Periodic Reporting for period 4 - COALA (Comprehensive molecular characterization of secondary organic aerosol formation in the atmosphere)
Reporting period: 2019-09-01 to 2020-02-29
The target of the COALA project was a comprehensive understanding of the role of organic emissions on aerosol formation using novel mass spectrometric techniques. In the atmosphere, volatile emissions are oxidized to produce vapors of various volatilities. The least volatile will condense and form aerosol, but the fraction of products able to do this (for a given molecule) has been hard to determine, in part due to a lack of methods for quantification of these molecules. The main objectives in COALA were to experimentally detect as large fraction as possible of the oxidation products from the most commonly emitted precursors in the atmosphere, and to utilize this data to map out a volatility distribution of the formed vapors. With such information, it is possible to evaluate how much of the organic aerosol is formed directly through condensation and whether additional chemistry occurring on the surface or inside the particles will influence the amount of organics. Constraints on the chemical and physical processes leading to organic aerosol formation will directly translate into better constraints on atmospheric models studying the influence of human activity on climate change.
The primary findings of the COALA project highlight the role of efficient and rapid uptake of the most highly oxygenated molecules (HOM) formed in the oxidation of volatile organic compound (VOC). We found that all major VOC types in the atmosphere, both of biogenic (e.g. monoterpenes) and anthropogenic (e.g. aromatics and alkanes) origin produced HOM at higher yields than had earlier been believed. This has major implications for the dynamics, aging and losses of aerosol particles in the atmosphere.
a. the simultaneous deployment of several different types of chemical ionization mass spectrometers, and
b. advanced statistical analysis techniques, together with
c. close collaboration with leading quantum chemists,
we have achieved new understanding on a variety of topics relating to VOC oxidation and SOA formation. These concern
1. the role of temperature on the level of oxygenation achieved during oxidation,
2. direct measurements of the condensability of oxidation products,
3. the role of aerosol particle acidity on reactive uptake of more volatile species,
4. the importance of oxidant concentrations on the potential to form organic aerosol from anthropogenic emissions, and
5. the role of nitrogen oxides on the formation and evolution of organic aerosol.