In Situ Measurements of Molecular Markers Facilitate Understanding of Dynamic Sources of Atmospheric Organic Aerosols

Abstract

Reducing the amount of organic aerosol (OA) is crucial to mitigation of particulate pollution in China. We present time and air-origin dependent variations of OA markers and source contributions at a regionally urban background site in South China. The continental air contained primary OA markers indicative of source categories, such as levoglucosan, fatty acids, and oleic acid. Secondary OA (SOA) markers derived from isoprene and monoterpenes also exhibited higher concentrations in continental air, due to more emissions of their precursors from terrestrial ecosystems and facilitation of anthropogenic sulfate for monoterpenes SOA. The marine air and continental–marine mixed air had more abundant hydroxyl dicarboxylic acids (OHDCA), with anthropogenic unsaturated organics as potential precursors. However, OHDCA formation in continental air was likely attributable to both biogenic and anthropogenic precursors. The production efficiency of OHDCA was highest in marine air, related to the presence of sulfur dioxide and/or organic precursors in ship emissions. Regional biomass burning (BB) was identified as the largest contributor of OA in continental air, with contributions fluctuating from 8% to 74%. In contrast, anthropogenic SOA accounted for the highest fraction of OA in marine (37 ± 4%) and mixed air (31 ± 3%), overriding the contributions from BB. This study demonstrates the utility of molecular markers for discerning OA pollution sources in the offshore marine atmosphere, where continental and marine air pollutants interact and atmospheric oxidative capacity may be enhanced.

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

“…The ratio was as high as 21.7 for linoleic acid during cooking, 72.5 for a fructose isomer during smoking, 118 for n ‐Heneicosane during incense burning, and 31.7 for n ‐Pentatriacontane during ritual candle burning. Interestingly, some biogenic SOA and hydroxyl dicarboxylic acids (OHDCA) that are considered to be secondarily formed 25 are also in Group B. This might be attributed to the enhancement of gas‐to‐particle partitioning, when the indoor PM loadings were significantly increased 28 .…”

“…It is noteworthy that the TAG used in this study was slightly different from the aforementioned SV-TAG in design of sample collection cell and could not measure the gas phase organics accurately. 25 With the combined application of a charcoal denuder and a PM 2.5 cyclone, the TAG measured condensed organics in PM 2.5 in the volatility range of C 16 -C 36 n-alkanes. Figure 1 presents several examples of the total ion chromatogram (TIC) obtained from TAG in this campaign.…”

“…23,24 In brief, it automates the processes of sample collection, transfer and detection and incorporates online derivatization and calibration with internal standards, enabling quantitative analysis of a wide range of both polar and non-polar organics. 25 Recently, a member in TAG family has been involved in studies on indoor PM-bound organics. [26][27][28] The first deployment of a SV-TAG (SV: semi-volatile) in a California residence revealed continuous emissions of semi-volatile organic compounds (SVOCs) from static indoor sources, while the abundances of SVOCs were almost unaffected by the number of occupants.…”

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

“…We identified 92 OA markers according to their retention time and mass spectra, and quantified the concentrations of 64 species at the time resolution of 1 hour. The operation principles, measurement configurations, calibrations, and data quality control of AMS and TAG were elaborated in Lyu et al 41 The accuracy and precision for the measurements were within the range of 1.5%‐21.2% and 4.1%‐33.9%, respectively.…”

“…For TAG data, the signal intensities were the peak areas of target compounds scaled by those of corresponding internal standards (ISs), that is, IS‐scaled peak areas. The ISs, comprising 41 deuterated compounds, were used to track and correct the changes in instrument sensitivity 41 . Therefore, it is reasonable to use the signal intensities for ratio analyses.…”