Comparison of two photolytic calibration methods for nitrous acid
Comparison of two photolytic calibration methods for nitrous acid
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DOI：
10.5194/amt-15-5455-2022
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发表时间：
2022-09
影响因子：
3.8
通讯作者：
Andrew J. Lindsay;E. Wood
中科院分区：
文献类型：
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作者：
Andrew J. Lindsay;E. Wood
抽象的。亚硝酸 (HONO) 在对流层氧化化学中发挥着重要作用，因为它是羟基自由基 (OH) 的前体。由于仪器干扰以及采样和校准困难，HONO 的测量历史上一直很困难。传统的校准方法包括通过氯化氢蒸气与亚硝酸钠反应生成 HONO，然后通过各种方法进行定量（例如，将 HONO 转化为一氧化氮 (NO)，然后进行化学发光检测）。或者，通过使NO与H2O光解产生的OH自由基反应，可以在气相中光解产生HONO。在这项工作中，我们描述并比较了两种用于校准碘化物加合物化学电离质谱仪 (CIMS) 的光解 HONO 校准方法。这两种方法均基于常用于 OH 和 HO2（统称为 HOx）校准的水蒸气光解方法。第一种方法是对常见化学光度测定法 HOx 校准方法的改进，其中 HONO 是根据 [O3]、[H2O] 和 [O2] 的量化值以及 H2O 和 O2 在 184.9 nm 处的吸收截面计算的。第二种新方法 HONO 主要在 N2 ([O2]=0.040 %) 中制备，并通过测量 NO 与 H2O 光解产生的 HO2 反应形成的 NO2 进行简单定量。两种校准方法均用于制备 ~400 至 8000 pptv 之间的各种 HONO 混合比。化学光量校准的不确定度为 27% (2σ)，与 HONO 浓度无关。 NO2 替代校准的不确定性与浓度相关，受到 NO2 测量不确定性的限制。这里提出的 NO2 代理校准不确定度 (2σ) 范围为 4.5% 到 24.4%（分别在 [HONO] =8000 pptv 和 [HONO] =630 pptv 时），与~1600 pptv 的混合比相关的不确定度为 10%，这是夜间在城市地区观察到的典型值。我们还描述了 NO2 代理方法在不确定性低于 15% (2σ) 的情况下校准 HOx 仪器（例如 LIF、CIMS）的潜在应用。
Abstract. Nitrous acid (HONO) plays an important role in tropospheric oxidation chemistry as it is a precursor to the hydroxyl radical (OH). Measurements of HONO have been difficult historically due to instrument interferences and difficulties in sampling and calibration. The traditional calibration method involves generation of HONO by reacting hydrogen chloride vapor with sodium nitrite followed by quantification by various methods (e.g., conversion of HONO to nitric oxide (NO) followed by chemiluminescence detection). Alternatively, HONO can be generated photolytically in the gas phase by reacting NO with OH radicals generated by H2O photolysis. In this work, we describe and compare two photolytic HONO calibration methods that were used to calibrate an iodide adduct chemical ionization mass spectrometer (CIMS). Both methods are based on the water vapor photolysis method commonly used for OH and HO2 (known collectively as HOx) calibrations. The first method is an adaptation of the common chemical actinometry HOx calibration method, in which HONO is calculated based on quantified values for [O3], [H2O], and [O2] and the absorption cross sections for H2O and O2 at 184.9 nm. In the second, novel method HONO is prepared in mostly N2 ([O2]=0.040 %) and is simply quantified by measuring the NO2 formed by the reaction of NO with HO2 generated by H2O photolysis. Both calibration methods were used to prepare a wide range of HONO mixing ratios between ∼400 and 8000 pptv. The uncertainty of the chemical actinometric calibration is 27 % (2σ) and independent of HONO concentration. The uncertainty of the NO2 proxy calibration is concentration-dependent, limited by the uncertainty of the NO2 measurements. The NO2 proxy calibration uncertainties (2σ) presented here range from 4.5 % to 24.4 % (at [HONO] =8000 pptv and [HONO] =630 pptv, respectively) with a 10 % uncertainty associated with a mixing ratio of ∼1600 pptv, typical of values observed in urban areas at night. We also describe the potential application of the NO2 proxy method to calibrating HOx instruments (e.g., LIF, CIMS) at uncertainties below 15 % (2σ).