Pollution assessment and risk area delineation of potentially toxic elements in agricultural soils with high geological background through an integrated framework

An integrated framework for potentially toxic elements (PTEs) pollution assessment and risk area delineation of agricultural soil in high geological background areas was developed using the western region of Guizhou Province, China, as a case study. The framework combining the finite mixture distribution model (FMDM), the influence index of comprehensive quality (IICQ), random forest (RF), geographically weighted regression (GWR) and Bayesian maximum entropy (BME) theory. The inclusion of agricultural product quality and environmental auxiliary variables in the IICQ and BEM models has enhanced the accuracy of PTEs pollution assessment and risk area delineation. The results indicated that 90.92 % of the sampled sites were at risk of PTEs pollution and showed a trend of watershed (rivers of Liuchong, Sancha and Beipan) distribution; 23.68 % of the points, at risk of heavy pollution, were mainly located in the farmland surrounding metal mining area in the upper reaches of the watershed; 18.82 % of the sites had crops exceeding the PTEs limit but no soil contamination, concentrated in the lower reaches of the watershed with low altitude and high annual average temperature. Mining and metallurgy activities, the primary risk factors causing farmland pollution, were introduced into the BME model to assist delineate pollution risk areas. The area at risk of PTEs pollution constituted 66.12 %, with heavily polluted risk areas covered 14.41 %, predominantly situated in the western and southern sectors of Bijie City, the western and northern parts of Liupanshui City, the eastern areas of Anshun City, and the northern and western regions of the Southwest Guizhou Autonomous Prefecture. The results of the study provide a reasonable assessment system for the risk delineation of PTEs contamination in arable soils in high geological background areas.