Session: Undergraduate Research Posters: Physical Chemistry:

Atmospheric aerosols and their influence on the activation and growth of cloud droplets are one of the least understood factors that contribute to climate change. Thus, accurate climate model parameters must be measured to improve the predictive power of climate models. The leading theory that describes the activation of insoluble atmospheric aerosols into cloud condensation nuclei (CCN) and their subsequent formation of cloud droplets is Frankel-Halsey-Hill adsorption activation theory (FHH-AT). However, its assumption of smooth, spherical surface morphology for insoluble aerosols, which have a notable degree of microstructure, is purported to have introduced inaccuracies in the theory. To validate FHH-AT, nanospheres were used as model insoluble atmospheric aerosols to measure water uptake by three different experimental methods to determine if the data generated cloud activation parameters that agree. Nanosphere samples, ranging from 150-450 nm, were purified by diluting, sonicating, and centrifuging the samples multiple times. For each sample, the nanospheres were aerosolized, dried, and size-selected using a Differential Mobility Analyzer. The ratio of the number of activated aerosols at a specific supersaturation to the total number of available aerosol particles was found by analyzing the sample on a CCN counter and Condensation Particle Counter (CPC). The critical supersaturation of the sample, where 50% of the sample had activated into CCN, was determined by plotting the activation ratio against supersaturation. Additionally, gravimetric and optical methods were used to measure water adsorption under sub-saturated water vapor conditions, using a Quartz Crystal Microbalance (QCM) and a Fourier Transform Infrared (FTIR) spectrometer, respectively. These data sets were assessed using FHH-AT to determine climate model parameters from the individual experimental methods and compared to determine the accuracy of the measurement.

Rebecca L Parham

Hendrix College

Appearances