Particulate matter in Earth's atmosphere impacts society in many ways. It is a pollutant known to be the main cause a variety of detrimental health effects, causing millions of premature deaths each year. In addition, airborne aerosol particles strongly impact the radiation balance of our planet: they can scatter sun light back into space or impact cloud properties and lifetimes. A large source of uncertainty in the anthropogenic influence on climate comes from the lack of understanding of aerosol particle formation, evolution and fate in the atmosphere.
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.
