Spatial distribution and main controlling factor of cadmium accumulation in agricultural soils in Guizhou, China

A large-scale investigation was conducted on the cadmium (Cd) content in the farmland soils of Guizhou to explore the spatial variation in soil Cd content, identify the main factors responsible for causing Cd pollution, and determine the zonation of Cd pollution. Multivariate statistical analysis, geographic information system (GIS) analysis, and decision tree methods were used to study the distribution, spatial variation, and pollution partitioning of Cd and the factors influencing the Cd accumulation in agricultural soils of the Guizhou province. Areas with high Cd content in agricultural soil were found to be concentrated in the high-altitude areas in the western region of Guizhou province. The results of the single factor pollution index showed that the proportion of sample sites with Cd class I (priority protection), II (security utilization), and III (strict control) in the agricultural soils of Guizhou province were 65.96%, 31.27%, and 2.77%, respectively. In high-altitude areas, the Cd content in the agricultural soils was mainly derived from the soil parent material. In contrast, mining activities and road traffic were the main factors Cd accumulation in agricultural soils in lower altitude areas.