- Title
- Rhizoremediation of petroleum hydrocarbon contaminated soil using Australian native vegetation
- Creator
- Hoang, Son Anh
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Rhizoremediation relies on the mutualistic symbiosis between plants and soil microorganisms in the root zones (rhizosphere microbiota). Plant root exudates facilitate microbial community establishment and dynamics (chemistry and biology) in the rhizosphere. In return, rhizosphere microbiota has a significant effect on the surrounding soil by encouraging the uptake of nutrients and contaminants. In the case of organic pollutants (e.g., petroleum hydrocarbons), the microbial consortia in the rhizosphere are capable of breaking down organic compounds, thereby ameliorating soil conditions and reducing phytotoxicity. Owing to the cooperative evolution and adaptation of microorganisms in the soil-plant-microbial systems and higher survivability under extreme conditions, the use of native wild plants is generally preferred over introduced plant species for hydrocarbon degradation. To date, most rhizoremediation studies have focused on grass species belonging to the Poaceae family. Despite this, there were only few studies evaluating the rhizoremediation potential of some grass species in Australia, and those of wild native plants outside grasses remain untapped. The overall objective of the thesis was to examine the potential of Australian native wild plant species on rhizoremediation of hydrocarbon contaminated soils and effectiveness of various soil amendments on the remediation. In order to achieve that, a microcosm system was developed using eight Australian native wild plants belonging to three families, namely Poaceae, Fabaceae and Proteaceae. These plants were selected due to their habitation of different climates and soil conditions, diverse taxa, and varied root morphologies. A clean clay loam soil collected from an area in Cobar Shire, New South Wales (-31.502085, 145.781435) was artificially contaminated with a 1:1 diesel/engine oil mixture. Plant tolerance to hydrocarbon compounds, which is the prerequisite factor in the rhizoremediation, was evaluated at selected contamination levels (5,000, 10,000 and 15,000 mg kg-1). In addition, various soil amendments were applied to the contaminated soil to enhance plant growth, soil microbial population and activity, and bioavailability of hydrocarbons, which all were expected to facilitate the removal of hydrocarbons in the rhizosphere. Plant growth and photosynthesis, soil microbial activity and specific gene abundance, and hydrocarbon removal rate were quantified. Data from a series of microcosm experiments provided evidence for varying tolerance of the selected plant species to hydrocarbon compounds. Only four out of eight plant species were considerably tolerant to soil hydrocarbon contamination. However, only two plant species, namely Chloris truncata (a member of Poaceae) and Hakea prostrata (a shrub and a member of Proteaceae) showed consistent tolerance and significant hydrocarbon removal throughout the experiments. Plant growth in the contaminated soil was significantly enhanced by the addition of nutrients such as mineral fertilizers and composted animal manure but hindered by a wood-chip-based biochar. Natural surface-active agents (surfactants) derived from an Australian native plant species significantly favoured plant and rhizosphere microbe performance and stimulated hydrocarbon bioavailability whereas an anionic synthetic surfactant (Triton-X100) caused adverse impact to the plants and their associated microbiota. Total soil microbial activity (assessed via dehydrogenase activity DHA and soil respiration) was not a good indicator for the presence and activity of hydrocarbon-degrading microorganisms in the soil because not all the microorganisms have the ability to metabolize petroleum hydrocarbon compounds. The abundance of alkane hydroxylase gene, which was driven by plant identity and soil amendment type, proved to be an excellent biomarker to monitor the efficiency of the remediation process. Similarly, photosynthesis via chlorophyll fluorescence measurement can be used as a quick and accurate assessment of plant performance in the polluted soil. This investigation identified two Australian native wild plant species (a grass and a shrub) which can be used for further in situ investigation about their rhizoremediation potential at any hydrocarbon contaminated site. There are considerable scopes for operational improvements in rhizoremediation of hydrocarbon contaminated sites regarding root exudate composition and metabolomes, genetic backgrounds of hydrocarbon-degrading microorganisms and microbial changes under various soil conditions, and methods to introduce exogenous beneficial microorganisms (i.e., bioaugmentation).
- Subject
- rhizoremediation; petroleum hydrocarbon; contaminated soil; native vegetation
- Identifier
- http://hdl.handle.net/1959.13/1508736
- Identifier
- uon:56151
- Rights
- Copyright 2022 Son Anh Hoang
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT01 | Thesis | 4 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 432 KB | Adobe Acrobat PDF | View Details Download |