Autoxidation of Anthropogenic Volatile Organic Compounds (AVOC) as a Source of Urban Air Pollution

Previous efforts to raise living standards have been based on relentlessly increasing combustion, causing environmental destruction at all scales.

In addition to climate-warming CO2, fossil fuel combustion also produces a large number of organic compounds and particulate matter, which deteriorate air quality.The atmosphere is cleansed from such pollutants by gas-phase oxidation reactions, which are invariably mediated by peroxy radicals (RO2).

Oxidation transforms initially volatile and water-insoluble hydrocarbons into water-soluble forms (ultimately CO2), enabling scavenging by liquid droplets.

A minor but crucially important alternative oxidation pathway leads to oxidative molecular growth, and formation of atmospheric aerosols.

Aerosols impart a huge influence on the atmosphere, from local air quality issues to global climate forcing, yet their formation mechanisms and structures of organic aerosol precursors remains elusive.In a paradigm change, RO2 was recently found to undergo autoxidation, enabling rapid aerosol precursor formation even at sub-second time-scales – in stark contrast to the long processing times (days - weeks) previously assumed to be necessary.

We have shown how abundant biogenic hydrocarbons (BVOC) autoxidize, but due to key structural differences, the same pathways are not available for anthropogenic hydrocarbons (AVOC), and thus they were not expected to autoxidize. My preliminary experiments reveal that AVOCs do autoxidize, but the mechanism enabling this remain unknown.

Crucially, the co-reactants shown to inhibit BVOC seem to enforce AVOC autoxidation – potentially explaining the recent mysterious discovery of new-particle formation in polluted megacities.

In ADAPT, I will use a combination of novel mass spectrometric detection methods fortified by theoretical calculations, to solve the mechanism of AVOC autoxidation. This will directly assist both air quality management, and the design of cleaner fuels and engines.