Liang Zhancong, Zhou Liyuan, Chan Chak K
Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
State Key Laboratory of Advanced Environmental Technology, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Environ Sci Technol. 2025 Sep 9;59(35):18749-18760. doi: 10.1021/acs.est.5c04050. Epub 2025 Aug 26.
Biomass burning (BB) is increasingly relevant to air quality as global warming intensifies wildfire activity. Levoglucosan (LEVO) is a widely used tracer for BB, but its oxidative decay is still less understood. While gas-phase hydroxyl radicals (•OH) have been considered the primary oxidants for LEVO decay in biomass burning organic aerosol (BBOA) particles, high particulate viscosity at low relative humidity (RH) limits •OH uptake. In this study, we demonstrate a less recognized pathway that leads to LEVO degradation in BBOA particles under light, which is primarily driven by triplet excited states (BBOA) via hydrogen transfer in photosensitization reactions. Unlike •OH oxidation that relies on mass transfer of oxidants from the gas phase, BBOA oxidation remains effective in viscous particles at low RH and accounts for ∼50% of LEVO decay, shortening its chemical lifetime in previous estimates by a half to ∼1.8 days. These findings highlight the importance of processes that generate oxidants within particles, such as photosensitization, and enhance our understanding of the atmospheric fate of LEVO to facilitate BB tracking.
随着全球变暖加剧野火活动，生物质燃烧（BB）与空气质量的相关性日益增加。左旋葡聚糖（LEVO）是一种广泛用于追踪BB的物质，但其氧化衰减仍不太为人所了解。虽然气相羟基自由基（•OH）被认为是生物质燃烧有机气溶胶（BBOA）颗粒中LEVO衰减的主要氧化剂，但在低相对湿度（RH）下高颗粒粘度限制了•OH的摄取。在本研究中，我们展示了一条较少被认识的途径，即在光照下导致BBOA颗粒中LEVO降解，这主要由三线态激发态（BBOA）通过光敏化反应中的氢转移驱动。与依赖气相氧化剂传质的•OH氧化不同，BBOA氧化在低RH的粘性颗粒中仍然有效，占LEVO衰减的约50%，将其在先前估计中的化学寿命缩短了一半至约1.8天。这些发现突出了颗粒内产生氧化剂的过程（如光敏化）的重要性，并增强了我们对LEVO大气归宿的理解，以促进BB追踪。
