Atmospheric Particle Nucleation and Growth Under Conditions Found in the Free Troposphere

This project is focused on the study of the formation and growth of particles in the upper troposphere. The effort includes an investigation into the interactions between oxidized organic compounds and inorganic acids leading to new-particle formation in regions of the cold upper troposphere, and the low-temperature growth of particles by the condensation of organic vapors. A better understanding of particle formation and growth will help improve the ability to predict the influence of aerosols on climate, a major uncertainty in the understanding of climate change. This research will address the following two questions: (1) Is the condensational growth of particles, especially from 1–10 nm, governed more by low volatility condensible vapors or by semi-volatile vapors (with either equilibrium partitioning or reactive uptake)? (2) What are the interactions among various nucleation pathways at low temperature, where relatively weak interactions still lead to stable molecular clusters? The effort seeks to discover the conditions under which inorganic (acid - base) reactions and clustering between organics and inorganics contribute to nucleation, and whether the growth of small particles is driven mostly by condensation of organic compounds that are intrinsically low volatility, or whether reactive uptake or semi-volatile partitioning also contributes to particle growth. Graduate students and a postdoctoral researcher will participate in this research that will be conducted both at Carnegie Mellon University and as part of the CLOUD consortium at CERN. 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.