Direct Measurement of pH in Individual Particles via Raman Microspectroscopy and Variation in Acidity with Relative Humidity

Joel D. Rindelaub, Rebecca L. Craig, Lucy Nandy, Amy L. Bondy, Cari S. Dutcher, Paul B. Shepson, Andrew P. Ault

Research output: Contribution to journalArticlepeer-review

55 Scopus citations

Abstract

Atmospheric aerosol acidity is an important characteristic of aqueous particles, which has been linked to the formation of secondary organic aerosol by catalyzing reactions of oxidized organic compounds that have partitioned to the particle phase. However, aerosol acidity is difficult to measure and traditionally estimated using indirect methods or assumptions based on composition. Ongoing disagreements between experiments and thermodynamic models of particle acidity necessitate improved fundamental understanding of pH and ion behavior in high ionic strength atmospheric particles. Herein, Raman microspectroscopy was used to determine the pH of individual particles (H2SO4+MgSO4) based on sulfate and bisulfate concentrations determined from νs(SO42-) and νs(HSO4-), the acid dissociation constant, and activity coefficients from extended Debye-Hückel calculations. Shifts in pH and peak positions of νs(SO42-) and νs(HSO4-) were observed as a function of relative humidity. These results indicate the potential for direct spectroscopic determination of pH in individual particles and the need to improve fundamental understanding of ion behavior in atmospheric particles.

Original languageEnglish (US)
Pages (from-to)911-917
Number of pages7
JournalJournal of Physical Chemistry A
Volume120
Issue number6
DOIs
StatePublished - Feb 18 2016

Bibliographical note

Funding Information:
This work was supported by startup funds from the University of Michigan and by the National Science Foundation Grant No. AGS-1228496.

Publisher Copyright:
© 2016 American Chemical Society.

Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.

Fingerprint Dive into the research topics of 'Direct Measurement of pH in Individual Particles via Raman Microspectroscopy and Variation in Acidity with Relative Humidity'. Together they form a unique fingerprint.

Cite this