Effect of Common Ions in Agricultural Additives on the Retention of Cd, Cu, and Cr in Farmland Soils

Abstract

The anions and cations in agricultural additives have crucial impacts on the retention of toxic heavy metals (HMs) in soil. However, the influence of these ions on the adsorption and desorption of Cd, Cr, and Cu in soil has not been clarified in previous studies. This study investigated the adsorption behavior of HMs, common anions, and dissolved organic matter (DOM) in alkaline soil from farmland under different experimental conditions. Nitrates, sulfates, and chlorides were used as HM sources to investigate the effects of different experimental anion environments on batch adsorption experiments and fluorescence quenching titration experiments. Batch sorption experiments showed that the sorption of Cd2+ was inhibited by the concomitant presence of Cr3+ and Cu2+, and the presence of Cl− and SO42− inhibited the binding of HMs to the soil matrix compared to NO3−. The fluorescence quenching titration with HMs suggested that SO42− significantly enhances the binding ability of Cr3+ to DOM in solution, which may be the reason SO42− inhibited Cr3+ retention in soil. These results provide detailed insights into the interactions of HMs with DOM and anions, which is of great significance for the targeted application of pesticides and HMs’ transport and removal in farmland soils.