New Particle Formation Experiments: Nucleation and Growth

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This project focuses on the formation and growth of new particles in the atmosphere. Laboratory experiments will be conducted to measure changes in the rate of new particle formation and growth with changes in composition, temperature, and relative humidity. The results are expected to lead to improved accuracy in predicting the impacts of new particle formation on climate, health and visibility.Laboratory research includes experiments to: (1) conduct measurements of nucleation rates in the ammonia - H2SO4 system as a function of reagent concentrations and temperature; (2) conduct measurements of the synergistic effect of ammonia on nucleation rates for the amine - H2SO4 system at low H2SO4 concentrations; (3) characterize growth rates using a Photolytic Flow Reactor with growth via H2SO4 and using a second flow reactor with growth agents injected in the vapor phase; (4) measure the nanoparticle size-dependency of the growth capabilities of select organic compounds; (5) estimate absolute growth rates (i.e., uptake efficiency) by incorporating measured gas-phase concentrations into model simulations; and (6) explore the capability of the Photolytic Flow Reactor as a tool for understanding growth via uptake of complex secondary oxidation products such as are produced in photo-oxidation of alpha-pinene.The Principal Investigator (PI) plans to use computational fluid dynamics (CFD) simulations of the flow reactor to bolster the interpretation of the experimental results. The CFD simulations allow for estimates of the free energies of small molecular clusters and extrapolations of the results to conditions in other experiments so that nucleation rates can be compared. The PI intends to compare the results from this project with global atmospheric particle formation measurements from the CERN CLOUD project.The project will help develop undergraduate research capabilities by exposing undergraduates to high-level experimental and computational work that will prepare them for careers in science.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.