AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Multiple New-Particle-Growth Pathways at the DOE Southern Great Plains Field Site in Oklahoma
ANNA HODSHIRE, Jeffrey R. Pierce, James N. Smith, Peter H. McMurry, Jun Zhao, Michael J. Lawler, John Ortega, David Hanson, Kelley C. Barsanti, Colorado State University
Abstract Number: 9934 Working Group: Aerosol Chemistry
Abstract New-particle formation (NPF) is a significant source of aerosol particle number in the atmosphere. However, these particles are initially too small to have climatic importance and must grow, primarily through net uptake of low-volatility species, from diameters 1 nm to 30-100 nm in order to impact climate. There are currently uncertainties in the physical and chemical processes associated with the growth of these particles that lead to uncertainties in aerosol-climate modeling. The 2013 campaign at the DOE Southern Great Plains (SGP) field site in Oklahoma provided measurements of gas-phase growth precursors, size distributions of new-particle growth events, and the composition of the growing aerosols. We show that the gas-phase and particle-phase compositions during new-particle growth events suggest three distinct growth pathways: (1) growth by sulfuric-acid/amines/organics; (2) growth by organics alone; (3) and growth by sulfuric-acid/ammonia. These event-specific mechanisms correspond to back trajectories that indicate different source regions (e.g. agriculture vs. cities). Finally, we show vertical aerosol number concentrations obtained from tethered balloon experiments demonstrating that nucleation likely starts aloft, at least on some days at SGP. We discuss potential hypotheses why the nucleation starts aloft and implications for nucleation/growth modeling.