Impacts of biogenic emissions from urban landscapes on summer ozone and secondary organic aerosol formation in megacities

Yang Gao, Mingchen Ma, Feifan Yan, Hang Su, Shuxiao Wang, Hong Liao, Bin Zhao, Xuemei Wang, Yele Sun, James R. Hopkins, Qi Chen, Pingqing Fu, Alastair C. Lewis, Qionghui Qiu, Xiaohong Yao, Huiwang Gao

Research output: Contribution to journalArticlepeer-review

Abstract

The impact of biogenic emissions on ozone and secondary organic aerosol (SOA) has been widely acknowledged; nevertheless, biogenic emissions emitted from urban landscapes have been largely ignored. We find that including urban isoprene in megacities like Beijing improves not only the modeled isoprene concentrations but also its diurnal cycle. Specifically, the mean bias of the simulated isoprene concentrations is reduced from 87% to 39% by adding urban isoprene emissions while keeping the diurnal cycle the same as that in non-urban or rural areas. Further adjusting the diurnal cycle of isoprene emissions to the urban profile steers the original early morning peak of the isoprene concentration to a double quasi-peak, i.e., bell shape, consistent with observations. The efficiency of ozone generation caused by isoprene emissions in urban Beijing is found to be twice as large as those in rural areas, indicative of vital roles of urban BVOC emissions in modulating the ozone formation. Our study also shows that in the future along with NOx emission reduction, isoprene emissions from urban landscapes will become more important for the formation of ozone in urban area, and their contributions may exceed that of isoprene caused by transport from rural areas. Finally, the impact of biogenic emissions on SOA is examined, revealing that biogenic induced SOA accounts for 16% of the total SOA in urban Beijing. The effect of isoprene on SOA (iSOA) is modulated through two pathways associated with the abundance of NOx emissions, and the effect can be amplified in future when NOx emissions are reduced. The findings of our study are not limited to Beijing but also apply to other megacities or densely populated regions, suggesting an urgent need to construct an accurate emission inventory for urban landscapes and evaluate their impact on ozone and SOA in air quality planning and management.
Original languageEnglish
Article number152654
Number of pages1
JournalScience of the Total Environment
Volume814
Early online date3 Jan 2022
DOIs
Publication statusPublished - 25 Mar 2022

Keywords

  • Biogenic emissions
  • Urban landscapes
  • Isoprene
  • Ozone
  • iSOA

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