Equilibrator-based measurements of dissolved nitrous oxide in the surface ocean using an integrated cavity output laser absorption spectrometer
Equilibrator-based measurements of dissolved nitrous oxide in the surface ocean using an integrated cavity output laser absorption spectrometer
复制标题
DOI：
10.5194/os-10-501-2014
复制
发表时间：
2014-01-01
期刊：
影响因子：
3.2
通讯作者：
Kaiser, J.
中科院分区：
文献类型：
--
作者：
Grefe, I.;Kaiser, J.
溶解的一氧化二氮(N2O)浓度通常用气相色谱(GC)测定。在这里，我们介绍了使用一种新的装置进行的实验室测试和初步的现场测量，该装置包括一台商业上可用的基于激光的N2O、一氧化碳和水蒸气分析仪，该分析仪与玻璃床平衡器相连。这种方法与传统的GC技术相比，劳动强度更低，并且提供了更高的时间和空间分辨率。连续平衡仪或大气空气测量的标准偏差为0.2nmol(-1)(平均超过5分钟)。参考气体测量在1h内的短期重复性为0.2nmoL~(-1)或更好。该分析仪长期稳定性的另一个指标是校准后的海洋空气中N2O摩尔分数的标准偏差，在0.5至0.7nmol(-1)之间。将平衡仪的测量结果与吹扫捕集-气相色谱-质谱仪(GC-MS)对南大洋离散样品中N2O浓度的分析进行了比较，结果表明，GC-MS方法的测量不确定度在2%以内。平衡器对水中浓度变化的响应时间从142到203 S，取决于顶空流速。该系统在大西洋从北向南的横断面上进行了海上测试。虽然副热带环流略有饱和，但赤道地区是大气中一氧化二氮的来源，这证实了先前的发现(Forster等人，2009年)。在高时间和空间分辨率下测量的能力揭示了溶解N2O浓度的亚中尺度变异性。热带和副热带大西洋的平均海-气通量在-1.6-0.11µmolm(-2)d(-1)之间，这证实了副热带大西洋不是进入大气的N2O的重要来源区域，而全球平均通量为0.6-2.4µmolm(-2)d(-1)。该系统可以很容易地进行修改，以便在自愿观测船(VOS)上实现自主操作。今后的工作应包括与其他溶解N2O分析方法进行实验室间比较。
Dissolved nitrous oxide (N2O) concentrations are usually determined by gas chromatography (GC). Here we present laboratory tests and initial field measurements using a novel setup comprising a commercially available laser-based analyser for N2O, carbon monoxide and water vapour coupled to a glass-bed equilibrator. This approach is less labour-intensive and provides higher temporal and spatial resolution than the conventional GC technique. The standard deviation of continuous equilibrator or atmospheric air measurements was 0.2 nmol mol(-1) (averaged over 5 min). The short-term repeatability for reference gas measurements within 1 h of each other was 0.2 nmol mol(-1) or better. Another indicator of the long-term stability of the analyser is the standard deviation of the calibrated N2O mole fraction in marine air, which was between 0.5 and 0.7 nmol mol(-1). The equilibrator measurements were compared with purge-and-trap gas chromatography-mass spectrometry (GC-MS) analyses of N2O concentrations in discrete samples from the Southern Ocean and showed agreement to within the 2% measurement uncertainty of the GC-MS method. The equilibrator response time to concentration changes in water was from 142 to 203 s, depending on the headspace flow rate. The system was tested at sea during a north-to-south transect of the Atlantic Ocean. While the subtropical gyres were slightly undersaturated, the equatorial region was a source of nitrous oxide to the atmosphere, confirming previous findings (Forster et al., 2009). The ability to measure at high temporal and spatial resolution revealed submesoscale variability in dissolved N2O concentrations. Mean sea-to-air fluxes in the tropical and subtropical Atlantic ranged between -1.6 and 0.11 mu mol m(-2) d(-1) and confirm that the subtropical Atlantic is not an important source region for N2O to the atmosphere, compared to global average fluxes of 0.6-2.4 mu mol m(-2) d(-1). The system can be easily modified for autonomous operation on voluntary observing ships (VOS). Future work should include an interlaboratory comparison exercise with other methods of dissolved N2O analyses.