Pollution assessment and source analysis of heavy metals in acidic farmland of the karst region in southern China—A case study of Quanzhou County

Abstract

This research focused on the concentrations, pollution assessment, and source identification of eight heavy metals in acidic farmland of the karst region in China. Two hundred eighty-eight soil samples (0–20 cm) were collected from farmland in the karst region of Quanzhou County, Guangxi Province and analysed using multiple methods. The results revealed that the average concentrations of Cd, Pb, Zn, Cr, As, and Hg were higher than the soil background values of China, but lower than the soil environmental quality risk control standards for soil contamination of agricultural land, except for Cd. Based on the spatial distribution and the geoaccumulation index (Igeo), the order of the Igeo values was Cd > Pb > NiZn > Cr > As > Hg > Cu. There was moderate pollution of Cd, slight pollution of Pb and As, and no pollution of Ni, Zn, Cr, Hg, and Cu. Multivariate statistical analyses showed that the accumulation of As, Cr, and Ni in the soils was attributed to weathering of parent carbonate rocks. The accumulation of Cu, Pb, Zn, and Hg was mainly affected by industrial and mining activities. However, Cd mainly originated from parent rock materials and terrain with high natural background levels, followed by agricultural activities (fertilisers). Considering the impacts of these potentially toxic elements on public health, the results of this study are essential for taking preventive actions for environmental protection and sustainable development in the region.