Geochemical conceptual model of BTEX biodegradation in an iron-rich aquifer

A geochemical conceptual model was developed to interpret long-term field monitoring data of the chemical speciation related to BTEX biodegradation in a tropical iron-rich aquifer that was contaminated by a large volume of jet fuel. Biodegradation under dissimilatory iron reduction is widely favored due to the abundance of iron oxides in the sediment. Concomitantly with iron-reduction, the methanogenesis pathway plays an important role in the microbial degradation of BTEX. The conceptual model was proposed to link the geochemical zonation with BTEX mineralization and secondary reactions. The representativeness of the chemical speciation of the studied hydrocarbon-contaminated aquifer is best supported when PCO2 is fixed and dissolved oxygen, potentially present due to mass transfer from entrapped air, is considered in the model. These findings emphasize the need of both constraints to properly interpret BTEX biodegradation in a tropical iron-rich aquifer.