Toxicity of metal oxide (CeO2, Fe3O4, SnO2) engineered nanoparticles on soil microbial biomass and their distribution in soil

► NPs pollution stress the microbial biomass in soil. ► A change of microbial population is suggested by the increase of their C/N ratio. ► Oxide-NPs show a low solubility in soil. ► NPs are found in small aggregates rich in labile organic C, microbial biomass, clay. ► ESEM study shows NPs unaltered and clustered in soil porosity.