Measuring available concentrations of ZnO NPs in soils using Nano-DGT

Abstract

Zinc oxide nanoparticles, ZnO NPs, are used in a range of commercially available products including sun tan lotions and semiconductors. Increasing number of ZnO NPs incorporated products will likely raise concentration of this nanomaterial in the environment. Available information suggests that ZnO NPs can easily enter soil and water resources. ZnO NPs have adverse effects on different components of the environment in particular because of their toxicological impacts. Zinc oxide nanoparticles are one of the most toxic nanomaterials and could inhibit the root growth of plants and embryonic development of some of marine species. To better understand fate and behaviour of these nanoparticles in the environment and their potential pathways, determining in-situ concentration of these nanomaterials is essential. We have recently used Nano-DGT in combination with standard DGT devices to determine available concentrations of zinc oxide nanoparticle and its ionic species in soil samples spiked with a range of concentrations from 100 mg/kg to 2200 mg/kg of ZnO NPs and Zn2+. The samples were aged approximately for 80 Days after spiking. For each soil sample a Nano-DGT and a standard DGT device were deployed for approximately 20 hours (in triplicates). The results showed that for the samples spiked with ZnO NPs, available concentrations of zinc species measured by DGT devices were notably higher than Nano-DGT devices. Nevertheless considerably high concentrations of available zinc were also measured by Nano-DGTs, which could partly be attributed to dissolution of ZnO NPs and released Zn2+ because of the soil pH (5.5). In the soil samples spiked with ionic zinc the available concentrations measured by Nano-DGT and DGT devices were approximately 1.5X higher for the spiked samples with 100, 225, 500 and 1100 mg/kg ZnO NP. This ratio was more than twice for the soil samples spiked with 2200 mg/kg ionic zinc.