This study was conducted to investigate the spatial distribution of heavy metals (Cu, Pb and Zn) and their chemical partitioning in agricultural soils and stream sediments in the Tongling mining area, Anhui, China. The heavy metal concentrations of the soils were in the decreasing order Cu > Zn > Pb. The concentrations of Cu were in a wide range of 78-2839 mg/kg, with an average of 619 mg/kg. Pb concentrations in soils also showed a large variability with a mean of 161 mg/kg. The total Zn concentrations varied from 78 to 1280 mg/kg, with an average of 354 mg/kg. Heavy metal concentrations in the soils showed a clear geographical diffusion pattern in the study area. The concentrations of all metals decreased with increasing distance from the mining site. Cu concentrations in the exchangeable, carbonate/specifically adsorbed, Fe-Mn oxide and organic fractions were higher than Pb and Zn. The Cu concentrations in the residual phase were in the range 28-1230 mg/kg, which accounted for 21-64% of the total Cu in the soils. The percentage of Pb associated with different fractions in all the soil samples was in the order: Fe-Mn oxide (46.3%) > residual (32.6%) > carbonate/specifically adsorbed (10.3%) > organic (9.6%) > exchangeable (1.2%). In all soils, Zn was primarily associated with the residual fraction, ranging from 48 to 74% of the total concentrations. Concentrations of Cu, Zn and Pb in the sediment samples exceeded the ecotox threshold values of 34, 150 and 47 mg/kg, respectively, developed by the US Environmental Agency.