GIS-based assessment of arable layer pollution of copper (Cu), zinc (Zn) and lead (Pb) in Baiyin District of Gansu Province

摘要

Recently, heavy metal pollution of Baiyin District has become more serious affecting the health of the people and threatening food security. This study was conducted in 2012 to determine the levels of contamination and pollution using geoaccumulation index and potential ecological risk index to evaluate pollution levels of arable layers. Both methods were used to evaluate the risk and determine the present situation of soil heavy metal [copper (Cu), zinc (Zn) and lead (Pb)] pollution characteristics in farmland. This will form the basis for the control of the soil heavy metal pollution, as well as for rational layout of the agricultural industry. Content and spatial distribution of the heavy metals recorded from 1,225 soil samples of arable layer in the study area had average concentration of Cu, Zn and Pb of 36.70, 122.20, and 33.80 mg/kg, respectively. The result shows fluctuating metal concentrations of the heavy metals with Cu, Zn and Pb recording 7.47, 11.07, and 14.46, which are higher than the environmental standard concentrations, respectively. The average pollution of the heavy metals in decreasing order was Pb > Zn > Cu with variation coefficient of 1.92, 2.00, and 2.92, respectively. Evaluation results of Geoaccumulation index show that Cu, Zn, and Pb pollutions of arable layer were mainly concentrated in urban areas, with pollution degree in the order of Pb, Zn, and Cu. Evaluation results of the potential ecological risk index show that the risk of Zn in arable layer is mild, and the risk of Cu and Pb in most of the arable land is also mild, except in surrounding areas of the city where the risk appears medium, and above medium, respectively.