AEROBIC ACETATE DEGRADATION NEAR THE CAPILLARY-FRINGE OFF ROADSIDE SOIL - FIELD SIMULATIONS FROM SOIL MICROCOSMS

We studied the aerobic degradation of acetate in a roadside soil to as sess the reduction of O-2 demand imposed by an alternative highway dei cing agent on groundwater. Aseptic uniform sand samples adjacent to th e capillary fringe of a state highway shoulder in southeastern Massach usetts were placed in sterile serum bottles at 5 degrees C, forming a series of aerobic soil microcosms. The samples were dosed with a reage nt-grade glacial acetic acid solution, then sampled at various time in tervals and analyzed by ion chromatography in a laboratory determinati on of the microbial degradation kinetics. The aerobic reaction rates w ere slower than those observed in loamy sand near the ground surface i n an earlier study. A steady state transport model for the alternative highway deicing agent calcium magnesium acetate [CMA; Ca-0.3 Mg-0.7(C 2H3O2)(2)] was derived, including infiltration and degradation. Simula tions were run using the observed microcosm kinetics for a range of as sumed snowmelt rates. The resulting profiles suggest that microbial ac tivity within the uniform sand near the capillary fringe has the poten tial to reduce O-2 demand by CMA on groundwater for slow (<5x10(-7) m/ s) snowmelt rates at 5 degrees C under aerobic conditions. More rapid infiltration passes more CMA to the underlying aquifer.