Review of Recent Smog Chamber Studies for Secondary Organic Aerosol

Abstract

A smog chamber has been an effective tool to study air quality, particularly secondary organic aerosol (SOA), which is typically formed by atmospheric oxidation of volatile organic compounds (VOCs). In controlled environments, smog chamber studies have validated atmospheric oxidation by identifying, quantifying and monitoring products with state-of-art instruments (e.g., aerosol mass spectrometer, scanning mobility particle sizer) and provided chemical insights of SOA formation by elucidating reaction mechanisms. This paper reviews types of smog chambers and the current state of smog chamber studies that have accomplished to find pathways of SOA formation, focusing on gas-particle partitioning of semivolatile products of VOC oxidation, heterogeneous reactions on aerosol surface, and aqueous chemistry in aerosol waters (e.g., cloud/fog droplets and wet aerosols). For future chamber studies, then, this paper discusses potential formation pathways of fine particles that East Asia countries (e.g., Korea and China) currently suffer from due to massive formation that gives rise to fatal health problems.

An Analysis on the Effectiveness of Nitrogen Oxide Reduction from Applying Titanium Dioxide on Urban Roads Using a Statistical Method

“…SOAs are formed through three main processes [24]. First, semi-volatile gas-phase products generated from reactions between atmospheric oxides (hydroxyl radical (OH), nitrate radical (NO 3 ), and ozone) move into the particulate phase through gas-particle partitioning.…”

“…SIAs are generated by chemical reactions of gas-phase precursors such as NOx, SO 2 , and NH 3 [21,24,25]. Ammonium nitrate (NH 4 NO 3 ) and ammonium sulfate ((NH 4 ) 2 SO 4 ) are the typical SIAs in the atmosphere, and ammonium nitrate is mainly generated by NOx emissions from mobile pollution sources dominant on roads during the daytime [23,26].…”

Review of Smog Chamber Experiments for Secondary Organic Aerosol Formation

“…Many previous researchers have identified key chamber parameters such as volume, surface-to-volume ratio (S/V), temperature, relative humidity, light intensity, and wall effect that influence the results of experiments, and they developed methodologies for more accurate simulation of atmospheric processes. Large chambers sized up to hundreds of cubic meters were built to reduce S/V, thereby reducing the wall loss [12][13][14]. EUPHORE (European Photoreactor) built in 1995 has dual 200 m 3 semispherical reactors [15].…”

“…HELIOS (cHambrE de simuLation atmosphérique à Irradiation naturel d'OrléanS) built in 2007 has a 90 m 3 semispherical reactor [17]. These chambers were built in semispherical or cylindrical shape to reduce the surface area at a given volume [13]. In addition, researchers have improved the SOA yield calculation method by measuring aerosol density instead of using aerosol density assumptions for more accurate calculation of SOA yield [18,19].…”

“…The characteristics of the chambers that influence the SOA simulation and the sources of uncertainties in the SOA yield data originated from the experimental systems and methodologies were identified. This review specifically focuses on chamber systems in SOA formation studies, offering a higher level of detail than that found in previous review papers on chamberbased atmospheric process studies [11][12][13]. The information summarized in this review will guide researchers in understanding the sources of uncertainties in SOA yield data and performing smog chamber experiments.…”