Changes in liquid water alter nutrient bioavailability and gas diffusion in frozen antarctic soils contaminated with petroleum hydrocarbons

Bioremediation has been used to remediate petroleum hydrocarbon (PHC)‐contaminated sites in polar regions; however, limited knowledge exists in understanding how frozen conditions influence factors that regulate microbial activity. We hypothesized that increased liquid water (θ liquid ) would affect nutrient supply rates (NSR) and gas diffusion under frozen conditions. If true, management practices that increase θ liquid should also increase bioremediation in polar soils by reducing nutrient and oxygen limitations. Influence of θ liquid on NSR was determined using diesel‐contaminated soil (0–8,000 mg kg −1 ) from Casey Station, Antarctica. The θ liquid was altered between 0.007 and 0.035 cm 3 cm −3 by packing soil cores at different bulk densities. The nutrient supply rate of NH   4 +and NO   3 − , as well as gas diffusion coefficient, D s , were measured at two temperatures, 21°C and −5°C, to correct for bulk density effects. Freezing decreased NSR of both NH   4 +and NO   3 − , with θ liquid linked to nitrate and ammonia NSR in frozen soil. Similarly for D s , decreases due to freezing were much more pronounced in soils with low θ liquid compared to soils with higher θ liquid contents. Additional studies are needed to determine the relationship between degradation rates and θ liquid under frozen conditions. Environ. Toxicol. Chem. 2012;31:395–401. © 2011 SETAC