Enhanced anoxic bioremediation of PAHs-contaminated sediment.

In this study, the biodegradation of 16 polycyclic aromatic hydrocarbons (PAHs) in marine sediment was investigated under three different anoxic conditions, i.e. sulfate-only, nitrate-only and mixed nitrate/sulfate as electron acceptors. All two-, three- and four-ring PAHs showed significant biodegradation with the removal efficiencies ranging from 42% to 77%, while five- and six-ring PAHs showed little degradation. The results illustrated that two- to three-ring PAHs could be degraded at a rate of 4.01×10(-2)-6.42×10(-2) d(-1) under nitrate-reducing condition, faster than that of under sulfate-reducing condition. Biodegradation of two- and three-ring PAHs followed first-order model well with the rate constants of 1.62×10(-2)-6.42×10(-2) d(-1). The biodegradation of four ring PAHs followed the zero-order kinetic model with the rate constants of 1.26×10(-2)-2.22×10(-2) mg/kg/d. Molecular analysis indicated that nahAc gene increased by two orders of magnitude during the biodegradation and served as a good indicator of PAHs-degrading bacterial population and biodegradation process.