Atomspheric oxidation mechanism of fluorene initiated by the OH radicals

IF 3.7 2区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES

Atmospheric Environment Pub Date : 2025-09-09 DOI:10.1016/j.atmosenv.2025.121534

Lingyu Wang , Yahong Chen , Liming Wang

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Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a large class of pollutants widely present in the environment and are the earliest discovered and studied carcinogens.The oxidation of PAHs can generate oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs), which are key precursors for the formation of SOA. However, the formation mechanism of OPAHs and NPAHs are unclear. Fluorene (FLN) is one of the most abundant PAHs discovered, and several studies have been conducted on the reaction of FLN. In this article, we investigated the oxidation mechanism of FLN initiated by OH radicals through high level quantum chemistry and chemical kinetics calculations. The oxidation starts by forming adducts FLN-n-OH (FLNn in short, n = 1, 2, 3, 4, 10, 11) which then react with O₂ and NO₂ in the atmosphere. When the overall reaction rate coefficient of FLNn with O₂ are slow, FLNn mainly react with NO₂ to form n-nitrofluorene in the atmosphere. Effective reaction rates of FLN1 with O₂ in the atmosphere are fast at of ∼1.90 × 10⁴ s⁻¹, suggesting the negligible reaction between FLN1 adduct and NO₂. Therefore, the main fate of FLN1 is reaction with O₂ followed by subsequent unimolecular isomerization routes, forming OPAHs only. The rate coefficient for reaction of FLN2, FLN4 and FLN10 with O₂ are obtained at of 7.44, 26.4 and 1.07 s⁻¹, respectively, suggesting the likely formation of 2-nitrofluorene 4-nitrofluorene and 10-nitrofluorene. In addition, the hydrogen atom abstraction from FLN and the generation of alkoxy groups from FLNn-i-OO resulted in formation of unsaturated compounds, which subsequently reacted with O₂ to form a large number of unsaturated oxygen-containing compounds and further transform to highly oxidized products.

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氢氧自由基引发芴在大气中的氧化机理

多环芳烃（PAHs）是广泛存在于环境中的一类污染物，是最早发现和研究的致癌物。多环芳烃的氧化可以生成氧化多环芳烃（OPAHs）和硝化多环芳烃（NPAHs），它们是形成SOA的关键前体。然而，OPAHs和NPAHs的形成机制尚不清楚。芴（FLN）是已发现的最丰富的多环芳烃之一，人们对FLN的反应进行了一些研究。本文通过高水平量子化学和化学动力学计算，研究了OH自由基引发FLN氧化的机理。氧化首先形成FLN-n-OH（简称FLNn， n = 1,2,3,4,10,11）加合物，然后与大气中的O2和NO2反应。当FLNn与O2的总反应速率系数较慢时，FLNn在大气中主要与NO2反应生成n-硝基芴。FLN1在大气中与O2的有效反应速率为~ 1.90 × 104 s−1，表明FLN1加合物与NO2的反应可以忽略不计。因此，FLN1的主要命运是与O2反应，然后是随后的单分子异构化途径，仅形成opah。FLN2、FLN4和FLN10与O2反应的速率系数分别为7.44、26.4和1.07 s−1，表明可能生成2-硝基芴、4-硝基芴和10-硝基芴。此外，FLN中的氢原子被抽离，FLNn-i-OO生成烷氧基，形成不饱和化合物，这些不饱和化合物随后与O2反应生成大量不饱和含氧化合物，并进一步转化为高氧化产物。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Atmospheric Environment 环境科学-环境科学

CiteScore

9.40

自引率

8.00%

发文量

458

审稿时长

53 days

期刊介绍： Atmospheric Environment has an open access mirror journal Atmospheric Environment: X, sharing the same aims and scope, editorial team, submission system and rigorous peer review. Atmospheric Environment is the international journal for scientists in different disciplines related to atmospheric composition and its impacts. The journal publishes scientific articles with atmospheric relevance of emissions and depositions of gaseous and particulate compounds, chemical processes and physical effects in the atmosphere, as well as impacts of the changing atmospheric composition on human health, air quality, climate change, and ecosystems.