Silent Threat Beneath the Leaves: Unveiling the Spatiotemporal Patterns and Exposure Risks of Ground-Level Ozone in China's Major Tea-Producing Regions.

Ground-level ozone (O3) pollution threatens global agroecological security. In China, the world's largest tea producer, widespread O3 exposure has reduced tea quality, largely due to stomatal uptake of O3 at phytotoxic concentrations. However, available approaches inadequately capture stomatal regulation dynamics and spatial heterogeneity, limiting precision risk management in tea cultivation. We developed a novel semi-mechanistic exploratory index () at 1 km resolution, integrating environmental exposure, physiological response and spatial weighting. Using a stomatal conductance model, we quantified the O3 stomatal-modulated exposure index and identified spatiotemporal risk patterns using decomposition methods. Ground-level O3 hotspots (characterized by multiyear mean daily maximum 8-hour average (MDA8) O3 concentrations of up to 56 ppb) were concentrated in the northeastern part of the study area and coastal regions, with a widespread upward trend observed across most tea-producing areas from 2000 to 2023. Provincial mean exhibited a fluctuating upward trend, peaking at 17.10 ppb·days of O3 exposure in Zhejiang by 2020, with 2017 as a critical inflection point. Spatial-temporal logarithmic mean Divisia index (ST-LMDI) analysis revealed a geographic dichotomy where environmental exposure intensity drives risk in industrialized regions, whereas planting density acts as the primary driver of increased O3 exposure in regions with high tea plantation density. For precision governance, a bivariate risk matrix was constructed, categorizing regions by static risk (grades I-IV) and dynamic annual growth rates (grades A-D). Grade I-A (core control) zones, representing the highest risk base and experience the most rapid deterioration, were predominantly located in parts of Sichuan, Fujian, and Henan. In this novel study, a comparative assessment is conducted and spatial maps of relative O3 exposure risks within tea production systems are constructed, supporting targeted mitigation strategies, sustainable tea production and ecological risk assessment in global leaf-based economic crop systems, with applicability across regions.