Emission source-based ozone isopleth and isosurface diagrams and their significance in ozone pollution control strategies.

In the past decade, ozone (O) pollution has been continuously worsening in most developing countries. The accurate identification of the nonlinear relationship between O and its precursors is a prerequisite for formulating effective O control measures. At present, precursor-based O isopleth diagrams are widely used to infer O control strategy at a particular location. However, there is frequently a large gap between the O-precursor nonlinearity delineated by the O isopleths and the emission source control measures to reduce O levels. Consequently, we developed an emission source-based O isopleth diagram that directly illustrates the O level changes in response to synergistic control on two types of emission sources using a validated numerical modeling system and the latest regional emission inventory. Isopleths can be further upgraded to isosurfaces when co-control on three types of emission sources is investigated. Using Guangzhou and Foshan as examples, we demonstrate that similar precursor-based O isopleths can be associated with significantly different emission source co-control strategies. In Guangzhou, controlling solvent use emissions was the most effective approach to reduce peak O levels. In Foshan, co-control of on-road mobile, solvent use, and fixed combustion sources with a ratio of 3:1:2 or 3:1:3 was best to effectively reduce the peak O levels below 145 ppbv. This study underscores the importance of using emission source-based O isopleths and isosurface diagrams to guide a precursor emission control strategy that can effectively reduce the peak O levels in a particular area.