Sulfur analyses as tracers of microbial degradation of hydrocarbons in the capillary fringe

Analyses of solid-phase sulfur species in soil cores indicate the role of sulfur redox cycling in the fate of a BTEX-rich natural gas condensate plume in a silt–clay aquitard at a gas well site in Alberta, Canada. These analyses confirmed that sulfate reduction has been a key anaerobic electron-accepting process in the plume. The observed concentrations (μg/g sediment) of the reduced solid-phase sulfur components provided evidence regarding the quantity of sulfate that has been reduced over time, and the extent of hydrocarbon plume degradation. The spatial distribution of these phases indicates that degradation of petroleum hydrocarbons linked to sulfate reduction was focused in the capillary fringe, where sulfides and elemental sulfur were the main inorganic sulfur species produced as a result of sulfate reduction.