Relative depletion rates of MTBE, benzene, and xylene from smear zone LNAPL

Smear zone light non-aqueous phase liquids (LNAPL) depletion rates of methyl tertiary butyl ether (MTBE), benzene, and xylene were studied from UST release sites where groundwater analyses had been performed for several years. A first-order decay function was fitted to time series analytical data sets from 15 non-remediation sites and eight remediation sites to calculate the initial concentration (CO) and decay constant (k) for each. Mean k's are similar for all analytes in both site groups, despite significant differences in predicted depletion rates assuming equilibrium partitioning. These data suggest mass transfer limitations can slow down the overall source depletion process considerably and effect the observed MTBE plume shape and length under conditions of natural attenuation, as well as limit the rate of MTBE removal during remediation