Influence of environmental factors on denitrification in sediment contaminated with JP-4 jet fuel

In 1975, the loss of approximately 83,000 gallons of JP-4 grade jet fuel resulted in contamination of the shallow aquifer near North Charleston, South Carolina. To identify those factors likely to influence microbial activity under denitrifying conditions, we examined the fate of amended NO₃, the effect of pH, NO₃, and PO₄ on denitrification, and the variability of denitrification in sediments collected at the site. Denitrification (N₂O-N production) accounted for 98% of the depletion of NO₃-N under anaerobic conditions. Both carbon mineralization and denitrification rates increased asymptotically with increasing NO₃ to a maximum at approximately 1 mM NO₃. Addition of up to 1 mM PO₄ did not significantly increase N₂O and CO₂ production. Denitrification rates were at least 38% lower at _pH = 4 than observed at _pH = 7. Comparison of samples with differing degrees of hydrocarbon contamination indicated that at least a tenfold variation in sediment denitrification occurs at the North Charleston site.