Impact of coordinated emission controls on concentrations and sources of PM2.5 in Beijing during “9·3”military parade :a numerical model

Nested Air Quality Prediction Modeling System  (NAQPMS) was used to simulate temporal and
 spatial variations in the mainmeteorological parameters and PM2.5 in Beijing and surrounding areas during the
parade. Anon-line tracer tagging  module was applied to calculate contributions of emission from  different
 source areas to PM2.5 concentration in the Beijing area under two scenarios: baseline and emission-control
 scenarios. The Modeling was found to generally reproduce the  main variation characteristics of PM2.5  in
 Beijing. Pollutant control measures were found to reduce PM2.5 concentration in Beijing effectively, with a>
31%reduction rate on September 3, 2015. Since pollutants tended to accumulate, the reduction of PM2.5 could
 have been higher when with convergence in wind field or with large emission of primary PM2.5. During the
 parade, local emissions were the most important source of PM2.5 inurban Beijing,maximum  daily average
 contribution to PM2.5 concentration was up to 48.6%. South east Hebei,central Hebeiand Henan Province
were majorex ternal sourcea reas, with maximum daily average contributions to PM2.5 concentration of 21.1%,
17.6%, 16.4% respectively. Contribution to PM2.5 in Beijing from the areas taking stronger emission control
 measure ments decreased more significantly, with decrease peak down to 2.2% in Beijing area.