资源环境科技发展态势分析平台

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 PM2.5 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 NO3-initiated oxidation reactions. Our results highlight that increased anthropogenic pollutant emissions (e.g., NOx and SO2) can significantly enhance the SOA burden in biogenically influenced urban areas.