Long-term trend of ozone pollution in China during 2014–2020: distinct seasonal and spatial characteristics

Abstract

Abstract. In the past decade, ozone (O3) pollution has become a severe environmental problem in major cities in China. Here, based on available observational records, we investigated the long-term trend of ozone pollution in China during 2014–2020. Ozone concentrations were higher in urban areas than in non-urban areas. During these seven years, the highest ozone concentrations primarily occurred in summer in northern China, and in autumn or spring in southern China. Although ozone precursors, including nitrogen oxides (NOx) and carbon monoxide (CO), continuously decreased throughout the seven years, four ozone metrics that were used to characterize ozone exposure levels increased from 2014 to 2017 and reached a plateau after 2017. The long-term trend of ozone concentrations differed across seasons; especially from 2019 to 2020 when ozone concentrations decreased in summer and increased in winter. To analyze the causes of this observed trend, a photochemical box model was used to investigate the change in ozone sensitivity regime in two representative cities – Beijing and Shanghai. Our model simulations suggest that the summertime ozone sensitivity regime in urban areas of China has changed from a VOC-limited regime to a transition regime during 2014–2020; by 2020, the urban photochemistry is in a transition regime in summer but in a VOC-limited regime in winter. This study helps to understand the distinct trends of ozone in China and provides insights into efficient future ozone control strategies in different regions and seasons.

Vigor and Health of Urban Green Resources under Elevated O3in Far East Asia

“…[56] (Figure 3). Beijing and its surrounding areas are typical composite pollution areas in North China, and the pollution degree has an obvious suburban gradient in somewhat [57][58][59], and plants have been threatened by high O 3 concentration [23,60]. Although ground-level ozone (O 3 ) concentrations are expected to increase over the twenty-first century, especially in east Asia, with increasing NO 2 [4,5].…”

“…Recently, efficient use of internet data offered an outline of the health and vigor of urban green in relation to air quality data (Air Quality Index: PM 2.5 ,PM 10 ,SO 2 ,NO 2 , CO, and O 3 ) from 206 monitoring stations from 27 provincial capital cities in China [23][24][25][26]. Over 90% of air quality variation could be explained by socio-economics and geo-climates, suggesting that air quality control in China should first reduce efflux from social economics, while geo-climatic-oriented ventilation facilitation design is also critical.…”

“…Visible injury symptoms in bioindicator plants are more perceptible and comprehensible for laymen than air pollution concentrations, which may help to enhance the environmental awareness to the general public. Therefore, it is an effective way to monitor the O 3 risk in urban and regional areas by investigating the typical characteristics of O 3 injury on plants as well as the street view [23][24][25][26]. These studies have identified sensitive species that could contribute to further investigated under controlled conditions.…”

“…How can we obtain a bigger scale from individual tree scale to town scale? A typical example is recently reported in China with the use of big internet data [23][24][25][26]. They could identify the association between greenness and air pollution from a street view scale, which can favor urban greenness management and evaluation in other regions where street-view data are available.…”

“…An epidemiological investigation is the most objective and practical method to determine the degree of O 3 damage by investigating the typical characteristics of O 3 damage to plants in the natural environment [19,20]. The highest O 3 concentrations primarily occurred in July and August in northern China and the central part of Japan [21][22][23], and in September or April and May in southern China [23][24][25][26], in April-June in northern Japan [21]. Ozone causes cellular damage in plants, reducing stomatal control, lower CO 2 assimilation rates, and the occurrence of visible leaf injury [9,27,28].…”