Factors contributing to elevated springtime surface ozone levels in eastern China

Springtime ozone levels in the North China Plain (NCP) exceed those in California by 50 %. The difference is even larger at 85 % when compared to the eastern U.S. Field measurements at a rural NCP site reveal reactive aromatics concentrations 6.2 times higher than California levels, respectively. Box model analysis demonstrates reactive aromatics contribute 73 % of the total ozone production. By redistributing reactive aromatics emissions based on industrial source patterns and implementing observation-constrained diurnal cycles, model performance improves significantly across the NCP region. This redistribution shifts the chemical regime from predominantly VOC-limited into a transition zone towards NO_x-limited regime, reversing the effect of NO_x reduction on ozone in the NCP region. The underestimation of reactive aromatics emissions has substantial public health implications through increased ozone-related mortality. Our findings underscore the critical need for improved characterization of industrial emissions in economically developing regions to enable effective air quality management strategies.