Characteristics Of Air Pollution And The Influence Of Mutual Transport In Jing-Jin-Ji Region

PM_2.5?particulate matter with a diameter less than 2.5?m?pollution is still severe in Jing-Jin-Ji region of China where PM_2.5 concentration is significantly higher than the new ambient air quality standard?GB3095-2012?of annual secondary standard limit,and PM_2.5 shows a strong regional and complex pollution characteristic,and regional transport of atmospheric pollutant always occurred.Using theautomatic monitoring data of urban station,comprehensiveobservation site and vertical observation data from captive balloon,Empirical Orthogonal Function?EOF?,Principal Component Analysis?PCA?and transmission flux accounting methods were applied.The spatial and temporal distribution characteristics of air pollutants,and the main sources of PM_2.5.5 in Jing-Jin-Ji regionwere studied.Using balloon observation data,the verticaldistributioncharacteristics of pollutant in different seasons and different weathers were analyzed,and transport flux of pollutants in the region were calculated,the results were obtained as follows.The Jing-Jin-Ji region was divided into seven districts,such as the first district including Xingtai,Shijiazhuang and Baoding,the second district including Beijing,the third district including Tianjin and Tangshan,the fourth district including Cangzhou,the fifth district including Langfang,the sixth district cluding Handan,and the seventh district including Qinhuangdao,Chengde and Zhangjiakou.The ozone characteristics are more regional and PM_2.5 and ozone should be cooperatively controlled.The major chemical constituents include OC,NO₃^-,SO₄^2-,NH₄⁺,EC,Cl^-,Si,Fe and Al.The component with highest content was SO₄^2-in summer,NO₃^-in spring and autumn,and OC in winter.The component NO₃^-was high in Beijing and Tianjin,OC was high in Baoding in winter,EC was high in Shijiazhuang in winter,and Si was high in Cangzhou in spring.The sources of PM_2.5 were analyzed by the PCA model.The major sources of PM_2.5 in Beijing-Tianjin-Hebei region included industrial emissions,mobiles sources,secondary inorganic particles,crustal materials and heavy diesels.The vertical distribution characteristics of air pollutants showed that the concentrations of all pollutants except ozone usually decreased with the increasing height.When the air quality reached the standard or meet the light pollution level,the ozone concentration increased with the increasing heightunder the low heights?under300m and 600m?,whereas decreased in the higher heights?between 600m and1000m?.When the air quality met the middle level pollution,the ozone concentrations increased with the increasing height.Below the mixing height PM concentration always increased with the increasing height,and above the mixing height PM concentration always decreased with the increasing height.During the heavy pollution episodes,the mixed layer was low with only 200 meters.The particulate matter concentrations showed unchangeable high levels under the mixing height.During the captive balloon observation the highest transmitted flux occurred in the southwest accounting for 51.5%of total flux and at the height of 156m.Under the height of 300 meters the flux account for 70%of total vertical flux.During the typical heavy pollution episodes,the most PM_2.5 transmitted flux came from the southwest and at the height of 156m.Under the height of 200m the dominated transport direction were southwest,and at the height of 296m,466m,676m and 926m the dominant directions were the northeast,southeast,northeast and southwest,respectively.This study has been applied by the environmentqal protection departments in Beijing-Tianjin-Hebei region,to provide support in various areas such as ambient air pollution protection,regional air quality foreast,heavy pollution warning,and the air quality guarantee of major event.