American Chemical Society
sp8b00028_si_001.pdf (1.73 MB)

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

Download (1.73 MB)
journal contribution
posted on 2018-05-08, 00:00 authored by Paola Massoli, Harald Stark, Manjula R. Canagaratna, Jordan E. Krechmer, Lu Xu, Nga L. Ng, Roy L. Mauldin, Chao Yan, Joel Kimmel, Pawel K. Misztal, Jose L. Jimenez, John T. Jayne, Douglas R. Worsnop
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 analysis revealed three isoprene-dominated and three monoterpene-dominated PMF factors. We observed significant amounts of isoprene- and monoterpene-derived organic nitrates (ONs) in most factors. The abundant presence of ONs was consistent with previous studies that have highlighted the importance of NOx-driven chemistry at the site. One of the isoprene-dominated factors had a strong correlation with SO2 plumes likely advected from nearby coal-fired power plants and was dominated by an isoprene-derived ON (C5H10N2O8). These results indicate that anthropogenic emissions played a significant role in the formation of low-volatility compounds from BVOC emissions in the region.