Spatial Characteristics and Potential Ecological Risk Factors of Heavy Metals in Cultivated Land in the Transition Zone of a Mountain Plain

Abstract

The purpose of this study was to explore the spatial distribution characteristics and potential ecological risk factors of heavy metal pollution in cultivated soil in the transitional zone of a typical mountain plain. In this study, a county in Sichuan Province, which has the typical transitional topography of the Chengdu Plain-Longmen Mountain transition zone, was taken as the study area. Geostatistics and potential ecological risk index methods were used to analyze the spatial distribution of Cd, Cr, Cu, Pb, and Zn from cultivated land in the study area, and a potential ecological risk assessment was carried out. This was combined with geographical detector analysis to further explore the main influencing factors leading to the spatial difference in potential ecological risk. The results showed that:① The average values of ω(Cd), ω(Cr), ω(Cu), ω(Pb), and ω(Zn) of cultivated land in the study area were 0.39, 123.00, 31.28, 51.04, and 119.66 mg·kg-1, respectively, which were more than 2.60, 1.59, 1.19, 2.00, and 1.54 times the soil background value in the study area. ② The high value areas of Cd and Cr in cultivated land in the study area were mainly distributed in the west of the mountain area, the south of the transition zone, and the west of the plain area; the high value areas of Cu and Zn were mainly distributed in the west of the mountain area; the high value areas of Pb were mainly distributed in the south of the transition zone and the west of the plain area; and the low values of the five heavy metals were mainly distributed in the north of the transition zone. ③ The soil of cultivated land in the study area was dominated by slight potential ecological risk, and the average value of potential ecological risk index of heavy metals was Cd(32.58) > Pb(3.12) > Cu(2.82) > Cr(1.58) > Zn(0.98). Cd was the main factor causing the potential ecological risk of cultivated land in the study area. ④ There were significant differences in the key influencing factors of soil potential ecological risk of cultivated land in different topographic regions of the study area. The distance from the river and the soil type were the key factors affecting the mountain area; the multiple cropping index and the distance from the industry and mine were the key factors affecting the transition zone, and the soil pH value and the amount of chemical fertilizer were the key factors affecting the plain area.