Fumigant Transport Modeling Using Hydrus: 3. Selection, Temperature Dependence and Sensitivity Analysis of Fumigant Physicochemical Properties
Abstract
Data sources and estimation procedures for fumigant diffusion coefficients, sorption coefficients, degradation rate constants, and Henry’s law constants are critically reviewed. Procedures for estimating temperature dependence are provided. A sensitivity analysis conducted using HYDRUS1D and HYDRUS2/3D shows that the aqueous diffusion coefficient has essentially no effect on fumigant flux under the scenarios studied, and fumigant sorption to soil generally has only a small effect. Among the physicochemical properties, the Henry’s law constant, gas phase diffusion coefficient and degradation rate constants have the greatest effect on simulated flux ratios (= total fumigant volatilized/fumigant applied). A simplified evaluation of temperature effects on flux suggests that fumigant property temperature dependence may contribute significantly to diurnal fumigant volatilization dynamics. The analysis suggests that accurate simulation of diurnal fumigant flux dynamics will require consideration of both tarp permeability and fumigant physicochemical property temperature dependence in some cases.