Harnessing native Australian plants and their rhizosphere microbes to enhance breakdown of environmentally persistent petrogenic hydrocarbons (PHCs) from oil spills is the focus of this project (rhizo-remediation). Plant roots exude compounds which may aid breakdown of PHCs either directly, or indirectly through promoting growth of certain soil microbes. The project aims to: 1) identify native plants able to grow in PHC-contaminated soils and enhance biodegradation of PHCs; 2) determine which root exudates contribute to PHC degradation; 3) identify key microbes involved in PHC degradation; and 4) investigate whether prior exposure will enhance ability of the microbial community to degrade PHCs (priming).
Much of the work to date on this project has been undertaken by UWA PhD student Navjot Kaur.
Navjot initially examined the germination of 28 plant species in sand amended with 4 rates of either diesel or crude oil (0, 1.5, 3, 6%). Species were primarily Australian natives, but exotics which well-tolerate PHC contamination were also included. Most species tolerated crude oil better than diesel and tolerance varied greatly among both native and exotic species.
A glasshouse experiment then used species that had good tolerance of contamination at either all rates or just low rates (7 natives, 2 exotics). Plants were grown for 3 months in soil with either no contamination or 1% aged crude oil. Plant-free pots were also maintained. At harvest, plant growth, rhizosphere carboxylates (low molecular weight organic acid anions) and remaining soil PHC levels were analysed. Results are being collated. In addition, soil collected at harvest is now included in a laboratory incubation to test if the previous presence of a plant and/or addition of oil primes the soil microbes and enhances degradation of a further addition of oil. Samples collected from the incubation will be sequenced for genes associated with degradation following DNA extraction.
This project is an ARC linkage project. Research is primarily located at The University of Western Australia (UWA) and at RMIT (Andy Ball), with support from industry partners including Horizon Power, ChemCentre WA, and Environmental Earth Sciences. International collaborators include Mark Tibbett (Cranfield, UK) and Gary Bending (Warwick, UK). Other UWA collaborators include Suman George, Chuck Price, Andy Whitely and Paul Greenwood.
- Professor Mark Tibbett, Cranfield University
- Dr Gary Bending, Warwick University