Aerobic Acetate Degradation near the Capillary Fringe of Roadside Soil: Field Simulations from Soil Microcosms

Abstract

Abstract We studied the aerobic degradation of acetate in a roadside soil to assess the reduction of O 2 demand imposed by an alternative highway deicing agent on groundwater. Aseptic uniform sand samples adjacent to the capillary fringe of a state highway shoulder in southeastern Massachusetts were placed in sterile serum bottles at 5°C, forming a series of aerobic soil microcosms. The samples were dosed with a reagent‐grade glacial acetic acid solution, then sampled at various time intervals and analyzed by ion chromatography in a laboratory determination of the microbial degradation kinetics. The aerobic reaction rates were slower than those observed in loamy sand near the ground surface in 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 2 H 3 O 2 ) 2 ] was derived, including infiltration and degradation. Simulations were run using the observed microcosm kinetics for a range of assumed snowmelt rates. The resulting profiles suggest that microbial activity within the uniform sand near the capillary fringe has the potential to reduce O 2 demand by CMA on groundwater for slow (<5×10 −7 m/s) snowmelt rates at 5°C under aerobic conditions. More rapid infiltration passes more CMA to the underlying aquifer.