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Sci Total Environ

Title:		"Decrease in ambient volatile organic compounds during the COVID-19 lockdown period in the Pearl River Delta region, south China"
Author(s):		Pei C; Yang W; Zhang Y; Song W; Xiao S; Wang J; Zhang J; Zhang T; Chen D; Wang Y; Chen Y; Wang X;
Address:		"State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangzhou Sub-branch of Guangdong Ecological and Environmental Monitoring Center, Guangzhou 510060, China; University of Chinese Academy of Sciences, Beijing 100049, China. State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong Provincial Academy of Environmental Sciences, Guangzhou 510045, China. State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China. State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China. State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China. State Environmental Protection Key Laboratory of Regional Air Quality Monitoring, Guangdong Ecological and Environmental Monitoring Center, Guangzhou 510308, China. Guangzhou Sub-branch of Guangdong Ecological and Environmental Monitoring Center, Guangzhou 510060, China. State Key Laboratory of Organic Geochemistry, Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: wangxm@gig.ac.cn"
Journal Title:		Sci Total Environ
Year:		2022
Volume:		20220208
Issue:
Page Number:		153720 -
DOI:		10.1016/j.scitotenv.2022.153720
ISSN/ISBN:		1879-1026 (Electronic) 0048-9697 (Print) 0048-9697 (Linking)
Abstract:		"During the COVID-19 lockdown, ambient ozone levels are widely reported to show much smaller decreases or even dramatical increases under substantially reduced precursor NOx levels, yet changes in ambient precursor volatile organic compounds (VOCs) have been scarcely reported during the COVID-19 lockdown, which is an opportunity to examine the impacts of dramatically changing anthropogenic emissions on ambient VOC levels in megacities where ozone formation is largely VOC-limited. In this study, ambient VOCs were monitored online at an urban site in Guangzhou in the Pearl River Delta region before, during, and after the COVID-19 lockdown. The average total mixing ratios of VOCs became 19.1% lower during the lockdown than before, and those of alkanes, alkenes and aromatics decreased by 19.0%, 24.8% and 38.2%, respectively. The levels of light alkanes (C < 6) decreased by only 13.0%, while those of higher alkanes (C >/= 6) decreased by 67.8% during the lockdown. Disappeared peak VOC levels in morning rush hours and the drop in toluene to benzene ratios during the lockdown suggested significant reductions in vehicle exhaust and industrial solvent emissions. Source apportioning by positive matrix factorization model revealed that reductions in industrial emissions, diesel exhaust (on-road diesel vehicles and off-road diesel engines) and gasoline-related emissions could account for 48.9%, 42.2% and 8.8%, respectively, of the decreased VOC levels during the lockdown. Moreover, the reduction in industrial emissions could explain 56.0% and 70.0% of the reductions in ambient levels of reactive alkenes and aromatics, respectively. An average increase in O(3)-1 h by 17% and a decrease in the daily maximum 8-h average ozone by 11% under an average decrease in NOx by 57.0% and a decrease in VOCs by 19.1% during the lockdown demonstrated that controlling emissions of precursors VOCs and NOx to prevent ambient O(3) pollution in megacities such as Guangzhou remains a highly challenging task"
Keywords:		*Air Pollutants/analysis *COVID-19/epidemiology China Communicable Disease Control Environmental Monitoring Humans *Ozone/analysis Vehicle Emissions/analysis *Volatile Organic Compounds/analysis Covid-19 NOx Ozone Prd Volatile organic compounds;
Notes:		"MedlinePei, Chenglei Yang, Weiqiang Zhang, Yanli Song, Wei Xiao, Shaoxuan Wang, Jun Zhang, Jinpu Zhang, Tao Chen, Duohong Wang, Yujun Chen, Yanning Wang, Xinming eng Netherlands 2022/02/13 Sci Total Environ. 2022 Jun 1; 823:153720. doi: 10.1016/j.scitotenv.2022.153720. Epub 2022 Feb 8"