Development of Methods for Quantifying Speciated Peroxy Radicals by Chemical Ionization Mass Spectrometry

Drexel University, Philadelphia PA

Investigators

Abstract

The goals of this project are to develop new methods for quantifying reactive species in the atmosphere and to improve the accuracy and reliability of the calibration methods used in their measurement. The focus is on the measurement of peroxy radicals, reactive species that participate in photochemical transformations of organic compounds that can lead to the formation of the secondary products, such as ozone and secondary aerosol. The results of this study will lead to an improved ability to evaluate atmospheric chemistry models that rely on a solid understanding of underlying radical chemistry. Two new methods for speciating peroxy radicals include an atmospheric pressure transverse ionization technique using ammonium or alkyl amine ions, and an indirect method in which peroxy radicals are chemically converted to hydroperoxides and then subsequently detected using iodide or bromide chemical ionization mass (CIMs) spectrometry. These new techniques will be tested during field deployments in New York City and in a forested area in New Jersey, spanning a wide range in nitrogen oxide (NOx) concentrations and volatile organic compound (VOC) precursors. This effort also includes the development of a new calibration source based on formaldehyde photolysis. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.