Constraining the Role of Gas-Phase Organic Oxidation in New-Particle Formation

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Atmospheric new-particle formation, cluster growth leading to secondary aerosol (SOA) formation, involves facile oxidation of organic compounds and is being revealed as a complex and challenging topic in atmospheric chemistry. Aerosol-climate interactions are a key source of uncertainty in climate forcing [IPCC], affecting both planetary radiation balances, and climate through direct and indirect changes in cloud formation and their properties. Uncertainty in aerosol radiative forcing terms limits our ability to project climate sensitivity (the global average temperature change caused by a given forcing) from currently observed climate change.Because of the range of chemical mechanisms occurring in natural atmospheres, chemists may choose to study the oxidation and condensation steps in the controllable environment of a chamber, typically interfaced to a desired set of analytical instruments to enable the progress of particle formation, condensation and growth to be optimally studied. Work under this project is directed towards improving understanding of particle formation steps involving interactions of low volatility hydrocarbons (e.g. terpene - ozone adducts) with sulfuric acid clusters. Graduate students will carry out a series of measurements, along with photochemical modelling, in chambers both at Pittsburgh (CMU), and the European CLOUD (Cosmics Leaving OUtdoor Droplets) atmospheric facility at CERN.