Due to recent developments in nanotechnology, nanomaterials (NMs) such as graphene oxide (GO) may enter the soil environment with mostly unknown consequences. We investigated the effects of GO on soil microbial activity in a 59-day soil incubation study. For this, high-purity GO was prepared and characterized. Soils were treated with up to 1 mg GO g^-1 soil, and the changes in the activities of 1,4-β-glucosidase, cellobiohydrolase, xylosidase, 1,4-β-N-acetyl glucosaminidase, and phosphatase and microbial biomass were determined. 0.5^-1 mg GO g^-1 soil lowered the activity of xylosidase, 1,4-β-N-acetyl glucosaminidase, and phosphatase by up to 50% when compared to that in the control soils up to 21 days of incubation. Microbial biomass in soils treated with GO was not significantly different from that in control soils throughout the incubation period, and the soil enzyme activity and microbial biomass were not significantly correlated in this study. Our results indicate that soil enzyme activity can be lowered by the entry of GO into soils in short term but it can be recovered afterwards.

Keywords: Nanomaterial; Microbial biomass; Soil incubation; Extracellular enzymes; Soil microorganisms.