Trevor Hansen, Utah State University
Biology
The use of metallic nanoparticles (NPs) in various applications presents the possibility for environmental contamination by these NPs. CuO and ZnO NPs have dose-dependent phytotoxicity. However, NPs are modified by different environmental factors such as salts: chlorides of Na, K, and Ca are used on roads for de-icing, dust control, irrigation, water treatments, and fertilizer production. At low concentrations these salts promote plant growth, but elevated concentrations become phytotoxic. This study examines the impact of Na, K and Ca chlorides on the phytotoxicity of CuO and ZnO NPs for wheat grown in sand. Atomic force microscopy and dynamic light scattering showed dose-dependent aggregation of the NPs in the wheat rhizosphere. The salts also caused NP-aggregation, but the degree of dissolution of the NPs was salt specific. Release of Cu from CuO NPs in the planted sand was reduced by all salt treatments whereas Zn release from ZnO NPs was reduced by Na and K but not Ca. Overall, a phytotoxic synergistic effect was seen at lower salt concentrations, but at higher salt levels, toxicity was mediated mainly by the salts. Therefore, effects upon plant growth of NPs and salts will vary according to concentrations.