Uptake and transformation of trichloroethylene by edible garden plants

Edible garden plants (carrots, spinach, and tomatoes) were grown to maturity inside continuous air-flow bioreactors, and were regularly irrigated with synthetic groundwater containing a mixture of C-14-labeled and unlabeled TCE. Two dose levels were tested (about 560 mu g/L and 140 mu g/L.). Following TCE exposure for 31 to 106 days, different plant 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 volatilized (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 concentration of C-14 label in edible plant tissue was higher than in the surrounding soil. On a harvest weight basis, accumulation factors ranged from 2.6 in high-dose tomato reactors to 32 in low-dose spinach reactors. If the radiolabel found by combustion of plants was TCE, the concentrations in edible tissue would range from 152 ppb for high-dosed tomatoes to 580 ppb for high-dosed spinach. However, neither TCE nor its commonly reported transformation products were detected by Purge & Trap GC-MS. Furthermore, the C-14 label found in plant tissue could not be extracted into the organic solvent CSI or into the inorganic solvent 10 N H2SO4. This suggests that TCE was taken up, transformed, and bound to plant tissue. Bound residues are generally believed to have lower toxicological effects than the parent compound. (C) 1997 Elsevier Science Ltd.