Atmospheric Nucleation Potential Model for Complex Mixtures

Jack Johnson, Dominic Casalnuovo, Darren Cheng, COTY JEN, Carnegie Mellon University

     Abstract Number: 96
     Working Group: Aerosol Chemistry

Abstract
Observations over the last decade have demonstrated that the atmosphere contains potentially hundreds of compounds that can react with sulfuric acid to nucleate stable aerosol particles. Consequently, modeling atmospheric nucleation requires detailed knowledge of nucleation reaction kinetics and spatially and temporally resolved measurements of numerous precursor compounds. Achieving these detailed measurements and incorporating their reaction kinetics into an aerosol microphysics model is challenging due to experimental limitations in exploring the entire nucleation reaction compound space and quantifying it in a simple nucleation model. This study presents the Nucleation Potential Model (NPM), a novel nucleation model that dramatically simplifies the diverse reactions between sulfuric acid and any combination of precursor gases. NPM predicted 1-nm nucleation rates are dependent on only two measurable gas concentrations, regardless of whether all precursor gases are known. NPM describes sulfuric acid nucleating with a parameterized base compound at an effective base concentration, [Beff]. [Beff] captures the ability of a compound or mixture to form stable clusters with sulfuric acid and is estimated from measured 1-nm particle concentrations. NPM is applied to experimental measurements of mixtures containing numerous atmospherically relevant compounds that could nucleate sulfuric acid to demonstrate how [Beff] varies for different mixture compositions. In addition, NPM is leveraged to estimate nucleation precursor concentrations from measured concentrations of 1-nm particles. NPM is a valuable tool that will enable more widespread measurements of nucleation precursors and a simple model to predict nucleation rates across diverse environments.