Status Study On AQI And PCDD/Fs In Atmosphere For Wuhu And Bengbu Cities

In recent years,regional air pollution incidents occur frequently in China,the air pollution is a compound situation and its treatment become more difficult.It is a puzzle in how to effectively improve the atmospheric environment.To make effective air pollution controlling measures basing on local atmospheric conditions,our study mainly focused on the status of air quality and atmospheric PCDD/Fs in Wuhu and Bengbu,which can provide basic theory for administration of regional air pollution.Among the six major pollutants,the concentration of PM_2.5,PM₁₀,SO₂ and CO decreased by 14.7%,19.8%,37.1%and 0%in Wuhu,and 17.1%,6.0%,38.5%and 30%in Bengbu.Otherwise,the concentration of NO₂ and O₃ rose by 9.9%,116.3%in Wuhu,and 7.9%,27.6%in bengbu.The concentration of CO in both cities and NO₂ in Bengbu can reach the national primary standards,the concentration of SO₂,O₃ in both cities and NO₂ in Wuhu were between the primary and secondary standards,and the concentration of PM_2.5 and PM₁₀ in both cities were all exceeded the secondary standard.It is worth noting that the days of O₃ concentration exceeding the primary and secondary standard in a year increased rapidly.To the seasonal distribution,the levels of PM_2.5,PM₁₀ and CO reached maximum in winter,and minimum in summer,while spring and autumn were medium.SO₂ concentration was slightly higher in winter,and there was no significant cyclical change in other seasons.The values of NO₂ in autumn and winter were higher than that in spring and summer.according to the concentration of O₃,it can be divided into three modes:?1?distributed evenly throughout four seasons,?2?reached maximum in autumn and minimum in winter,while spring and summer were medium.?3?the levels were higher in spring and summer,followed by autumn,and that in winter was low.The air quality in the two cities followed by:summer>fall>spring>winter.Overall,the air quality was excellent and good in spring,but that proportion reduced greatly in summer.The deterioration of air quality in spring and summer were mainly caused by O₃ pollution,and the heavy air pollution situation in Bengbu was caused by PM₁₀.In autumn,air quality was stably dominanted by excellent or good status,the most common primary pollutant changed from PM_2.5 to O₃.In Wuhu,excellent or good air quality was stable and the situation of pollution has improved in winter,PM_2.5 and NO₂were the primary pollutants.While the change of air quality in Bengbu was complex but generally steady in winter,and the primary pollutants were PM_2.5 and PM₁₀.The increasing O₃ pollution impact different air quality levels followed by:good>Mild pollution>Moderately polluted,and almost not present effect on severe and serious pollution situation.The total PCDD/Fs-WHO₂₀₀₅-TEQ content and PM_2.5-bound total PCDD/Fs-WHO₂₀₀₅-TEQ was significantly lower in summer than in other seasons.The fractions of gas phase total PCDD/Fs-WHO₂₀₀₅-TEQ concentration followed by:summer>fall>spring>winter,which was higher than particle phase in summer,but lower in other three seasons.And gas phase fraction of low molecular homologues was higher than polymer homologues in the same season.The sensitivity of PM_2.5-bound total PCDD/Fs-WHO₂₀₀₅-TEQ in Wuhu followed by:PCDD/Fs concentration>PM₁₀concentration>temperature>PM_2.5 concentration.The two cities have similar dry and wet deposition levels with Nanjing,and the dry deposition was lower than northen area,Harbin and Shijiazhuang,but higher than southern area,Guangzhou and Taiwan.Which were all low in winter and high in summer.While the wet deposition was higher than northen area and lower than southern area,which was high levels in summer and low in winter in Wuhu,but the values were higher in spring and summer than that in autumn and winter in Bengbu.The total deposition of these two citis were similar with Nanjing and Harbin,that in Shijiazhuang was lower and Guangzhou was higher.The seasonal distribution was similar with dry deposition.The sensitivity of total-PCDD/Fs-WHO₂₀₀₅-TEQ scavenging ratio in Wuhu followed by:PCDD/Fs concentration and PM₁₀ concentration>PM_2.5 concentration>temperature,the sensitivity wet deposition of that followed by:temperature>PCDD/Fs concentration>PM₁₀ and PM_2.5concentration>rainfall.