Cloud droplet growth of biogenic and anthropogenic Cloud Condensation Nuclei

Aerosols have the ability to impact the earth's climate and hydrological cycle because of their potential to activate and become cloud droplets. Understanding the chemical and thermodynamic aerosol properties that control cloud droplet growth is necessary for constraining impacts on the hydrological cycle and uncertainties from the aerosol indirect effect. Quantifying organic anthropogenic effects are important for predicting Cloud condensation nuclei (CCN) concentrations and understanding climate changes due to human influence. In this study, we observe significant changes in cloud droplet growth due to the extent of mixing of biogenic and anthropogenic species. Specifically, we investigate changes in droplet growth of biogenic secondary organic aerosol (SOA) modified by the presence of two types of anthropogenic primary organic aerosol (POA); POA from a flash vaporized mixture of motor-oil and fuel and POA emitted by a diesel engine. The aerosol are sampled from a 12 meter-cubed chamber and an Aerodyne quadrapole aerosol mass spectrometer (Q-AMS) measures changes in aerosol chemical composition and a continuous flow thermal gradient CCN counter measures droplet growth rates. We present and characterize the droplet sizes of alpha-pinene SOA, motor-oil fuel and diesel exhaust POA and their subsequent mixtures. We also explore high-resolution AMS fragments to understand the carbonaceous composition of the organics and their influence on droplet growth rates