Study On The Pollution Characteristics Of Polycyclic Aromatic Hydrocarbon In Harbin

Polycyclic aromatic hydrocarbons（PAHs）are common persistent toxic substance in atmospheric environment,which were mainly from incomplete combustion of fossil fuels and biomass.In recent years,PAHs have been attracted more and more attention in the world due to its multiple pollution sources,wide distribution,long range atmospheric transport and carcinogenicity.As an important old industrial base in northeast China,Harbin has many sources for PAHs and special climate conditions,which is important for significance to the study of PAHs in the atmosphere of Harbin.Based on the monitoring data of 16 kinds of PAHs in the atmosphere of Harbin within one year,the concentration,composition and seasonal variation of PAHs in the atmosphere were analyzed.The pollution sources of PAHs were analyzed qualitatively and quantitatively by using three receptor models.The source area of PAHs in Harbin atmosphere was analyzed from multiple angles by the backward trajectory model and potential source contribution function model.The gas-particle partitioning,an important parameter for the study of air pollution,was analyzed using both the equilibrium-state model and the steady-state model.For the study of the concentrations,composition characteristics and seasonal variation of PAHs in Harbin,a total 41 pairs of gas and particle phases air samples（20 pairs for heating season and 21 pairs for non-heating season）was collected.The Soxhlet extraction and silica gel purification method were used for the pretreatment of air sample,16 PAHs were analyzed by an Agilent 6890 N GC coupled with Agilent 5973 mass spectrometer detector（GC/MS）.The results showed that the annual average concentration of total PAHs in Harbin atmosphere was 97.5 ng/m3,with the highest concentration of phenanthrene,followed by fluoranthrene and pyrene.There is no significant difference between the annual average PAHs concentration in gas phase and particle phase,with the concentrations of 54.20 ng/m3 and 43.29 ng/m3,respectively.The negative correlation between the concentration of PAHs in the atmosphere and temperature is significant.The concentration in heating period is much higher than that in non-heating period.The proportion of phenanthrene and the proportion of the three rings PAHs to total PAHs were the highest in different seasons.During the whole year,under different temperatures and different pollution sources,low ring PAHs tend to exist in the gas phase,while high ring PAHs tend to exist in the particle phase.The ratio of four rings PAHs in the gas phase to total concentration that in atmosphere（gas + particle）varies by nearly 80% in heating season and non-heating season,while other PAHs are not significantly different.For the study on the types of pollution sources and distribution of PAHs in Harbin atmosphere,different models are applied in this.Using diagnostic ratios,principal component analysis（PCA）and positive matrix factorization（PMF）,the result showed that the main source of PAHs in the atmosphere is coal combustion.The main sources of PAHs are different in different seasons.The main sources of PAHs in the atmosphere during heating season are coal combustion,straw burning and engine emission.The main sources of PAHs in the atmosphere during non-heating season are engine emission,coke oven combustion and surface volatilization.The backward trajectory model and the potential source contribution algorithm model were used to analyze the distribution of pollution sources.The results showed that the main source area of PAHs in Harbin atmosphere comes from the northwest and southeast regions with different seasonal variation.The PAHs pollution during heating season mainly comes from the northwest of Harbin,while it was from the east and southwest of Harbin during non-heating season.For the study of the gas-particle partitioning of PAHs in Harbin atmosphere,three models are applied in this paper,two equilibrium-state models(P_l⁰ and K_OA)and the steady-state model.The gas-particle partitioning obtained from the actual monitoring data of PAHs in Harbin atmosphere are not in good agreement with the equilibrium-state model and the steady-state model.The slope values obtained by the equilibrium model of the gas-particle partitioning of PAHs in the atmosphere at different periods had no significant difference.The slope values of PAHs with different ring PAHs obtained by the equilibrium-state model are quite different.The four rings PAHs are in good agreement with the equilibrium-state model theory with the slope values close to 1,while the slope values of the others PAHs are close to 0 which is similar to the slope value of PBDEs with high octanol-gas distribution values in the steady-state model.But the gasparticle partitioning coefficient of PAHs in the special domain of the octanol-gas distribution values is different from the steady-state model for PBDEs.