A Novel Approach to Phytoremediaton of Persistent Organic Pollutants

The chemical stability and slow natural attenuation of certain persistent organic pollutants (POPs) such as polychlorinted biphenyls (PCBs) and DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane). DDT makes remediaton of these compounds a particularly intractable environmental challenge. The problems posed by such organic pollutants are reflected in their listing as Persistent Biological and Toxic Chemicals by the USEPA, and in numeroud studies such as a 2001 National Research Council report recommending further research on PCB treatment technologies. Improved treatment of POP-contaminated soils and sediments could significantly reduce the risk of contamination to the food chain, and lower the costs of storing, transporting and tracking POP-contaminated materials that must be sent to landfills. The bioavailability of POPs can decrease with time, as the chemicals gradually sorb to soil fractions. Recent research indicates that this procedss is reversible, however, as low molecular weight orgnaic acids (LMWOAs) exuded by plant roots can break POP-soil bonds. Consequently, sequestration of POPs may not survive exposure to the rhizosphere. Such results not only highlight the need to remove or degrarde POPs in the environment rather than to rely on natural attenuation, but also suggest a novel method for addressing this need. In this Phase I SBIR proposal Edenspace Systems Corporation seeks to develop an innovative LMWOA-based phytoremediaton technology for the removal of POPs from soils and excavated sediments. In cooperation with the Connecticut Agricultura Experiment Station, recently-identified plant species that naturally produce large amounts of LMWOA root exudates, mobilizing chlorinated organic pesticide compounds for plant uptake, will be tested for DDT and DDD removal in weathered soild. Second, LMWOAs will be applied directly to such soils to measure enhanced contaminant uptake by such naturally-accumulating plants and by Indian mustard. Successful Phase I results will be followed in Phase II with testing plant uptake of other POPs (e.g., PCBs and dioxin); determine optimal LMWOAs (e.g., malate, citrate) for various POPs; developing additonal plant selection, cultivation and treatment techniques to increase performance; assessing possible incrases in the rate of POP degradation as a result of increased microbial activity around plant roots; assessing cost-effectiveness and ecological risks; and conduction a field demonstration at a POP-contaminated site. The overall result of this Phase I and Phase II research is expected to be a demonstrated POP phytoremediaton technique that uses commercially-available plants and rapidly biodegradable LMWOAs to provide cost-effectivecleanup of many POP-contaminted soils.