Regional Characteristics And Source Apportionment Of Ambient Carbonyl Compounds In Taiyuan Based On The Observation Results Of Years

Carbonyl compounds are critical components of volatile organic compounds（VOCs）,that play an important role in atmospheric chemistry.In addition,carbonyl compounds are also important precursors of ozone（O₃）,secondary organic aerosol（SOA）,peroxyacetyl nitrate（PAN）and various oxidative radicals,and they have significant influence on environment and human health.In recent years,with the increase of atmospheric O₃,the ozone pollution has attracted extensive attention.Taiyuan suffered from heavy ozone pollution in summer,but the investigation of carbonyls level and their contribution to O₃.13 ambient carbonyl species in the downtown of Taiyuan were detected with the 2,4-dinitrophenylhydrazine（DNPH）/high-performance liquid chromatography-ultraviolet（HPLC-UV）method from 2018 to 2020.The pollution levels,components characteristics,seasonal distribution of carbonyl compounds were analyzed.The sources of carbonyl compounds were identified based on the diagnose ratios analysis,correlation analysis and principal component analysis（PCA）.Multiple linear regression was used to identify formaldehyde sources.And using the propylene-equivalent（Prop-Equiv）,the OH radical loss rate(L_OH)and increment reactivity（MIR）method to calculate the reactivity and ozone formation potential（OFP）.At last,the integrated lifetime cancer risk（ILTCR）and non-cancer risk（HQ）of formaldehyde and acetaldehyde were estimated.The main conclusions were as followed:（1）The average concentrations of total carbonyl compounds in Taiyuan was16.01±6.51 ppbv from 2018 to 2020.Formaldehyde contributed half of thetotal carbonyls,followed by and acetone（27.12%）and acetaldehyde（15.05%）,they accounted for 87.50%of the total carbonyl compounds.Thetotal carbonyl compounds showed the highest concentration in summer,andlower in winter,and the levels of carbonyl compounds were 2-3 times ofthat in winter.（2）The ranges of formaldehyde/acetaldehyde（C₁/C₂）andacetaldehyde/propionaldehyde（C₂/C₃）were 0.59-8.33 and 4.51-27.16,respectively,with average ratios of 3.14±1.31and 11.23±4.32,respectively.The ratios of C₁/C₂ and C₂/C₃ showed high values in summer and autumn,and low values in spring and winter,indicating that the photochemicalreactions contributed positively to carbonyls formation,and the primaryemissions were important sources of carbonyls in winter.（3）The results of correlation analysis and PCA showed that the photochemicalreaction was the major contributor of formaldehyde with coal combustionand vehicular emission contributed partly,primary emissions（includingvehicular emissions,coal combustion and solvent usage）and photochemicalreaction both had important contributions to acetone,the coal combustionand vehicular emission were critical sources of acetaldehyde withphotochemical reaction contributed partly.The linear regression analysisshowed that primary sources and secondary sources were the dominantsources of carbonyls in winter and summer,respectively.（4）The L_OH,Prop-Equiv and OFP of carbonyl compounds exhibited the highestvalue in summer and lowest value in winter.Formaldehyde,acetaldehydeand hexaldehyde were the three main contributors of L_OH,Prop-Equiv andOFP,they together accounted for 82.41%,69.81%and 85.74%of the totalL_OH,Prop-Equiv and OFP of 13 carbonyl compounds.The range offormaldehyde ILTCR and acetaldehyde ILTCR were 2.39-7.70×10^-5 and0.90-1.59×10^-5,exceeding the value of 1×10^-6.They had high cancer risk.The study describes the levels and seasonal characteristics of ambient carbonyls compounds.The sources of carbonyl compounds are identified and quantified roughly.And the contributions of carbonyl compounds to atmospheric chemistry activity and ozone formation potential are estimated.Health risk of formaldehyde and acetaldehyde are evaluated at last.The results of this study could help facilitate the development of control strategies of key industries and the government to find the cause of ozone pollution episode.