A. When a DGT passive sampler is deployed in a soil or sediment it continuously removes the analyte of interest from the immediately adjacent porewater. If there is a dynamic equilibrium between solute in the solid phase and in solution, the locally lowered concentration in the porewater causes resupply of solute from the solid phase to solution. Harper et al1,2, developed a numerical model of the dynamics of DGT in contact with a porous solid phase medium, known as DGT induced fluxes in sediments or soils, DIFS. Key terms within DIFS are the size of the pool of labile analyte in the solid phase and the rate of release of the analyte from solid phase to solution. Ernstberger et al3, showed that by measuring the mass accumulated by DGT when it is deploying in homogenized soils for different times it was possible to use DIFS to obtain the labile pool size and the dissociation rate. In other experiments where there are alternative estimates of the pool size, DIFS can be used to calculate release rates directly4,5. DIFS was initially formulated as a one-dimensional model, perpendicular to the DGT surface, but later a two-dimensional version became available6. A thorough review of the development and application of DIFS, its limitations and other modelling possibilities is available in the DGT book7.
To obtain the software, please email Hao Zhang directly: h.zhang@lancaster.ac.uk
- P. Harper, W. Davison, H. Zhang, W. Tych, Kinetics of metal exchange between solids and solutions in sediments and soils interpreted from DGT measured fluxes. Geochimica et Cosmochimica Acta,, 62:16 (1998), 2757–2770.
- P. Harper, W. Davison, W. Tych, DIFS—a modelling and simulation tool for DGT induced trace metal remobilisation in sediments and soils. Environmental Modelling & Software, 15:1 (2000), 55-66.
- Ernstberger, W. Davison, H. Zhang, A. Tye, S. Young, Measurement and dynamic modeling of trace metal mobilization in soils using DGT and DIFS. Environmental Science and Technology, 36:3 (2002), 349-354.
- Zhang, E. Lombi, E. Smolders, S. McGrath, Kinetics of Zn Release in Soils and Prediction of Zn Concentration in Plants Using Diffusive Gradients in Thin Films. Environmental Science and Technology, 38:13 (2004), 3608-3613.
- J. Fitz, W. W. Wenzel, H. Zhang, J. Nurmi, K. Stipek, Z. Fischerova, P. Schweiger, G. Kollensperger, L. Q. Ma, G. Stingeder, Rhizosphere characteristics of the arsenic hyperaccumulator Pteris vittata L. and monitoring of phytoremoval efficiency. Environmental Science and Technology, 37:21 (2003), 5008-5014.
- Ł. Sochaczewski, W. Tych, B. Davison, H. Zhang, 2D DGT induced fluxes in sediments and soils (2D DIFS). Environmental Modelling & Software, 22:1 (2007), 14-23.
- J. Lehto, Principles and Applications in Soils and Sediments, In: Diffusive Gradients in Thin-Films for Environmental Measurements, Ed. W. Davison, Cambridge University Press, Cambridge, 2016, pp146-173.