美国自然基金委推荐测量湿地脱氮速率专用仪器

反硝化速率和脱氮速率科研的强大工具

高精度溶解气体测量仪器

前言：

氮气（N₂）、氧气（O₂）、二氧化碳（CO₂）是湿地、河流、湖泊、海洋等水体中的重要溶解气体，是生态环境变化过程中的重要参数指标。例如，溶解氧是衡量海气扩散过程、水团混合、大洋环流以及海水中生物化学过程的重要指标；水体中CO₂对于研究全球碳循环和全球气候变化具有重要作用；而水体中溶解N₂则对于研究水体反硝化速率、农业氮肥利用率、水体富营养化等相关问题具有至关重要的作用。目前，测量水体海洋中溶解气体的传统方法是先采集水样，然后在实验室内或者船上进行检测，但由于很多参数会随时空的变化而发生改变，从而得不到实时原位的准确数据。水体及沉积物反硝化速率的测定方法主要有乙炔抑制法、N₂通量法、质量平衡法、化学计量法和同位素法，但这些方法大多存在人为扰动大、操作繁琐、误差大的不足，因而无法精确测定淹水环境下的反硝化速率。膜进样质谱仪（MIMS）则能够实时、原位、连续监测水体中的溶解气体（N₂、O₂、CO₂），并且能够精确测定淹水环境下水体、沉积物的反硝化速率，已被国内外众多研究机构广泛应用，并被美国自然科学基金委推荐用来测定湿地脱氮速率。同时，膜进样质谱仪还能够应用于稳定同位素（¹⁵N 、¹⁸O、¹³C）的检测、光合呼吸、生物反应器等方面的研究。

主要特点：

• 可实时、原位检测
• 测量精度高、重复性好
• 所需样品量少，仅5ml
• 操作简便，样品分析快，仅90s
• 不需要顶空平衡，可实现水气分离
• 可将空气中高浓度背景气体分离开，避免了样品的污染
• 专用软件（QuickData）高效评估收集的信号和数据

图1 QuickData软件

主要应用：

• 环境（水体、沉积物）反硝化速率的研究
• 原位测量水体（海洋\湖泊\河流\地表水\地下水）中O₂、CH₄、DMS、CO₂和Ar浓度
• 海洋总初级生产力的测定
• 贫瘠水域的呼吸作用研究
• 稳定同位素的测定（¹⁵N 、¹⁸O、¹³C）

图2   MIMS在反硝化中的应用，将原状沉积物和上覆水取回在室内进行培养，研究反硝化过程中N2的排放速率

图3   利用已知CH₄浓度和测量出来的信号值进行拟合曲线，进而测量未知水体中CH₄浓度

图4   MIMS可用于水生生态系统代谢和氧气动力学研究

图5   MIMS可与液相氧电极或叶绿素荧光仪联用测量光合和呼吸作用

MIMS典型应用：

表1   标样连续测定10h后信号偏移情况（李晓波等，2013）

表2   MIMS与IRMS在测量海洋总初级生产力时的数据比较

图7   利用MIMS测量出11种中国典型稻田土壤下的反硝化、厌氧氨氧化、DNRA的贡献率（Shan J et. al, 2016）

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