Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS/Université Joseph Fourier-Grenoble 1, Grenoble, France.
J Chem Phys. 2012 Jan 28;136(4):044311. doi: 10.1063/1.3666852.
The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)∗) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen.
臭氧分子具有独特而显著的（17）O 过剩（Δ（17）O），可通过氧化作用转移到一些大气分子中。这种同位素信号可用于追踪大气中的氧化反应。然而，这种方法依赖于对氧转移机制的稳健和定量理解，而目前对于气相 NO(2) + O(3) 反应（大气硝酸盐夜间生成的重要步骤）缺乏这种理解。在本研究中，通过一系列实验室实验研究了气相 NO(2) + O(3) → NO(3) + O(2)反应中臭氧向硝酸根自由基（NO(3)）转移Δ（17）O 的情况。通过同位素比质谱法测定了反应中生成的臭氧和氧气的同位素组成（δ(17)O，δ(18)O）。确定了 NO(2) + O(3) 反应的Δ(17)O 转移函数为：Δ(17)O(O(3)∗) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99)。评估了臭氧的分子内氧同位素分布，结果表明过剩的富集主要存在于臭氧的末端氧原子上。本研究的结果将有助于解释大气硝酸盐中测量到的高Δ(17)O 值，从而更好地了解大气活性氮的自然循环。
