Sorption, dissolution and pH determine the long-term equilibration and toxicity of coated and uncoated ZnO nanoparticles in soil

► Triethoxyoctylsilane coated ZnO-NP is more toxic than uncoated ZnO-NP. ► ZnO-NP addition causes Zn porewater concentrations to increase for >1 year. ► Soluble Zn decreases at higher concentrations due to dose-related increases in pH. ► Toxicity of uncoated ZnO-NP to F. candida decreased after 3 months equilibration. ► Toxicity of triethoxyoctylsilane coated ZnO-NP decreased only after one year.