Ozone pollution mitigation in guangxi (south China) driven by meteorology and anthropogenic emissions during the COVID-19 lockdown

Abstract

With the implementation of COVID-19 restrictions and consequent improvement in air quality due to the nationwide lockdown, ozone (O 3 ) pollution was generally amplified in China. However, the O 3 levels throughout the Guangxi region of South China showed a clear downward trend during the lockdown. To better understand this unusual phenomenon, we investigated the characteristics of conventional pollutants, the influence of meteorological and anthropogenic factors quantified by a multiple linear regression (MLR) model, and the impact of local sources and long-range transport based on a continuous emission monitoring system (CEMS) and the HYSPLIT model. Results show that in Guangxi, the conventional pollutants generally declined during the COVID-19 lockdown period (January 24 to February 9, 2020) compared with their concentrations during 2016–2019, while O 3 gradually increased during the resumption (10 February to April 2020) and full operation periods (May and June 2020). Focusing on Beihai, a typical Guangxi region city, the correlations between the daily O 3 concentrations and six meteorological parameters (wind speed, visibility, temperature, humidity, precipitation, and atmospheric pressure) and their corresponding regression coefficients indicate that meteorological conditions were generally conducive to O 3 pollution mitigation during the lockdown. A 7.84 μg/m 3 drop in O 3 concentration was driven by meteorology, with other decreases (4.11 μg/m 3 ) explained by reduced anthropogenic emissions of O 3 precursors. Taken together, the lower NO 2 /SO 2 ratios (1.25–2.33) and consistencies between real-time monitored primary emissions and ambient concentrations suggest that, with the closure of small-scale industries, residual industrial emissions have become dominant contributors to local primary pollutants. Backward trajectory cluster analyses show that the slump of O 3 concentrations in Southern Guangxi could be partly attributed to clean air mass transfer (24–58%) from the South China Sea. Overall, the synergistic effects of the COVID-19 lockdown and meteorological factors intensified O 3 reduction in the Guangxi region of South China.

Effects of COVID-19 on the environment: An overview on air, water, wastewater, and solid waste

“…Table 3 below demonstrated the observed increase in O 3 concentrations in many countries during the COVID-19 lockdown ( Fu et al, 2020 ). An increase of up to 183% in Chandigarh, India, 525% in Baghdad, Iraq, 56.3% in Spain, 14% in California, USA, and 49.8% in Wuhan, China.…”

“…An increase of up to 183% in Chandigarh, India, 525% in Baghdad, Iraq, 56.3% in Spain, 14% in California, USA, and 49.8% in Wuhan, China. Figure 6 below shows the relative changes in overall air quality index (AQI) in relation to changes in NO 2 and O 3 concentration as demonstrated in Guangxi region, China in 2020 compared to the relative average over the same time period in 2016-2019 ( Fu et al, 2020 ). The figure shows the interaction between NO 2 and O 3 concentration as expressed by the above reversible reactions in complex interaction.…”

“…The figure shows the increase of O 3 concentration during the lockdown period as compared to the pre-lockdown time.

Figure 6 The relative changes in a) air quality index, b) NO 2 , c) O 3 in Guangxi region, China over different lockdown and quarantine periods relative to the average of 2016-2019 of the same period ( Fu et al, 2020 ).

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“… The relative changes in a) air quality index, b) NO 2 , c) O 3 in Guangxi region, China over different lockdown and quarantine periods relative to the average of 2016-2019 of the same period ( Fu et al, 2020 ). …”

Impact of the inversion and air pollution on the number of patients with Covid-19 in the metropolitan city of Tehran

“…Quarantine not only reduces day-to-day infections by reducing personal contact with the person, but also delays the spread of the virus by reducing air pollution, which has a positive effect on controlling and reducing virus transmission. In Guangxi, southern China, normal pollutants in air reduced during quarantine compared to the same period during 2016–2019 (January 24 to February 9) while O3 gradually increased ( Fu et al, 2020 ). The results show that prolonged exposure to ozone and other climatic factors can affect Covid-19 transmission and onset, but its severity and mortality depend on other factors.…”