Bioremediation treatability assessment of hydrocarbon-contaminated soils from Eureka, Nunayut

The bioremediation potential of three hydrocarbon-contaminated soil samples with diverse soil physical/chemical characteristics from Eureka, Ellesmere Island, Nunavut, was assessed. Microbial enumeration by viable plate counts and MPN analyses combined with molecular analysis (PCR and colony hybridization) for hydrocarbon catabolic genes (alkB(+), xylE(+), ndoB(+)) demonstrated the presence of significant numbers of aerobic cold-adapted hydrocarbon-degrading organisms in the three contaminated soils. The degradative activities of the indigenous microbial populations were assessed by mineralization of C-14-labelled hexadecane (C16) and naphthalene at 5 degreesC or 23 degreesC in untreated and treated soil microcosms. Although very low rates of C16 and naphthalene mineralization were observed in untreated microcosms, nutrient supplementation with a commercial inorganic fertilizer (20:20:20) markedly increased mineralization in the soil microcosms, indicating that these soil are nutrient-deficient. Increasing the incubation temperature to 23 degreesC markedly decreased the acclimation period and increased the rate of mineralization in soil microcosms supplemented with 20:20:20. Optimal treatments resulting in the greatest rates and levels of mineralization for each soil were determined: Soil #1, 20:20:20 + tilling; Soil #2, 20:20:20 + peat moss; Soil #3, 20:20:20 + water to 60% WHC. Total petroleum hydrocarbon (TPH) analysis of cold soil microcosms revealed that, similar to the soil mineralization assays, the optimal treatments' increased TPH degradation compared with fertilizer treatment alone. TPH levels in the contaminated Eureka soils were reduced from 5166 to 2966 ppm in Soil #1, from similar to 4256 to 2466 ppm. in Soil #2, and from 4500 to 1933 ppm in Soil #3 following the appropriate treatment after 16 weeks incubation at 5 degreesC. These results indicate that the bioremediation potential of the Eureka soils at low ambient summer temperatures is considerable. It is suggested that the on-site treatment planned for the 2000 summer include the application of a commercial fertilizer and, if feasible, additional treatments such as tilling, addition of peat moss, or water, depending on the contaminated soil's physical/chemical characteristics. (C) 2001 Published by Elsevier Science B.V.