*2.2. Particulate Matter Datasets*

The atmospheric environment monitoring network in Xi'an is composed of 13 national air quality real-time monitoring stations: the Voltage Switchgear Factory (VS), the Xingqing Community (XQ), Textile City (TC), Xiaozhai (XZ), People's Stadium (PS), High-tech District (HT), the Economic Development District (ED), Chang'an District (CA), Yanliang District (YL), Lintong District (LT), Caotan (CT), Qujiang (QJ), and Guangyun Lake (GY) (Figure 1). The daily mean concentrations of particulate matter (PM10 and PM2.5) at each station, from 1 January 2013 to 31 December 2017, were used in the analysis. These data are publicly available at the Xi'an Ecology and Environment Bureau (http://xaepb.xa.gov.cn/, accessed on 9 July 2021).

**Figure 1.** Distribution of air monitoring stations and atmosphere monitoring station.

According to the emissions standards of air pollutants from the Ambient Air Quality Standard (GB 3095-2012) [23]. Grade 1 concentration limits (24 h average) of PM10 and PM2.5 are 50 μg/m<sup>3</sup> and 35 μg/m3, which are the maximum concentrations healthy for humans. Grade 3 concentration limits of PM10 and PM2.5 are 150 μg/m<sup>3</sup> and 75 μg/m3, which are unhealthy for humans.
