Molecular Characterization of Organosulfates in Highly Polluted Atmosphere Using Ultra‐High‐Resolution Mass Spectrometry

Abstract

Organosulfates (OSs) have recently been observed to be a potentially important constituent of secondary organic aerosol (SOA); however, their molecular characterization in highly polluted atmospheres has not been probed in detail. This study thoroughly presents the characterization of OSs in polluted air and demonstrates their seasonal and diurnal variations, formation mechanisms, and contributions to organic aerosol. Atmospheric PM 2.5 samples were collected from an urban Shanghai site across the winter and summer of 2017. OSs were characterized by ultra-high-performance liquid chromatography (UHPLC) coupled with Orbitrap mass spectrometry (MS). Based on exact mass formulae in conjunction with previous chamber studies, hundreds of sulfur-containing compounds were tentatively identified as OSs. The number and abundance of OSs increased significantly during pollution episodes. The OSs in the clean aerosol samples were dominant in biogenic products, whereas the OSs in the polluted winter samples had distinctive anthropogenic characteristics. Aromatics and long-chain alkanes from anthropogenic emissions might be their precursors. By using synthesized standards, the total concentrations of 14 quantified OSs ranged 21.6-161 ng m −3 in summer and 5.85-84.3 ng m −3 in winter, respectively. Among these OSs, glycolic acid sulfate was the most abundant species (1.13-122 ng m −3 ). Further analysis of their seasonal and diurnal variations suggests possible contributions from multiple formation mechanisms, including acid-catalyzed and NO 3 -initiated oxidation reactions. Our results highlight that increased anthropogenic pollutant emissions (e.g., NO x and SO 2 ) can significantly enhance the SOA burden in biogenically influenced urban areas.

SO<sub>2</sub> and NH<sub>3</sub> emissions enhance organosulfur compounds and fine particle formation from the photooxidation of a typical aromatic hydrocarbon

“…In TMB / NO x / NH 3 photooxidation, the net SOA yield increased slightly from 3.5 % to 5.1 % as the NH 3 initial level increased from 0 to 200 ppb (Table 1). Our result is consistent with the finding of Chen et al (2020a), who showed that NH 3 did not significantly affect SOA formation from toluene / NO x photooxidation under dry conditions. In-Figure 6.…”

Reply on RC2

“…The finding of the current study suggests that the organosulfur compound (MW = 240) may also be produced from the photooxidation of 1,2,4-trimethylbenzene in the presence of SO2. In addition, in the absence of authentic standard and chromatographic conditions, the MW 226, 240, and 268 organosulfur compounds were designated as biogenic-derived organosulfates in previous field studies (Cai et al, 2020;Boris et al, 2016). Our results show the detection of OS-226, OS-240, and OS-268 organosulfates, which are also isomers of organosulfates derived from isoprene (Cai et al, 2020), limonene (Cai et al, 2020), and limonene (Boris et al, 2016), respectively.…”

“…In addition, in the absence of authentic standard and chromatographic conditions, the MW 226, 240, and 268 organosulfur compounds were designated as biogenic-derived organosulfates in previous field studies (Cai et al, 2020;Boris et al, 2016). Our results show the detection of OS-226, OS-240, and OS-268 organosulfates, which are also isomers of organosulfates derived from isoprene (Cai et al, 2020), limonene (Cai et al, 2020), and limonene (Boris et al, 2016), respectively. More studies need to be undertaken to differentiate various sources of organosulfates in the ambient aerosols through chemical synthesis of authentic organosulfates standards.…”

“…Recently, some sulfur-containing compounds from field measurements were designated as compounds of unknown origin. For example, the MW 214 organosulfate has been detected in PM2.5 collected from the highly polluted megacity Shanghai (Cai et al, 2020). However, the VOC precursor for this organosulfate formation was not reported.…”

Formation mechanism of secondary organic aerosol in aerosol liquid water: A review

“…于分析技术的进展, 尤其是质谱技术的发展 [6] . 带电液滴, 进入质谱后对大分子进行检测, ESI-MS广 泛应用于对有机硫酸酯的检测中 [95,96] . FTICR-MS技术 则通过傅里叶变换得到高强磁场中带电离子回旋运动 频率, 从而获得精确的分子量和元素组成信息.…”