Aerosols affect climate and human health both directly and indirectly. Atmospheric aerosols are either primary or secondary. Primary aerosol particles enter the atmosphere directly and include sources such as soot, mineral dust, sea salt and pollen. Secondary aerosols form in the atmosphere by the condensation of gases. The formation and growth of secondary particles is typically modeled using nucleation theory. However, the number aerosol particles in the atmosphere predicted by models is smaller than what is actually measured. Radical- molecule complexes may act as an initial nucleating site for particle formation. HO2 radical is the most abundant peroxy radical in the atmosphere and forms a strong hydrogen-bonded complex with water. We studied aerosol nucleation through HO2-H2O complex formation using a flow reaction coupled to a scanning mobility particle sizer (SMPS). We measured the size distribution (between 0.8 and 1000 nm) and concentration of aerosol particles with respect to reaction time, initial concentration of HO2 radical, and concentration of water vapor. The aerosol concentration is directly proportional to the HO2 and water vapor concentration. Experimental results indicate that HO2-H2O complex can act as a nucleating agent for new particle formation. Future work will investigate the ability of other radicals to initiate particle formation.

Aerosol formation initiated by nucleation of radical- water complexes

249th National Meeting (2015)

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