Widespread potential for microbial MTBE degradation in surface-water sediments

Microorganisms indigenous to stream and lake bed sediments, collected from 11 sites throughout the United States, demonstrated significant mineralizat ion of the fuel oxygenate, methyl-tert-butyl ether (MTBE). Mineralization o f [U-C-14]MTBE to (CO2)-C-14 ranged from 15 to 66% over 50 days and did not differ significantly between sediments collected from MTBE contaminated si tes and from sites with no history of MTBE exposure. This result suggests t hat even the microbial communities indigenous to newly contaminated surface water systems will exhibit some innate ability to attenuate MTBE under aer obic conditions. The magnitude of MTBE mineralization was related to the se diment grain size distribution. A pronounced, inverse correlation (p < 0.00 1; r(2) = 0.73) was observed between the final recovery of (CO2)-C-14 and t he percentage content of silt and clay sized grains (grain diameter < 0.125 mm). The results of this study indicate that the microorganisms that inhab it the bed sediments of streams and lakes can degrade MTBE efficiently and that this capability is widespread in the environment. Thus aerobic bed sed iment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States and may contribu te to the reported transience of MTBE in some surface waters.