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An integrated approach for the phytoremedation of organic pollutants in the rhizosphere


Enhanced degradation of organic pollutants in the rhizosphere of plants has received considerable interest in recent years. It shows promise as a cheap and environmentally sustainable technology for the in situ and on-site treatment of surface-contaminated land, and for treating residual contamination in pre-treated soil. However, to date rates of pollutant degradation have not always been satisfactory. The most critical limiting factor in the microbial degradation of organic pollutants is their sorption behaviour and their limited concentration in solution phase.
The proposed project will develop an integrated concept for the in situ remediation of organic pollutants in soil through enhanced degradation by rhizosphere-inhabiting microorganisms. The project will focus on the phytoremediation of polyaromatic hydrocarbons (PAHs), which are toxic to humans and the environment, and persist in soils for many years. The aim is to provide a remediation technology of PAHs that can be tested in pilot-scale studies at the end of the three-year project period.

The project will investigate the potential of plant-symbiotic rhizobia and arbuscular mycorrhiza in mixed grass-legume systems to degrade PAHs directly or to enhance PAH availability to and degradation by free-living microorganisms in the rhizosphere.
Suitable leguminous plants, grasses and symbiotic microorganisms will be selected from long-term polluted soils, and known collections of further strains will also be used.

The tolerance and PAH-degrading ability of AM-fungi and rhizobia will be assessed in short-term experiments, as well as the effect of the AM fungi and rhizobia/plant systems on the sorption/desorption behaviour and microbial bioavailability of PAHs in the rhizosphere. Long-term PAH-polluted soils and soils spiked with PAHs will be used, in short term experiments and a microcosm experiment using soil columns over a period of 10 months, during which pollutant biodegradation will be monitored. The experimental setup will be such as to be able to measure the potential for accumulation of PAHs in the plants, and to assess the depth of effective rhizosphere degradation in contaminated soil. The survival of inoculated microorganisms in soil will be monitored by molecular techniques of DNA fingerprinting. It is essential not only to measure the disappearance of target pollutants during the remediation process, but also to monitor their toxicity in the environment. The project will develop and validate various ecotoxicological tests, using bacteria, algae, plants and soil invertebrae. The tests will then be used to monitor the progress of PAH remediation by the plant-rhizobe- mycorrhiza system. Preliminary work has been done within the Partner consortium on the role of mycorrhizae and rhizosphere bacteria in PAH-degradation, and on PAH-ecotoxicology. This will allow rapid attainment of research milestones. The results obtained during the project will be used to assess the feasibility of bioremediation in the rhizosphere considering common objectives for risk assessment, the potential for damage to humans and ecosystems. Further development towards commercial use of the system will be done in close association with the industrial project partner, which is an owner of large areas of contaminated land.


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Participants (3)

United Kingdom
S60 3AR Rotherham
20,Konrad Lorenzstrasse 20
3430 Tulln
United Kingdom
West Common
AL5 2JQ Harpenden