The Response of Atmospheric Pollutants to COVID-19 Lockdown in Guangzhou

In order to evaluate the effect of air pollution emission reduction in Guangzhou,the temporal and spatial variation characteristics of air pollutants before and after the COVID-19 lockdown period were analyzed combined with meteorological elements and travel intensity.Compared with the same period of 2017 to 2019,the meteorological conditions of the lockdown period （January 24 to February 9） showed no significant difference in atmospheric horizontal diffusion conditions,better wet removal conditions and worse ozone generation meteorological conditions.The concentrations of NO₂,PM₁₀,PM_2.5,SO₂ and CO reached the lowest value,and the concentration of O₃ was at the second lowest value since 2017 for the same period.Under similar meteorological conditions,the concentrations of six air pollutants during the lockdown period were all lower than those before the lockdown period and during the resumption period.Among them,NO₂,PM₁₀ and PM_2.5 were more sensitive to the epidemic control,while SO₂ and CO were relatively weak.Due to the combined action of meteorological conditions and gaseous precursors,the change of O₃ concentration before and after shutdown appeared to be more complicated,and showed lower range of change.The response of air pollutants to epidemic control varied in different regions.The response of air pollutants to epidemic in urban areas control was greater than that in suburban areas,while in industrial parks with concentrated air pollution emissions,the response became more sensitive than that in both urban and suburban areas.NO₂ and PM₁₀ were more sensitive to strict control measures,the correlation coefficients between their concentrations and travel intensity/wind speed were 0.87 and 0.74,respectively,showing a strong positive correlation.