Al. Baehr et Rj. Baker, USE OF A REACTIVE GAS-TRANSPORT MODEL TO DETERMINE RATES OF HYDROCARBON BIODEGRADATION IN UNSATURATED POROUS-MEDIA, Water resources research, 31(11), 1995, pp. 2877-2882
A mathematical model is presented that simulates the transport and rea
ction of any number of gaseous phase constituents (e.g. CO2, O-2, N-2,
and hydrocarbons) in unsaturated porous media. The model was develope
d as part of a method to determine rates of hydrocarbon biodegradation
associated with natural cleansing at petroleum product spill sites. T
he one-dimensional model can be applied to analyze data from column ex
periments or from field sites where gas transport in the unsaturated z
one is approximately vertical. A coupled, non-Fickian constitutive rel
ation between fluxes and concentration gradients, together with the ca
pability of incorporating heterogeneity with respect to model paramete
rs, results in model applicability over a wide range of experimental a
nd field conditions. When applied in a calibration mode, the model all
ows 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 constitu
ent 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 desig
ned to determine the aerobic degradation rate of toluene in sediments
collected from a gasoline spill site in Galloway Township, New Jersey.