Secondary organic aerosol formation from monocyclic aromatic hydrocarbons: insights from laboratory studies

Abstract

This review summarizes in detail the current knowledge in the chemical compositions, formation mechanisms, and physicochemical properties of secondary organic aerosols formed from monocyclic aromatic hydrocarbons.

Wildfire plume ageing in the Photochemical Large Aerosol Chamber (PHOTO-LAC)

“…BrC formation from toluene photooxidation under high NO x conditions is well-known 72 and coherent with the observed trends of AAE 460/630 . The enhanced absorption in the lower visible UV range was attributed to nitrogen-containing species, particularly to nitrophenolic species.…”

“…The enhanced absorption in the lower visible UV range was attributed to nitrogen-containing species, particularly to nitrophenolic species. 73 However, the absorption properties of such brown carbon species are affected by the pH of the liquid particle phase, 72 which is unknown in this study, but biases a direct comparison to previous studies. The molecular composition of the toluene-derived SOA was investigated by high-resolution mass spectrometry.…”

“…For the detected nitrophenolic species, the OH-toluene adduct may first react with O 2 to cresol, which may further react with methylcatechol and finally with methylnitrocatechol or directly from cresol to methylnitrocatechol as later-generation oxidation products. 72 Additionally, an intense peak in the ESI mass spectrum was observed at m / z 231.0256 with a sum formula of C 7 H 7 N 2 O 7 − , which is likely a non-aromatic SOA compound due to its low double bond equivalent. 73 Alternatively, the OH attack on toluene starts at its methyl group, forming a benzyl radical, which reacts with benzaldehyde as a first-generation oxidation product.…”

Polyurethane Foam Face Masks as a Dosimeter for Quantifying Personal Exposure to Airborne Volatile and Semi-Volatile Organic Compounds

“…Linalool, a fragrance allergen which is commonly used in scented consumer products, , was detected in all nine microenvironments that were influenced by aroma diffusers (namely, female bedrooms 1, 2, 4, and 5, male bedroom 5, living room 2, department store, hair salon, and hotel room) at concentrations ranging from 159 to 23,400 ng/m 3 , illustrating its potential as an indicator compound for the presence of a fragrance allergen in aroma diffuser/scented consumer products. Other than being fragrance allergens, terpenes such as linalool may react with ozone and form secondary organic aerosol and ultrafine particles which may greatly affect the indoor air quality and cause adverse health effects. − Using the PUF mask sampling method and linalool as a potential tracer may be an easy approach to establish routine monitoring for evaluating the indoor concentration level of fragrance allergens. As for the tracer compound of environmental tobacco smoke, nicotine was detected at concentrations ranging from 5860 to 7320 ng/m 3 near two smoking hotspots, which were comparable to our previous study …”

Combined Smog Chamber/Oxidation Flow Reactor Study on Aging of Secondary Organic Aerosol from Photooxidation of Aromatic Hydrocarbons

“…During the photochemical process, VOCs can be oxidized by oxidants (including OH, NO 3 , Cl radicals, and O 3 ) to form first-, second-, and multigeneration gas-phase products. − Most of these gas-phase organic intermediates tend to eventually contribute to SOA formation via gas-particle partitioning − as their vapor pressures gradually decrease as the oxidation reaction progresses. Aromatic hydrocarbons, as a type of highly reactive VOC, are of particular interest in atmospheric chemistry due to their potential role in SOA formation. − Many studies have focused on understanding the chemical mechanisms that lead to the formation of SOA from aromatic hydrocarbons, as well as the factors that influence the yield and composition of SOA. − In particular, the effects of oxidant concentration and exposure time on SOA formation and its physicochemical properties (e.g., oxidation state and hygroscopicity) have been intensively studied. − However, these previous laboratory studies mainly relied on either smog chamber (SC) simulations or oxidation flow reactor (OFR) simulations, while their respective limitations, mentioned below, may limit the elucidation of SOA formation mechanisms . Meanwhile, the levels of SOA predicted by the air quality models are always inconsistent with the actual values observed in field observations. , Therefore, the continued study of SOA formation mechanisms is essential in conducting a closure study for SOA.…”