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(493) The relationship between nutrient uptake and bioavailability of soil-bound pollutants.
Eitzer, B.1, Mattina, M.J.1, White, J.1, Ianucci-Berger, W., 1 The Connecticut Agricultural Experiment Station, New Haven, CT, USA
ABSTRACT- Phytoremediation is developing rapidly from scenarios for its application toward fundamental research into its mechanistic basis. Significant data have been reported regarding the soil/plant chemistries for phytoremediation of elemental constituents in soil. More modest progress has been made on these same issues with respect to organic pollutants. Research conducted over several years at The Connecticut Agricultural Experiment Station supports the hypothesis that plant efficiency for phytoremediation of pollutants is related to the physiology of plant nutrition. Plant roots exude chemicals, such as organic acids, to the rhizosphere; these chemicals break down the soil structure, release and complex with nutrients, and make the nutrients available for uptake. This hypothesis proposes that pollutants become amenable to phytoremediation as "tag-alongs". That is, the same mechanism that makes nutrients bioavailable makes pollutants bioavailable. Understanding of the processes occurring in the rhizosphere are, therefore, central to an understanding of the mechanism of phytoremediation. Rhizotrons were constructed and filled with soil contaminated with weathered chlordane as well as arsenic and lead. Low molecular organic acid exudation from the roots of C. pepo L. 'Black Beauty,'Cucumis sativis 'Marketmore,' and Lupinus albus 'Homer' was measured in situ. For the two Cucurbitacea, citric, malic, and succinic acids were identified; in all cases malic acid was found in the highest amount. At destructive harvest of the plants the xylem sap was collected. Chlordane and heavy metals were identified in the sap. The relationship between exudation of the organic acids and contamination concentration in the sap will be discussed.
Key words: bioaccumulation, phytoremediaition, chlordane, POPs
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