URANIUM SPECIATION, PLANT UPTAKE, AND PHYTOREMEDIATION

Phytoremediation of uranium (U) contaminated soil has been hampered by a lack of information relating U speciation to plant uptake. The goals of the present study are to (1) provide fundamental information regarding uptake of U by plants: and (2) improve the phytoextraction of U from contaminated soil. The first was achieved through speciation modeling and hydroponic experiments that demonstrated that the uranyl (UO 2+ 2) cation is the chemical species of U most readily accumulated in plant shoots. A subsequent soil incubation experiment examined the solubilization of U from contaminated soil by synthetic chelates and organic acids. The results indicated that citric acid solubilized >100 times more U than the other amendments. The results of the hydroponic and soil experiments were then integrated in a study that grew red beets in U-contaminated soils amended with citric acid or N-hydroxylethylene diamine triacetic acid. Citric acid was again a highly effective amendment, increasing shoot U content by 14-fold compared to controls. In addition to providing fundamental information regarding the uptake of U by plants, this study illustrates the importance of basic research to phytoremediation.