ENHANCED MIGRATION OF GASOHOL FUELS IN CLAY SOILS AND SEDIMENTS

Clay soils have low hydraulic conductivities in the presence of high p olarity pore fluids, such as water, Low polarity fluids, including hyd rocarbon fuels and halogenated organic solvents, typically cannot migr ate into clay pores because they cannot displace water. Oxygenated add itives in gasoline, such as alcohols and methyl-tert-butyl ether, are increasingly being used to control air pollution emissions, These rela tively polar and water-soluble compounds may facilitate displacement o f pore water and enhance migration of fuels and solvents through clay- rich soil strata. In the reported research, the migration of gasoline- alcohol fuel mixtures (gasohol) through consolidated clay was examined , Prepared kaolinite clay samples were consolidated from slurry, and v arious combinations of gasoline, alcohol, and water were applied to th e clays under 152 Pa pressure in a fixed-wall permeameter, Movement of the fluids into the clay samples was monitored by measuring displaced pore fluid and by magnetic resonance imaging of the samples, Changes in clay aggregate structure were examined using environmental-scanning electron microscopy. Results of the research suggest that alcohol add ed to hydrocarbon fuels can enhance their migration through clays, Gas oline did not migrate into water-saturated clay, even after 14 days un der pressure, The gasohol mixture migrated readily into the clay in on ly 20 minutes, Increased hydraulic conductivity of the clay in the pre sence of gasohol is hypothesized to be due to the collapse of the clay 's pores thereby creating larger pores, Increasing pore diameter decre ases the capillary pressure needed for the gasohol to replace water an d allows gasohol to migrate through the clay.