Rhizoremediation of hydrocarbon contaminated soil using Australian native grasses Sharyn E. Gaskin ⁎, Richard H. Bentham Department of Environmental Health, Flinders Medical Science and Technology, Flinders University, Adelaide, Australia abstract article info Article history: Received 9 February 2010 Received in revised form 4 May 2010 Accepted 4 May 2010 Available online xxxx Keywords: Phytoremediation Rhizosphere Diesel Microbial abundance Lipase activity Rhizoremediation involves the breakdown of contaminants in soil resulting from microbial activity that is enhanced in the plant root zone. The objective of this study was to assess Australian native grasses for their ability to stimulate removal of aliphatic hydrocarbons from a mine site soil. Time-course pot experiments were conducted in a greenhouse with three grass species (Cymbopogon ambiguus, Brachiaria decumbens, and Microlaena stipoides) in a mine site soil experimentally contaminated with a 60:40 diesel:oil mixture at 1% (w/w) concentration. Plants were cultivated for 100 days with periodic evaluation of changes in soil total petroleum hydrocarbon (TPH) concentration, soil lipase activity, and abundance of hydrocarbon-degrading microorganisms. Results were compared to unplanted control treatments. Significantly lower endpoint TPH concentrations were recorded in planted soil compared to unplanted soil (p = 0.01). Final TPH concentrations and rates of TPH removal varied between grass species, with total TPH removal of between 50% and 88% achieved in planted treatments. The presence of grasses significantly increased the abundance of hydrocarbon-degrading microorganisms and soil lipase activity relative to unplanted soil (p b 0.05). Residual TPH concentration was found to be closely (negatively) correlated with abundance of hydrocarbon- degrading microorganisms and to a lesser extent with soil lipase activity. Australian native grass species were identified that effectively enhance the remediation of diesel/oil contaminated soil, without any requirement for nutrient supplementation. Results may have extensive application to the nationwide problems associated with hydrocarbon contaminated sites. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Global industrialisation over the past two centuries has resulted in widespread contamination of the environment with persistent organic and inorganic pollutants. Aliphatic hydrocarbons (e.g. diesel fuel and engine oils) make up a substantial proportion of organic contamination in the terrestrial environment (Stroud et al., 2007). This class of contaminant is characterised by saturated and unsaturated linear or branched open-chain structures and is subject to physicochemical processes which can affect the fate and behaviour in soil such as degree of removal, sequestration and interaction with microflora (Germida et al., 2002). The physical properties of aliphatic hydrocarbons (e.g. high K ow ) determine their susceptibility to microbial attack and the potential for degradation in soils (Mougin, 2002). There have been increasing international efforts to remediate hydrocarbon contaminated sites using “green” technologies, either to mitigate risks of adverse health or environmental effects or to enable site redevelopment (Vidali, 2001). The use of plants and their associated microorganisms to detoxify hydrocarbon pollutants for the treatment of contaminated soils has gained increasing acceptance as a viable cleanup technology (Alkorta and Garbisu, 2001; Arthur et al., 2005; van der Lelie et al., 2001). Such technology is referred to as rhizoremediation and is suggested to be the primary mechanism responsible for hydrocarbon degradation in plant-assisted remediation efforts (Frick et al., 1999; Hutchinson et al., 2003; Yateem et al., 2007). Until recently, the potential for any Australian native plants in rhizoremediation of hydrocarbon contaminated soil has not been explored. The extent of soil contamination in Australia is uncertain; one commonly cited source estimated 80,000 sites impacted by petroleum hydrocarbon pollutants (NEPC, 1999). Rhizoremediation technology that has been developed overseas cannot be readily transferred to Australian conditions due to significant differences in climate, soil types, endemic plant species and environmental regulation performance criteria (Michael et al., 2007). Recent work has identified three hydrocarbon tolerant Australian native grass species (Poaceae) as suitable candidates for further investigation of their rhizoremediation potential (Gaskin et al., 2008). The study did not explore the individual species' potential to stimulate hydrocarbon degradation. The provision of a viable remediation technology would offer an economically feasible and environmentally sustainable option for the rehabilitation of hydrocarbon contaminated sites in Australia. The aims of the study were to (i) evaluate the potential of these previously identified Australian native grasses for the rhizoremediation of aliphatic hydrocarbon contaminated soil sourced from a mine site, Science of the Total Environment xxx (2010) xxx–xxx ⁎ Corresponding author. GPO Box 2100, Adelaide, 5001, Australia. Tel.: + 61 8 7221 8600; fax: +61 8 7221 8590. E-mail addresses: sharyn.gaskin@flinders.edu.au (S.E. Gaskin), richard.bentham@flinders.edu.au (R.H. Bentham). STOTEN-11983; No of Pages 6 0048-9697/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2010.05.004 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv ARTICLE IN PRESS Please cite this article as: Gaskin SE, Bentham RH, Rhizoremediation of hydrocarbon contaminated soil using Australian native grasses, Sci Total Environ (2010), doi:10.1016/j.scitotenv.2010.05.004