Biodegradation of gasoline constituents in a fractured aquitard: a field study

摘要

Natural attenuation of groundwater contaminants in fractured media is difficult to demonstrate because it is difficult to ensure that a downgradient monitoring point is located in the flow path of the affected groundwater. At a field site in Wisconsin, a gasoline release from a leaky underground storage tank reached the water table and dissolved gasoline constituents were observed in groundwater in a fractured dolomite aquitard. Groundwater flow in the aquitard was dominated by migration through a diffuse fracture zone approximately 400 feet downgradient of the source area. The plume of dissolved gasoline constituents persisted in shallow groundwater at total concentrations of thousands of #mu#g/L until the fracture zone was reached. After groundwater entered the fracture zone, the aromatic hydrocarbons were attenuated by two or more orders of magnitude, to single #mu#g/L until the fracture zone was reached. After groundwater entered the fracture zone, the aromatic hydrocarbons were attenuated by two or more orders of magnitude, to single #mu#g/L concentrations, while the MTBE was attenuated by only 30