AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Computational Prediction of UV-Visible Absorbance Spectra of Carbonyl-Containing Aqueous Aerosol Mimics
Mengjie Fan, Ziwei Dai, JOSEPH WOO, Lafayette College
Abstract Number: 693 Working Group: Aerosol Chemistry
Abstract In this work, an empirical model for the estimation of the light-absorbing properties of ammonium sulfate solutions that contain common carbonyl and dicarbonyl mixtures is presented. The formation of light-absorbing oligomers from carbonyl-containing compounds in aqueous aerosol mimics is well-known, but the cross-interactions that exist between similarly-structured species have not been extensively characterized. High-resolution UV-visible light spectra are measured for a wide range of glyoxal/methylglyoxal/acetaldehyde concentrations and aging times, and regressed as composite sums of Gaussian curves. These curves are then represented as functions of initial organic concentration; the resulting functions can be used to predict complex mixtures’ absorbance spectra, based upon these values. Concentration-dependent functions for absorbance data can be used for the estimation of aerosol “brown carbon” properties in laboratory-scale aging studies, or as an additional tool to infer a collected aerosol’s apparent carbonyl concentration based upon its measured spectrum. This model can also be readily interfaced with existing gas-aerosol chemistry models, to provide ab initio estimates of an aerosol’s light absorbance properties.