Soil heavy-metal speciation and wheat phytotoxicity in the vicinity of an abandoned lead-zinc mine in Shangyu City, eastern China

Sixteen soil samples were collected from the vicinity of an abandoned lead-zinc mine in Shangyu City, eastern China, and the heavy-metal speciation and wheat phytotoxicity in the soils were studied. The results showed that the concentrations of free Cu2+, Zn2+, Cd2+ and Pb2+ were highly variable and ranged from < 0.01 to 0.32, 0.06 to 10.62, < 0.01 to 1.40 and 0.02 to 37.10 mu mol l(-1), respectively. The concentrations of soluble Cu, Zn, Cd and Pb ranged from 0.38 to 3.24, 0.72 to 78.74, < 0.01 to 1.95 and 0.15 to 639.34 mu mol l(-1), respectively. The general trend of mean solid/liquid partition coefficient and percentage of free metal ion to total soluble metal concentration were Cu > Pb > Zn > Cd and Cd > Zn > Cu > Pb, respectively. Stepwise multiple linear regression with pH, log(total metal) and log(organic matter) showed that log(total metal) was an important factor that controlled log(free metal ion) and log(soluble metal). Of the variability in log(free Cu2+), log(free Cd2+) and log(free Pb2+), 55.2, 58.6 and 64.3% could be explained by log(total Cu), log(total Cd) and log(total Pb) alone, respectively. Of the variability in log(soluble Cu) and log(soluble Cd), 77.1 and 72.5% could be explained by log(total Cu) and log(total Cd) alone, respectively. Wheat root length was controlled by the various metals with different free and soluble concentrations, and 99.2% of the variability in root length could be explained by concentrations of free and soluble Pb, soluble Cu and total Zn in the soils.