NEWS TECHNOLOGY Sunflowers remove radionuclides from water in ongoing phytoremediation field tests Planting rows of sunflower plants to remove radionuclides from soil and water is being touted by one entrepreneur as a cost-effective alternative to more traditional treatment processes. But is this phytoremediation technology ready for regular use at government nuclear cleanup sites? Some researchers say not yet. Results from field tests at a former Department of Energy uranium-processing facility and at the Chernobyl nuclear accident site were presented Feb. 28 at the American Institute of Chemical Engineers annual meeting by Burt Ensley, president of Phytotech of Monmouth Junction, NJ. Working with Rutgers University professor of plant biology Ilya Raskin and others the tests used sunflower plants to pull radionuclides from a pond contaminated by the 1986 Chernobyl accident and from water taken from the DOE site According to Enslev these tests demonstrate that rhizofiltration is a practical way to treat radionuclides including uranium cestrontium found in i
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Although scientists have known for years that plants accumulate metals, locating the right plant to take up radionuclides has taken some time. Selecting from thousands of plants, Raskin found that the roots of the sunflower cultivar (Helianthus annuus L.), when submerged in water, quickly accumulate heavy metals and radionuclides. At last year's DOE tests in Ashtabula, Ohio, roots of the sunflower plants were submerged in contaminated water in a miniature rhizofiltration system inside a portable greenhouse. Uranium concentrations in the water (100400 parts per billion) declined by 95% within the first 24 hours, below EPA's groundwater standard of 20 ppb, Ensley reported. "These results met or exceeded our goals for system performance with site water " he added Ensley's team established a
Scientists evaluate cesium and strontium uptake by sunflower plants in a pond near Chernobyl. Tests here and at an Energy Department site show promise in treating radionuclide contamination.
project in 1994 with the International Institute of Cell Biology to evaluate the use of plants to treat a pond contaminated with cesium and strontium 1 km from the Chernobyl reactor. Researchers grew sunflowers on 1 m 2 Styrofoam rafts that were placed in the pond. After four to eight weeks, the plants were harvested and dried. The results showed that the highest coefficient for cesium was measured in the sunflower roots and the higher coefficient for strontium was in the sunflower shoots Ensley and Phytotech researcher Yoram Kapulnik highlight the use of site water as their most significant achievement to date. Most of the laboratory research done in this area has used purified lab water contaminated with pure chemicals, Kapulnik says. "But the real world is a very messy place," Ensley says. Pond water or water drawn out of the surface is full of different types of metals that compete with the plant's uptake of the radionu-
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clides, which are already in very low concentrations. Ensley estimates that the cost of removing radionuclides with sunflower plants would range from $2 to $6 per thousand gallons of water treated, including waste disposal and capital costs. But others working on phytoremediation say there is just not enough data available on this technology to convince government regulators that it is reliable, consistent and cost-effective. Lee Wolfe, an environmental chemist at EPA's National Exposure Research Laboratory in Athens, Ga., says the research done by the Phytotech-Rutgers team so far is very good. "But it's certainly not a field test. I would like to see a longer study." Wolfe says he would like to know more about the function of the enzymes involved in the process, including the uptake mechanism, and the effect of the life cycle of the plant on uptake and seasonal variation. "The users and regulators are going to require a good solid scientific and engineering understanding of the process," Wolfe adds. Rita Colwell, president of the University of Maryland Biotechnology Institute, also praises Phytotech's work. Colwell also would like more information on where the heavy metal is taken up in the plant. For example, is the uranium incorporated into the plant or is it simply a bacterial uptake of the uranium which then adheres to the plant? Ensley is hoping that new field tests getting under way this spring—this time using Indian mustard {Brassica juncea) to remove lead—will further acceptance of phytoremediation. The tests will take place at a "brownfield" site in Trenton, N. J., a former battery recycling plant, and build on research by Raskin and colleagues at Rutgers {EnviSci Technol 1995 29 1232 1239) Like the experiments in Chernobyl and Ohio the plants will be harvested after a short riod in this months CATHERINE M. COONEY
