Study On Distribution Characteristics And Variation Law Of VOCs In Ambient Air Of Lanzhou City

Volatile organic compounds?VOCs?of the ambient air are a class of pollutants involved in atmospheric chemical processes.Its own teratogenic,carcinogenic and other characteristics pose a serious threat to human health;In addition,volatile organic compounds?VOCs?also have secondary pollution in atmospheric chemical processes,also has great harm.Environmental air VOCs and secondary pollutants are becoming more and more harmful to human health,which is one of the outstanding environmental problems that need to be properly solved.Due to the physical characteristics of volatile organic compounds?VOCs?and the contribution value of participation in atmospheric chemical processes;the complexity of their components makes the difficulty of tracer analysis of source components increase.Therefore,from a regional perspective,it is necessary to analyze the concentration,spatial-temporal distribution characteristics,class composition,atmospheric chemical activity and source characteristics of VOCs in ambient air;Provide basic data support for the determination of regional atmospheric environmental conditions and air pollution control;in order to provide a basis for the basic application of environmental air VOCs in human health risk assessment and the source of environmental air VOCs.In this study,the Lanzhou City was used as the research area,and five sampling points were selected,using the intermittent sampling mode;By collecting samples of volatile organic compounds?VOCs?from November 2017 to June 2018,According to EPA TO-17,TO-14 using TENAX adsorption tube sampling,analysis of VOCs data by thermal desorption gas chromatography-mass spectrometry?TD-GC/MS?:?1?Obtain 106 species of VOCs and quantitatively analyze 54 species of VOCs;Obtained the characteristics of the characteristics and content of VOCs in five functional areas,at the same time,the meteorological factors including temperature,humidity,air quality index,etc.are collected for significant analysis;Ozone generation potential?OFP?was used to evaluate the atmospheric reactivity of the functional zone.The maximum incremental reactivity coefficient?MIR?was used to estimate the contribution of VOCs to OFP,and factor analysis was used for source analysis.?2?The levels of 10 normal paraffins detected between the low-carbon n-alkanes C₅^C₁₉in the atmosphere from November 2017 to June 2018,and the regional composition characteristics,spatial distribution status,and composition Significant correlation analysis with meteorological factors;The atmospheric chemical reactivity parameters were used to evaluate the OFP,OH radical consumption rate and secondary organic aerosol formation potential of volatile organic compounds.The atmospheric activity contribution analysis of low-carbon n-alkanes was analyzed by factor analysis.?3?Extracting the unknown amount of information for 10 special VOCs?low-carbon n-alkanes?species,and analyzing the source of all acquired VOCs.The results show:?1?A total of 106 volatile organic compounds were identified,and the characteristics of VOCs in each functional area were significantly different from those in time and space.Meteorological factors were significantly correlated with VOCs.The most important active species are toluene and styrene.The key active components in each functional zone are 2-methylpentane,trichloroethylene,styrene,benzene,toluene,ethylbenzene,m-xylene,o-xylene,naphthalene.,acetone,etc.,indicating that these VOCs have the largest contribution to OFP;The data show that the percentage of components of the VOCs category is consistent with the proportion of the OFP contribution value;the factor analysis method indicates that the four factors of the five functional zones have an interpretation of the information content of the air VOCs source component of 85.32%or more;The content of the factors will be an important concern.The data show that the percentage of components of the VOCs category is consistent with the proportion of the OFP contribution value;the factor analysis method indicates that the four factors of the five functional zones have an interpretation of the information content of the air VOCs source component of85.32%or more;The content of the four factors will be an important concern.?2??1?The lowest average value of C₅^C₈ in the low carbon number normal alkanes is 18.99?g/m³,and the highest concentration between C₉^C₁₉ is nineteen alkanes,the average concentration is 2.24?g/m³;?2?The highest contribution values of OFP and OH radical consumption rates were n-hexane and n-octane,respectively,accounting for 37.71%and 37.64%;?3?The most important contribution to the secondary organic aerosol formation potential is n-octane,accounting for 50.02%;n-octane and n-hexane become the two key active components of n-alkanes between C₅ and C₁₉;?4?In the significant correlation analysis of atmospheric chemical reactivity parameters,the total mass concentration of low-carbon n-alkanes has a significant correlation with ozone generation potential?r₁?and OH radical consumption rate?r₂??r₁=0.895;r₂=0.948?;?5?In the factor analysis of atmospheric chemical reaction parameters,the five factors fitted by principal component analysis explained the information amount of 94.51%of the chemical reactivity of 10n-alkanes between C₅ and C₁₉.Studies have shown that the ozone-forming potential of low-carbon n-alkanes under atmospheric normal conditions in Lanzhou City also has significant changes in the atmospheric environment;There is also a significant correlation between atmospheric reactivity parameters;n-octane is one of the compounds with the highest contribution to atmospheric chemical reactivity,and is also the source of automobile exhaust emissions;n-hexane is a product of anthropogenic and natural sources.?3?According to the extraction and source analysis of the information amount of the compound,the results show that:Traffic emissions,diesel combustion and industrial coating release are the main sources;biological sources,other sources of human activities,and environmental backgrounds are also sources that cannot be ignored;The concentration of VOCs in the Xi-gu District?industrial zone?and the down winding An-ning District is relatively high.The analysis of meteorological parameters and atmospheric circulation shows that the direction of wind direction and airflow have a certain influence on the variation of VOCs concentration;However,Lanzhou's special topographical factors have a profound impact on the regional environment and human health.