AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Role of Nitrate in New Particle Formation: Results from Ambient Measurements and Models
LEA HILDEBRANDT RUIZ, James N. Smith, Ilona Riipinen, Kelley C. Barsanti, Juliane L. Fry, Taina Yli-Juuti, Tuukka Petäjä, Markku Kulmala, Peter McMurry, National Center for Atmospheric Research
Abstract Number: 434 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract A crucial but poorly understood component of new particle formation (NPF) is the growth of nanoparticles from their smallest size (~ 1 nm in diameter) to tens of nanometers. Studies conducted by our group and others have shown that sulfuric acid condensation can often only explain a minor fraction of this early particle growth. We previously developed the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) to measure the chemical composition of 10-30 nm particles. We have recently upgraded the TDCIMS with a high-resolution time-of-flight mass spectrometer by Tofwerk AG, which allows us to collect data at higher time and mass resolution. We report the first measurements with this upgraded instrument during the Hyytiälä spring 2011 measurement campaign. TDCIMS measurements show that nitrate is the dominant species in 10-30 nm particles, suggesting its importance in nanoparticle growth. The abundance of nitrate in the particles is consistent with other measurements taken at the site.
We developed a box model to better understand the species and processes involved in NPF, building on a previous model developed to understand atmospheric nucleation. Using results from laboratory chamber experiments we developed parameterizations for the role of organic nitrate compounds in NPF. We compare model results of the relative contributions of sulfate and nitrate on nanoparticle growth to measurements in Hyytiälä and Atlanta, two very different environments.