Approach for estimating microbial growth and biodegradation of hydrocarbon contaminants in subsoil based on field measurements: 2. Application in a field lysimeter experiment.

A new approach was applied to represent the natural attenuation of hydrocarbon (HC) contaminants as observed in a field lysimeter experiment. The approach describes the microbial growth on HC contaminants and linked HC biodegradation under natural precipitation conditions. The HC contaminants contained an inert component (n-dodecane) and soluble components (toluene, ethylbenzene, xylene isomers, and naphthalene), and their attenuation processes were predicted. The respiratory quinone profile method is used to indicate temporary changes in in situ microbial biomass possessed by HC-degrading microorganisms in soils. On the basis of field measurements conducted during the initial 92 days post-HC contamination, the kinetic parameters of HC-degrading microorganisms were estimated, which were used for the prediction of microbial growth and linked HC-contaminant depletion in the contaminated soil for the subsequent 259 days. The prediction was in good agreement with the measured HC concentration and corresponding respiratory quinones from HC-degrading microorganisms. The results indicate that the proposed approach can provide a reliable prediction of HC depletion in subsoil on the basis of field measurements. Further efforts are expected to incorporate the approach into a multiphase flow and multicomponent transport model for application to actual HC-contaminated sites.