Uptake of trichloroethylene by hybrid poplar trees grown hydroponically inflow-through plant growth chambers

Phytoremediation is being promoted as a cost-effective treatment option for shallow groundwater and soils contaminated with trichloroethylene (TCE). H owever, its effectiveness is difficult to assess due to contradictory repor ts regarding the magnitude of plant uptake and phytovolatilization. Experim ental artifacts and plant stress, resulting from the use of static or low-H ow plant growth laboratory systems, may account for part of the discrepancy . High exposure concentrations and short durations may also cause artifacts in laboratory studies. A dual-chamber plant growth system designed to mini mize experimental artifacts was used to determine the uptake of [C-14] TCE by hydroponically grown hybrid poplar as a function of plant stress (aerobi c and oxygen-reduced root zone), exposure concentration (1-70 mg/L), and ex posure duration (12 or 26 d). The [C-14]TCE recoveries ranged from 92 to 10 1% in 11 dosed chambers. Trichloroethylene mass equivalent concentrations i n the shoot tissue (2-168 mg/kg) were dependent on the amount of water tran spired and the exposure concentration. Root-zone oxygen status did not sign ificantly impact TCE uptake. Transpiration stream concentration factors (TS CFs) determined in these studies (0.02-0.22) were independent of exposure d uration and are much lower than those previously reported and predicted. Th e role of TSCF and other factors in estimating the significance of plant up take in the phytoremediation of TCE-contaminated groundwater is discussed.