DENITRIFICATION MEASURED DIRECTLY USING A SINGLE-INLET MASS-SPECTROMETER AND BY ACETYLENE INHIBITION

Most published efforts to measure total denitrification losses directly by mass spectrometry have employed dual-inlet mass spectrometers, which correct for instrumental drift between samples. Here we have employed a simpler and cheaper single-inlet instrument to measure fluxes from, and concentrations of denitrification gases, a clay loam under grass in southeast Scotland. The method involves periodic recalibration of the individual detectors using standard gas mixtures, and online sample pretreatment with an elemental analyser. Results exhibit the same patterns as more conventional measurements using field application of the acetylene inhibition technique, but consistently exceed them. This provides further evidence that the acetylene technique is not satisfactory for heavy-textured soils.