Multicomponent reactive transport modelling of natural attenuation in a phenol-contaminated sandstone aquifer

A complex mixture of phenolic compounds and inorganic species has contamina- ted a consolidated sandstone aquifer in the English Midlands, UK. Multicomp- onent reactive transport modelling was conducted to simulate the evolution of the contaminant plume chemistry under the influence of biogeochemical and inorganic reactions. Effective biodegradation rates by the various electron acceptors and the future potential for natural attenuation were estimated by matching the simulated concentrations of organic contaminants, electron acceptors, inorganic reaction products and pH to field-observed data. The modelling illustrates that some degradation processes (oxygen and nitrate reduction) are well constrained. However, a better understanding of reductive dissolution of Fe and Mn oxides, sulphate reduction and methanogenesis would improve predictions of future degradation at the site. An apparent mismatch between observed and simulated dissolved total inorganic carbon (TIC) concentrations may be explained by aerobic degradation of the contaminants in the unsaturated zone that occurred before the polluted water recharged into the saturated portion of the aquifer.