Study On The Characteristic And Grading Standard Of Photochemical Smog In Shanghai

In this study, based on the observation data from nine different function areas in Shanghai,the feature of ozone and the changes of aerosol and meteorological condition are analyzed duringthe ozone exceeding period. The parameters most relevant with the photochemical smog areselected to make the photochemical smog grading standard table of Shanghai area, which isverified with the data from other sites in Shanghai. The main conclusions are as follows:(1) The photochemical pollution is serious in summer (especially from May to August)around Shanghai. The pollution occurrence in the surrounding urban is more frequent than in thecentral area and the pollution in different functional areas are quite different. During theoccurrence of photochemical pollution, the aerosol mass (PM10, PM1, PM2.5, turbidity)concentration shows a significant increase especially PM1, which causes the proportion of PM1inPM2.5further rises. According to the analyzing results of aerosol particle spectrum, the increaseof number concentration of particle whose size is lower than0.5μm is about40%during the ozoneexceeding period, so PM1is one of the obvious productions of photochemical pollution. Ozonepollution plays a certain role in the generation of secondary aerosols which is relevant with PM1closely. Ozone could be the important reference index for judging the severity of photochemicalsmog in photochemical smog grading standards.(2) In the event of photochemical pollution, the meteorological parameters excpetatmospheric pressure show significant regular correlation with the ozone concentration. Duringthe ozone exceeding period the visibility decreases about10-30%, the temperature in each site isover30℃and the humidity is30%lower. However, Neither temperature nor humidity shows lowcorrelation with photochemical smog, the wind speed changes before and after ozone exceedingbut just like the wind direction is obviously different in each site. So visibility could be used as astandard parameter in photochemical smog grading standards.(3) According to the relevance to photochemical smog, ozone, PM1, visibility are choosed asmajor parameters of photochemical smog grading standard. Refering Ambient air qualitystandards, Air quality guidelines published by the WHO, Technical Regulation onAmbientAir Quality Index (on trial), Observation and forecasting levels of haze, Visibility grade and forecast, the US standard ofAQI, etc, classification is discussed. Due to there is no relevant limitof PM1in the current domestic and foreign standards, so PM1/PM2.5equal85%that is selected toconversion by studying.(4) In terms of discution of the Technical Regulation on Ambient Air Quality Index (ontrial) and Air quality guidelines published by the WHO, the preliminary table of photochemicalsmog grading standard that suits to the whole areas in Shanghai is draught. In this table the ozoneparameter is separated into160-200μg/m3,200-300μg/m3,300-400μg/m3and>400μg/m3four concentration ranges. Visibility is divided into5-10km、3-5km�'�<3km three distanceintervals. PM1is divided into30-45μg/m3、45-65μg/m3�'�>65μg/m3three concentrationranges. In accordance with the severity, pollution is divided into four levels, corresponding toblue, yellow, orange and red.(5) Using the data comes from Pudong station, Dongtan station, and Jinshan station i, the thephotochemical smog grading standard table is vertified. Jinshan photochemical smog pollution ismost serious, level two appears5.5days per year; The condition of Pudong station photochemicalsmog pollution is similar to Jinshan in2007-2010, but in2011-2013has improved markedly, leveltwo and level two appear0.7day and0.3day. The condition of Dongtan station air quality is bestand does not appear three and four levels of pollution in five consecutive years.(6) Photochemical reaction is not necessary and sufficient condition to photochemical smogpollution, not only the ozone should be considered parameter,but also the analysis to the conditionchanges of visibility and aerosol are needed. Through the analyzing and researching, thepreliminary table of photochemical smog grading standard that suits to the whole areas inShanghai is draught.