Chemical Compositions,Pollution Characteristics And Source Analysis Of PM_2.5 During The Winter In Liaocheng City

To investigate the chemical compositions and pollution characteristics of aerosols in Liaocheng City during winter,PM_2.5.5 samples were performed from 17 January to 15February 2017 at Liaocheng University.In this paper,characteristics and sources of each component under different atmospheric pollution conditions were discussed by analyzed 8kinds of water-soluble inorganic ions and 70 kinds of organic compounds and clarified the health effects on children and adults in terms of inhalation.The results showed that:（1）Liaocheng city achieved certain results in the battle against air pollution in 2017,the mass concentration of PM_2.5.5 in winter decreased by 27%compared with the same period last year.PM_2.5.5 pollution was the most serious in haze days follow by the Lantern Festival（fireworksⅡ）during the sampling period,which was mainly due to industrial emissions,adverse meteorological conditions and firework buring,respectively.（2）The concentration of water-soluble inorganic ions during winter was 68.6±37.4μg?m^-3,which contributed 48%of measured PM_2.5.The secondary ion components(NO₃^-,SO₄^2-and NH₄⁺)were the dominated species,accounting for 76%of the total water-soluble inorganic ions.PM_2.5.5 was weakly acidic with the equation of anion and cation balance was y=1.12x-0.10,and the calculation result of thermodynamic model（ISORROPIA-Ⅱ）was pH_is=5.9±0.9.NH₄⁺in PM_2.5.5 mostly existed in the forms of（NH₄）₂SO₄ and NH₄NO₃ during clean and haze days,while existed in the forms of NH₄HSO₄ and NH₄NO₃ during fireworks events.The results of diagnostics ratios and PCA suggested that water-soluble inorganic ions were mainly sourced from human activities,such as coal burning,vehicle emissions,biomass burning and secondary oxidation.（3）The average concentration of organic compounds was 3601.2±2261.1ng?m^-3,which contributed 2.68%of measured PM_2.5.Fatty acids were the dominated species,followed by n-alkanes,saccharides and aromatic acids,PAHs were relatively low.n-Alkanes were mainly derived from the coal burning and fossil fuels such as and petroleum,the CPI and%Wax C_n were 1.2 and 12.2%,respectively.PAHs mainly originated from coal combustion and vehicle exhaust,and dominated by 4-ring and 5-ring congeners in winter.Levoglucosan was the dominant saccharide,indicating that biomass combustion has important influence on atmosphere in winter.Fatty acids were organic acids with the highest mass concentration,and secondary pollution in winter was more serious with the value of C_18:0/C_18:1.The results of diagnostics ratios and PCA suggested that organic compounds were mainly originated from coal burning,biomass burning and vehicle emissions.（4）The TEQ in Liaocheng during wniter was 6.37ng?m^-3,the ILCR of children and adults were 2.19×10^-66 and 1.07×10^-5,indicating potential risk of PAHs exposure for residents in Liaocheng city,that means the estimated lifetime cancer risk for PAHs reached0.24 and 1.16 per 100,000 exposed children and adults,respectively.Due to the relatively high toxic equivalent concentration and increased risk of cancer during haze days,residents should reduce their exposure to pollutants.The above results systematically clarify the chemical components,characteristics,sources and health effects of PM_2.5.5 in Liaocheng City,which has filled in the blanks of research on organic aerosols and health effects,in order to provide basic data and scientific basis for further atmospheric pollution causes and treatment work in Liaocheng City.