Production and use of many synthetic halogenated trace gases are regulated internationally due to their contribution to stratospheric ozone depletion or climate change. In many applications they have been replaced by shorter-lived compounds, which have become measurable in the atmosphere as emissions increased. Non-target monitoring of trace gases rather than targeted measurements of well-known substances is needed to keep up with such changes in the atmospheric composition. We regularly deploy gas chromatography (GC) coupled to time-of-flight mass spectrometry (TOF-MS) for analysis of flask air samples and in situ measurements at the Taunus Observatory, a site in central Germany. TOF-MS acquires data over a continuous mass range that enables a retrospective analysis of the dataset, which can be considered a type of digital air archive. This archive can be used if new substances come into use and their mass spectrometric fingerprint is identified. However, quantifying new replacement halocarbons can be challenging, as mole fractions are generally low, requiring high measurement precision and low detection limits. In addition, calibration can be demanding, as calibration gases may not contain sufficiently high amounts of newly measured substances or the amounts in the calibration gas may have not been quantified. This paper presents an indirect data evaluation approach for TOF-MS data, where the calibration is linked to another compound which could be quantified in the calibration gas. We also present an approach to evaluate the quality of the indirect calibration method, select periods of stable instrument performance and determine well suited reference compounds. The method is applied to three short-lived synthetic halocarbons: HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E). They represent replacements for longer-lived hydrofluorocarbons (HFCs) and exhibit increasing mole fractions in the atmosphere.The indirectly calibrated results are compared to directly calibrated measurements using data from TOF-MS canister sample analysis and TOF-MS in situ measurements, which are available for some periods of our dataset. The application of the indirect calibration method on several test cases can result in uncertainties of around 6 % to 11 %. For hydro(chloro-)fluoroolefines (denoted H(C)FOs), uncertainties up to 23 % are achieved. The indirectly calculated mole fractions of the investigated H(C)FOs at Taunus Observatory range between measured mole fractions at urban Dübendorf and Jungfraujoch stations in Switzerland.

中文翻译：

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适用于陶努斯天文台第四代合成卤烃时间序列的痕量气体非目标量化的间接校准方法（德国）

许多合成卤化痕量气体的生产和使用因其对平流层臭氧消耗或气候变化的贡献而受到国际监管。在许多应用中，它们已被寿命较短的化合物所取代，随着排放量的增加，这些化合物在大气中变得可测量。需要对痕量气体进行非目标监测，而不是对众所周知的物质进行有针对性的测量，以跟上大气成分的这种变化。我们定期将气相色谱 (GC) 与飞行时间质谱 (TOF-MS) 结合使用，用于分析烧瓶空气样品并在位于德国中部的陶努斯天文台进行原位测量。TOF-MS 采集连续质量范围内的数据，可以对数据集进行回顾性分析，这可以被视为一种数字空气档案。如果新物质投入使用并且其质谱指纹被识别，则可以使用该档案。然而，量化新的替代卤代烃可能具有挑战性，因为摩尔分数通常很低，需要高测量精度和低检测限。此外，校准可能很苛刻，因为校准气体可能未包含足够多的新测量物质，或者校准气体中的含量可能尚未量化。本文介绍了一种 TOF-MS 数据的间接数据评估方法，其中校准与可以在校准气体中量化的另一种化合物相关联。我们还提供了一种方法来评估间接校准方法的质量、选择仪器性能稳定的时期并确定非常合适的参考化合物。该方法适用于三种短寿命合成卤代烃：HFO-1234yf、HFO-1234ze(E) 和 HCFO-1233zd(E)。它们代表了寿命更长的氢氟烃 (HFC) 的替代品，并且在大气中的摩尔分数不断增加。 间接校准的结果与使用来自 TOF-MS 罐样品分析和 TOF-MS 原位测量数据的直接校准测量进行比较，这些数据是可用的对于我们数据集的某些时期。在几个测试案例中应用间接校准方法可能会导致大约 6% 到 11% 的不确定性。对于氢（氯-）氟烯烃（表示为 H(C)FO），其不确定度高达 23%。