Impacts of Relative Humidity on Organic New Particle Formation in the Atmosphere

This project focuses on an investigation of the effects of relative humidity on organic new particle formation in the atmosphere. The hypothesis is that water modifies and/or accelerates chemical processes that increase the instantaneous concentrations of oxidized, low volatility products and rapidly favors the formation of new particles. An integrated chemical/physical description of enhancements in particle formation due to relative humidity will be developed through environmental chamber research to help bridge the gap between modeled and measured organic aerosols in the atmosphere. The goals of this effort are to: (1) explore the relative humidity sensitivity of new particle formation for representative atmospheric organic aerosol precursors at atmospherically relevant mixing ratios of volatile organic compounds, humidities and organic seed aerosol loadings; and (2) use n-butanol, cyclohexane and hydrogen peroxide as hydroxyl radical scrubbers to identify the roles of different oxidative pathways in relative humidity sensitivity of organic particle formation. Systematic laboratory studies will be undertaken to measure organic particle formation (rates, yields, geometric mean diameters), as well as chemical profiles of freshly nucleated organic nanoparticles. This project will provide research experience and mentorship to graduate, undergraduate and high school students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.