Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland.
Rapid Commun Mass Spectrom. 2011 Jun 15;25(11):1497-502. doi: 10.1002/rcm.4917.
Mid-summer N(2) profiles were analyzed from nine oxygen-stratified, humic-acid-rich lakes using a continuous flow isotope ratio mass spectrometer and a Gasbench II device. Sample preparation steps were performed under water to avoid air contamination. The instrument precision for the δ(15)N measurement was high (0.03‰), but for the whole sampling and analysis procedure the mean deviation between replicate samples was 0.13‰ for the δ(15)N measurements and 5.5% for the N(2) gas concentration analysis. The results show that the Gasbench peripheral was suitable for measurement of the (15)N natural abundance of dissolved nitrogen gas, with denitrification indicated by the oversaturation and slightly (<1‰) depleted δ(15)N values of the dissolved N(2) gas in the suboxic zones of some of the study lakes. Calculated values for the denitrified (excess) N(2) varied between -5.3 and 0.7‰. The denitrification potential was determined using the (15)N tracer method, with results showing nitrate-inducible denitrification and no signs of anaerobic ammonium oxidation (anammox).
采用连续流动同位素比质谱仪和 Gasbench II 设备，对 9 个富腐殖酸、分层的湖泊的夏季中期 N(2) 剖面进行了分析。为避免空气污染，样品制备步骤在水下进行。δ(15)N 测量的仪器精度较高（0.03‰），但在整个采样和分析过程中，重复样品之间的平均偏差为δ(15)N 测量值为 0.13‰，N(2)气体浓度分析值为 5.5%。结果表明，Gasbench 外围设备适用于测量溶解氮气的（15）N 自然丰度，一些研究湖泊的亚缺氧区中，由于反硝化作用，溶解 N(2)气体的过饱和和略微（<1‰）贫化δ(15)N 值表明存在反硝化作用。计算得出的反硝化（过剩）N(2)值在-5.3 到 0.7‰之间变化。利用（15）N 示踪法测定了反硝化潜力，结果表明存在硝酸盐诱导的反硝化作用，没有厌氧氨氧化（anammox）的迹象。
