Impact of ozone pollution on gross primary productivity during a large-scale emission reduction: Implications for strengthening carbon sink over megacity clusters in China

Abstract

Ozone (O 3 ) pollution poses a significant threat to plant growth and diminishes ecosystem carbon sequestration capacity in China, representing a critical challenge to achieving “dual carbon” goals. A large-scale emission reduction that occurred during the Coronavirus disease 2019 lockdown offered a great opportunity to understand the complex mechanisms behind the impact of meteorology and emissions on gross primary productivity damage (GPP d ). Hence, a state-of-the-art air quality model was used to assess the underlying linkages between O 3 , relative humidity (RH), and GPP d during the lockdown period, and to calculate the contribution of individual physical processes and chemical reaction on GPP d levels across six megacity clusters in China. The results showed that RH was more important in dry climate areas, which enhanced GPP d by 2%-4%, whereas MDA8 O 3 enhanced GPP d by 3%-4% in humid areas. A strong relationship observed between O 3 and GPP d variations and the O 3 precursor sensitivity (OPS) depicted that transferring the OPS to the NO x -limited regime is a prerequisite for achieving synergistic benefits in O 3 pollution reduction and GPP d mitigation. By tracking GPP d change response to the emission reduction, GPP d can be mitigated to varying degrees in six megacity clusters as anthropogenic emission reduction measures are implemented, especially across the tipping point of 40%. This study has important implications for achieving synergistic benefits in pollution reduction and carbon emission mitigation and highlights the importance of implementing sustained and deep NO x emission control measures to transfer OPS to the NO x -limited regime under carbon peaking and carbon neutrality vision.