Exploring formation mechanism and source attribution of ozone during the 2019 Wuhan Military World Games:Implications for ozone control strategies

A series of emission reduction measures were conducted in Wuhan,Central China,to ensure good air quality during the 7th Military World Games(MWG)in October 2019.To better understand the implications for ozone(O_(3))pollution control strategies,we applied integrated analysis approaches based on the de-weathered statistical model,parameterization methods,chemical box model,and positive matrix factorization model.During the MWG,concentrations of O_(3),NO_x,and volatile organic compound(VOCs),OFP(O_(3)formation potential),L_(OH)(OH radical loss rate)were 83μg/m^(3),43μg/m^(3),26 ppbv,188μg/m^(3),and 3.9 s^(-1),respectively,which were 26%,18%,3%,15%,and 13%lower than pre-MWG values and 6%,39%,30%,33%,and 50%lower than post-MWG values,respectively.After removing meteorological influence,O_(3)and its precursors during the MWG decreased largely compared with post-MWG values,and only O_(3),NO_(2),and oxygenated VOCs(OVOCs)declined compared with pre-MWG values,which revealed the emission reduction measures during the MWG played an important role for O_(3)decline.For six VOCs sources,the mass contributions of biomass burning and solvents usage during the MWG decreased largely compared with pre-MWG values.O_(3)production was sensitive to VOCs and the key species were aromatics,OVOCs,and alkenes,which originated mainly from solvents usage,biomass burning,industrial-related combustion,and vehicle exhaust.Decreasing O_(3)concentration during the strict control was mainly caused by OVOCs reduction due to biomass burning control.Generally,the O_(3)abatement strategies of Wuhan should be focused on the mitigation of high-reactivity VOCs.

Exploration of the formation mechanism and source attribution of ambient ozone in Chongqing with an observation-based model

An intensive field campaign was conducted in Chongqing during the summer of 2015 to explore the formation mechanisms of ozone pollution. The sources of ozone, the local production rates, and the controlling factors, as well as key species of volatile organic compounds(VOCs), were quantified by integrating a local ozone budget analysis, calculations of the relative incremental reactivity, and an empirical kinetic model approach. It was found that the potential for rapid local ozone formation exists in Chongqing. During ozone pollution episodes, the ozone production rates were found to be high at the upwind station Nan Quan, the urban station Chao Zhan, and the downwind station Jin-Yun Shan. The average local ozone production rate was 30×10^(-9) V/V h^(-1) and the daily integration of the produced ozone was greater than 180×10^(-9) V/V. High ozone concentrations were associated with urban and downwind air masses. At most sites, the local ozone production was VOC-limited and the key species were aromatics and alkene, which originated mainly from vehicles and solvent usage. In addition, the air masses at the northwestern rural sites were NO_x-limited and the local ozone production rates were significantly higher during the pollution episodes due to the increased NOx concentrations. In summary, the ozone abatement strategies of Chongqing should be focused on the mitigation of VOCs. Nevertheless, a reduction in NO_x is also beneficial for reducing the regional ozone peak values in Chongqing and the surrounding areas.