ETHANOL IN GROUNDWATER AT A NORTHWEST TERMINAL

摘要

In March 1999, a 19,000-gallon release of neat ethanol occurred from an aboveground storage tank at a Bulk Fuel Terminal located in the Northwest United States ("Northwest Terminal"). Ethanol is completely miscible in water and at high concentrations (>20,000 mg/L) can enhance the solubilization of benzene, toluene, ethylbenzene, and the xylenes (BTEX) from nonaqueous phase liquid (NAPL). Ethanol can be degraded in both aerobic and anaerobic environments. The presence of ethanol appears to enhance the mobility of NAPL, as shown by increasing apparent NAPL thickness in two monitoring wells. Cosolvent effects of ethanol and lower benzene transformation rates are suggested by increasing benzene concentrations in one downgradient monitoring well. The presence of ethanol has created a strongly anaerobic groundwater system, demonstrated by low or nondetectable dissolved oxygen, depleted sulfate and nitrate, and elevated methane concentrations. The monitoring well network is adequate to delineate the ethanol plume.