Source Analysis of Heavy Metals in Typical Farmland Soils Based on PCA-APCS-MLR and Geostatistics

Abstract

Human activities often increase the content of heavy metals in surface soils, thus affecting the precise quantification and evaluation of heavy metals in regional soils. In order to systematically study the spatial distribution characteristics and contribution rate of heavy metal pollution sources in typical farmland soil around stone coal mines in western Zhejiang Province, heavy metals such as Cd, Hg, As, Cu, Zn, and Ni in topsoil samples of arable land and agricultural products were collected and analyzed, with an emphasis on the geochemical characteristics of each element and ecological risk assessment of agricultural products. Correlation analysis, principal component analysis (PCA), and the absolute principal component score-multiple linear regression receptor model (APCS-MLR) were used to discuss the source and source contribution rate of soil heavy metal pollution in this area. Meanwhile, the spatial distribution characteristics of the contribution rate of Cd and As pollution sources of the soil in the study area were also expounded in detail by the geostatistical analysis method. The results showed that the contents of six heavy metal elements including Cd, Hg, As, Cu, Zn, and Ni in the study area all exceeded the risk screening value. Among them, two elements exceeded the risk control value, Cd and As, and the point-exceeding rates were 36.11% and 0.69%, respectively. The Cd in agricultural products was also seriously exceeded. According to the analysis, there were two main sources of heavy metal pollution in the soil in the study area. Source one (Cd, Cu, Zn, and Ni) was coming from mining activities and natural sources, and the contribution rates to Cd, Cu, Zn, and Ni were 78.53%, 84.41%, 87%, and 89.13%. Source two (Hg and As) was mainly an industrial source, and the contribution rates to As and Hg were 82.41% and 83.22%, respectively. Cd was the heavy metal with the greatest pollution risk in the study area, and measures should be taken to reduce the pollution risk. There was an abandoned stone coal mine rich in elements such as Cd, Cu, Zn, and Ni. Located in the northeastern part of the study area under the action of atmospheric deposition, the confluence of mine wastewater into irrigation water and farmland sediment was one of the important factors for forming the source of farmland pollution. The settled fly ash was the main pollution source of As and Hg, which was also closely related to agricultural production. The above research can provide technical support for the precise implementation of ecological and environmental management policies.