Li Yao, Ren Hong, Zhou Shengzhen, Pei Chenglei, Gao Min, Liang Yuxuan, Ye Dian, Sun Xijing, Li Fenghua, Zhao Jun, Hang Jian, Fan Shaojia, Fu Pingqing
School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China.
Air Environmental Modeling and Pollution Controlling Key Laboratory of Sichuan Higher Education Institute, Chengdu University of Information Technology, Chengdu 610225, China.
Sci Total Environ. 2024 Nov 10;950:175326. doi: 10.1016/j.scitotenv.2024.175326. Epub 2024 Aug 6.
Secondary organic aerosol (SOA) accounts for a large fraction of fine particulate matter (PM), but the lack of vertical observations of SOA in the urban boundary layer (UBL) limits a comprehensive understanding of its sources and formation mechanisms. In this study, PM samples were simultaneously collected at 3 m, 118 m, and 488 m on the Canton Tower in Guangzhou during winter. Typical SOA tracers, including oxidation products of isoprene (SOA), monoterpene (SOA), sesquiterpene (SOA), and toluene (ASOA), were investigated alongside meteorological parameters and gaseous/particulate pollutants. Total concentrations of SOA tracers showed an increasing trend with height, with daytime levels exceeding nighttime levels. C-alkene triols and 2-methylglyceric acid displayed a significant increase with height, potentially affected by nighttime chemistry in the residual layer, determining the overall vertical trend of SOA tracers. Concentrations of later-generation SOA (SOA) tracers also increased with height, while those of first-generation SOA (SOA) tracers decreased, indicating relatively aged SOA in the upper layers. SOA and ASOA tracers exhibited higher enhancement under polluted conditions, likely impacted by biomass burning and anthropogenic emissions. The yields of SOA tracers varied with temperature in the vertical profile. The formation of SOA tracers was negatively correlated with relative humidity, liquid water content, and pH, affecting their vertical distributions. The effect of O on SOA formation enhanced significantly with height, influenced by air mass transport, and likely contributed to the higher yields of SOA in the upper layer. However, at ground level, SOA formation was primarily driven by high local emissions of both NO and volatile organic compounds. We also observed the roles of SO in SOA generation, particularly at 118 m. This study demonstrates the vertical diurnal characteristics of SOA tracers in the UBL, highlighting the varying effects of meteorological conditions and anthropogenic pollutants on SOA formation at different heights.
二次有机气溶胶（SOA）在细颗粒物（PM）中占很大比例，但城市边界层（UBL）中缺乏对SOA的垂直观测限制了对其来源和形成机制的全面理解。在本研究中，冬季期间在广州塔的3米、118米和488米处同时采集了PM样本。研究了典型的SOA示踪剂，包括异戊二烯氧化产物（SOA）、单萜氧化产物（SOA）、倍半萜氧化产物（SOA）和甲苯氧化产物（ASOA），以及气象参数和气态/颗粒污染物。SOA示踪剂的总浓度随高度呈增加趋势，白天水平超过夜间水平。碳烯烃三醇和2 - 甲基甘油酸随高度显著增加，可能受残留层夜间化学过程影响，决定了SOA示踪剂的整体垂直趋势。后期生成的SOA（SOA）示踪剂浓度也随高度增加，而第一代SOA（SOA）示踪剂浓度降低，表明上层的SOA相对老化。SOA和ASOA示踪剂在污染条件下表现出更高的增强，可能受生物质燃烧和人为排放影响。SOA示踪剂的产率在垂直剖面中随温度变化。SOA示踪剂的形成与相对湿度、液态水含量和pH呈负相关，影响其垂直分布。O对SOA形成的影响随高度显著增强，受气团传输影响，可能导致上层SOA产率较高。然而，在地面，SOA形成主要由NO和挥发性有机化合物的高本地排放驱动。我们还观察到SO在SOA生成中的作用，特别是在118米处。本研究展示了城市边界层中SOA示踪剂的垂直日变化特征，突出了气象条件和人为污染物在不同高度对SOA形成的不同影响。
