Description
The devices Diffusive Gradients in Thin-films (DGT) continuously remove labile metal species from where they are deployed. Adsorption and desorption processes of metals from soil solid phases to porewater are of the utmost importance since metal species in porewater are potentially available to plants and organisms. In this study, we proved that the one-dimensional DGT-induced Fluxes in Soils and Sediments code (1D-DIFS) generates different results with the input of different deployment times, while using the same other parameters. 1D-DIFS considers the free metal ions as the only diffusing species, but it does not include partially labile metal complexes. Lehto et al. (2012) developed a more advanced 1-D model with commercial software, where ligands were incorporated into diffusion process. However, we propose a new model by extending that of Lehto’s, which is implemented in a robust open-source code (SSOC, for “Sediments and SOils with Complexation”). The main difference between the SSOC and 1D-DIFS is that the adsorption of SSOC does not follow a linear adsorption isotherm, but rather a non-linear isotherm. It means that the SSOC model treats the soil accessible sites internally as an immobile ligand where the concentration of soil sites is variable; therefore, the soil accessible sites are not always in ligand excess conditions (Puy et al., 2016). By using Laplace transforms, we also derived an analytical solution for the case of just diffusion (i.e. Rdiff). To test SSOC code and the analytical solution, we first validated that their outputs agreed for specific parameters. We found that, typically, taking just a couple of terms in the series of the analytical solution yields enough accuracy. Besides, three selected cases from the literature were applied in the SSOC. We also tested the impact of different input physicochemical parameters on the results of SSOC: the thickness of the resin gel disc, the amount of soil sites, the stability constant of metal complexes (KML) in the solid phase, etc. This model (and its code) can advance the understanding on the role of the metal complexes in the distribution kinetics of metals between porewater and solid phase.Bibliography:
Lehto, N. J.; Davison, W.; Zhang, H. The use of ultra-thin diffusive gradients in thin-films (DGT) devices for the analysis of trace metal dynamics in soils and sediments: A measurement and modelling approach. Environ. Sci. 2012, 9, 415-423.
Puy, J.; Galceran, J.; Rey- Castro, C. Interpreting the DGT Measurement: Speciation and Dynamics in Diffusive Gradients in Thin-films for Environmental Measurements; Davison, W., Ed.; Cambridge university press: Lancaster, 2016; pp 1-9
| Periode | 11 okt 2023 → 13 okt 2023 |
|---|---|
| Gehouden op | L'Institut de Radioprotection et de Sûreté Nucléaire, France |
| Mate van erkenning | International |