Applying cavity ring-down spectroscopy for the measurement of dissolved nitrous oxide concentrations and bulk nitrogen isotopic composition in aquatic systems: Correcting for interferences and field application
Applying cavity ring-down spectroscopy for the measurement of dissolved nitrous oxide concentrations and bulk nitrogen isotopic composition in aquatic systems: Correcting for interferences and field application
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DOI：
10.1002/lom3.10032
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发表时间：
2015-08-01
影响因子：
2.7
通讯作者：
Eyre, B. D.
中科院分区：
文献类型：
--
作者：
Erler, D. V.;Duncan, T. M.;Eyre, B. D.
激光光谱是一种新兴的测量环境中一氧化二氮（N2 O）动态的技术，但大多数研究都集中在大气应用上。我们将市售的光腔衰荡光谱仪（CRDS）（Picarro G5101-I同位素N2 O分析仪）耦合到空气/水气体平衡装置以收集连续的原位溶解N2 O摩尔浓度和本体氮同位素（Δ N-15-N2 O）数据。由CRDS单元测量的Δ N-15-N2 O值被发现受到O-2、CO、CH 4和CO2混合比变化的显著影响。N_2O混合比对Δ N-15-N_2O也有影响。建立了一系列方程，以校正O-2的基体效应和CH 4的光谱干扰。化学捕集器有效地防止了CO和CO2的干扰。N2 O混合比和O-2基质效应所需的最大校正分别为1%（混合比为1.2 ppmv）和11%（O-2含量为0%）。CH 4校正仅在混合比大于500 ppmv（>0.5%）时才变得重要。来自CRDS同位素N2 O分析仪的N2 O摩尔浓度和Δ N-15-N2 O的测量与同位素比质谱法测量的那些相似。我们展示了实用的激光为基础的系统与现场部署在亚热带澳大利亚的三个河口潮沟。未来的工作应集中在应用激光为基础的系统来测量N2 O同位素在水生生境，允许进一步限制N2 O在水生系统中的循环途径。
Laser spectroscopy is an emerging technology for measuring nitrous oxide (N2O) dynamics in the environment, but most studies have focused on atmospheric applications. We have coupled a commercially available cavity ring-down spectroscope (CRDS) (Picarro G5101-I isotopic N2O analyzer) to an air/water gas equilibration device to collect continuous in situ dissolved N2O molar concentration and bulk nitrogen isotopic (delta N-15-N2O) data. The delta N-15-N2O values measured by the CRDS unit were found to be significantly affected by changes in the mixing ratios of O-2, CO, CH4, and CO2. There was also an effect of N2O mixing ratio on delta N-15-N2O. A series of equations was developed to correct for the matrix effect of O-2 and the spectral interference by CH4. Chemical traps effectively prevented interferences by CO and CO2. The maximum corrections required for N2O mixing ratio and O-2 matrix effects, were 1% (at a mixing ratio of 1.2 ppmv), and 11% (at 0% O-2 content), respectively. The CH4 correction only became important at mixing ratios greater than 500 ppmv (>0.5%). Measurements of N2O molar concentration and delta N-15-N2O from the CRDS isotopic N2O analyzer were similar to those measured with isotope ratio mass spectrometry. We demonstrated the utility of the laser-based system with field deployments in three estuarine tidal creeks in subtropical Australia. Future work in this field should focus on the application of the laser-based system to the measurement of N2O isotopologues in aquatic habitats, allowing for further constraints to be placed on the pathways of N2O cycling in aquatic system.