Real‐time molecular characterization of air pollutants in a Hong Kong residence: Implication of indoor source emissions and heterogeneous chemistry

Abstract

Due to the high health risks associated with indoor air pollutants and long‐term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor‐to‐outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle‐phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5‐dimethylfuran, stigmasterol, iso‐/anteiso‐alkanes, and fructose isomers for smoking, C28‐C34 even n‐alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality.

Emission characteristics, sources, and airborne fate of speciated organics in particulate matters in a Hong Kong residence

“…The ERs were calculated as the ratios of average concentrations (or IS-scaled abundances for unquantified species) in presence of activity to those in absence of activity at the same time slots. 9 The total NIC of quantified speciated organics followed the same order as NIC of PM 1 -OM, that is, cigarette smoking (1776 ng/ m 3 ) > incense burning (1131 ng/m 3 ) > cooking (463 ng/m 3 ) > ritual candle burning (396 ng/m 3 ). Marginal increases were observed for the concentrations of PM-bound organics during scented candle burning, for which the NICs were hardly computable.…”

“…Indeed, the IS‐scaled abundances of the C 27 –C 33 iso‐/anteiso‐alkanes were remarkably enhanced during smoking, with the ERs of 46–195 (Table S5). The other unquantified organics with high ERs included stigmasterol, glucose, β‐sitosterol, and mannose, some of which have been introduced in Lyu et al 9 Interestingly, a well‐shaped peak of vitamin E was identified from the TAG chromatograms disturbed by smoking, which was not found during the undisturbed period, and thus, the ER was not computable. It is unclear whether the vitamin E was an additive specific to the cigarette used in this study or ubiquitously present in cigarettes.…”

“…During specific activities, Group A also included some primary species (Table S4). For example, two biomass burning tracers (e.g., levoglucosan and mannosan) presented higher outdoor concentrations during cooking, which was not discovered by examining the overall I/O ratio of saccharides (2.57 ± 2.11) in Lyu et al 9 This unexpected pattern for levoglucosan and mannosan was likely During the undisturbed period, most (~87%) of the species were in Group A, comprising SIA, many secondary organic aerosol (SOA) species and some primary organic aerosol (POA) species, such as n-alkanes, fatty acids, n-alcohols, aromatic acids, biomass burning tracers, and PAHs (Figure S3). Group B contained tetratriacontane, iso-nonacosane, anteiso-tritriacontane, and 9-oxononanoic acid (Figure 3B).…”

“…organics, 9,10 which eventually enhances the traceability of indoor air toxicity. Therefore, studies on speciated organics provide a fundamental insight on indoor air quality.…”

“…An earlier paper gave an overview of the measurements, together with air pollutants in gas phase. 9 With a special focus on PM-bound speciated organics, here we discussed their high level indoors and emissions from prescribed activities. Furthermore, the sources and airborne fate of indoor PM-bound organic matters (OM) were explored.…”