Fate and Persistence of Aromatic Hydrocarbons Dissolved in Ground Water: Results from Controlled Field Experiments

James F. Barker, Edward O. Sudicky, Colin I. Mayfield, Robert W. Gillham, Guy C. Patrick, Karen L. Berry-Spark

Benezene, toluene, ethlybenzene, and xylenes (BTEX) pose a serious environmental threat in ground waters contaminated by petroleum products. Their migration in a sand aquifer has been evaluated in a series of natural gradient injection experiments. The organics were dissolved in ground water along with inorganic tracers and injected below the water table into the well-characterized shallow sand aquifer at Borden, Ontario, Canada. The contaminants then migrated under both the natural hydraulic gradient and the natural ground-water biogeochemical environment through a detailed ground-water monitoring network.

BTEX migration is controlled by (1) ground-water flow including dispersive mixing, (3) retardation due to sorption, and (3) biodegradation. These processes were defined by both field and laboratory studies. Mathematical models integrated these studies to identify the processes controlling BTEX behavior in the field experiments. Biodegradation was most important in limiting the migration of BTEX. BTEX mass loss was rapid aerobically, but very slow anaerobically. Biodegradation was controlled mainly by hydrogeological factors, which governed the transport of oxygen into BTEX-contaminated ground waters. Small-scale variations in hydraulic properties appear to exert a major influence on the transport of oxygen in many aquifers. Therefore, more effort may be required to define these variations at sites of groundwater contamination by petroleum products to adequately assess both the existing environmental impact and possible remedial strategies.

AAPG Search and Discovery Article #91024©1989 AAPG Pacific Section, May 10-12, 1989, Palm Springs, California.