Movement of MTBE through soil after groundwater contamination

Since the late seventies, methyl-tert-butyl ether (MTBE) has become one of the most widely produced chemicals in Europe and the USA due to its use as a fuel additive. MTBE was first used as a substitute for the environmental poison tetraethyl lead because of its anti-knock properties. Statutory requirements for minimum volumes of oxygen-containing additives in motor fuels, to protect the atmosphere against the climate-relevant trace gases carbon monoxide (CO) and ozone (O_3), greatly increased the demand for MTBE in the USA. One consequence was an increasing number of groundwater and soil contaminations as well as complaints of damage to health associated with MTBE. Since the air had been kept clean at the expense of the groundwater and the soil, the use of MTBE is prohibited in the USA after 2003. In Europe increased numbers of MTBE-contaminations in the groundwater and surface waters have been reported. Goal of this project was the investigation of the MTBE mass transport into the atmosphere after a contamination of the groundwater. For this studies a tripartite experimental concept was selected: First of all, a soil column experimental set-up for studying mass transport in undisturbed soil monoliths was designed, constructed and validated. With this facility it was possible to create under defined and reproducible experimental conditions an aquifer below the soilcore, variable in height, in which a contamination with MTBE had been simulated in a real concentration range of 100 to 200 mg L"-"1. A stream of air flowed over the soil surface through the artificial atmosphere, and was collected and analysed with respect to the composition of volatile organic chemicals. Adsorption onto multibed solid adsorbent material with subsequent thermal desorption GC/MS analysis was developed for air collection and displayed good sampling performance with excellent detection limits. The groundwater samples were analysed by radioactivity-HPLC, -GPC or a new direct injection-GC/MS analytical technique. For this liquid-injection-methods the detection limit still has to be improved. (orig.)Available from TIB Hannover: RA 831(4072) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman