The impact of size on the fate and toxicity of nanoparticulate silver in aquatic systems.

•Citrate-coated AgNPs aggregated unless humic acid present.•PVP-coated AgNPs did not aggregate significantly in any medium.•Humic acid reduced toxicity but did not have a strong effect on dissolution.•Greater AgNP dissolution for higher chloride concentrations.•Toxicity was in the order micron silver ≪ nanoparticulate silver < ionic silver.