| Abstract: | An acetylene inhibition method was satisfactorily used for the in situ measurement of denitrification in two sediment-water systems incubated for not more than 22 h. In the presence of added nitrate, denitrification acted as a source of nitrous oxide in a drainage pond, but acted as a sink in its absence. The averaged rates of nitrous oxide accumulation with nitrate enrichment in the absence and presence of acetylene were 0.15 and 0.30 mg of N m−2h−1, respectively. Acetylene reduction at an average rate of 0.07 mmol of C2H4 formed m−2h−1 was simultaneously measured in the absence of added nitrate. In a small eutrophic lake where nitrogen was nonlimiting, the in situ rates of sediment denitrification were 0.09 and 0.11 mg of N m−2h−1 in the presence and absence of macrophytes, respectively, and no acetylene reduction activity was found. |
