Abstract
Due to the irreversibility of heavy metal pollution, the presence of heavy metals in farmland soil is associated with severe ecological risks that endanger both the environment and human health. Cadmium (Cd) and mercury (Hg) are two toxic heavy metals found widely in polluted soil. Cd is not readily fixed in the soil and is therefore easily accumulated by plants, while Hg has a wide range of pollution sources. The aims of this study were to explore the spatial variation in Cd and Hg concentrations in farmland soil in Poyang Lake Plain, China, and to assess their potential ecological risks as influenced by natural and human factors. A total of 283 soil samples were obtained from Fengcheng city, central Jiangxi Province. Data were then analyzed using geostatistics, the potential ecological risk index, Pearson’s correlation analysis, and Geodetector. The results showed moderate variation in soil Cd and Hg concentrations, with a remarkable difference in their spatial distribution. Cd concentrations in the northwest and northeast of Fengcheng were below the regional background level in Jiangxi; in most remaining areas, Cd concentrations were between the regional background level and national risk screening value. Areas with Hg concentrations lower than the regional background level were largely concentrated in the south, east and north of Fengcheng, and gradually increased towards the central, where they exceeded the regional background level but were below the national risk screening value. Overall, the potential ecological risk level of Cd was predominantly low, while that of Hg was moderate. The comprehensive potential ecological risk was low in most areas for both Cd and Hg, with some scattered areas of moderate risk. Moreover, the comprehensive potential ecological risk index of both Cd and Hg was significantly correlated with soil pH, total phosphorous, elevation, distance from a river (p < 0.01), and distance from a road (p < 0.05). The most significant factor influencing the comprehensive potential ecological risk index of these two heavy metals was soil pH of 5.2–5.6, followed by total p ≤ 0.52 mg kg−1. In conclusion, moderate pollution of Cd and Hg occurred in farmland soil in Poyang Lake Plain where their comprehensive potential ecological risk level was generally low and mainly influenced by soil pH and total phosphorous.
Highlights
Heavy metals are an inherent component of soil, and there are more or less heavy metals in soils with different parent materials
We investigated the distribution and spatial differentiation characteristics of Cd and Hg in farmland soil of Fengcheng City in the Poyang Lake Plain, and simulated the spatial structure and change of heavy metals in farmland soil by geostatistics combined with semi-variogram, which has the advantage of visualization for the spatial distribution and uncertainty analysis of heavy metals (Ha et al, 2014)
The results show that a handful of areas with Cd concentrations below the regional background level were found in the northwest and northeast; most other areas had a soil Cd concentration above this background level, with only a few areas in the central and southeast possessing a soil Cd concentration higher than the national risk screening value
Summary
Heavy metals are an inherent component of soil, and there are more or less heavy metals in soils with different parent materials. Human factors such as industrial development and the application of pesticides and fertilizers have led to the accumulation of heavy metals in farmland soil and subsequent heavy metal pollution (Aelion et al, 2008; Chabukdhara and Nema, 2013; Kelepertzis, 2014). The level of heavy metal pollution in farmland soil is closely associated with the quality and safety of agricultural products as well as severe ecological risks related to the toxicity, persistence, and bioaccumulation characteristics of heavy metals (Barlas et al, 2005; Ihedioha et al, 2016; Zhou et al, 2020). Spatial distribution and risk assessment of heavy metals in soil has attracted wide attention from governments and scientists (Yuan et al, 2015; Zhao and Luo, 2015)
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