Nault Benjamin A, Garland Charity, Wooldridge Paul J, Brune William H, Campuzano-Jost Pedro, Crounse John D, Day Douglas A, Dibb Jack, Hall Samuel R, Huey L Gregory, Jimenez José L, Liu Xiaoxi, Mao Jingqiu, Mikoviny Tomas, Peischl Jeff, Pollack Ilana B, Ren Xinrong, Ryerson Thomas B, Scheuer Eric, Ullmann Kirk, Wennberg Paul O, Wisthaler Armin, Zhang Li, Cohen Ronald C
Department of Meteorology, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Cooperative Institute for Research in the Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States.
J Phys Chem A. 2016 Mar 10;120(9):1468-78. doi: 10.1021/acs.jpca.5b07824. Epub 2015 Nov 25.
NOx (NOx ≡ NO + NO2) regulates O3 and HOx (HOx ≡ OH + HO2) concentrations in the upper troposphere. In the laboratory, it is difficult to measure rates and branching ratios of the chemical reactions affecting NOx at the low temperatures and pressures characteristic of the upper troposphere, making direct measurements in the atmosphere especially useful. We report quasi-Lagrangian observations of the chemical evolution of an air parcel following a lightning event that results in high NOx concentrations. These quasi-Lagrangian measurements obtained during the Deep Convective Clouds and Chemistry experiment are used to characterize the daytime rates for conversion of NOx to different peroxy nitrates, the sum of alkyl and multifunctional nitrates, and HNO3. We infer the following production rate constants [in (cm(3)/molecule)/s] at 225 K and 230 hPa: 7.2(±5.7) × 10(-12) (CH3O2NO2), 5.1(±3.1) × 10(-13) (HO2NO2), 1.3(±0.8) × 10(-11) (PAN), 7.3(±3.4) × 10(-12) (PPN), and 6.2(±2.9) × 10(-12) (HNO3). The HNO3 and HO2NO2 rates are ∼ 30-50% lower than currently recommended whereas the other rates are consistent with current recommendations to within ±30%. The analysis indicates that HNO3 production from the HO2 and NO reaction (if any) must be accompanied by a slower rate for the reaction of OH with NO2, keeping the total combined rate for the two processes at the rate reported for HNO3 production above.
氮氧化物（氮氧化物≡一氧化氮 + 二氧化氮）调节对流层上层的臭氧和氢氧自由基（氢氧自由基≡羟基 + 过氧化氢自由基）浓度。在实验室中，难以测量在对流层上层特有的低温和低压条件下影响氮氧化物的化学反应速率和分支比，因此在大气中进行直接测量尤为有用。我们报告了一次闪电事件后空气团化学演化的准拉格朗日观测结果，该闪电事件导致了高浓度的氮氧化物。在深对流云和化学实验期间获得的这些准拉格朗日测量结果，用于表征白天氮氧化物转化为不同过氧硝酸盐、烷基硝酸盐和多官能团硝酸盐之和以及硝酸的速率。我们推断出在225 K和230百帕时的以下生成速率常数[单位为（立方厘米/分子）/秒]：7.2（±5.7）×10⁻¹²（过氧乙酰硝酸酯）、5.1（±3.1）×10⁻¹³（过氧硝酸）、1.3（±0.8）×10⁻¹¹（过氧丙酰硝酸酯）、7.3（±3.4）×10⁻¹²（过氧丁酰硝酸酯）和6.2（±2.9）×10⁻¹²（硝酸）。硝酸和过氧硝酸的速率比目前推荐值低约30 - 50%，而其他速率与目前推荐值的偏差在±30%以内。分析表明，羟基与二氧化氮反应生成硝酸（如果有）的过程中，羟基与二氧化氮反应的速率必须较慢，以使这两个过程的总速率保持在上述报道的硝酸生成速率。
