Characteristics And Sources Of PM_2.5Components In The Eastern Part Of North China Plain

In order to study the composition characteristics and source apportionment of PM2.5 in eastern part of North China Plain,manual samples during the two-year heating period of 2016 and 2017 were collected in seven cities,including Hengshui,Cangzhou,Jinnan,Dezhou,Binzhou,Zibo and Liaocheng.The results showed that the average values of p(PM2.5)during the observation periods were 137.23 μg·m-3 and 111.83 μg·m-3,respectively,which exceeded the daily average secondary standard limit of GB 3095-2012 "Environmental Air Quality Standard" 1.8 and 1.5 times.The mean mass of water-soluble ions accounted for 53.32%and 47.04%of ρ(PM2.5)respectively,of which SNA(NO3-,SO42-and NH4-)were the main ions.During the 2016 and 2017 observation periods,NO3-/SO42-increased from 1.35 to 1.60,while the concentration of Cl-decreased,indicating a decrease in the impact of coal burning.Compared with the 2016 heating period,the secondary conversion of inorganic ions in the 2017 heating season slightly reduced.The proportions of secondary organic carbon(SOC)in organic carbon(OC)were 71.63%and 55.35%,respectively,indicating the source of secondary organic carbon had decreased.Analysis of characteristic elements Fe/Al and B a/Ni showed that dust sources and vehicle sources had increased significantly.The backward trajectories of air mass analysis showed that during the two-year observation period,the contaminated air mass in the region mainly originated from the northwest,but the contaminated air mass from the local and surrounding provinces and cities has a large impact.A stable weather would promote the accumulation of particulate matter.During the heating seasons,the main contribution sources of the central and eastern regions of Beijing,Tianjin,and Hebei are the same,including coal combustion sources,secondary sources,biomass sources,motor vehicle sources,and dust sources.Among them,coal combustion sources and secondary sources account for the largest contribution rate,and other sources contribute relatively less.