Particle Growth Mechanisms During Ambient New Particle Formation

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New particle formation (NPF) in the atmosphere has been observed all over the globe, from remote boreal forests in Finland to polluted megacities such as Mexico City. Although it is pervasive, NPF is not that well understood owing in large part to its chemical complexity, which encompasses everything from gas phase species, to molecular clusters, to "bulk" nanoparticulate matter. This project will employ a unique Nano Aerosol Mass Spectrometer (NAMS) to measure the elemental composition of individual size-selected particles (10-30 nm size range) during two multi-investigator field campaigns, one in Pittsburgh, Pennsylvania in 2012 and another at the Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains site in northern Oklahoma in 2013. The results will allow particle growth by sulfate vs. organics and other inorganic species during NPF to be quantified. Measured growth rates will be compared to predicted growth rates based on gas phase concentrations and used to assist development of models for particle growth. The NAMS will also provide key information to help determine how much cationic nitrogen exists in nanoparticles beyond that needed to neutralize inorganic acids. The results will give a more quantitative measure of the impact of amines on particle growth. In addition, the NAMS will quantify how changes in ambient particle composition correlate with changes in hygroscopicity/volatility. The results will provide an independent assessment of how well indirect measurements of chemical composition based on laboratory studies of hygroscopicity/volatility give an indication of the true ambient composition.Scientific impacts will derive from better understanding of NPF and their linakge to cloud condensation nucleus (CCN) concentrations which, in turn, have important impacts on precipitation patterns and Earth's energy balance. Educational broader impacts will include promotion of teaching and learning through the support of two graduate students. Outreach efforts will include engaging the broader community via an annual "Coast Day" event during which the principal investigator will present some aspects of the work.