*2.2. Data Source and Processing*

The O3 data used in this study were obtained from the national urban air quality real-time release platform of the China National Environmental Monitoring Centre (http: //106.37.208.233:20035/) (accessed on 6 May 2021). The daily surface monitoring data of O3 in the NCP from 2016 to 2020 were used. This study analyzed data from 230 sites within the study area. The selection was performed after removing the inactive sites and those with incomplete data. According to Ambient Air Quality Standards (GB 3095-2012), the daily maximum 8-h moving average of O3 is considered the actual O3 concentration (hereafter referred to as O3-8h). In addition, the daily arithmetic average of O3-8h in a calendar month is taken as the monthly average concentration. Note that it is implied that spring lasts from March to May, summer lasts from June to August, autumn lasts from September to November, and winter lasts from December to February of the following year. The quarterly average concentrations were calculated from the arithmetic average of the daily O3-8h concentrations. The arithmetic average of daily O3-8h concentrations in a calendar year was taken as the annual average concentration. The meteorological data were obtained from the China Meteorological Data Service Centre (http://data.cma.cn) (accessed on 12 May 2021). More specifically, temperature (TEM, ◦C) and air pressure (Pa, hPa) from 54 meteorological stations in the NCP from 2016–2020 were selected. The point of interest data for the plants were obtained from AutoNavi (https://amap.com/) (accessed on 1 August 2021). The administrative boundary vector data and the digital elevation model (DEM 500 m) data were obtained from the Institute of Geographical

Sciences and Natural Resources Research, CAS (https://www.resdc.cn/) (accessed on 12 May 2021). To this end, the statistical data for 2016–2020 were obtained from the China Statistical Yearbook, China Urban Statistical Yearbook, China Environmental Statistical Yearbook, and the Local Statistical Bulletin of National Economic and Social Development (http://www.stats.gov.cn/tjsj/ndsj/, https://data.cnki.net/NewHome/Index) (accessed on 2 December 2021). The time described in this study is Chinese Standard Time (CST).
