The development of fast-response analysers for the measurement of nitrous oxide (N₂O) has resulted in exciting opportunities for new experimental techniques beyond commonly used static chambers and gas chromatography (GC) analysis. For example, quantum cascade laser (QCL) absorption spectrometers are now being used with eddy covariance (EC) or automated chambers. However, using a field-based QCL EC system to also quantify N₂O concentrations in gas samples taken from static chambers has not yet been explored. Gas samples from static chambers are often analysed by GC, a method that requires labour and time-consuming procedures off-site. Here, we developed a novel field-based injection technique that allowed the use of a single QCL for (1) micrometeorological EC and (2) immediate manual injection of headspace samples taken from static chambers. To test this approach across a range of low to high N₂O concentrations and fluxes, we applied ammonium nitrate (AN) at 0, 300, 600 and 900 kg N ha⁻¹ (AN₀, AN₃₀₀, AN₆₀₀, AN₉₀₀) to plots on a pasture soil. After analysis, calculated N₂O fluxes from QCL (F_{N2O_QCL}) were compared with fluxes determined by a standard method, i.e. laboratory-based GC (F_{N2O_GC}). Subsequently, the comparability of QCL and GC data was tested using orthogonal regression, Bland–Altman and bioequivalence statistics. For AN-treated plots, mean cumulative N₂O emissions across the 7 d campaign were 0.97 (AN₃₀₀), 1.26 (AN₆₀₀) and 2.00 kg N₂O-N ha⁻¹ (AN₉₀₀) for F_{N2O_QCL} and 0.99 (AN₃₀₀), 1.31 (AN₆₀₀) and 2.03 kg N₂O-N ha⁻¹ (AN₉₀₀) for F_{N2O_GC}. These F_{N2O_QCL} and F_{N2O_GC} were highly correlated (r=0.996, n=81) based on orthogonal regression, in agreement following the Bland–Altman approach (i.e. within ±1.96 standard deviation of the mean difference) and shown to be for all intents and purposes the same (i.e. equivalent). The F_{N2O_QCL} and F_{N2O_GC} derived under near-zero flux conditions (AN₀) were weakly correlated (r=0.306, n=27) and not found to agree or to be equivalent. This was likely caused by the calculation of small, but apparent positive and negative, F_N2O when in fact the actual flux was below the detection limit of static chambers. Our study demonstrated (1) that the capability of using one QCL to measure N₂O at different scales, including manual injections, offers great potential to advance field measurements of N₂O (and other greenhouse gases) in the future and (2) that suitable statistics have to be adopted when formally assessing the agreement and difference (not only the correlation) between two methods of measurement.

中文翻译：

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一种新颖的注入技术：使用基于场的量子级联激光器来分析源自静态腔室的气体样品

用于测量一氧化二氮（N ₂ O）的快速响应分析仪的开发为新的实验技术带来了令人兴奋的机遇，超越了常用的静态腔室和气相色谱（GC）分析。例如，现在将量子级联激光（QCL）吸收光谱仪与涡动协方差（EC）或自动室一起使用。但是，使用基于现场的QCL EC系统也可以量化N ₂尚未研究从静态腔室中采集的气体样品中的O浓度。静态腔室中的气体样本通常通过GC分析，这种方法需要在现场进行人工和耗时的过程。在这里，我们开发了一种新颖的基于场的进样技术，该技术允许将单个QCL用于（1）微气象EC和（2）立即手动进样从静态腔室采集的顶空样品。为了在从低到高的N ₂ O浓度和通量范围内测试该方法，我们以0、300、600和900 kg N ha ^-1（AN ₀，AN ₃₀₀，AN ₆₀₀，AN ₉₀₀）施用了硝酸铵（AN））到牧场上的地块。经过分析，计算出N ₂将来自QCL的O通量（F _{N2O_QCL}）与通过标准方法测定的通量进行比较，即基于实验室的GC（F _{N2O_GC}）。随后，使用正交回归，Bland–Altman和生物等效性统计数据测试了QCL和GC数据的可比性。对于经AN处理的地块，整个7 d活动的平均N ₂ O累积排放量分别为F _{N2O_QCL}和0.99（AN ₃₀₀），分别为0.97（AN ₃₀₀），1.26（AN ₆₀₀）和2.00 kg N ₂ O-N ha ^-1（AN ₉₀₀）。），1.31（AN ₆₀₀）F _{N2O_GC}为2.03 kg N ₂ O-N ha ^-1（AN ₉₀₀）。这些F _{N2O_QCL}和F _{N2O_GC}在正交回归的基础上高度相关（r = 0.996，n = 81），符合Bland–Altman方法（即均值的±1.96标准偏差以内），并且表明适用于所有意图和目的相同（即等同）。的˚F _{N2O_QCL}和˚F _{N2O_GC}接近零通量条件（AN下衍生₀）的相关性很弱（r = 0.306，n = 27）并且未发现一致或等效。这可能是由于计算了很小但明显的正负F _N2O而引起的，而实际上实际通量低于静态腔室的检测极限。我们的研究表明（1），使用一个QCL来测量n的能力₂在不同尺度O，包括手动注射剂，对N的预先场测量提供了巨大潜力₂在将来和O（和其他温室气体）（2）在正式评估两种测量方法之间的一致性和差异（不仅是相关性）时，必须采用适当的统计数据。