Determination of HCl Solubility in Proxies for Wildfire Smoke Aerosol

RAE POOLEY, Megan Willis, Colorado State University

     Abstract Number: 497
     Working Group: Aerosol Chemistry

Abstract
The stratospheric ozone layer, which protects us from harmful UV radiation, is anticipated to recover by approximately 2066 following global production bans of most long-lived gaseous halocarbons, the primary sources of catalytic ozone-destroying chlorine radicals. Reactive stratospheric chlorine mostly resides in reservoir species such as hydrogen chloride (HCl) and is efficiently re-released when the reservoirs partition to and undergo multiphase reactions on stratospheric particles. Large wildfire blowups, becoming increasingly frequent with climate change, can inject aerosol into the stratosphere. Modeling studies suggest the observed negative ozone perturbations after wildfire events arise from the high solubility of HCl in organic particle matrices compared to sulfuric acid background particles. However, existing HCl solubility data are limited for organics pertinent to aged wildfire aerosols, introducing uncertainty in models relying on these fundamental physical-chemical properties to predict the effect of wildfires on ozone layer recovery.

To quantify how organic molecular structure impacts HCl solubility, we employ a new method involving a closed recirculating system equipped with a Fourier transform infrared spectrometer that monitors concentration changes in gaseous HCl as it equilibrates with either a pure organic liquid or organic solution. By varying experiment temperature to produce solubility curves, we will measure HCl heats of solvation. We will also provide estimated contributions of HCl intermolecular interactions to measured (effective) solubility through composition measurements of resulting HCl-organic solutions. Results from our solubility measurements will facilitate more accurate stratospheric chemistry models by quantifying HCl solubility in carboxylic and dicarboxylic acids, acetates, alcohols, phenols, and carbohydrates.