Secondary organic aerosol formation from photooxidation of furan: effects of NO<sub>x</sub> level and humidity

Abstract

<p><strong>Abstract.</strong> Atmospheric furan is both primary and secondary pollutants in the atmosphere, and their emission contributes to the formation of ultrafine particles and ground-level ozone. We investigate the effects of NO<sub>x</sub> level and humidity on the formation of secondary organic aerosol (SOA) generated from the photooxidation of furan in the presence of NaCl seed particles. The particle mass concentration and size distribution were determined with a scanning mobility particle sizer (SMPS). SOA mass concentration and yield were determined under different NO<sub>x</sub> and humidity levels. Owing to condensation and coagulation, the particle number concentration decreases with increasing particle size. A significant difference is observed both in the SOA mass concentration and SOA yield variation with the initial experiment conditions. A relatively high NO<sub>x</sub> level, ranging from 16.8 to 97.5<span class="thinspace"></span>ppb, contributes to effective formation of SOA in the presence of NaCl seed particles, with the mass concentration of SOA and SOA yield ranging from 0.96<span class="thinspace"></span>μg<span class="thinspace"></span>m<sup>−3</sup> to 23.46<span class="thinspace"></span>μg<span class="thinspace"></span>m<sup>−3</sup> and from 0.04<span class="thinspace"></span>% to 1.01<span class="thinspace"></span>%, respectively. Likewise, the SOA mass concentration and yield increase with increasing humidity, because the increasing RH increases the aerosol liquid water content, which contributes to the liquid phase reactions. Nine organic nitrate species were detected by electrospray ionization exactive orbitrap mass spectrometry (ESI-Exactive-Orbitrap MS). The -COOH，-OH，-C<span class="thinspace"></span>=<span class="thinspace"></span>O and NO<sub>2</sub> functional groups were assigned in the FTIR spectra and used as the indicator for the mechanism inference. The present study directly addresses NO<sub>x</sub> effects and reinforces the implication of humidity on SOA formation during the furan-NO<sub>x</sub>-NaCl photooxidation. Furthermore, the results illustrate the importance of studying SOA formation over a comprehensive range of environmental conditions. Only such evaluations can induce meaningful SOA mechanisms to be implemented in air quality models.</p>

Brown Carbon Formation from Nighttime Chemistry of Unsaturated Heterocyclic Volatile Organic Compounds

“…The low SOA mass production from furan is consistent with the low SOA yields from OH oxidation of furan reported in other studies. , Together these observations reveal that furan may not be a major contributor to SOA mass under a variety of common oxidation conditions. Conversely, the larger SOA mass formed from thiophene and pyrrole indicates that NO 3 chemistry with these compounds may be an important SOA source, particularly in biomass burning plumes where these compounds are readily found …”

Aging Effects on Biomass Burning Aerosol Mass and Composition: A Critical Review of Field and Laboratory Studies

“…Differences in fuel mixtures and conditions (e.g., fuel-moisture content) can lead to differing emissions of gas- and particle-phase species between different burns, leading to potential differences in initial distributions of mass across volatility bins and composition markers. Emission factors (EFs) from BB for a given gas or aerosol species can vary by more than an order of magnitude across different biomasses. ,, Selimovic et al found that laboratory burns of both individual and grouped fuels were in reasonable agreement with field data for select trace gases, although this study has limited PM and VOC measurements and more field-to-lab emissions comparisons are required. Emissions vary with time, but the impact of this variability on mass and composition has not yet been well-characterized.…”

Spatial Association Pattern of Air Pollution and Influencing Factors in the Beijing–Tianjin–Hebei Air Pollution Transmission Channel: A Case Study in Henan Province

“…However, under low-pressure systems, the weather is often wet and air is moving, causing the dispersion and deposition of pollutants [20]. In terms of relative humidity, some studies have reported that high humidity conditions can promote the formation of nitrate and secondary organic aerosols [41], and that relative humidity is positively related to air pollution [36]. However, others have argued that pollutant particles can absorb more water, agglomerate, and fall to the ground more easily at a higher relative humidity [16,20].…”