Variability of Biological Degradation of Aromatic Hydrocarbons in an Aerobic Aquifer Determined by Laboratory Batch Experiments

The biological aerobic degradation of 7 aromatic hydrocarbons (benzene, toluene, o-xylene, p-dichlorobenzene, o-dichlorobenzene, naphthalene and biphenyl) was studied for 149 days in replicate laboratory batch experiments with groundwater and sediment from 8 localities representing a 15 m × 30 m section of an aerobic aquifer. Compared to biologically deactivated control experiments all compounds were biologically degraded. Degradation curves were very reproducible for some compounds (benzene, toluene, o-xylene, o-dichlorobenzene and p-dichlorobenzene) and less reproducible for other (naphthalene and biphenyl). Based on observed length of lag phases, length of the degradation periods and percent degradation, the variation among the 8 localities appears to be modest. However, detailed examination of the degradation rates revealed statistically significant variation among localities for benzene, toluene, naphthlene and biphenyl, but not for o-xylene, o-dichlorobenzene, and p-dichlorobenzene. The maximum variation in degradation rates was 15 times in the case of biphenyl. Significant co-variation in degradation rates was found between benzene and toluene, and between p- and o-dichlorobenzene.