Crude oil bioremediation in Arctic seashore sediments

Abstract

Oil is an important energy source but also an environment pollutant. Crude oil spills along Arctic shorelines might occur due to the expected increase in offshore oil production. To reduce adverse effects on the environment in the case of a spill, it is important to develop approaches to remove spilled oil. Bioremediation with addition of nutrients has shown promising results in enhancing oil degradation rates. This research focuses on determining the effect of different environmental conditions on the rate of crude oil biodegradation in laboratory experiments, as a proxy for oil spills at Arctic seashores. Laboratory microcosms were set up containing beach sediments collected from Barrow, spiked with North Slope Crude. These microcosms were incubated at varying temperatures (3°C vs. 20°C), salinities (30 vs. 35 g/L) and crude oil concentrations (1 vs. 5 mL/kg), all with a standard concentration of nutrients. Measurements of respiration rates (breakdown of hydrocarbons to CO₂), hydrocarbons remaining in the sediment (GC/FID), and hydrocarbons volatilized and sorbed to activated carbon (GC/MS) were performed. In all microcosms, higher respiration rates by naturally occurring microorganisms were observed at 20ºC compared to 3°C. Surprisingly, volatile organic compounds (VOC) release was similar at both temperatures, for different crude oil concentration and salinities. High total petroleum hydrocarbon (TPH) levels remained at 3°C for microcosms with high initial crude oil concentration. Regardless of temperature, increased salinity had a positive impact on the rate of crude oil removal, i.e. high CO₂ release, high VOC production and low amount of TPH in sediments. At higher crude oil dosages, a larger amount of volatiles was released, however CO₂ production did not significantly increase with the contaminant concentration. The results of this study will assist decision-makers in choosing effective spill response strategies for future crude oil spills in Arctic shorelines.