| Monitored natural attenuation (MNA) processes were evaluated in methyl tert-butyl ether (MTBE) contaminated sediments in the vicinity of a gasoline station in Ronan, MT. MTBE showed a toxic and well-defined dose-response relationship in aqueous samples using the Microtox RTM test. The EC50 values of MTBE were found to be more than two orders of magnitude smaller than the EC50 values for TBA, which indicated a detoxification pathway for MTBE biodegradation. The sediments were non-toxic as defined by the solid-phase Flash assay.;Mineralization of MTBE was observed in sediment microcosms using sediment collected from three areas from the groundwater/surface water interface (GSI), as well as in bacterial isolates in individual bacteria isolated from sediment at the Ronan MTBE site.;Information generated in this study add evidence to an earlier mathematical modeling study conducted at Montana State University that identified MNA as a viable remediation alternative at the Ronan MTBE site. |
