FT-IR and ACSM Functional Groups Parameterization

As part of the ASCENT project, we are striving to increase the chemical specificity of organic aerosol measurements from the ACSM. The goal is to measure organic functional groups with high time resolution using the ACSM. ACSM ion fragments are known to relate to organic functional groups but there has not been a quantitative, consistent relationship observed between an individual m/z and a given functional group such as carboxylic acid, even though m/z = 44 is the COO+ ion. In this work, organic functional groups (carboxylic acid, non-acid carbonyl, total carbonyl, alkane CH and alcohol OH) are measured by Fourier transform infrared spectroscopy (FT-IR) from teflon filter samples collected over 24-hour periods by collocated IMPROVE or IMPROVE-like samplers. ACSM organics data is averaged to match the 24-hour filter data and together with the functional groups data are inputs to statistical models that generate parameterizations using multiple m/zs to predict organic functional groups. The parameterizations can be used to predict hourly concentrations of organic functional groups.  Proof of concept for this project began with using data from the Atlanta ASCENT site.