Study On The Characteristics Of PM_2.5 Pollution During Heating Season In Harbin

Atmospheric fine particulate matter(PM_2.5)is the concentrated embodiment of regional haze pollution in China at the present stage,and its chemical composition and environmental impact are very complex.It has always been an international frontier and a hot issue in the field of atmospheric environment research.Harbin,as a representative city in the cold region of northeast China,has a large emission of air pollutants,a complex emission system and special climatic conditions.It is not only different from the relatively traditional key areas of air pollution prevention and control,such as the Beijing-Tianjin-Hebei region,but also different from European and American cities in similar or higher latitude.Therefore,its atmospheric environment is unique in the world.Based on the emission characteristics and climate characteristics of typical cities in the cold region of northeast China,this study carried out long-term continuous field observation of PM_2.5 covering the whole heating season in the urban area of Harbin.Based on chemical species analysis,it was found that the daily variation characteristics of PM_2.5 were basically consistent with levoglucosan,indicating that biomass combustion was an important source of PM_2.5 in the heating season of Harbin.The maximum daily concentration of levoglucosan reached 14.56 ?g/m3,which was much higher than the observed results in north China and east China,indicating that the biomass combustion pollution was still very serious in Harbin and its surrounding areas.Carbonaceous substances,including organic aerosol OM and elemental carbon EC,contribute up to about 65% of PM_2.5,and are the most important chemical components of PM_2.5.Due to the interference of the primary emission from biomass combustion,it is difficult to accurately estimate the secondary organic aerosol by OM/EC ratio.In the heating season of Harbin,the water-soluble inorganic ions are mainly sulfate,nitrate,ammonium salt and chloride ions.With the increase of PM_2.5 concentration,the proportion of secondary inorganic ions in PM_2.5 decreased.This is contrary to most observations in winter in the Beijing-Tianjin-Hebei region.The results of this study indicate that the chemical composition and variation of PM_2.5 are special in cities in the cold northeast China.