Side Effects of Acetylene on the Conversion of Nitrate in Soil

Abstract

AbstractLaboratory studies were conducted to determine if acetylene affects the rate of NO3− reduction to N2O and N2, if C2H2 ist anaerobically metabolized in the presence of nitrate, and if C2H2 affects soil carbon metabolism. These studies in water saturated soil, incubated under air or N2 atmosphere, with or without acetone‐free acetylene, show that C2H2 can accelerate NO3− reduction. Acetylene inhibited carbon mineralization when NO3− was limited but accelerated it when sufficient NO3− was available. After three days, only two per cent or less of the added C2H2 was directly oxidized to CO2, however, up to 28 % of the added C2H2 carbon remained in the soil. The residual C2H2 carbon was oxidized aerobically and anaerobically when NO3− was added. These data suggest that when C2H2 is used in denitrification studies, the results must be carefully scrutinized. Once a soil is exposed to C2H2 it should not be used again soon to assess denitrification.