Characteristics of atmospheric PM2.5, NOx, SO2 and O3 in Beibei district,Chongqing
Chongqing is an industrial powerhouse in Southwestern China with significant air pollution.In this paper,automatic on-line continuous monitoring equipments are used to acquire the ambient concentrations of PM2.5,NOx,SO2 and O3 from Jan.2012 to Feb.2014 in Beibei district of Chongqing.The results indicated that PM2.5 was the most serious pollutant,with the annual mean values of (67.5t31.9) and (66.6t37.5) μg·m-3 in 2012 and 2013,respectively,1.9 times the National Ambient Air Quality standard (35 μg·m-3).In 2012 and 2013,there were 119 and 126 days with PM2.5 concentrations exceeding the corresponding values of the new National Ambient Air Quality Standards,respectively.Annual mean value of NOx,SO2,O3was (57.1t24.6) and (55.1±36.6),(43.1±24.0) and (35.0±21.9),(31.1±24.9) and (48.5±37.4) μg·m-3 in 2012 and 2013,respectively.The atmospheric pollutants concentration has obvious seasonal variation characteristics.PM2.5 and NOx pollution was the most severe in winter,with winter averages value 33.6％ and 59.6％ higher than annual average in 2012 and 43.2％ and 8.5％ higher than 2013.The concentration of O3 was the highest in summer and lowest in winter,while SO2 was the highest in spring.NOx and PM2.5 showed bimodal distribution in the morning and evening in their diurnal variation,corresponding to urban traffic peak hour emissions.In comparison,daily variation of SO2 and O3 concentration show unimodal type distribution.SO2 peak appeared at 10:00-12:00 when the boundary layer expanded,while O3 peak appeared at 16:00 when local photochemical reaction is the most significant.Simultaneous reduction on direct emission of particulate matter,industrial emissions of NOx and SO2,and vehicle emissions of NOx and VOCs may gradually reduce the serious air pollution of Chongqing district.
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