Assessment of Cd–Pb Pollution in Soils of the Youjiang River Basin, South China

To determine the distribution, migration, and accumulation characteristics of heavy metal pollution in the Youjiang River basin in South China, 71 shallow soil samples were collected from, and amounts of Cd and Pb were determined. Heavy metal pollution in the river basin was assessed using pollution index methods, potential ecological risk index, and geo-accumulation index. The spatial distribution characteristics of Cd and Pb pollution were analyzed by kriging spatial interpolation. The results show that Cd and Pb levels were elevated to some extent in the study area. Results from the single-factor pollution index calculation show that a few Cd samples reached the level of severe pollution and was distributed in the southeastern part of the study area adjacent to Pingguo large bauxite production base. Moderately polluted area accounted for approximately 20% of the total samples and was distributed along the edge of the severely polluted area, in the center (Tiandong county), midwest (near Baikuang power plant), and west (city of Baise) of the study area. The highest levels of Pb pollution only reached the level of slight contamination. The spatial distribution of Pb was similar to the severely polluted area of Cd. The calculation and spatial distribution of the single potential ecological risk index also showed the same result. Cd pollution greatly exceeded Pb pollution in the study area. The spatial distributions of pollution index and potential ecological risk index for Cd and Pb were consistent. The area of severe pollution was concentrated in the southeast, and moderate pollution was found in the northwest of the study area. This indicated that the development of mineral resources, population agglomeration, and thermal power plant were the main cause of Cd and Pb pollution; it also indicated that the spatial migration ability of heavy metals in the study area was not strong. The calculation and spatial distribution of geo-accumulation indexes both showed a similar pollution degree for Cd and Pb.