Investigation of PM2.5 pollution during COVID-19 pandemic in Guangzhou, China

Wen, Luyao; Yang, Chun; Liao, Xiaoliang; Zhang, Yanhao; Chai, Xuyang; Gao, Wenjun; Guo, Shulin; Bi, Yinglei; Tsang, Suk-Ying; Chen, Zhi Feng; Qi, Zenghua; Cai, Zongwei

doi:10.1016/j.jes.2021.07.009

Cited by 26 publications

(12 citation statements)

References 36 publications

(57 reference statements)

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“…However, the emission benefit from public buses in terms of NO and CO 2 may be uncertain when the bus occupancy rates are low, as observed in Taichung City buses. Although many recent studies showed improved ambient air quality, a positive environmental implication, due to restricted mobility during the pandemic [ 9 , 15 – 17 , 19 ], our analysis of tailpipe emissions per PKT of buses suggested that the benefit of public buses in terms of NO and CO 2 emissions per PKT over private modes of transportation became doubtful in the context of the COVID-19 pandemic. In other words, public bus transit systems can be less efficient in terms of emissions per PKT than private transport modes in the changing scenario due to the COVID-19 pandemic if appropriate measures are not adopted to increase bus usage.…”

Section: Resultsmentioning

confidence: 66%

“…With the onset of the novel coronavirus disease (COVID- 19), several countries around the globe have been imposing curtailments on outdoor movement and activities of people in an effort to keep the pandemic from further spreading. The restrictions include lockdowns and the requirement to maintain social distancing.…”

Section: Introductionmentioning

confidence: 99%

“…Several prior studies have analyzed the effect of the COVID-19 pandemic and subsequent restrictions, such as lockdowns, on ambient air quality [9,[15][16][17][18][19]. Most of those studies showed that less vehicular traffic and the decrease in other emission activities during the pandemic improved ambient air quality.…”

Section: Introductionmentioning

confidence: 99%

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Effects of the COVID-19 pandemic on public bus occupancy and real-world tailpipe emissions of gaseous pollutants per passenger kilometer traveled

Dhital

Wang

Yang

et al. 2022

Sustain Environ Res

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Public buses typically have less emission per passenger kilometer traveled (PKT) than private cars and motorcycles, and the emission benefit of public buses increases with ridership. However, the drop in public bus usage during the novel coronavirus (COVID-19) pandemic could lead to an increase in air pollutant emissions per PKT, making the emission benefits of public buses questionable. This study investigated the effects of the COVID-19 pandemic on public bus occupancy rates in Taichung City, Taiwan, and also compared real-world emissions per PKT of carbon monoxide (CO), total hydrocarbons (THC), nitric oxide (NO), and carbon dioxide (CO2) of a public bus before and during the pandemic. Mean bus occupancy rates were 11–25% on different bus routes before the pandemic, indicating that only a fourth or less of the bus passenger capacity was utilized. During the pandemic, mean bus occupancy rates dropped to 4–15%. Moreover, the public bus was less polluting based on CO and THC emissions than the car and motorcycle, even at the low passenger occupancy rates observed during the pandemic. However, NO and CO2 emissions per PKT of the bus were remarkably higher during the pandemic than those of the car and motorcycle. Furthermore, we estimated the break-even passenger occupancy rate for buses as 15%, which was the minimum threshold occupancy rate below which the buses would be more polluting than cars and motorcycles in terms of CO, THC, and CO2 emissions per PKT. Our findings will help transport management authorities and policymakers to optimize bus route designs and frequencies and implement anti-pandemic measures to maximize the environmental benefits of the public bus transit systems.

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Section: Resultsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

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Effects of the COVID-19 pandemic on public bus occupancy and real-world tailpipe emissions of gaseous pollutants per passenger kilometer traveled

Dhital

Wang

Yang

et al. 2022

Sustain Environ Res

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“…For example, during the COVID-19 blockade, severe haze still occurred in northern China due to high relative humidity and poor air [47]. Other factors such as transportation and secondary pollution offset the reduction of PM 2.5 concentration [48].…”

Section: Population Exposure Risks Of Pm25mentioning

confidence: 99%

Spatiotemporal Distribution Patterns and Exposure Risks of PM2.5 Pollution in China

Song

Liu

et al. 2022

Remote Sensing

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The serious pollution of PM2.5 caused by rapid urbanization in recent years has become an urgent problem to be solved in China. Annual and daily satellite-derived PM2.5 datasets from 2001 to 2020 were used to analyze the temporal and spatial patterns of PM2.5 in China. The regional and population exposure risks of the nation and of urban agglomerations were evaluated by exceedance frequency and population weight. The results indicated that the PM2.5 concentrations of urban agglomerations decreased sharply from 2014 to 2020. The region with PM2.5 concentrations less than 35 μg·m−3 accounted for 80.27% in China, and the average PM2.5 concentrations in 8 urban agglomerations were less than 35 μg·m−3 in 2020. The spatial distribution pattern of PM2.5 concentrations in China revealed higher concentrations to the east of the Hu Line and lower concentrations to the west. The annual regional exposure risk (RER) in China was at a high level, with a national average of 0.75, while the average of 14 urban agglomerations was as high as 0.86. Among the 14 urban agglomerations, the average annual RER was the highest in the Shandong Peninsula (0.99) and lowest in the Northern Tianshan Mountains (0.76). The RER in China has obvious seasonality; the most serious was in winter, and the least serious was in summer. The population exposure risk (PER) east of the Hu Line was significantly higher than that west of the Hu Line. The average PER was the highest in Beijing-Tianjin-Hebei (4.09) and lowest in the Northern Tianshan Mountains (0.71). The analysis of air pollution patterns and exposure risks in China and urban agglomerations in this study could provide scientific guidance for cities seeking to alleviate air pollution and prevent residents’ exposure risks.

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“…To reduce severe air pollution, the local government has made enormous efforts to reduce PM 2.5 concentrations since 2013. Through strict control measures, the annual average PM 2.5 concentrations in Guangzhou decreased continuously from 52 μg/m 3 in 2013 to 23 μg/m 3 in 2020 (Wen et al., 2022). At the same time, O 3 concentration displayed an increasing trend and appeared as the dominant pollutant in Guangzhou (Gong et al., 2022; Wang, Guo, et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of Ozone Formation Sensitivities in Different Height Layers via MAX‐DOAS Observations in Guangzhou

et al. 2022

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Diagnosing the vertical distributions of ozone formation sensitivities within the boundary layers is the prerequisite for formulating proper ozone control strategies. From 1 January 2020, to 20 August 2021, a multi‐function MAX‐DOAS instrument was set up in Guangzhou to detect the NO2 and HCHO vertical profiles. The ozone formation sensitivities in different height layers were diagnosed using the FNRsec, which was defined as the ratio of secondary HCHO to NO2 VMRs (HCHOsec/NO2). The secondary sources in ambient HCHO participate in the photochemical reactions directly, and the FNRsec can indicate the ozone formation sensitivities more accurately. Therefore, the secondary source was separated from ambient HCHO via a multi‐linear regression method, and its relative contribution was approximately 66.9 ± 6.3%. The sensitivity thresholds of ozone formation were determined by the slope of the linear regression analysis for O3 versus the normalized secondary HCHO or NO2 mixing ratios for different FNRsec ranges, which were 0.22 and 0.36. For the ground layer, the VOC‐limited, transitional, and NOx‐limited regimes accounted for 40.66%, 32.42%, and 26.92%, respectively. Diurnally, the ground layer was usually in the VOC‐limited regime in morning, but in the transitional regime in noon and afternoon. Vertically, the ozone formation sensitivity changed with altitude from VOC‐limited (0.02–0.22 km) to transitional (0.22–0.42 km) to NOx‐limited (0.42–2.02 km). These findings can help formulate proper ozone control strategies in time according to the varying local conditions.

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Investigation of PM2.5 pollution during COVID-19 pandemic in Guangzhou, China

Cited by 26 publications

References 36 publications

Effects of the COVID-19 pandemic on public bus occupancy and real-world tailpipe emissions of gaseous pollutants per passenger kilometer traveled

Effects of the COVID-19 pandemic on public bus occupancy and real-world tailpipe emissions of gaseous pollutants per passenger kilometer traveled

Spatiotemporal Distribution Patterns and Exposure Risks of PM2.5 Pollution in China

Diagnosis of Ozone Formation Sensitivities in Different Height Layers via MAX‐DOAS Observations in Guangzhou

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