Regional ozone pollution and key controlling factors of photochemical ozone production in Pearl River Delta during summer time

An intensive field campaign including measurements from the environmental monitoring network and from two super sites took place in the Pearl River Delta region in summer 2006. Using routinely measured O 3 and NO x concentrations, the spatial and temporal variation of O 3 and of the total oxidant concentrations was characterized. According to the spatial variability of NO 2 /NO, the two super sites were found to be representative of polluted urban and downwind suburban conditions. In addition, both sites were located in high O 3 regions. In-depth diagnostic of photochemical ozone production processes and their key controlling factors are achieved with an observation-based model (OBM) to gain regional perspectives. Budget analysis and sensitivity model runs show that aldehyde and HONO chemistry had significant impacts on local photochemical ozone production rates. The analysis of calculated Relative Incremental Reactivities shows that photochemical ozone production rates are mainly sensitive to anthropogenic hydrocarbons (HCs) in the polluted urban areas. In the suburban areas, sensitivity to nitrogen oxide (NO) concentrations dominated. Key anthropogenic HCs in both areas are alkenes and aromatics. Significant differences of ozone production efficiencies are identified between the urban and suburban regions, consistent with the OBM diagnosed results.