Sulfate Land Application Enhances Biodegradation in a Petroleum Hydrocarbon Smear Zone

Delivery of sulfate to petroleum hydrocarbons (PHCs) source zones and groundwater plumes is desirable enhance biodegradation rates when treatment has become limited due depletion sulfate. Sulfate land application involves spreading salts on ground surface allowing their dissolution infiltration into subsurface. The objectives this pilot-scale investigation were capture the vertical transport beneath an area, confirm that reduction was occurring, explore how added affected benzene toluene. Approximately 4000 kg gypsum spread over a 30 m × study area above smear zone located approximately 2 below-ground surface. Precipitation augmented by two irrigation events. Groundwater samples, collected 1058 days from multilevel wells conventional long-screened monitoring well, analyzed for benzene, toluene, ethylbenzene, xylenes (BTEX), sulfate, bromide, dissolved inorganic carbon (DIC) methane. Compound-specific isotope analyses (CSIA) 13C-DIC 34S-SO42− performed. Following application, increase in concentration noted zone. enrichment indicated mineralization PHCs enhanced. CSIA results provided unequivocal evidence anaerobic After depleted, methane concentrations about three times greater than baseline conditions suggesting syntrophic benefit delivered Observations support viability shallow PHC zones.