Supplementary material to "Development of Ozone Reactivity Scales for Volatile Organic Compounds in a Chinese Megacity (original) (raw)

Environmental Monitoring Center Station (23.12° N, 113.27° E, 51 m above sea level). It is a typical urban site located at Jixiang Road, Yuexiu District of Guangzhou, an urban area surrounded by massive residential and commercial buildings. The pillar industries are business industry, financial industry, cultural creativity industry, and health care over the area, therefore, the site is mainly subjected to traffic emissions and rarely impacted by industrial source. The site is set up on the rooftop of an eightfloor building with an altitude of ~40 m above the ground level and the data collected here can reflect urban pollution characteristics. Real-time measurements of trace gases, including O3, NO, NO2, CO, SO2, and VOCs were implemented using standard commercial techniques. O3 was measured by a UV photometric ozone analyzer (Thermo 49i) with a detection limit of 0.50 ppbv. NO and NO2 were monitored using a chemiluminescence analyzer (Thermo 42i) with a detection limit of 0.40 ppbv. CO was measured by a gas filter correlation, non-dispersive infrared analyzer (Thermo 48i) with a detection limit of 40 ppbv. SO2 was measured by a pulsed fluorescence gas analyzer (Thermo 43i) with a detection limit of 1 ppbv. The quality assurance and quality control procedures were implemented according to "Technical Specifications for Automatic Monitoring of Ambient Air Quality (HJT193-2005)". VOCs were measured using the GC866 online analyzer (Chromatotec) with a detection limit of 0.01 ppbv. The detection system consists of two analyzers: the low-carbon analyzer is responsible for the collection and detection of C2-C6 hydrocarbons, and the high-carbon analyzer is responsible for the collection and detection of C6-C12 hydrocarbons. Both analyzers use flame ionization detector for detection, and totally 57 hydrocarbons (specified by the Photochemical Assessment Monitoring Stations of US Environmental Protection Agency (USEPA)) were detected. Meteorological parameters including ambient temperature, relative humidity (RH), and pressure were obtained from a commercial meteorological station (Vaisala, Finland). 2. Model configuration The model was run based on the platform of F0AM (Framework for 0-D Atmospheric Modeling) (Wolfe et al., 2016), and the adopted chemical mechanism was the state-of-the-art Master Chemical Mechanism version 3.3.1 (MCMv3.3.1), which near-explicitly describes the atmospheric degradation of 143 VOC species and has been extensively used to elucidate the non-linear photochemistry between O3 and its precursors (NOx and VOCs) (Chen et al., 2020; Xue et al., 2014). In addition to the comprehensive chemistry, the model also considers several physical processes, including solar radiation, diurnal evolution of the PBL, dry deposition, and dilution with background air (Chen et al.,