Pollution Characteristics and Source Apportionment of VOCs in Urban Areas of Shijiazhuang in Spring
Samples of ambient volatile organic compounds(VOCs)were collected using SUMMA canisters at three Country Control Sites in Shijiazhuang during the spring of 2019,2021,and 2022,which were detected using gas chromatography/mass spectrometry(GC/MS).To investigate the characteristics and temporal variations of VOCs mass concentration levels,the online monitoring data of ozone(O3)and PM2.5 at the same site were also collected.Subsequently,the ozone formation potential(OFP)and secondary organic aerosol formation potential(SOAFP)were utilized to assess the chemical activity of VOCs.Additionally,the potential source areas of VOCs in spring in Shijiazhuang were further identified using the potential source contribution factor(PSCF)method and concentration weight trajectory analysis(CWT).Hence,the major VOCs sources were evaluated with the VOCs initial mixing ratio.The results demonstrated that the averaged concentration of VOCs during the polluted period and clean period of spring in Shijiazhuang were 191.17 μg·m-3 and 122.18 μg·m-3,respectively.Meanwhile,the OFP was 361.23 μg·m-3 during the polluted period and 266.96 μg·m-3 during the clean period,whereas the SOAFP was 1.98 μg·m-3 and 1.61 μg·m-3,respectively.Therefore,effective control of benzene,toluene,ethylbenzene,and xylene(BTEX)is crucial for reducing PM2.5 and O3 pollution.Based on the results obtained from weight PSCF and CWT,the potential source areas of VOCs were further identified to be primarily located in the eastern Yuhua District,the high-tech district,and the northern Luancheng District of Shijiazhuang.These areas were influenced not only by local emissions but also by transport from neighboring regions,in which consistency between the CWT and PSCF results further supported these findings.Furthermore,the results obtained from the benzene/toluene/ethylbenzene(B/T/E)and xylene/benzene(X/B)ratios indicated that the main sources of VOCs in Shijiazhuang in spring were vehicle exhaust sources and burning sources,leading to a more serious air mass aging phenomenon.Hence,controlling vehicle emissions and implementing regional cooperative measures are the effective strategies for optimizing the air quality of Shijiazhuang.
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