Investigating Contributors to Nanoparticle Growth Using an Ambient Air-Tracking Chamber

XUANLIN DU, Jeremy Wakeen, Samuel O'Donnell, Jeffrey R. Pierce, James Smith, Don Collins, University of California, Riverside

     Abstract Number: 506
     Working Group: Urban Aerosols

Abstract
New particle formation (NPF) and subsequent growth of atmospheric aerosols play a critical role in generating cloud condensation nuclei (CCN), which significantly impact cloud properties and climate. However, there are still large uncertainties in the mechanisms and rates of NPF and particle growth. Previous measurements in Houston’s urban setting observed NPF events but did not include a comprehensive analysis of the factors that may contribute to the NPF frequency and growth rates.

This work presents data from the TRACER-Ultrafine aerosol Formation and Impacts (TRACER-UFI) campaign, conducted in Houston, TX during July and August 2022. We utilized a 2-cubic meter portable chamber, operating with entirely or mostly ambient gases under natural light conditions. We observed daily NPF events inside the chamber, with multiple events occurring on many days. The growth of newly formed particles was tracked using a scanning mobility particle sizer and their composition was measured with a thermal desorption chemical ionization mass spectrometer. We investigated the influence of meteorological factors, ambient gas-phase pollutant concentrations, and aerosol chemistry on particle growth rate in the chamber. Notably, our analysis revealed distinct correlations between growth rate and meteorological variables during July and August, possibly due to variations in the dominant chemical compounds contributing to growth across these two months. Furthermore, we observed a negative correlation between growth rate and particle volatility.