Phytovolatilization of Oxygenated Gasoline-Impacted Groundwater at an Underground Storage Tank Site Via Conifers

A stand of five conifers (Pinus sp.) bordering a gasoline service station was studied to estimate the methyl tert-butyl ether (MTBE) emission rate from gasoline-impacted groundwater. Groundwater was impacted with gasoline oxygenates MTBE and tert-butyl alcohol (TBA) at combined concentrations exceeding 200,000 microg/L. Condensate from trees was collected in sealed environmental chambers and analyzed. Concentrations of MTBE in condensate ranged from 0.51 to 460 microg/L; TBA ranged from 12 to 4100 microg/L (n=19). Transpirate concentrations were derived from MTBE air-liquid partitioning data exhibited in controls spiked with known concentrations of analyte. Tree emissions were estimated by multiplying average transpirate concentrations by transpiration rates derived from evapotranspiration data. Stand evapotranspiration was calculated using meteorological data from the California Irrigation Management Information System (CIMIS) applied in the Standardized Reference Evapotranspiration Equation.