Investigation of PM2.5 Pollution During COVID-19 Pandemic in Guangzhou,China

The COVID-19 pandemic has raised awareness about various environmental issues,includ-ing PM2.5 pollution.Here,PM2.5 pollution during the COVID-19 lockdown was traced and an-alyzed to clarify the sources and factors influencing PM2.5 in Guangzhou,with an emphasis on heavy pollution.The lockdown led to large reductions in industrial and traffic emissions,which significantly reduced PM2.5 concentrations in Guangzhou.Interestingly,the trend of PM2.5 concentrations was not consistent with traffic and industrial emissions,as minimum concentrations were observed in the fourth period(3/01-3/31,22.45 μg/m3)of the lockdown.However,the concentrations of other gaseous pollutants,e.g.,SO2,NO2 and CO,were corre-lated with industrial and traffic emissions,and the lowest values were noticed in the sec-ond period(1/24-2/03)of the lockdown.Meteorological correlation analysis revealed that the decreased PM2.5 concentrations during COVID-19 can be mainly attributed to decreased in-dustrial and traffic emissions rather than meteorological conditions.When meteorological factors were included in the PM2.5 composition and backward trajectory analyses,we found that long-distance transportation and secondary pollution offset the reduction of primary emissions in the second and third stages of the pandemic.Notably,industrial PM2.5 emis-sions from western,southern and southeastern Guangzhou play an important role in the formation of heavy pollution events.Our results not only verify the importance of control-ling traffic and industrial emissions,but also provide targets for further improvements in PM2.5 pollution.