Effects of Zn and ZnO nanoparticles and Zn²⁺on soil enzyme activity and bioaccumulation of Zn inCucumis sativus

The increased production and commercial use of nanoparticles (NPs), combined with a lack of regulation regarding their disposal, may result in the unwanted introduction of NPs to soils. In this study, the toxicity on soil enzyme activity and growth of Cucumis sativus treated with Zn or ZnO NPs was evaluated in pot soils. Specifically, C. sativus was cultivated in soils treated with Zn NPs, ZnO NPs or Zn2+ for eight weeks, after which the treatment effects on biomass and bioaccumulation were evaluated. In addition, the treatment effects on soil dehydrogenase, β -glucosidase and acid phosphatase were investigated. Soil enzyme activities were influenced by all treatments, with an especially large decrease in dehydrogenase activity in response to Zn2+ treatment. Biomass and root length also decreased in response to Zn2+ treatment. Finally, the Zn contents of C. sativus were much lower in the Zn NP and ZnO NP treatment groups than in the Zn2+ treatment group. Therefore, toxicity on soil microbial activity may have a greater influence than phytotoxicity due to immobilisation and aggregation of NPs in the soil.