The Combination of Lime and Plant Species Effects on Trace Metals (Copper and Cadmium) in Soil Exchangeable Fractions and Runoff in the Red Soil Region of China

The water-soluble heavy metal ions in contaminated soil may enter aquatic ecosystem through runoff, thus causing negative impact on the water environment. In this study, a two-year in situ experiment was carried out to explore an effective way to reduce the runoff erosion and water-soluble copper (Cu) and cadmium (Cd) in a contaminated soil (Cu: 1,148 mg kg(-1), Cd: 1.31 mg kg(-1)) near a large Cu smelter. We evaluated the ability to influence soil properties by four Cu-tolerance plant species (Pennisetum sp., Elsholtzia splendens, Vetiveria zizanioides, Setaria pumila) grown in a contaminated acidic soil amended with lime. The results show that the addition of lime can significantly reduce the exchangeable fraction (EXC) of Cu and Cd in soil (81.1-85.6% and 46.3-55.9%, respectively). Plant species cannot change the fraction distributions of Cu and Cd in the lime-amended soils, but they can reduce the runoff generation by 8.39-77.0%. Although water-soluble Cu concentrations in the runoff were not significantly differed and water-soluble Cd cannot be detected among the four plant species, the combined remediation can significantly reduce 35.9-63.4% of Cu erosion to aquatic ecosystem, following the order: Pennisetum sp. > Elsholtzia splendens > Vetiveria zizanioides > Setaria pumila. The implication of this study would provide valuable insights for contaminated soil management and risk reduction in the Cu and Cd contaminated regions.

Automated summary

Adding lime significantly reduces the exchangeable fraction of copper and cadmium in soil, while plant species can decrease runoff generation. Different copper-tolerant plant species have varying effects on water-soluble copper concentrations, but combined remediation effectively reduces copper erosion to aquatic ecosystems.