Aromatic Photo-oxidation, A New Source of Atmospheric Acidity.
Aromatic Photo-oxidation, A New Source of Atmospheric Acidity.
复制标题
芳香光氧化，大气酸度的新来源。
DOI：
10.1021/acs.est.0c00526
复制
发表时间：
2020
影响因子：
11.4
通讯作者：
Wang Xinming
中科院分区：
文献类型：
--
作者：
Wang Sainan;Newl;Mike J;Deng Wei;Rickard Andrew R;Hamilton Jacqueline F;Muñoz Amalia;Ródenas Milagros;Vázquez Monica M;Wang Liming;Wang Xinming
甲酸（HCOOH）是地球大气中最重要和最普遍的有机酸之一，对大气酸度有很大贡献，并影响水相中的pH依赖性反应。然而，根据目前的机械理解，即使是最先进的化学模型，与地面和高海拔的环境观测相比，也大大低估了HCOOH的浓度，从而低估了其对大气的影响。在这里，我们揭示了新的化学途径HCOOH形成从O3和OH与烯酮烯醇，这是重要的，迄今未发现的中间体产生的芳烃和呋喃的光氧化反应。我们强调，从烯酮-烯醇氧化的HCOOH的估计产量是高达60%，在污染的城市地区和大于30%，即使在大陆背景。我们的理论计算得到了进一步的支持室实验评估。考虑到芳香族化合物是高度反应性的，并且贡献了约20%的碳。全球非甲烷碳氢化合物排放量的10%和城市地区的20%，这里提出的新氧化途径应该有助于缩小HCOOH和其他小有机酸的预算差距，并且可以在任何具有高芳烃排放的环境中使用，包括城市地区和生物质燃烧羽流。
Formic acid (HCOOH), one of the most important and ubiquitous organic acids in the Earth’s atmosphere, contributes substantially to atmospheric acidity and affects pH-dependent reactions in the aqueous phase. However, based on the current mechanistic understanding, even the most advanced chemical models significantly underestimate the HCOOH concentrations when compared to ambient observations at both ground-level and high altitude, thus underrating its atmospheric impact. Here we reveal new chemical pathways to HCOOH formation from reactions of both O3and OH with ketene-enols, which are important and to date undiscovered intermediates produced in the photo-oxidation of aromatics and furans. We highlight that the estimated yields of HCOOH from ketene-enol oxidation are up to 60% in polluted urban areas and greater than 30% even in the continental background. Our theoretical calculations are further supported by a chamber experiment evaluation. Considering that aromatic compounds are highly reactive and contribute ca. 10% to global nonmethane hydrocarbon emissions and 20% in urban areas, the new oxidation pathways presented here should help to narrow the budget gap of HCOOH and other small organic acids and can be relevant in any environment with high aromatic emissions, including urban areas and biomass burning plumes.