Chemical and Meteorological Controls on New Particle Formation in the Southern Great Plains

BRI DOBSON, Harald Stark, Daniel Katz, Jordan Krechmer, Chongai Kuang, Manjula Canagaratna, Douglas Worsnop, Eleanor Browne, University of Colorado Boulder & CIRES

     Abstract Number: 279
     Working Group: Aerosol Chemistry

Abstract
New particle formation (NPF) is estimated to account for 40 – 70 % of cloud condensation nuclei and therefore plays a central role in our understanding of aerosol-cloud interactions. It is well established that the likelihood of NPF is influenced by both chemical precursors, such as sulfuric acid, ammonia, amines, and organic compounds, as well as physical atmospheric conditions. However, the complexity of the process leads to large uncertainties in the representation of NPF in models. A complete understanding of the conditions that lead to NPF requires observations of both gas-phase composition as well as physical and meteorological conditions. Additionally, these measurements must be made in diverse ecosystems as both chemical and physical conditions vary by region.

We investigated NPF in an agricultural region, a land-use category that has been understudied compared to urban and forested regions. We deployed an atmospheric-pressure interface time-of-flight mass spectrometer (APi-TOF) and a chemical ionization time-of-flight mass spectrometer with ethanol reagent ion (EtOH-CIMS) to the US Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in rural Oklahoma in October 2021 and April/May 2022. Using these mass spectrometry measurements of gas-phase compounds along with the long-term meteorological measurements from the ARM SGP site we investigate the chemical and physical conditions that contribute to NPF. I will discuss select NPF and growth events, which were identified using the nano scanning mobility particle sizer at the SGP site. Analysis focuses on the role of amines and ammonia in NPF. Additionally, differences in HYSPLIT back trajectories between event days suggest different gaseous precursors may be transported to the site and available to participate in nucleation and growth on different days. These factors, along with varying atmospheric conditions cause differences in new particle formation and growth over the course of a few days at the same location.