Source Analysis And Impact Study Of Volatile Organic Compounds In Built-up Areas Of Yuncheng City

In order to provide scientific basis for VOCs control in Yuncheng City,O₃ and PM_2.5 to provide reference for collaborative management and control,and help enhance the overall environmental and social effects of Yuncheng.This study analyzed the pollution characteristics of VOCs in Yuncheng and the change characteristics of VOCs during the period of COVID-19.The PMF model is used to judge the emission sources of VOCs,and the pollution transmission path and potential pollution source area of VOCs are studied by HYSPLIT,PSCF and CWT models;The OFP and SOA_p of VOCs in Yuncheng City were calculated and analyzed by MIR method and FAC method respectively.At the same time,the non carcinogenic and carcinogenic risks of VOCs in Yuncheng City were studied by health risk assessment model.Through the above analysis,the main research conclusions are as follows:（1）The average concentration of VOCs in Yuncheng City in 2020 is 75.92μg·m^-3,the species with the highest mass fraction is alkane,and its concentration and mass fraction are31.07μg·m^-3 and 40.93%respectively.The seasonal variation of VOCs concentration is characterized by"high in winter and low in summer",in which substances such as ethane in winter are significantly higher than those in other seasons,and the concentration and mass fraction of OVOCs and aromatic hydrocarbons are low.The diurnal variation of VOCs concentration in Yuncheng City shows a bimodal distribution,and the peaks appear at 08:00and 20:00 respectively.The highest concentration of VOCs in cloudy days during the observation period was 111.30μg·m^-3,higher than that in sunny days(79.87μg·m^-3),rainy days(63.10μg·m^-3)and snow(49.43μg·m^-3)。According to the person correlation analysis,VOCs in Yuncheng City has a significant negative correlation（-0.491）with air temperature and a significant positive correlation（0.410）with air pressure.The high value area of VOCs in Yuncheng city is mainly distributed in the northeast and East,which is greatly affected by Nanfeng Industrial Park and commercial residential areas.During the period of COVID-19,the concentration of VOCs in Yuncheng City was 67.97μg·m^-3,the concentration decreased compared with the the normal period.Meanwhile,the concentrations of alkanes,aromatics and OVOCs decreased during the period of COVID-19,and the concentrations of olefins and alkynes increased compared with the the normal period.（2）The PMF model is used to analyze the main emission sources of five types of VOCs,which are vehicle exhaust emission source（30.67%）,fossil fuel combustion source（28.61%）,industrial emission source（26.65%）,solvent use source（9.66%）and plant emission source（4.42%）.Therefore,it is necessary to pay attention to the impact of vehicle exhaust emission sources on VOCs Pollution in Yuncheng City.The potential source areas of VOCs Pollution in Yuncheng City are distributed in Northern Shaanxi,northern Ningxia and Southern Inner Mongolia in the northwest.Therefore,it is necessary to strengthen the joint prevention and control of VOCs among the polluted areas.（3）According to the ratio method,the type of O₃ control area in the shipping city belongs to VOCs control area,and there is NO_x titration effect at the same time.The OFP of VOCs in Yuncheng City in 2020 was 248.69μg·m^-3,in which the OFP of OVOCs is the highest.Seasonally,the OFP of VOCs is the highest in winter;From the perspective of emission sources,industrial emission sources have the highest contribution rate to OFP.The SOA_p of VOCs is 0.49μg·m^-3,in which the soap of aromatic hydrocarbons is the highest.From the perspective of season,the SOA_p is the highest in autumn.The carcinogenic risk index of VOCs in Yuncheng city is 7.45×10^-6,safety threshold exceeded(1.00×10^-6),which indicates that VOCs in Yuncheng City are at risk of cancer.From the perspective of VOCs species,it is necessary to control the emission of benzene and acetaldehyde.From the perspective of emission sources,it is necessary to strengthen the control of industrial emission sources,fossil fuel combustion sources and motor vehicle exhaust emission sources.