Unknown 'extra' atmospheric oxidizing agent

Ozone, the hydroxyl radical and nitrate are thought to be the main agents that act to remove trace gases, including pollutants, from the atmosphere. In this paper, the authors combine atmospheric observations from a forested region of Finland, laboratory experiments and theoretical considerations to identify another, previously unknown compound with significant capacity to oxidize sulphur dioxide and perhaps other trace gases. The compound seems to be a stabilized Criegee intermediate — a carbonyl oxide with two free-radical sites — or its derivative and could potentially enhance the reactivity of the atmosphere, contributing to the production of sulphuric acid and, consequently, atmospheric-aerosol formation. The chemistry investigated here is tightly connected with the presence of biogenic volatile organic compounds, and thereby with forest emissions.