ANAEROBIC DEGRADATION OF BENZENE IN DIVERSE ANOXIC ENVIRONMENTS

Benzene has often been observed to be resistant to microbial degradati on under anoxic conditions. A number of recent studies, however, have demonstrated that anaerobic benzene utilization can occur. This study extends the previous reports of anaerobic benzene degradation to sedim ents that varied with respect to contamination input, predominant redo x condition, and salinity. In spite of differences in methodology, mic robial degradation of benzene was noted in slurries constructed with s ediments from various geographical locations and range from aquifer sa nds to fine-grained estuarine muds, under methanogenic, sulfate-reduci ng, and iron-reducing conditions. In aquifer sediments under methanoge nic conditions, benzene loss was concomitant with methane production, and microbial utilization of [C-14]benzene yielded (CO2)-C-14 and (CH4 )-C-14. In slurries with estuarine and aquifer sediments under sulfate -reducing conditions, the loss of sulfate in amounts consistent with t he stoichiometric degradation of benzene or the conversion of [C-14]be nzene to (CO2)-C-14 indicates that benzene was mineralized. Benzene lo ss also occurred in the presence of Fe(lll) in sediments from freshwat er environments. Microbial benzene utilization, however, was not obser ved under denitrifying conditions. These results indicate that the pot ential for the anaerobic degradation of benzene, which was once though t to be resistant to non-oxygenase attack, exists in a variety of aqua tic sediments from widely distributed locations.