METHYL TERT-BUTYL ETHER (MTBE) AND BENZENE SORPTION IN FINE GRAIN MATERIALS FROM NORTHERN ILLINOIS AND MEXICO

Methyl tert-butyl ether (MTBE) is a fuel oxygenate that is used to enhance gasoline combustion, therefore reduces carbon monoxide and hydrocarbons emissions. However, the USGS identifies MTBE as one of the most common contaminant of urban aquifers in the United States imparting a bad taste to the water at concentrations higher that 40 ppb. Previous studies indicate that MTBE is unable to sorb to soils and sediments. However, this study demonstrated the potential for some sorption of MTBE in fine-grain materials, especially one rich in organic matter. Isotherms were performed with various concentrations of MTBE and benzene (10, 50, 100, 500 and 1000 ppb) at 10 °C and 25 °C for loess from DeKalb, Illinois and lacustrine clays from Chalco, Mexico. The results for the loess indicate that as the amount of organic carbon content decrease from 1.5% at the surface to < 0.1% at 2 m so does the sorption of benzene. In these same samples however, the amount of organic carbon had no effect on MTBE sorption but there was increased sorption over low organic sand. These results indicate that there is at least a modest amount of sorption of MTBE in fine grain materials. On the other hand, lacustrine samples collected in Mexico at three different sites all had similar organic carbon content (5%). The sorption for MTBE was almost twice as high as the sorption in the loess samples indicating that finer grain materials with higher organic carbon are needed for sorption of MTBE. These results point out the importance of the geological setting on the fate and transport of MTBE.