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Multitracer and Filter‐Separated Half‐Cell Method for Measuring Solute Diffusion in Undisturbed Soil
Author(s) -
Laegdsmand Mette,
Moldrup Per,
Schjønning Per
Publication year - 2010
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0285
Subject(s) - thermal diffusivity , loam , soil water , tracer , soil science , diffusion , sorption , leaching (pedology) , chemistry , filter (signal processing) , desorption , soil test , environmental science , thermodynamics , adsorption , physics , organic chemistry , computer science , nuclear physics , computer vision
Solute diffusion controls important processes in soils: plant uptake of nutrients, sorption–desorption processes, degradation of organic matter, and leaching of radionuclides through clay barriers. We developed a new method for measuring the solute diffusivity (solute diffusion coefficient in the soil relative to water) in intact soil samples (the Multiple Tracer, Filter Separated half‐cell method using a Dynamic Model for parameter estimation [MT‐FS‐DM]). The MT‐FS‐DM method consists of half‐cell diffusion of two pairs of counterdiffusing anionic tracers and a parameter estimation scheme that allows diffusion coefficients for tracers in the two half‐cells to be estimated on the basis of two concentration profiles in each sample. The parameter estimation scheme uses a fully dynamic (time‐resolved) simulation model. From sensitivity and uncertainty analyses of the dynamic model, we found that the MT‐FS‐DM method provided reliable results. We compared diffusivities measured on a sandy loam soil using the MT‐FS‐DM method with diffusivities from six sandy loam test soils from the literature. The new method can be used to estimate solute diffusivity in intact structured soil and provides a more confident estimate for solute diffusion due to the use of two tracer profiles in the same soil sample. Especially when we are interested in determining the diffusivity of a single intact soil sample, such as when relating solute diffusivity to other properties of the soil (e.g., microbial activity), this method will be an improvement over existing methods.