Pollution Characteristics And Source Analysis Of Polycyclic Aromatic Hydrocarbons And Aromatic Acids In PM_2.5 In Zhengzhou High-tech Zone

With the publication of Air Pollution Prevention and Control Action Plan and the"2+26" pollution prevention and control measures in Beijing-Tianj in-Hebei and surrounding key cities,the air quality of Chinese country’s cities has improved,but heavy pollution weather still occurs frequently,exceeding the ambient air quality standards limits from time to time.Zhengzhou is the capital of Henan Province and one of the "26" cities in the pollution transmission channel.In recent years,the overall environmental pollution has shown a downward trend,but it still faces frequent occurrences of heavily polluted days in autumn and winter.With the in-depth study of fine particulate matter(PM_2.5)in the atmosphere,the harm of PM_2.5 to human health has been gradually widely recognized.Among them,aromatic compounds come from incomplete combustion of coal and biomass,and are the important components of the organic aerosols.It also has an important contribution to the formation of secondary organic aerosols.Aromatic compounds have carcinogenic and teratogenic properties,seriously endangering human health.In this study,a sampling site was set up in Zhengzhou University in,Zhengzhou High-tech Zone,and PM_2.5 samples were collected in the typical months of different seasons from April 2019 to January 2020.The 36 aromatic compounds in the samples were systematically analyzed,including 28 Polycyclic Aromatic Hydrocarbons（PAHs）and 8 Aromatic Acids（AAs）.Their pollution characteristics were explored in terms of concentration levels,seasonal variation characteristics,health risks,and diagnostic ratios.To quantitatively analyze the sources of identified compounds,this study used the Positive Matrix Factorization model.To analyze the sources and regional transport pathway of pollutants in different seasons,this study used the Hybrid Single-Particle Lagrangian Integrated Trajectory model.The main conclusions of this study were as follows:（1）The annual average mass concentration of PM_2.5 in Zhengzhou during the sampling period was（70.3±9.4）μg m^-3,which was two times of the annual average limit of the secondary standard of the ambient air quality standard（GB3095-2012）(35μg m^-3).The pollution days exceeded the standard daily limit(75 μg·m^-3)during the sampling period accounted for 31.8%of the total sampling days,and the maximum PM_2.5 concentration was 210.1 μg·m^-3,indicating that Zhengzhou PM_2.5 pollution was still serious.OC and EC accounted for 13.7%and 2.3%of PM_2.5 respectively,suggesting carbonaceous components were important components of PM_2.5.The correlation between OC and EC was stronger in autumn and winter,indicating OC and EC came from similar pollution emission sources in these two seasons.The annual average concentration of total organic compounds in this study was 283.5 ng m^-3,and the mass concentration of AAs was 4.3 times that of PAHs.（2）The annual mean mass concentration of ∑₂₈-PAHs during the sampling period was 53.4 ng·m^-3,and the seasonal trends of ∑₂₈-PAHs and PM_2.5 were similar,which were winter>autumn>spring>summer.Winter was the main emission season of PAHs.The 5 rings-and 4 rings-PAHs were the dominant homologues,accounting for 68.7%in total.The eigenratio method found the main sources of PAHs were coal combustion sources,biomass combustion sources and vehicle emission sources.The carcinogenic risk of PAHs for both children and adults in Zhengzhou was at an acceptable risk level(10^-6).The annual average mass concentration of ∑₈-AAs was 230.1 mg·m^-3,and the changing rule of different seasons was as follows winter>autumn>summer>spring.Phthalic acid was the most abundant aromatic acid in this study,accounting for 50.6%of the total aromatic acid compounds.There was a significant correlation between the 1,3,5-benzenetricaboxylic acid,1,2,3-benzenetricaboxylic acid and 1,2,4-benzenetricaboxylic acid,indicating that their source precursors were similar and all came from secondary generation.（3）The Positive Matrix Factorization model was used to quantitatively analyze the sources of PAHs and aromatic acids in PM_2.5 in Zhengzhou.The results showed that the sources of atmospheric carbonaceous aerosols in Zhengzhou were coal combustion emissions（26.8%）,biomass combustion emissions（22.2%）,motor vehicle emissions（19.5%）,secondary photochemical oxidation（17.7%）and industrial emissions（13.8%）respectively.The analysis of the backward trajectory showed the sources were different in different seasons during the sampling period.The influence of monsoon weather was more significant in summer.The other three seasons were mainly affected by the transmission of air pollution in the Beijing-Tianj in-Hebei region,followed by the pollution transmission in the northwest direction.The concentration weight trajectory indicated that intra-provincial transport was the main source of pollutants,followed by the borders of neighboring provinces.