Naphthalene mineralization coupled to sulfate reduction in aquifer-derived enrichments

Naphthalene was microbially transformed in sulfate-reducing laboratory microcosms established under strictly anaerobic conditions using sediment from two sulfate-rich, coal tar-contaminated aquifers and enriched over a 3-year period. As much as 66% of [¹⁴C]naphthalene was mineralized to CO₂ over 13 days. Addition of sodium molybdate inhibited sulfidogenesis and resulted in a 44% reduction in total [¹⁴C]naphthalene mineralized. Methane was never detected in active naphthalene-degrading microcosms, and formation of sulfide during naphthalene degradation was confirmed using a ³⁵SO²⁻₄ radiotracer technique. GC/MS analyses of stabilized naphthalene-degrading consortia indicated the formation of naphthalenol as a potential metabolic intermediate. These results demonstrate that naphthalene oxidation may be coupled to sulfate reduction in aquifer-derived sediments.