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Non-Steady State Fickian Diffusion Model Decrease the Estimated Gel Layer Diffusion Coefficients Uncertainty for Diffusive Gradients in Thin-Films Passive Samplers
Citation:
Hodges, S., D. Wahman, L. Haupert, H. Pham, M. Bozarth, M. Howland, AND J. Fairey. Non-Steady State Fickian Diffusion Model Decrease the Estimated Gel Layer Diffusion Coefficients Uncertainty for Diffusive Gradients in Thin-Films Passive Samplers. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 57(26):9793-9801, (2023). https://doi.org/10.1021/acs.est.3c01861
Impact/Purpose:
Analyte mass transport in diffusive gradients in thin-films (DGT) passive samplers is restricted to molecular diffusion through a gel layer. Gel diffusion coefficients (DGel) are typically determined in two-compartment diffusion cell tests using a standard analysis (SA) based on Fick’s first law assuming pseudo-steady state (P-SS) flux. However, this work demonstrates that non-steady state flux occurs in diffusion cell tests with nitrate. A finite difference model (FDM) based on Fick’s second law is developed to determine the specific conditions under which such non-steady state flux is expected to be significant. The results of this research have important implications for the deployment and analysis of passive samplers to determine the concentrations of contaminants in drinking water sources.
Description:
Diffusion coefficient measurements in passive sampler gel layers typically assume pseudo-steady state flux. This study reports non-steady state flux occurs in diffusion cell tests with implications for environmental compliance monitoring.
URLs/Downloads:
DOI: Non-Steady State Fickian Diffusion Model Decrease the Estimated Gel Layer Diffusion Coefficients Uncertainty for Diffusive Gradients in Thin-Films Passive Samplers
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