UPTAKE AND TRANSFORMATION OF TRICHLOROETHYLENE BY EDIBLE GARDEN PLANTS

Edible garden plants (carrots, spinach, and tomatoes) were grown to ma turity inside continuous air-flow bioreactors, and were regularly irri gated with synthetic groundwater containing a mixture of C-14-labeled and unlabeled TCE. Two dose levels were tested (about 560 mu g/L and 1 40 mu g/L.). Following TCE exposure for 31 to 106 days, different plan t tissues and bioreactor compartments were analyzed for the C-14 label . Radiolabel recoveries ranged from about 50% for low-dose reactors to about 70% for high-dose reactors. Most of the recovered C-14 label vo latilized (74-95%) and was trapped in the Orbo(R) tubes that filtered the air exiting the reactors. A portion of the recovered label (5-25%) was sorbed to the soil. Although the percentage of the recovered C-14 label found in plant material was relatively small (1-2%), the concen tration of C-14 label in edible plant tissue was higher than in the su rrounding soil. On a harvest weight basis, accumulation factors ranged from 2.6 in high-dose tomato reactors to 32 in low-dose spinach react ors. If the radiolabel found by combustion of plants was TCE, the conc entrations in edible tissue would range from 152 ppb for high-dosed to matoes to 580 ppb for high-dosed spinach. However, neither TCE nor its commonly reported transformation products were detected by Purge & Tr ap GC-MS. Furthermore, the C-14 label found in plant tissue could not be extracted into the organic solvent CSI or into the inorganic solven t 10 N H2SO4. This suggests that TCE was taken up, transformed, and bo und to plant tissue. Bound residues are generally believed to have low er toxicological effects than the parent compound. (C) 1997 Elsevier S cience Ltd.