The acetylene block technique was employed to study denitrification in intertidal estuarine sediments. Addition of nitrate to sediment slurries stimulated denitrification. During the dry season, sediment-slurry denitrification rates displayed Michaelis-Menten kinetics, and ambient NO3− + NO2− concentrations (≤26 μM) were below the apparent Km (50 μM) for nitrate. During the rainy season, when ambient NO3− + NO2− concentrations were higher (37 to 89 μM), an accurate estimate of the Km could not be obtained. Endogenous denitrification activity was confined to the upper 3 cm of the sediment column. However, the addition of nitrate to deeper sediments demonstrated immediate N2O production, and potential activity existed at all depths sampled (the deepest was 15 cm). Loss of N2O in the presence of C2H2 was sometimes observed during these short-term sediment incubations. Experiments with sediment slurries and washed cell suspensions of a marine pseudomonad confirmed that this N2O loss was caused by incomplete blockage of N2O reductase by C2H2 at low nitrate concentrations. Areal estimates of denitrification (in the absence of added nitrate) ranged from 0.8 to 1.2 μmol of N2 m−2 h−1 (for undisturbed sediments) to 17 to 280 μmol of N2 m−2 h−1 (for shaken sediment slurries).
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机译：乙炔嵌段技术用于研究潮间带河口沉积物的反硝化作用。在沉淀泥浆中添加硝酸盐可促进反硝化作用。在干旱季节，沉积物-泥浆的反硝化速率表现出Michaelis-Menten动力学，并且环境NO3 - + NO2 -浓度（≤26μM）低于表观Km（50） （μM）硝酸盐。在雨季，当周围的NO3 - + NO2 -浓度较高（37至89μM）时，无法获得Km的准确估算值。内源性反硝化作用仅限于沉积物柱的上方3 cm。但是，向更深的沉积物中添加硝酸盐表明可以立即产生N2O，并且在所有采样深度（最深为15厘米）都存在潜在的活性。在这些短期沉积物孵育过程中，有时会观察到存在C2H2时N2O的流失。对海洋假单胞菌的沉积物浆料和洗涤过的细胞悬浮液进行的实验证实，这种N2O损失是由于低硝酸盐浓度下C2H2对N2O还原酶的不完全阻滞引起的。根据反硝化作用的区域估算（在不添加硝酸盐的情况下），N2的m2（sup> −2 h −1 ）为0.8至1.2μmol（未扰动沉积物）为17至280μmol N2 m −2 h −1 的值（用于摇动的泥浆）。
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