Volatile Organic Compounds Pollution and Ozone Generation Potential in Xi'an
In recent years,ozone(O3)pollution in Xi'an,Shaanxi Province,has become increasingly sever.In order to explore the characteristics of VOCs and O3,online continuous observations of 69 VOCs were conducted in Xi'an from January 1 to December 31,2021.The results showed that during the observation period,the average total VOCs(TVOCs)in Xi'an was 39.4x10-9,with alkanes accounting for the highest proportion at 41％,followed by oxygenated volatile organic compounds(OVOCs)(27％),aromatics(18％),alkenes(10％),and alkynes(4％).The volume fractions of alkanes,aromatics,and OVOCs were the lowest in August,at 9.24×10-9,3.71×10-9,and 2.79×10-9,respectively;the volume fractions of alkanes and aromatics were the highest in January,at 30.40×10-9 and 10.42×10-9,respectively;and the volume fraction of OVOCs was the highest in December,at 34.74x10-9.The main sources of VOC emissions in Xi'an were traffic and biomass combustion from January to August,and emissions from chemical enterprises,traffic,and solvent use from September to December.The diurnal variation of alkenes showed a bimodal distribution,with peaks at 24:00 and 10:00,reaching minimum values at 16:00-17:00.The peak time of the highest VOCs volume fraction in winter(02:00)was 1 hour later than in spring,summer,and autumn.The annual average ozone formation potential(OFP)of TVOCs in Xi'an was 378.37 μg/m3,with the order of seasons being winter(462.71 μg/m3)＞autumn(417.75 μg/m3)＞spring(394.25 μg/m3)＞summer(242.46 μg/m3).Throughout the year,the dominant species contributing to OFP were ortho-,meta-xylene,acetaldehyde,ethylene,toluene,and para-xylene.Ortho-and meta-xylene contributed significantly to OFP throughout the year,with contribution rates of 14％to 20％.Formaldehyde was the dominant species in summer(7％),and acetaldehyde was dominant in autumn and winter(14％to 20％).Aromatic compounds,which accounted for less than 25％of the volume fraction,contributed to over 98％of the secondary organic aerosol formation potential(SOAP),with benzaldehyde contributing 47.00％in summer.
NETL
NSTL
万方数据
