Spatial distribution and pollution of mercury and cadmium in Weibei apple orchard soils of Shaanxi Province

The influences of the concentrations, pollution, spatial distribution of mercury and cadmium in apple orchard soils of Shaanxi Province on the production of green eatable apple were investigated. The 481 apple orchards were chosen from all 27 apple bases of Shaanxi Province from 2003 to 2006. The 20 sampling sites were selected using “S” method in each orchard, and the soil specimens at 0 cm to 40 cm deep were collected for the concentration analysis of mercury and cadmium. The experimental results indicated that the soils of orchard were slightly polluted by mercury and cadmium. The frequency fraction distributions of mercury and cadmium in soils were logarithm normal school. The appropriate expression methods of their concentrations were geometric mean values. The concentrations of mercury and cadmium were 0.051 mg/kg and 0.055 mg/kg, respectively. The concentrations of mercury and cadmium in soils were influenced by the pH value of the soil. In the range of pH 7.6～9.7, the concentrations increased with the increase of soil pH value. The soils were slightly polluted by mercury and cadmium, which did not do harm to the production of green eatable apple.