Analysis of a Typical Heavy Air Pollution Process and Causes in Winter in Dingzhou City
Taking the heavily air pollution in Dingzhou City Hebei Province from December 6 to 17,2019 as an example,the weather situation,pollution characteristics,pollution causes,transportation paths,and potential source areas of this heavily polluted weather process were analyzed using a combination of characteristic radar charts,HYSPLIT-4 backward trajectory model,numerical simulation,and observation data statistics.The results indicate that:① In this air pollution process,static stability,high humidity,inversion,and lower boundary layer are external factors,and local accumulation and regional transmission lead to increased pollution.With the in-crease of humidity,PM2.5/PM10 aggregates towards the range of 50％～100％,indicating that the increase of hu-midity has a significant impact on the acceleration of the secondary conversion rate of particulate matter;The pol-lution characteristics of Dingzhou City are characterized by a relatively large proportion of comprehensive,sec-ondary,and coal-fired types(31％,28％,and 16％respectively).During high pollution periods,secondary trans-formation is mainly affected.Under unfavorable meteorological conditions,gaseous pollutants transform into par-ticulate matter,and the increase in particle moisture absorption significantly increases PM2.5 concentration,which is locally affected by coal-fired sources.The heavy pollution process this time is mainly affected by local pollu-tion sources(accounting for 30％to 58％)emissions,followed by significant contributions from surrounding are-as such as Baoding City(17％to 34％)and Shijiazhuang City(8％to 27％).The contribution from long-distance transportation such as Shandong,Shanxi,and Henan is relatively small.Among local emission sources,township pollution is prominent.(2)Dingzhou City launched an emergency orange warning for heavy pollution from De-cember 6 to 17,2019.The reduction in pollutants was not significant,with a reduction of about 11.37 μg/m3 and a reduction ratio of 12％.The air quality increased from 4 days before the control to 5 days after the control in Hebei.In addition to the contributions of the local and Hebei provinces,about 10％of Dingzhou City comes from Shandong,Henan,and Shanxi.Therefore,although the early warning measures only target the entire Hebei Prov-ince with certain emission reduction effects,they still cannot achieve the desired effect,especially for transporta-tion in distant regions.To avoid serious air pollution under poor atmospheric diffusion conditions,cooperation be-tween regions is particularly important.
heavy air pollution processpollution characteristicspollution causestransport paths and potential source areas
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