Reliable, sensitive, and widely available hydrogen chloride (HCl) measurements are important for understanding oxidation in many regions of the troposphere. We configured a commercial HCl cavity ring-down spectrometer (CRDS) for sampling HCl in the ambient atmosphere and developed validation techniques to characterize the measurement uncertainties. The CRDS makes fast, sensitive, and robust measurements of HCl in a high-finesse optical cavity coupled to a laser centred at 5739 cm⁻¹. The accuracy was determined to reside between 5 %–10 %, calculated from laboratory and ambient air intercomparisons with annular denuders. The precision and limit of detection (3σ) in the 0.5 Hz measurement were below 6 and 18 pptv, respectively, for a 30 s integration interval in zero air. The response time of this method is primarily characterized by fitting decay curves to a double exponential equation and is impacted by inlet adsorption/desorption, with these surface effects increasing with relative humidity and decreasing with decreasing HCl mixing ratios. The minimum 90 % response time was 10 s and the equilibrated response time for the tested inlet was 2–6 min under the most and least optimal conditions, respectively. An intercomparison with the EPA compendium method for quantification of acidic atmospheric gases showed good agreement, yielding a linear relationship statistically equivalent to unity (slope of 0.97 ± 0.15). The CRDS from this study can detect HCl at atmospherically relevant mixing ratios, often performing comparably or better in sensitivity, selectivity, and response time than previously reported HCl detection methods.

中文翻译：

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用于测量对流层气态氯化氢的新型腔衰荡光谱仪的验证

可靠、灵敏且广泛使用的氯化氢 (HCl) 测量对于了解对流层许多区域的氧化作用非常重要。我们配置了商用 HCl 腔衰荡光谱仪 (CRDS) 来对环境大气中的 HCl 进行采样，并开发了验证技术来表征测量不确定性。CRDS 在与中心为 5739 cm ^-1的激光器耦合的高精密光学腔中对 HCl 进行快速、灵敏和稳健的测量。准确度被确定为 5%–10%，根据实验室和环境空气与环形剥脱器的比对计算得出。精密度和检测限 (3 σ) 在 0.5 Hz 测量中分别低于 6 和 18 pptv，在零空气中的 30 秒积分间隔。该方法的响应时间的主要特征是将衰减曲线拟合为双指数方程，并受入口吸附/解吸的影响，这些表面效应随着相对湿度的增加而增加，随着 HCl 混合比的降低而减少。在最佳和最差条件下，最小 90% 响应时间为 10 秒，测试进样口的平衡响应时间分别为 2-6 分钟。与用于量化酸性大气气体的 EPA 纲要方法进行的比对显示出良好的一致性，产生了统计上等同于 1 的线性关系（斜率为 0.97  ± 0.15）。本研究中的 CRDS 可以检测与大气相关的混合比的 HCl，通常在灵敏度、选择性和响应时间方面的性能与之前报道的 HCl 检测方法相当或更好。