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

Abstract

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.

Application Method and Biochar Type Affect Petroleum Hydrocarbon Degradation in Northern Landfarms

“…Although NH 4 + and PO 4 3− availability were higher in injected treatments, there was no consistency between locations. This could result from local differences in soil properties between Iqaluit and Whitehorse, such as θ liquid and the initial amount of PHC contamination (Supplemental Table S2), both of which can affect NH 4 + (Harvey et al, 2012) and PO 4 3− (Mouat and Nes, 1985) availability.…”

Manipulation of Unfrozen Water Retention for Enhancing Petroleum Hydrocarbon Biodegradation in Seasonally Freezing and Frozen Soil

“…Previous bioremediation experiments indicate that the presence of unfrozen water is critical for extending hydrocarbon biodegradation in frozen contaminated soil. ,− However, the relationship between the manipulation of unfrozen water retention via controllable soil factors and the enhancement of petroleum hydrocarbon biodegradation is not understood. Unfrozen water content, influenced by a variety of factors, gradually decreases as soils undergo seasonal freezing, before stabilizing at a minimum threshold in deeply frozen soil .…”