AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Measuring pH of Atmospheric Aerosol Particle Microenvironments Using a Raman Microspectroscopic Method
REBECCA CRAIG, Andrew Ault, University of Michigan
Abstract Number: 456 Working Group: Aerosol Chemistry
Abstract Assessing the pH of atmospheric aerosol particles is of great interest, due to the impact of acidic particles on the environment and human health. Many atmospheric particle phase chemical processes are dependent on acidity, such as secondary organic aerosol formation and gas-particle partitioning. As aerosol chemical composition determines hygroscopicity and contributes to cloud condensation nuclei activity, the pH of a particle can impact composition, cloud droplet nucleation and, ultimately, climate forcing. Traditional methods of estimating aerosol pH through indirect measurement or assumptions often disagree with thermodynamic model predictions of particle acidity. Raman microspectroscopy was recently used to develop a method to determine the acidity of individual particles generated from H2SO4/MgSO4 standard solutions. The method utilized sulfate and bisulfate concentrations determined from νs(SO42-) and νs(HSO4-), the acid dissociation constant, and activity coefficients from extended Debye-Hückel calculations to determine [H+] and pH. This spectroscopic method will be expanded and applied to study more complex systems and various aerosol particle microenvironments in order to improve fundamental understanding of pH and ion behavior in high ionic strength atmospheric particles.