The OH Burst from Aerosols at the DOE Southern Great Plain ARM site
JIAQI SHEN, Catherine Banach, Suzanne E. Paulson,
University of California, Los Angeles Abstract Number: 552
Working Group: Aerosols, Clouds and Climate
AbstractOH-mediated cloud water chemistry has direct and indirect impacts on air quality and climate by modifying aerosol mass concentration, chemical speciation and size distributions. Studies have observed a fast OH formation phenomenon called OH burst in newly formed cloud droplets. In this study, we measured OH burst in newly formed cloud droplets using a direct-to-liquid spot sampler at the DOE Southern Great Plain ARM site during March and April, a period that typically experiences a contribution from both local biomass burning aerosols and biomass burning particles that have undergone long-term transport. We observe a wide range in the size of OH burst formation from aerosols collected on different dates, ranging from less than 100 nM up to about 700 nM, normalized by aerosol mass, corresponding to a v:v aerosol:water dilution ratio of 25,000, a typical cloud water dilution ratio. We will discuss how the OH burst activity depends on chemical composition determined by the Aerosol Chemical Speciation Monitor (ACSM), Particle Soot Absorption Photometer (PSAP) and Single Particle Soot Photometer (SP2) and soluble metals measured using ICP-MS. Results from airmass back trajectories derived from Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model along with the meteorological data from NCEP Global Data Assimilation System and their insights into the relationship between the degree of cloud processing and the OH burst will also be discussed.