10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Uptake of Dicarboxylic Acid Molecules by α-Pinene Secondary Organic Material and Implications for the Role of Particle Phase State and Relative Humidity
YUEMEI HAN, Jianhuai Ye, Zhaoheng Gong, Pengfei Liu, Suzane de Sá, Karena McKinney, Scot T. Martin, Harvard University
Abstract Number: 945 Working Group: Aerosol Chemistry
Abstract Secondary organic material (SOM) particles can exhibit different phase states in amorphous solid, semisolid, and liquid depending on a variety of factors such as relative humidity (RH), temperature, and the reaction history of precursor hydrocarbons. Increasing relative humidity lowers the viscosity of SOM particle and thereby improves their potential for dynamic exchange and reactivity with gas-phase molecules. Given that large amounts of gas-phase organic species are present in the real atmosphere, however, the influence of particle phase state and relative humidity on the uptake of those organic molecules by SOM particles remains poorly understood. This study investigates the uptake of gas-phase dicarboxylic acid molecules at variable RH conditions by atmospherically relevant SOM particles generated from dark ozonolysis of α-pinene. 13C-labeled dicarboxylic acids were applied as probe molecules for quantifying the amount of uptake with aerosol mass spectrometry. A continuously increased uptake of 13C-labeled oxalic, malonic, and α-ketoglutaric acids by α-pinene SOM particles were observed with increasing RH while a saturation of uptake was not reached for RH up to 80%. The studied dicarboxylic acid molecules were possibly well-miscible with α-pinene SOM particles, as indicated from their similar ranges in terms of Hansen Solubility Parameters, an approach used to predict the miscibility of organic materials. A higher uptake amount was obtained as the increase of gas-phase concentration and the decrease of volatility, suggesting these are important factors governing the uptake of the dicarboxylic acid molecules.