新冠疫情期间四川盆地空气质量及影响因素分析

Analysis of Air Quality and Influencing Factors in Sichuan Basin During the COVID-19 Outbreak

基于污染源排放调查、空气质量和组分站观测数据,利用WRF/SMOKE/CMAQ模式系统,分析2020年新冠疫情期间污染源和气象条件变化对空气质量的影响.结果表明:①2020年新冠疫情期间,四川盆地除ρ(O_(3))同比上升外,ρ(SO_(2))、ρ(NO_(2))、ρ(CO)、ρ(M_(2.5))和ρ(M_(10))均同比下降,下降幅度为8%~41%.②疫情期间成都市M_(2.5)组分与2019年同期相比,ρ(Cl^(-))、ρ(K^(+))、ρ(Si)、ρ(Al)、ρ(Ca)和ρ(EC)的占比均同比下降,说明疫情期间施工工地、机动车、工业燃煤和生物质燃烧排放减少是ρ(M_(2.5))下降的主要原因.③疫情期间,工业源SO_(2)、NO_(x)、M_(10)、M_(2.5)和VOCs排放量分别同比下降32%、31%、40%、39%和41%;成都市机动车车流量仅为正常时段的40.3%,车速提升19.7%,NO_(x)、VOCs和CO日排放量降幅分别为44.7%、49.6%和38.0%,污染物的非等比例下降使得机动车排放贡献的大气氧化性进一步增强.④2020年疫情期间四川盆地气象条件同比不利,使得ρ(M_(2.5))、ρ(NO_(2))、ρ(SO_(2))、ρ(O_(3))和ρ(M_(10))分别上升2%、4%、23%、6%和8%,扣除气象条件变化影响后,ρ(M_(2.5))、ρ(NO_(2))、ρ(SO_(2))和ρ(M_(10))分别下降21%、45%、31%和30%,ρ(O_(3))上升12%.

Based on the pollution emission survey and the observation data of air quality and component stations,the WRF/SMOKE/CMAQ model system was adopted to analyze the impact of pollution sources and changes in meteorological conditions on air quality during the COVID-19 outbreak.The results showed that during the COVID-19 outbreak in 2020,in addition to the year-on-year increase inρ(O_(3))in the Sichuan Basin,ρ(SO_(2)),ρ(NO_(2)),ρ(CO),ρ(PM_(2.5)),andρ(PM_(10))all decreased year-on-year,with decreases ranging from 8%to 41%.Compared with levels from the same period in 2019,ρ(Cl^(-)),ρ(K^(+)),ρ(Si),ρ(Al),ρ(Ca),andρ(EC)in Chengdu decreased year-on-year,indicating that the emission reduction of construction sites,motor vehicles,industrial coal burned,and biomass combustion were the main reasons for the decrease in PM_(2.5) concentration.During the COVID-19 outbreak,the SO_(2),NO_(x),PM_(10),PM_(2.5),and VOCs industrial emissions decreased by 32%,31%,40%,39%,and 41%,respectively.The traffic volume of motor vehicles in Chengdu was only 40.3%of that during the normal period,and the speed of traffic increased by 19.7%.The daily emissions of NO_(x),VOCs,and CO were reduced by 44.7%,49.6%,and 38.0%,respectively.The non-equal decrease in pollutants made the atmospheric oxidability contributed by motor vehicle emissions relatively further enhanced.The unfavorable weather conditions in the Sichuan Basin causedρ(PM_(2.5)),ρ(NO_(2)),ρ(SO_(2)),ρ(O_(3)),andρ(PM_(10))to rise by 2%,4%,23%,6%,and 8%,respectively.After deducting the influence of changes in weather conditions,the concentrations ofρ(PM_(2.5)),ρ(NO_(2)),ρ(SO_(2)),and PM_(10) decreased by 21%,45%,31%,and 30%,respectively,andρ(O_(3))increased by 12%.