西安夏季PM2.5化学组成及有机气溶胶来源时间序列数据集（2019年）

本数据集采用高分辨率气溶胶质谱仪(SP-LToF-AMS)于西安开展在线观测，分析NR-PM2.5化学组成和来源，并重点讨论了西安夏季二次有机气溶胶(SOA)的生成机制。研究结果显示，SOA对夏季OA的平均贡献为69%，对NR-PM2.5的贡献为43%，表明SOA对西安夏季气溶胶的重要贡献。对比分析雨雾期与非雨雾期SOA的生成差异发现，西安夏季SOA生成以光化学氧化途径为主，主要促进LO-OOA以及MO-OOA的生成；但在雨雾期液相化学贡献显著增加，aq-OOA在OA总浓度中的占比从非雨雾期的2%升高至雨雾期的19%。进一步的特征事件对比分析结果显示，持续的高湿度环境是aq-OOA生成的决定性因素，在此基础上，高Ox环境进一步促进其生成；同时来自东南方向气团传输有利于形成持续的高湿度雨雾天气，促进aq-OOA生成。

This dataset is based on in-situ observations conducted in Xi'an using a High-Resolution Aerosol Mass Spectrometer (SP-LToF-AMS), which was applied to analyze the chemical compositions and sources of non-refractory PM2.5 (NR-PM2.5), with a focus on discussing the formation mechanisms of summer secondary organic aerosols (SOA) in Xi'an. The research findings indicate that SOA accounts for an average of 69% of summer organic aerosol (OA) and 43% of NR-PM2.5, demonstrating the substantial contribution of SOA to summer aerosols in Xi'an. A comparative analysis of the disparities in SOA formation between rain-fog and non-rain-fog periods reveals that summer SOA formation in Xi'an is primarily driven by photochemical oxidation pathways, which mainly facilitate the generation of low-volatility oxygenated organic aerosol (LO-OOA) and medium-volatility oxygenated organic aerosol (MO-OOA). However, the contribution of aqueous-phase chemistry to SOA formation increases notably during rain-fog periods, with the proportion of aqueous oxygenated organic aerosol (aq-OOA) in total OA concentration rising from 2% during non-rain-fog periods to 19% during rain-fog periods. Further comparative analysis of characteristic events shows that sustained high-humidity environments are the decisive factor for aq-OOA formation, and high Ox concentrations further promote its generation on this basis; meanwhile, air mass transport from the southeastern direction favors the formation of sustained high-humidity rain-fog weather, which boosts aq-OOA formation.