Numerical evaluation of lateral diffusion inside diffusive gradients in thin films samplers.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Accurate solute concentration measurements in water are crucial for environmental monitoring.
• Diffusive Gradients in Thin Films (DGT) samplers are widely used for in-situ water analysis.
• Understanding diffusion dynamics within DGT samplers is key to data reliability.

Purpose of the Study:

• To investigate the effect of lateral diffusion within DGT samplers on solute flux.
• To re-evaluate previous assumptions about the constancy of lateral diffusion effects.
• To develop a correction method for lateral diffusion in DGT analysis.

Main Methods:

• Numerical simulations of diffusion processes within DGT samplers.
• Analysis of solute flux as a function of diffusion layer thickness and sampling window size.
• Comparison of simulation results with existing 1D diffusion models.

Main Results:

• Lateral diffusion's effect on solute flux is a non-linear function of sampler geometry (diffusion layer thickness and sampling window size).
• The flux increase due to lateral diffusion in standard samplers is approximately 8.8%, significantly lower than the previously estimated 20%.
• Lateral diffusion influences the diffusive boundary layer (DBL), causing a greater mass uptake reduction than predicted by 1D models.

Conclusions:

• Previous models overestimated the impact of lateral diffusion in DGT samplers.
• A novel correction procedure for lateral diffusion improves DGT data accuracy.
• This work enhances the reliability of DGT-based solute concentration measurements in aquatic environments.