“…The Huai River-Qin Mountains, a geographical dividing line acted as a barrier which leaded to differences in climate, air pollution and agricultural diversity, was used to geographically divide SC and NC (Li et al, 2017a;Lin, 2017;Wu et al, 2013;Xue et al, 2008). It was known that mega cities and city clusters in China had severe O 3 pollution problems due to larger amounts of anthropogenic emission sources especially in BTH (Qu et al, 2014;Tang et al, 2012), YRD (Li et al, 2012a;Wang et al, 2006), and PRD Shao et al, 2009). Therefore, the regions of SC, NC, PRD, YRD and BTH were designed as the receptor regions of O 3 concentration.…”