Direct Measurement of pH in Individual Particles via Raman Microspectroscopy and Variation in Acidity with Relative Humidity
| Autor: | Joel D. Rindelaub, Paul B. Shepson, Andrew P. Ault, Rebecca L. Craig, Amy L. Bondy, Cari S. Dutcher, Lucy Nandy |
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| Rok vydání: | 2016 |
| Předmět: |
Activity coefficient
Aqueous solution 010504 meteorology & atmospheric sciences Analytical chemistry 010501 environmental sciences 01 natural sciences Acid dissociation constant Aerosol chemistry.chemical_compound chemistry Ionic strength Organic chemistry Particle Relative humidity Physical and Theoretical Chemistry Sulfate 0105 earth and related environmental sciences |
| Zdroj: | The Journal of Physical Chemistry A. 120:911-917 |
| ISSN: | 1520-5215 1089-5639 |
| Popis: | 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(SO4(2-)) and νs(HSO4(-)), the acid dissociation constant, and activity coefficients from extended Debye-Hückel calculations. Shifts in pH and peak positions of νs(SO4(2-)) 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. |
| Databáze: | OpenAIRE |
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