Characteristics and seasonal variations of high-molecular-weight oligomers in urban haze aerosols

• DOI: 10.1016/j.scitotenv.2020.141209
• Publication Date: 2020-07-23T15:32:26Z
• Authors: Shuo Yang; Fengkui Duan; Yongliang Ma; Hui Li; Jiali Wang; Zhenyu Du; Yunzhi Xu; Ting Zhang; Lidan Zhu; Tao Huang; Takashi Kimoto; Lifei Zhang; Kebin He
• Keywords: 13. Climate action; 11. Sustainability; 01 natural sciences; 0105 earth and related environmental sciences

Organic aerosols (OA) undergo sophisticated physiochemical processes in the atmosphere, playing a crucial role in extreme haze formations over the Northern China Plain. However, current understandings of the detailed composition and formation pathways are limited. In this study, high-molecular weight (HMW) species were observed in samples collected year-round in urban Beijing, especially in autumn and winter, during 2016-2017. The positive-ion-mode mass spectra of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) showed that higher signal intensities were obtained in the mass-to-charge (m/z) ranges of 200-500 and 800-900, with repetitive mass difference patterns of m/z 12, 14, 16, and 18. This provided sound evidence that high-molecular-weight oligomers were generated as haze episodes became exacerbated. These oligomer signal intensities were enhanced in the presence of high relative humidity, aerosol water content, and PM2.5 (particles with an aerodynamic diameter ≤ 2.5 μm) mass, proving that the multiphase reaction processes play a fundamental role in haze formation in Beijing. Our study can form a basis for improved air pollution mitigation measures aimed at OA to improve health outcomes.