Research progress for toxic effect of nanomaterials in soil

Nanomaterials are released inevitably into the environment due to mass production and extensive uses．In the environment, the soil serves as the main sink for released nanomaterials．The environmental impact and biological toxicity of soil nanomaterials have been extensively investigated．Here we review the sources and concentrations of nanomaterials in the soil, toxicity of nanomaterials (on soil microorganisms, plants, animals), enrichment and toxicity of nanomaterials in the food chain．Major factors (e.g. physicochemical properties of nanomaterials and environmental factors) modulating toxicity of nanomaterials are summarized, as well as possible mechanisms of nanomaterial toxicity (oxidative stress, toxic metal ion release and physical contact)．Remaining challenges and problems regarding soil nanomaterial toxicity are listed, as well as future directions for further research (toxicity at the food chain level, compensation models for lack of experimental methods, long-term toxicity, combined toxicity of nanomaterials and other pollutants)．