Category

CHEM

P03

Direct measurment of pH of Atmospheric Aerosol Particles

Abstract

The impact of highly acidic aerosol particles in the atmosphere affect,

not only climate change but human health as well. Atmospheric

aerosols impact climate by scattering or absorbing solar radiation.

These particles can also go through chemical reactions that lead to the

formation of secondary organic aerosols. The formation of SOA

particles is dependent on aerosol acidity. But, determining the exact pH

of atmospheric aerosol particles has proved to be a tough task, due to

the microscopic size of aerosol particles. Previous experimentation

includes the use of equations, thermodynamic equilibrium models, and

Raman microspectroscopy in relation to relative humidity, yet these

methods came along with many limitations. In this study, a variety of

different methods and instruments were used to test the pH of

atmospheric aerosols. The testing was done on six bulk solutions made

from various mixtures of salts and acids that resembled atmospheric

aerosols particles. The methods in this experiment included the use of

a pH probe and pH paper that were dipped inside the six bulk

solutions,titrations used for a pH equation, and image processing using

a Matlab script generated from the pH strips. A nebulizer was also used

to impact aerosol particles onto pH paper. The results of the experiment

yielded the conclusion that the best instrument used to test the pH of

atmospheric aerosols was the pH probe. Though image processing was

relatively effective when compared to the titration calculations, the pH

probe most accurately matched the desired pH of the six bulk solutions.

Bibliography

Prather, K.A. et.al. Analysis of Atmospheric Aerosols. Annu. Rev. Anal.

Chem. 2008 Rindelaub, J.D et.al Direct measurement of pH in individual

aerosol particles via Raman microspectroscopy and variation in

particle acidity with relative humidity. J Phys. Chem. A. 2016

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