Abstract:
The spatial distribution characteristics of the heavy metal contents and the heavy metal fractionation in farm land soils around the Lantian smelter, Xi'an city, Shaanxi province were studied by analyzing, investigating and sampling in the field, and the heavy metal pollution level was evaluated with the pollution index method. The results showed that the highest contents of Pb,Zn,Cu and Cd in the topsoil with a distance of 100 meters from the smelter were up to 1 341693, 188877, 251015 and 21810 mg/kg, and were 3833,0630,2510 and 36349 times that of the national soil environment quality standard(level 2), respectively. The contents of four heavy metals in topsoil arisen, then declined, and finally tended to steady with the distance between sampling spot and smelter. Heavy metal contents decreased with soil depth in soil profile, and it decreased significantly in the layers of 0～30 cm, while changed smoothly below 30 cm soil layers. The combined pollution index of all the sampling spots in topsoil were beyond 3, which indicated that the study area has been polluted severely. In topsoil, Pb was dominantly associated with reducible fraction, Cu was primarily associated with the residual fraction with the average value of 74619 mg/kg, and the dominant fractions of Zn were reducible fraction and residual fraction, while 72508% of Cd was associated with reducible and residual fraction.
