Probabilistic multicompartmental model for interpreting DGT kinetics in sediments.

Area of Science:

• Environmental Science
• Geochemistry
• Analytical Chemistry

Background:

• The Diffusive Gradients in Thin-Films (DGT) technique is widely used to measure metal bioavailability in soils and sediments.
• The standard DGT-Induced Fluxes in Soils and Sediments (DIFS) model has limitations in accurately interpreting DGT measurements, particularly concerning complex accumulation kinetics and parameter uncertainty.

Purpose of the Study:

• To address the limitations of the DIFS model in interpreting DGT measurements.
• To propose a new probabilistic model, DGT-PROFS, that accounts for multiple kinetic stages and provides uncertainty ranges for model parameters.

Main Methods:

• A novel probabilistic model, DGT-PROFS, was developed, incorporating two types of particulate binding sites instead of the single pool assumed by DIFS.
• Probability Distribution Functions (PDFs) were used to fit experimental data and determine parameter uncertainty, moving beyond single-value estimations.
• The DGT-PROFS model was validated using three formulated sediments with varying iron oxide content.

Main Results:

• DGT-PROFS successfully fitted complete DGT experimental data sets, outperforming the DIFS-2D model.
• The model provided a range of uncertainty values for each parameter, offering a more robust assessment of model fit.
• Interpretation of parameter PDFs enabled differentiation of various geochemical behaviors and provided insights into metal dynamics.

Conclusions:

• The DGT-PROFS model offers a significant advancement for interpreting DGT measurements in soils and sediments.
• This probabilistic approach enhances the accuracy and reliability of geochemical assessments, particularly in complex matrices.
• DGT-PROFS provides valuable information on metal dynamics and bioavailability, improving our understanding of environmental processes.