Chemical Characterization of Highly Functionalized Organonitrates Contributing to Night-Time Organic Aerosol Mass Loadings and Particle Growth

Abstract

Reactions of volatile organic compounds (VOC) with NO3 radicals and of reactive intermediates of oxidized VOC with NO x can lead to the formation of highly functionalized organonitrates (ON). We present quantitative and chemical information on ON contributing to high night-time organic aerosol (OA) mass concentrations measured during July–August 2016 in a rural area in southwest Germany. A filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS) was used to analyze the molecular composition of ON in both the gas and particle phase. We find larger contributions of ON to OA mass during the night. Identified ON are highly functionalized, with 4 to 12 oxygen atoms. The diel patterns of ON compounds with 5, 7, 10, or 15 carbon atoms per molecule vary, indicating a corresponding behavior of their potential precursor VOC. The temporal behavior of ON after sunset correlates with that of the number concentration of ultrafine particles, indicating a potential role of ON in night-time new particle formation (NPF) regularly observed at this location. We estimate an ON contribution of 18–25% to the mass increase of newly formed particles after sunset. Our study provides insights into the chemical composition of highly functionalized ON in the rural atmosphere and the role of anthropogenic emissions for night-time SOA formation in an area where biogenic VOC emissions dominate.

Composition and origin of PM<sub>2.5</sub> aerosol particles in the upper Rhine valley in summer

“…S10, m/z 129 C 5 H 7 NO + 3 has a similar trend as m/z 131 NaNO 2 NO − 3 and it is more pronounced in the LAAPTOF spectra of aged sea salt. In the sodium-chloride-rich episode, in general m/z 129 C 5 H 7 NO + 3 has a similar trend as organonitrate mass concentrations estimated by AMS results and the results of a molecular analysis using FIGAERO-HR-ToF-CIMS (a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer) in a companion study by Huang et al (2019). The method for organonitrate estimation can be found in Farmer et al (2010) and the parameters used here are the same as those used by Huang et al (2019).…”

“…Model results cover peak 1 and 2, as well as the first part of peak 3. Analysis of the model results shows that the three peaks were caused by different factors including meteorological conditions, regional transport, and local or in situ new particle formation and growth (such as night-time new particle formation; Huang et al, 2019). As shown in Fig.…”

“…Therefore, the measurement site is potentially subject to urban and industrial emissions, especially for southerly wind directions. Apart from that, there are several nearby biogenic emission sources, e.g., forests, sunflower fields, and other agricultural areas (Hagemann et al, 2014;Huang et al, 2019). Local traffic emissions from the minor road near the measurement site were identified by measurements with high time resolution.…”

“…The instrumentation for this campaign has been described in detail in previous publications (Huang et al, 2019;Shen et al, 2019a). Briefly, the data we use here are from the 6week (26 July to 31 August 2016) deployment of a laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF; AeroMegt GmbH) and a high-resolution timeof-flight aerosol mass spectrometer (HR-ToF-AMS; Aerodyne Inc.; hereafter AMS).…”

Understanding of atmospheric aerosol particles with improved particle identification and quantification by single particle mass spectrometry

“…It is important to note that the CE can vary depending on composition and phase of the particles (Bahreini et al, 2005). In this study, we applied a CE value 0.5, in accordance with previous studies (Canagaratna et al, 2007;Middlebrook et al, 2012) and in a related paper by Huang et al (2018), the composition dependent CE has been calculated to have a very close value to 0.5.…”