Year

2009

Degree Name

Bachelor of Advanced Environmental Science (Honours)

Department

School of Biological Sciences

Abstract

Accidental fuel spills on sub-Antarctic Macquarie Island have caused considerable contamination. Due to the island‘s high latitude position, its climate, and the fragility of its ecosystems, traditional methods of remediation are unsuitable for onsite clean up. However, if left untreated, even minor to moderate fuel spills could take decades before natural attenuation reduces the petroleum to environmentally acceptable concentrations. Currently, low cost, low disturbance in-situ methods to enhance biodegradation of fuel products, such as nutrient additions and air sparging, are under examination on Macquarie Island. This study investigated the potential of the sub-Antarctic native tussock grass, Poa foliosa, to contribute to such remediation efforts. This species was selected as it is common in areas of contamination and displays criteria which enhance phytoremediation efficiency. Growth trials were conducted with seedlings of P. foliosa in soil artificially spiked with Special Antarctic Blend (SAB) diesel at concentrations of 0, 1 000, 5 000, 10 000, 20 000 or 40 000 mg/kg. Replicate pots, containing single seedlings, were compared with paired unplanted pots at each SAB soil concentration. Pots were kept under controlled conditions (8°C; photoperiod of 8.75/13.25 hours) to simulate the growth environment on Macquarie Island. Plants were harvested destructively at 0, 2, 4 and 8 months. Tolerance of P. foliosa to SAB, and the effects of fuel contaminants on plant health and productivity (biomass production, plant morphology, pigments and photosynthetic health) were assessed. The rate of SAB degradation and the microbial communities within the rhizosphere (total heterotrophs and hydrocarbon degraders) were compared between planted and unplanted treatments. This study found P. foliosa to be highly tolerant across all SAB concentrations tested with respect to biomass, although higher concentrations of 20 000 and 40 000 mg/kg caused slight reductions in leaf length, width and area. Total Petroleum Hydrocarbons (TPH) were degraded 35 - 48% faster in planted soils compared to unplanted soil and were approaching soil background levels within four months. Although P. foliosa significantly stimulated the growth of both total heterotrophs and hydrocarbon degraders at low concentrations of 0 and 1 000 mg/kg, the presence of microbes in the root zone did not appear to be the sole driving force behind TPH degradation. This study provides persuasive evidence that phytoremediation using P. foliosa is a valuable technology in the suite of current in-situ remediation methodologies being adopted at these sites, and may be applicable to the remediation of spills in other cold climate regions.

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