Analysis of Characteristics and Sources of Heavy Metals in Farmland Soils in the Xijiang River Draining of Guangxi

Abstract

In order to determine the distribution characteristics of heavy metal pollution in farmland soils and related influencing factors in the Xijiang River Basin, 2187 farmland soil samples were collected and their heavy metal contents were tested. The spatial structure and distribution characteristics of heavy metal elements were studied using a combination of geostatistics theory and GIS spatial interpolation. The potential ecological risk index was employed for risk assessment. Multivariate statistical methods, such as correlation analysis and principal component analysis, were used to analyze heavy metal sources. Results showed that farmland soils in the Basin were enriched with seven kinds of heavy metal to some extent, with Cd accumulation being the most evident. T-test independent samples results showed significant differences in heavy metal content between dry and field paddy soils (P<0.05). Cd content in paddy soils was significantly higher than in corresponding dry land soils. Cd in farmland soils in Xijiang River exhibited higher potential ecological risk. Correlation analysis and principal component analysis showed that enrichment of Pb, Zn, As, Cd, and Cu in soil was due to anthropogenic factors such as mining activities, traffic, and sewage irrigation, while Ni and Cr were influenced by natural factors, such as soil parent material. High-content areas of As, Cd, Pb, Zn, and Cu in the upper reaches of the basin are all distributed in the Diaojiang River basin and the Dahuanjiang River basin. Cd was most widely distributed. The most intensive sampling sites indicated that mining activities have caused some degree of heavy metal pollution in local farmland soils.