ENHANCEMENT AND INHIBITION OF MICROBIAL ACTIVITY IN HYDROCARBON-CONTAMINATED ARCTIC SOILS - IMPLICATIONS FOR NUTRIENT-AMENDED BIOREMEDIATION

Bioremediation is being used or proposed as a treatment option at many hydrocarbon-contaminated sites. One such site is a former bulk-fuel s torage facility near Barrow, AK, where contamination persists after ap proximately 380 m(3) of JP-5 was spilled in 1970. The soil at the site is primarily coarse sand with low organic carbon (1%) and low moistur e (1-3%) contents. We examined the effects of nutrient additions on mi croorganisms in contaminated soil from this site in laboratory microco sms and in mesocosms incubated for 6 weeks in the field. Nitrogen was the major limiting nutrient in this system, but microbial populations and activity were maximally enhanced by additions of both nitrogen and phosphorus. When nutrients were added to soil in the field at three l evels of N:P (100:45, 200:90, and 300:135 mg/kg soil), the greatest st imulation in microbial activity occurred at the lowest, rather than th e highest, level of nutrient addition. The total soil-water potentials ranged from -2 to -15 bar with increasing levels of fertilizer. Semi- volatile hydrocarbon concentrations declined significantly only in the soils treated at the low fertilizer level. These results indicate tha t an understanding of nutrient effects at a specific site is essential for successful bioremediation.