Spatial variations in MTBE-biodegradation activity near a biobarrier in Port Hueneme, California

MTBE has been found to be resistant to natural attenuation processes at many sites creating very large plumes. In Port Hueneme, California, a long MTBE plume has been extensively characterized. In this plume, MTBE-degrading cultures were injected more than four years ago and this biobarrier has been effective in degrading MTBE. The objective of this study was to determine the current spatial distribution of the microbial activity along the biobarrier, and to determine which portions of the aquifer are actively degrading MTBE. The approach used was to collect discrete soil aquifer samples and groundwater near the biobarrier. Microcosms were prepared and MTBE was periodically monitored for any degrading activity. The main result from this study was the recognition of heterogeneous MTBE-degrading activity zones throughout the biobarrier. Of special interest is that well oxygenated zones, where no MTBE is presently being biodegraded, showed a high MTBE-degrading activity.