Ronald J. Baker Arthur L. Baehr 1995 <p><span>A mathematical model is presented that simulates the transport and reaction of any number of gaseous phase constituents (e.g. CO</span>₂<span>, O</span>₂<span>, N</span>₂<span>, and hydrocarbons) in unsaturated porous media. The model was developed as part of a method to determine rates of hydrocarbon biodegradation associated with natural cleansing at petroleum product spill sites. The one-dimensional model can be applied to analyze data from column experiments or from field sites where gas transport in the unsaturated zone is approximately vertical. A coupled, non-Fickian constitutive relation between fluxes and concentration gradients, together with the capability of incorporating heterogeneity with respect to model parameters, results in model applicability over a wide range of experimental and field conditions. When applied in a calibration mode, the model allows for the determination of constituent production/consumption rates as a function of the spatial coordinate. Alternatively, the model can be applied in a predictive mode to obtain the distribution of constituent concentrations and fluxes on the basis of assumed values of model parameters and a biodegradation hypothesis. Data requirements for the model are illustrated by analyzing data from a column experiment designed to determine the aerobic degradation rate of toluene in sediments collected from a gasoline spill site in Galloway Township, New Jersey.</span></p> application/pdf 10.1029/95WR02077 en American Geophysical Union Use of a reactive gas transport model to determine rates of hydrocarbon biodegradation in unsaturated porous media article