AEROBIC DEGRADATION OF CALCIUM MAGNESIUM ACETATE IN ROADSIDE SOILS - FIELD SIMULATIONS FROM SOIL MICROCOSMS

Aseptic soil samples from the 0.2-m loamy sand cover and underlying sa nd fill of a state highway shoulder in southeastern Massachusetts were placed in sterile serum bottles at 5-degrees-C, forming a series of a erobic soil microcosms. The sand fill belonged to the Carver coarse sa nd series (Mesic, uncoated Typic Quartzisamment), while the loamy sand was of unknown origin. The samples were dosed with reagent grade glac ial acetic acid and commercially available calcium magnesium acetate [ (CMA; Ca0.3Mg0.7(C2H3O2)2] solutions without acclimation, then sampled at various time intervals and analyzed by gas chromatography in a lab oratory determination of the microbial degradation kinetics. The aerob ic reaction rate varied strongly and directly with depth but was unifo rm with distance along and normal to the highway. A simple steady stat e transport simulation model balancing infiltration and degradation wa s derived and run with the observed microcosm kinetics for a range of assumed snowmelt rates. The resulting simulated profiles suggested tha t the loamy sand cover had the potential to reduce O2 demand by CMA on groundwater for slow (10(-7) m/s-1 snowmelt rates at 5-degrees-C unde r aerobic conditions. Shoulders with more rapid infiltration, colder t emperatures, and thinner loamy sand covers would pass more CMA to the underlying aquifer.