Measuring ZnO nanoparticles available concentrations in contaminated soils using the diffusive gradient in thin-films...

Area of Science:

• Environmental Science
• Nanotechnology
• Analytical Chemistry

Background:

• Assessing nanomaterial behavior in the environment requires reliable measurement tools for available concentrations.
• Zinc oxide nanoparticles (ZnO NPs) pose environmental risks due to their dissolution into toxic Zn²⁺.
• Soil properties like pH and organic matter significantly influence ZnO NP dissolution rates.

Purpose of the Study:

• To evaluate the efficacy of diffusive gradients in thin films (DGT) for measuring available ZnO NP concentrations in soils.
• To investigate the dissolution kinetics of ZnO NPs in soils with varying pH and organic matter content.
• To compare the performance of DGT with and without dialysis membranes for differentiating nanoparticulate and dissolved zinc.

Main Methods:

• Utilized paired DGT devices, with and without 1000 MWCO dialysis membranes, to measure available ZnO NPs and dissolved zinc in spiked soils.
• Employed two soil types, Woburn (pH ≈ 6.9, OM ≈ 1.8%) and Lufa (pH ≈ 5.9, OM ≈ 4.2%), with consistent initial ZnO NP spiking (500 mg/kg).
• Monitored available concentrations over 180 days at multiple time intervals.

Main Results:

• DGT successfully measured available ZnO NP concentrations and dissolved zinc in soils.
• ZnO NP dissolution and the availability of both nanoparticulate and dissolved zinc were significantly higher in Lufa soil compared to Woburn soil.
• The study demonstrated the influence of soil pH and organic matter on ZnO NP bioavailability.

Conclusions:

• Diffusive gradients in thin films (DGT) provide a simple and reliable method for determining available ZnO NP concentrations in soils.
• DGT can be used to probe the dissolution kinetics of ZnO NPs under different environmental conditions.
• Understanding ZnO NP behavior in soils is critical for environmental risk assessment and management.