REDOX CONDITIONS AT FUEL OXYGENATE RELEASE SITES

摘要

Members of the Soil and Groundwater Technical Task Force of the American Petroleum Institute (API) have identified a number of service station sites on the East and West Coasts where, based on plume evaluations, natural attenuation of MTBE appeared to be occurring. In order to characterize redox conditions and identify the predominant metabolic processes, Microseeps field personnel sampled 18 of these gasoline stations made available by the API members BP, Chevron and ExxonMobil. The sites were in California (13), New Jersey (4) and Pennsylvania (1). Six wells were sampled at most of the sites. Analytical results are being compiled and Microseeps personnel are preparing an interpretive report. A review of that project is presented, and includes 1) the screening criteria for choosing sites; 2) the analytical program that was chosen; 3) the sampling methodologies used; and 4) the preparation of data to evaluate the conditions graphically. Additionally, conclusions drawn from the overall review of the project are discussed. These conclusions will address the range of redox conditions found, the range of geochemistries surveyed and the role of controlling indicators. Several criteria to assess potential for natural attenuation of MTBE are discussed. Four different categories of sites are defined (e.g. methanogenic - sulfate-depleted) and assigned. A subset of the sites is recommended for microcosm studies to evaluate the field observation of MTBE natural attenuation.