University of Helsinki, Department of Physics, FI-00014 Helsinki, Finland.
Nature. 2012 Aug 9;488(7410):193-6. doi: 10.1038/nature11278.
Atmospheric oxidation is a key phenomenon that connects atmospheric chemistry with globally challenging environmental issues, such as climate change, stratospheric ozone loss, acidification of soils and water, and health effects of air quality. Ozone, the hydroxyl radical and the nitrate radical are generally considered to be the dominant oxidants that initiate the removal of trace gases, including pollutants, from the atmosphere. Here we present atmospheric observations from a boreal forest region in Finland, supported by laboratory experiments and theoretical considerations, that allow us to identify another compound, probably a stabilized Criegee intermediate (a carbonyl oxide with two free-radical sites) or its derivative, which has a significant capacity to oxidize sulphur dioxide and potentially other trace gases. This compound probably enhances the reactivity of the atmosphere, particularly with regard to the production of sulphuric acid, and consequently atmospheric aerosol formation. Our findings suggest that this new atmospherically relevant oxidation route is important relative to oxidation by the hydroxyl radical, at least at moderate concentrations of that radical. We also find that the oxidation chemistry of this compound seems to be tightly linked to the presence of alkenes of biogenic origin.
大气氧化是一种关键现象，它将大气化学与全球性的环境挑战问题（如气候变化、平流层臭氧损耗、土壤和水酸化以及空气质量对健康的影响）联系起来。臭氧、羟基自由基和硝酸根自由基通常被认为是引发痕量气体（包括污染物）从大气中去除的主要氧化剂。在这里，我们展示了来自芬兰一个北方森林地区的大气观测结果，这些结果得到了实验室实验和理论考虑的支持，使我们能够识别出另一种化合物，可能是一种稳定的 Criegee 中间体（具有两个自由基位点的羰基氧化物）或其衍生物，它具有显著的氧化二氧化硫和潜在其他痕量气体的能力。这种化合物可能会增强大气的反应性，特别是对于硫酸的生成，从而影响大气气溶胶的形成。我们的研究结果表明，与羟基自由基的氧化相比，这种新的与大气相关的氧化途径至少在中等浓度的羟基自由基条件下更为重要。我们还发现，这种化合物的氧化化学似乎与生物源烯烃的存在紧密相关。
