The effect of multi-walled carbon nanotubes on soil microbial activity

Nanomaterials such as multi-walled carbon nanotubes (MWCNTs) are applied to various industrial products and thus may be released to soils, but their potential environmental impacts remain largely undetermined. We investigated the short-term effect of MWCNTs on the activity and biomass of microorganisms inhabiting two different soil types in an incubation study. Up to 5000 mu g MWCNT g(-1) soil was applied and the activities of 1,4-beta-glucosidase, cellobiohydrolase, xylosidase, 1,4-beta-N-acetylglucosaminidase, and phosphatase and microbial biomass were measured. In both soil types, most enzyme activities showed a tendency to be repressed under 500 mu g MWCNT g(-1) soil, and all enzymatic activities as well as microbial biomass C and N were significantly lowered under 5000 mu g MWCNT g(-1) soil. Our results suggest that high concentrations of MWCNTs could lower the microbial activity and biomass in soils, and they may serve as an important guideline in regulating the release of MWCNTs to the soil environment. (C) 2011 Elsevier Inc. All rights reserved.