Rapid economic growth has given rise to a significant increase in ozoneprecursor emissions in many regions of China, especially in the denselypopulated North China Plain (NCP) and Yangtze River Delta (YRD). Improvedunderstanding of ozone formation in response to different precursoremissions is imperative to address the highly nonlinear ozone problem and toprovide a solid scientific basis for efficient ozone abatement in theseregions. A comparative study on ozone photochemical production in summer hasthus been carried out in the megacities of Tianjin (NCP) and Shanghai (YRD).Two intensive field campaigns were carried out respectively at an urban anda suburban site of Tianjin, in addition to routine monitoring of trace gasesin Shanghai, providing data sets of surface ozone and its precursorsincluding nitrogen oxides (NO) and various non-methane hydrocarbons(NMHCs). Ozone pollution in summer was found to be more severe in theTianjin region than in the Shanghai region, based on either the frequency orthe duration of high ozone events. Such differences might be attributed tothe large amount of highly reactive NMHCs in Tianjin. Industry relatedspecies like light alkenes were of particular importance in both urban andsuburban Tianjin, while in Shanghai aromatics dominated. In general, theozone problem in Shanghai is on an urban scale. Stringent control policieson local emissions would help reduce the occurrence of high ozoneconcentrations. By contrast, ozone pollution in Tianjin is probably aregional problem. Combined efforts to reduce ozone precursor emissions on aregional scale must be undertaken to bring the ozone problem under control.
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