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Abstract

Remediation of petroleum hydrocarbons in polar environments is more costly and
logistically and technically more difficult than corresponding temperate and tropical
contaminated sites. Bioremediation and in-situ chemical oxidation (ICO) are possible
strategies which may overcome the financial and technical challenges associated with
polar-region site remediation. ICO involves introducing reactive chemicals to
contaminated soils so that organic contaminants such as petroleum hydrocarbons are
oxidised to environmentally innocuous compounds, while bioremediation relies on
microbial activity to achieve this.
At Old Casey Station, East Antarctica (66°17'S, 110°32'E) more than 20 000 L of
Special Antarctic Blend (SAB) diesel fuel was spilt over 15 years ago. Concentrations in
the spill zone are still about 20 000 ppm and the rates of natural attenuation are
relatively slow. The application of oxidative chemicals to the site did not significantly
reduce petroleum hydrocarbon concentrations and would likely hinder biodegradation
through the destruction of the subsurface microbial communities to below the level of
detection for over 2 years. Bioremediation is considered the only likely viable alternative
to natural attenuation or dig-and-haul procedures.
The factors which were suspected of limiting microbial degradation of petroleum
contaminants were temperature, nutrients and water availability. Their potential
limitations were investigated with a series of radiometric treatability (microcosm)
studies. A positive correlation between temperatures (between -2 and 42°C) and the rate
of 14C-octadecane mineralisation was found. The high rate of mineralisation at 37 and
42°C was surprising, as most continental Antarctic microorganisms have an optimal
temperature between 20 and 30°C and a maximal growth temperature of less than 37°C. 14C-octadecane mineralisation at nine different inorganic nitrogen concentrations
(ranging from 85 to over 27 000 mg N kg-soil-H20 -1 ) was monitored. Total
mineralisation increased with increasing nutrient concentration peaking in the range
1000-1600 mg N kg-soil-H20-1 . Higher N concentrations reduced the rate of
mineralisation, highlighting the importance of avoiding over-fertilisation. Gas
chromatographic analysis of the aliphatic components of the SAB diesel in the
contaminated soil showed good agreement with the radiometric microcosm outcomes.
Ratios of n-C17: pristane and n-C18: phytane indicated that low nutrient concentrations
rather than water were the main limiting factor for biodegradation of hydrocarbons in the
soil collected from Old Casey Station when incubated at 10°C. The high rate of
mineralisation at 42°C and the microbial population dynamics were also investigated in
a series of non-radiometric microcosm studies. Denaturing gradient gel electrophoresis
of nutrient-amended contaminated soil after 40 days incubation at 4, 10 and 42°C
indicated significant differences between the microbial communities at each of the
incubation temperatures. 16S rRNA gene sequences and fatty acid methyl ester analysis
indicate that the dominant hydrocarbon degrading bacteria at 4 and 10°C are
Pseudomonas spp., while Paenibacillus spp. are likely to be the dominant hydrocarbon
degrading bacteria at 42°C. The main implication for bioremediation in Antarctica from
this study is that a high-temperature treatment would yield the most rapid biodegradation
of the contaminant. In situ biodegradation using nutrients and other amendments is still
possible at soil temperatures that occur naturally during summer in Antarctica. However,
because the soils from this site are characterised by low water holding capacities, it
would be difficult to maintain optimal nutrient concentrations during full scale treatment, and thus the use of a controlled release nutrient should be considered for full
scale remediation of petroleum contaminated soil in Antarctica.

Item Type:	Thesis - PhD
Authors/Creators:	Ferguson, Susan Harriet
Keywords:	Soil pollution, Soil remediation, Hazardous waste site remediation, Oil pollution of soils
Copyright Holders:	The Author
Copyright Information:	Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (Ph.D.)--University of Tasmania, 2004. Includes bibliographical references
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