Changes in stoichiometric characteristics of ambient air pollutants pre-to post-COVID-19 in China

Abstract

To prevent the Corona Virus Disease 2019 (COVID-19) spreading, Chinese government takes a series of corresponding measures to restrict human mobility, including transportation lock-down and industries suspension, which significantly influenced the ambient air quality and provided vary rare time windows to assess the impacts of anthropological activities on air pollution. In this work, we divided the studied timeframe (2019/12/24–2020/2/24) into four periods and selected 88 cities from 31 representative urban agglomerations. The indicators of PM 2.5 /PM 10 and NO 2 /SO 2 were applied, for the first time, to analyze the changes in stoichiometric characteristics of ambient air pollutants pre-to post-COVID-19 in China. The results indicated that the ratios of NO 2 /SO 2 presented a responding decline, especially in YRD (−5.01), YH (−3.87), and MYR (−3.84), with the sharp reduction of traffic in post-COVID-19 periods (P3–P4: 2.34 ± 0.94 m/m) comparing with pre-COVID-19 periods (P1–P2: 4.49 ± 2.03 m/m). Whereas the ratios of PM 2.5 /PM 10 increased in P1–P3, then decreased in P4 with relatively higher levels (>0.5) in almost all urban agglomerations. Furthermore, NO 2 presented a stronger association with PM 2.5 /PM 10 variation than CO; and PM 2.5 with NO 2 /SO 2 variation than PM 10 . In summary, the economic structure, lockdown measures and meteorological conditions could explain the noteworthy variations in different urban agglomerations. These results would be in great help for improving air quality in the post-epidemic periods.

How does COVID-19 lockdown affect air quality: Evidence from Lanzhou, a large city in Northwest China

“…The epidemic control measures significantly reduced the NO 2 /SO 2 ratio by 1.11 (95%CI: 0.81–1.42) in the T C period and 0.02 (95%CI: −0.38–0.41) in the T B period ( Fig. 4 ), which was largely due to the fact that mobile sources such as transport, represented by NO 2 in Lanzhou, decreased more but at concentrations several times higher than SO 2 , causing a less than expected decrease than in other areas for this ratio ( Bai et al, 2022 ). Moreover, this ratio increased with COVID-19 lockdown during the T A period, mainly due to the “challenges in the resumption of work and production”, triggering a sharp short-term decline in SO 2 instead of an increase in NO 2 .…”

“…Previous studies have also used the NO 2 /SO 2 ratio to account for the contribution of mobile and stationary sources to air pollution ( Bai et al, 2022 ). High and low NO 2 /SO 2 ratios indicate high contribution from mobile and stationary sources, respectively.…”

Variation characteristics and coordinated emission reduction of air pollutants in megacity of Chengdu-Chongqing economic circle under dual carbon goal

“…Exploring the change in the proportional relationship of different pollutant concentrations can determine the source or type of pollutants, which helps to improve the accuracy of pollution control. PM 2.5 and PM 10 have different physical and chemical properties, and previous studies have revealed that the ratio of PM 2.5 /PM 10 can indirectly provide some indicators, such as pollutant composition, source contribution, and impact on health [124][125][126][127][128]. Overall, a lower PM 2.5 /PM 10 ratio demonstrate a predominance of PM 10 (mainly from natural sources), and a higher ratio indicates more air pollution from anthropogenic sources [124][125][126].…”

Low-processing data enrichment and calibration for PM2.5 low-cost sensors

“…Pollutant concentrations in ambient air have been measured and regulated for many decades now, to prevent negative effects of air pollution to health and the environment [1]. Evidence on adverse effects of ambient air pollution has been mounting steadily, and public interest in the quality of the air we breathe has been on the rise especially since the outbreak of COVID-19 pandemic [2,3]. While until recently, monitoring of air quality has been done by professional agencies, today, the availability of portable, low cost microsensor devices and the exponential growth of IoT (Internet of Things) in everyday life has enabled widespread monitoring of air quality also by lay people [4,5].…”