Spatial Distribution and Pollution Assessment of Heavy Metals in Soils in the Jiefangzha Irrigation Area of the Hetao Irrigation District, China

Abstract

To explore the characteristics of heavy metal pollution in farmland soils in the Jiefangzha Irrigation Area of the Hetao Irrigation District, Inner Mongolia, 60 samples of the surface soil (0–20 cm) were collected to detect and analyze the content of typical heavy metal elements, Cu, As, and Pb, in the soil. The methods utilized included the single factor index method, the Nemerow index method, the geological accumulation index method, and the potential ecological hazard index method to evaluate their pollution and ecological risks, and these were combined with geostatistical methods using GIS (Geographic Information System) technology to quantitatively analyze their spatial distribution characteristics. The results showed that the average contents of Cu, As, and Pb did not exceed the background values in the Hetao Irrigation Area, and the contents showed a moderate variation, with the order of variation as As > Cu > Pb. The multivariate statistical analysis results showed that the three elements, Cu, As, and Pb, had similar sources, i.e., primarily the use of agrochemicals, such as fertilizers and pesticides. The semi-variance function model fitting results showed that Pb followed a spherical model, and Cu and As followed Gaussian models. Kriging interpolation showed that the contents of As, Pb, and Cu, in general, showed a trend that was higher in the northwest and lower in the southeast, with a change of gradient increasing from the southeast to the northwest. Human activities were the primary factors causing the distribution difference.