ADDING SODIUM DODECYL-SULFATE AND PSEUDOMONAS-AERUGINOSA UG2 BIOSURFACTANTS INHIBITS POLYCYCLIC AROMATIC HYDROCARBON BIODEGRADATION IN A WEATHERED CREOSOTE-CONTAMINATED SOIL

The effect of two anionic surfactants was assessed during biodegradati on of 13 of the 16 USEPA priority polycyclic aromatic hydrocarbons (PA H) in a wood-preserving soil contaminated with creosote and pentacholo rophenol for a period of at least 20 years. Sodium dodecyl sulfate (SD S) and biosurfactants from Pseudomonas aeruginosa UG2 were utilized at concentrations of 10, 100 and 500 mu g/g soil. Because both surfactan ts are readily biodegradable, the microcosms received a fresh spike of surfactant every 2 weeks. Biodegradation of aged PAH residues was mon itored by GC/MS for a period of 45 weeks. Results indicated that the b iodegradation of the three-ring PAH was rapid and almost complete but was slowed by the addition of 100 mu g/g and 500 mu g/g chemical surfa ctant. Similarly, at the same concentrations, the two surfactants sign ificantly decreased the biodegradation rate of the four-ring PAH. In t his case, the inhibition was more pronounced with SDS. High-molecular- mass PAH (more than four rings) were not biodegraded under the test co nditions. It was suggested that the preferential utilization of surfac tants by PAH degraders was responsible for the inhibition observed in the biodegradation of the hydrocarbons. The high biodegradability and the inhibitory effect of these two surfactants would have a significan t impact on the development of both above-ground and in situ site recl amation processes.