Temporospatial variations and Spearman correlation analysis of ozone concentrations to nitrogen dioxide, sulfur dioxide, particulate matters and carbon monoxide in ambient air, China

Ozone has been an important pollutant in China since 2013. The increasing number of days with over-standard ozone (O3) has been observed in many cities. In this study, what we mainly focus on are shown as follows: sampling of ambient air in 365 days in 2017 from 338 main cities; comparing concentration levels of ozone, nitrogen dioxide, sulfur dioxide, particulate matters and carbon monoxide in ambient air; investigating air quality conditions related to monthly variations of ozone, in this study, five areas with relatively higher O-3-8 h over-standard days were identified and illustrated. An inverted V shape curve in North and a multiple M shape curve in South were identified in ozone monthly changes. Furthermore, possible reasons for spatial and temporal distribution were discussed. Spearman correlation analyses of ozone to nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matters (PM) and carbon monoxide (CO) in every chosen city were performed, and the distribution patterns were illustrated in maps. The results revealed that ozone concentrations in most north cities have negative correlations with concentrations of other pollutants in 2017, while some cities in south appeared positive correlations. As ozone pollution is not easily monitored by ordinary people without equipment, people in the cities where ozone concentrations were significantly related to PM or other pollutants, could primarily predict ozone pollution and take protective actions.