Articles | Volume 16, issue 19
Atmos. Chem. Phys., 16, 12631–12647, 2016
Atmos. Chem. Phys., 16, 12631–12647, 2016

Research article 11 Oct 2016

Research article | 11 Oct 2016

Photochemical organonitrate formation in wet aerosols

Yong Bin Lim1,2, Hwajin Kim1,3, Jin Young Kim1,3, and Barbara J. Turpin4 Yong Bin Lim et al.
  • 1Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
  • 2Department of Environmental Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA
  • 3Department of Energy and Environmental Engineering, University of Science and Technology, Daejeon 34113, Republic of Korea
  • 4Department of Environmental Science and Engineering, University of North Carolina, Chapel Hill, North Carolina 27599, USA

Abstract. Water is the most abundant component of atmospheric fine aerosol. However, despite rapid progress, multiphase chemistry involving wet aerosols is still poorly understood. In this work, we report results from smog chamber photooxidation of glyoxal- and OH-containing ammonium sulfate or sulfuric acid particles in the presence of NOx and O3 at high and low relative humidity. Particles were analyzed using ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS).

During the 3 h irradiation, OH oxidation products of glyoxal that are also produced in dilute aqueous solutions (e.g., oxalic acids and tartaric acids) were formed in both ammonium sulfate (AS) aerosols and sulfuric acid (SA) aerosols. However, the major products were organonitrogens (CHNO), organosulfates (CHOS), and organonitrogen sulfates (CHNOS). These were also the dominant products formed in the dark chamber, indicating non-radical formation. In the humid chamber (> 70 % relative humidity, RH), two main products for both AS and SA aerosols were organonitrates, which appeared at m ∕ z 147 and 226. They were formed in the aqueous phase via non-radical reactions of glyoxal and nitric acid, and their formation was enhanced by photochemistry because of the photochemical formation of nitric acid via reactions of peroxy radicals, NOx and OH during the irradiation.

Short summary
We report that organonitrates were photochemically formed in wet aerosols via aqueous chemistry in the NOx–O3 chamber at high humidity. Organonitrates are considered to form in the gas phase (peroxy radical–NO during the daytime or VOC–NO3 during the nighttime); however, our chamber study results suggest daytime organonitrate formation in polluted and humid areas. Besides organonitrates, organonitrogens, organosulfates, and organonitrogen sulfates were also dominant photooxidation products.
Final-revised paper