Ellen N M Woolfenden

Abstract: Diesels and lubricants used at research stations can persist in terrestrial and marine sediments for decades, but knowledge of their effects on the surrounding environments is limited. In a 5 year in situ investigation, marine sediment spiked with Special Antarctic Blend (SAB) diesel was placed on the seabed of O'Brien Bay near Casey Station, Antarctica and sampled after 5, 56, 65, 104 and 260 weeks. The rates and possible mechanisms of removal of the diesel from the marine sediments are presented here. The hydrocarbons within the spiked sediment were removed at an overall rate of 4.7 mg total petroleum hydrocarbons kg−1 sediment week−1, or 245 mg kg−1 year−1, although seasonal variation was evident. The concentration of total petroleum hydrocarbons fell markedly from 2020±340 mg kg−1 to 800±190 mg kg−1, but after 5 years the spiked sediment was still contaminated relative to natural organic matter (160± 170 mg kg−1). Specific compounds in SAB diesel preferentially decreased in concentration, but not as would be expected if biodegradation was the sole mechanism responsible. Naphthalene was removed more readily than n-alkanes, suggesting that aqueous dissolution played a major role in the reduction of SAB diesel. 1,3,5,7- Teramethyladamantane and 1,3-dimethyladamantane were the most recalcitrant isomers in the spiked marine sediment. Dissolution of aromatic compounds from marine sediment increases the availability of more soluble, aromatic compounds in the water column. This could increase the area of contamination and potentially broaden the region impacted by ecotoxicological effects from shallow sediment dwelling fauna, as noted during biodegradation, to shallow (b19 m) water dwelling fauna.

Abstract:

Abstract: Degradation of oil occurs by numerous processes such as weathering, dissolution, dispersal, migration and biodegradation. Biodegradation of oils are known to take longer in cold climates, increasing potential environmental and ecotoxicological hazards. Antarctic aerobic microbial communities in marine sediments from bays surrounding Casey Station have shown potential to degrade hydrocarbons within various oils used at Australian Antarctic bases. After analysis of 0-10 mm surface sections of Special Antarctic Blend (SAB) diesel spiked marine sediment cores, taken from a water depth of 13-19m over a 5 year period at O’Brien Bay, Casey Station, it was apparent that biodegradation was not the most abundant degradation process occurring (Fig. 1). If biodegradation was taking place, the n-alkanes would degrade prior to the low molecular weight aromatics hydrocarbons. However, in these samples methylnaphthalenes degrade more rapidly than the n-alkanes and the C3 alkylbenzenes (Fig. 1). This could be a result of preferential dissolution; methylnaphthalenes are more water soluble than the n-alkanes present in SAB diesel. In addition, ratios of specific isomers within compound groups (e.g. 2-MN/1-MN) can be used to establish whether biodegradation is occurring. These ratios did not change in the analysed samples, providing supporting evidence that biodegradation is not the prominent degradation process in the surface marine sediments in O’Brien Bay (Woolfenden et al., submitted). To address this issue, samples have been taken at 10 mm intervals from deeper (10-80 mm) in these marine sediment cores. Analytical results are expected to show more prominent biodegradation close to the surface (20-50 mm), as the physical processes should not have affected more than 20 mm deep into the sediments, but there should have been a significant population of aerobic microbial communities that would have consumed hydrocarbons. At 80 mm the results are expected to show very little biodegradation of SAB diesel, as the microbial communities become anaerobic and consume hydrocarbons at a much slower rate. Woolfenden E. N. M, Hince G., Powell S. M., Stark S. C., Snape I., George S. C., (submitted) The Rate of Degradation and the Compositional Changes of Diesel in Antarctic Marine Sediment. Organic Geochemistry

Abstract: Antarctica is still regarded as the cleanest continent [1], but contamination from past waste disposal practices and fuel spills are of concern because of the rare nature of Antarctic habitat and the potential longevity of impacts. Diesel fuel and lubricating oils are among the most common causes of contamination, and hydrocarbons and heavy metals from these oils can have environmental impacts. At Casey Station, East Antarctica, station waste was historically disposed of in an uncovered landfill located near the coastline. Each year during the warmer season’s ice, including that in and around the waste disposal sites, melts mobilizing contaminants from the waste sites to terrestrial and marine sediments [2]. In a previous series of investigations it was found that hydrocarbon contamination near Casey Station had a significant effect on biological communities [3]. These findings gave rise to a long-term (5 year) multi-disciplinary field experiment (SRE4), which investigated the rates of degradation of different lubricating oils and SAB (Special Antarctic Blend) diesel fuels and their biological effects. Marine sediment from near Casey Station was experimentally polluted with the fuels and oils and placed in trays on the seabed near the Station. The work presented here focuses on the degradation of SAB diesel fuel over 5 years. The marine sediment samples were collected at 5 intervals during 5 years of in situ incubation. At each retrieval time 8 samples were collected. The data presented here are averages of these 8 replicates. The sediment was solvent extracted and analysed by gas chromatography-mass spectrometry (GC-MS). Internal standards of known concentration were used with their relative peak area to calculate the concentration of other identified compounds in the SAB. Degradation of compounds in SAB occur at different rates (Fig. 1). At T0 (deployment) the SAB had a concentration of 2020 (±342) mg total petroleum hydrocarbons kg-1 sediment, mainly comprised of n-alkanes (27%), with isoprenoids (7%), methylnaphthalenes (4%) and dimethylnaphthalenes (4%) in decreasing abundances. Over the first 5 weeks, from (T0 - T1) there is a large percentage loss of all compounds. During a previous investigation [4] it was thought that up to 20% of total petroleum hydrocarbons (TPH) were lost due to physical processes such as dispersion of fine particulates and water washing. Although n-alkanes are generally considered to be the most biodegradable group of hydrocarbons, in this study n-alkanes in the SAB are more recalcitrant than methylnaphthalenes. At T5 (5 years) the SAB was at a concentration of 790 (±190) mg kg-1 and is composed of 8% n-alkanes, and only 3% isoprenoids, 0.7% methylalkanes and 0.4% alkylcyclohexanes. Fig. 1. The rate of degradation of groups of components within SAB diesel at normalized concentrations. ACH = alkylcyclohexanes; AB = alkylbenzenes; MN = methylnaphthalenes; TeMN = tetramethylnaphthlenes. %RSD = 34 - 123% Further work will investigate this unexpected degradation pattern, and the impact of the recalcitrant compounds on the Antarctic fauna. References [1] Kennicutt, M.C., McDonald, T.J., Denoux, G.J., McDonald, S.J. (1992) Mar. Poll. Bull. 24, 499-506. [2] Snape, I., Morris, C.E.. Cole, C.M. (2001) Cold Reg. Sci. Tech. 32, 157-174. [3] Thompson, B.A.W., Goldsworthy, P.M., Riddle, M.J., Snape, I., Stark, J.S. (2007) J. Exp. Mar. Biol. Ecol. 340, 213-226. [4] Thompson, B.A.W., et al. (2006) Env. Tox. Chem. 25, 356-366.

Abstract: For years Antarctica has been considered a clean environment, but as interest in the continent has grown, the number of people visiting Antarctica has also grown, giving rise to a waste disposal problem. Diesel fuel and lubricating oils are some of the most common causes of contamination, and the hydrocarbons and heavy metals from these can have major environmental impacts. At Casey Station, East Antarctica, station waste was historically disposed an uncovered landfill located near the coastline adjacent to Brown Bay. Ice-melts occur naturally each year during the annual warming season, resulting in the ground ice, including that in and around the waste disposal sites, melting. The ice-melts aid the mobility of contaminants from the waste site to land and marine sediments, leaving near shore and marine systems at high risk of contamination. xD;In a previous series of investigations related to the landfill it was found that sediment contamination in Brown Bay had a significant effect on biological communities, in particular hydrocarbons had a subtle but significant effect on biota. These findings gave rise to a long term (5 years) multi-disciplinary manipulative field experiment which investigated the rates of degradation of different lubricating oils and SAB (Special Antarctic Blend) diesel fuels. For this long-term experiment, marine sediment from near Casey Station was experimentally polluted with the fuels and oils and placed in trays on the seabed near the Station. The work presented here focuses on the degradation of SAB fuel, and Biodegradable, used and unused Synthetic oil over 5 years. xD; During the five years of in situ incubation, six sediment samples were collected. The results showed that some of the SAB fuel components (e.g. n-alkanes) degraded over the five year period, and that the degradation rate is faster for some hydrocarbons than others. The rate of hydrocarbon degradation has been suggested to be dependant upon the oxygen and water availability in the sediment, the microbial communities present, and temperature. With these factors at an optimum, hydrocarbons degrade preferentially, with the n-alkanes degrading rapidly. The results show that degradation results in an obvious UCM (Unresolved Complex Mixture) in the degraded SAB samples after five years. Further work will investigate the link between the more resistant hydrocarbons and the impact on biological communities.