An electrostatic model predicting Cu and Ni toxicity to microbial processes in soils

► We evaluated the factors that influence the toxicity of Cu and Ni to soil microbial processes. ► The negativity of bacterial surfaces varied with soil types and decreased with soil metal concentrations. ► Microbial processes were limited by the electrical potential, ion activities of cell membrane surface and osmotic effects. ► The electrostatic toxicity model was developed to relate microbial processes to these influencing factors.