Ambient Measurements of Highly Oxidized Gas-Phase Molecules during the Southern Oxidant and Aerosol Study (SOAS) 2013

Abstract

We present measurements of highly oxidized multifunctional molecules (HOMs) detected in the gas phase using a high-resolution time-of-flight chemical ionization mass spectrometer with nitrate reagent ion (NO3– CIMS). The measurements took place during the 2013 Southern Oxidant and Aerosol Study (SOAS 2013) at a forest site in Alabama, where emissions were dominated by biogenic volatile organic compounds (BVOCs). Primary BVOC emissions were represented by isoprene mixed with various terpenes, making it a unique sampling location compared to previous NO3– CIMS deployments in monoterpene-dominated environments. During SOAS 2013, the NO3– CIMS detected HOMs with oxygen-to-carbon (O:C) ratios between 0.5 and 1.4 originating from both isoprene (C5) and monoterpenes (C10) as well as hundreds of additional HOMs with carbon numbers between C3 and C20. We used positive matrix factorization (PMF) to deconvolve the complex data set and extract information about classes of HOMs with similar temporal trends. This analy...