Secondary organic aerosol (SOA) particles make up a substantial fraction of airborne particles and significantly impact air quality and climate.  Yet despite their importance, there remain large uncertainties in the physical and chemical processes that govern how these aerosols form and grow to diameters that are sufficiently large to impact climate, visibility and human health.  In the present work we investigate the uptake and incorporation of three gaseous organic nitrates (2-ethylhexyl nitrate, β-hydroxyhexyl nitrate, and β-hydroxypropyl nitrate) into SOA particles formed from the ozonolysis of α-pinene in a large-volume aerosol flow reactor at room temperature, between 7 minutes and 31 minutes reaction time and both with and without cyclohexane as an OH scavenger.  The size distributions were monitored using a scanning mobility particle sizer.  The uptake of the organic nitrates into the particles was quantified using both attenuated total reflectance (ATR) FTIR and a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), from which bulk partition coefficients were calculated.  The data confirm the importance of the structure and functional groups of both the gas and the condensed phase in determining incorporation from the gas phase.  The kinetics and molecular processes governing incorporation of these organic nitrates in the particles via mass accommodation and solubility will be discussed and the implications for quantitative modeling of particle growth in the atmosphere explored.

Investigating particle growth and organic nitrate uptake into secondary organic aerosol particles from the ozonolysis of α-pinene

2019 Fall National Meeting

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