Accelerated Photochemical Generation of Reactive Species in Microdroplets by Humic-Like Substances: Role of the Air-Water Interface and Molecular Mechanism

作     者：Longgang Chu Haoran Yu Xinhao Wang Zhaoyue Sun Danning Lu Ruobing Wang Hongjian Li Zhanghao Chen Juan Gao Davide Vione Cheng Gu 

作者机构：State Key Laboratory of Pollution Control and Resource Reuse School of Environment Nanjing University Nanjing 210023 P. R. China. Institute of Soil Science Chinese Academy of Sciences Nanjing 211135 P. R. China. Dipartimento di Chimica Università di Torino Via Pietro Giuria 5 Torino 10125 Italy. 

出 版 物：《Environmental science & technology》 (Environ. Sci. Technol.)

年 卷 期：2025年第59卷第24期

页      面：2025 Jun 11页

基　　金：CPSF, (GZC20240683) Jiangsu Funding Program for Excellent Postdoctoral Talent, (2024ZB812) National Natural Science Foundation of China, NNSFC, (D13C22003520001, 42207028) National Natural Science Foundation of China, NNSFC China Postdoctoral Science Foundation, (2024M751388) China Postdoctoral Science Foundation 

主　　题：interface reaction microdroplet organic matter photochemistry reactive oxygen species 

摘      要：Atmospheric humic-like substances (HULIS) are crucial components of aerosols that absorb light and produce reactive species, influencing air quality, climate change, and human health. However, most studies on the photochemical processes of HULIS have focused on bulk solutions, neglecting microdroplets, ubiquitous in aerosols, and exhibiting distinct physicochemical properties from bulk phases. Here, we report on the photochemical production of reactive species by three HULIS representatives. The steady-state concentrations of O, HO, OH, and excited triplet states (HS*) in microdroplets were significantly higher than those in the bulk aqueous phase. The partial solvation effect and high electric field in microdroplets could facilitate charge separation in light-excited HS, with the enhanced production of HS and HS* species. HS could increase the generation of O and HO and subsequent formation of OH. Fluorescence excitation-emission matrix spectroscopy combined with ion cyclotron resonance mass spectrometry showed that condensed aromatics and lignin were the most active HULIS components. These findings underscore the significant contribution of photosensitization by HULIS in microdroplets to the atmospheric oxidation capacity, which can have significant implications for the conversion of aqueous secondary organic aerosols and the overall quality of the atmospheric environment.