AGS-PRF: Understanding the Early Growth of Atmospheric Nanoparticles

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Dr. Lea Hildebrandt was awarded an Atmospheric and Geospace Sciences Postdoctoral Research Fellowship to conduct a research project at the National Center for Atmospheric Research in Boulder, Colorado and with colleagues at Portland State University and the University of Minnesota. Her project combines theoretical, laboratory and field measurements using newly developed instruments to explain chemical and physical processes affecting the growth rates of nanoparticles in the atmosphere. A main objective of the work is to understand the processes by which organic salts formed by reactions of organic acids (e.g., formic or acetic acid) and bases (e.g., methylamine, dimethylamine or trimethylamine) are taken up onto preexisting particles of known size. Seed particles 20-50 nanometers in size will be generated from sulfuric acid and ammonium salts, as well as from the nucleation of organic compounds. The effects of temperature, relative humidity, pH and organics will be varied to assess mechanisms of particle growth and the contribution of the amines and organic acids to this growth. Outdoor measurements will be taken in Boulder and at a rural site to learn about particle formation and growth under different conditions. The data will be used to develop and constrain models for nanoparticle growth rates.Nanoparticles range in size from about 1 to 10 nanometers. These atmospheric particles affect Earth's climate directly by scattering or absorbing solar radiation and indirectly by acting as seeds for water condensation and thereby influencing the formation and properties of clouds. Nanoparticles also affect human health by, for example, damaging respiratory and cardiovascular systems. The fundamental processes underlying new particle formation are not yet understood and consequently particle concentrations cannot be predicted reliably. The planned work will provide insights into the chemical and physical processes of atmospheric particle formation. Improved understanding of atmospheric particles will enable better prediction of cloud formation and development of better-informed policy actions concerning health effects.This project will also have education and training benefits because it supports the career development of a young scientist through mentorship, an opportunity to learn new techniques and skills, and development of a broader collegial network.