Impacts of Urbanization on Atmospheric Oxygen: High‐Resolution Observational Evidence

Abstract Oxygen (O 2 ), a fundamental constituent of Earth's atmosphere, sustains aerobic life and maintains the equilibrium of global biogeochemical cycles. However, rapid urbanization is increasingly perturbing the natural O 2 balance, yet the distinct mechanisms driving these perturbations remain poorly understood. Here, we report the first simultaneous, high‐precision in situ O 2 observations at two contrasting sites: an industrial urban valley (Lanzhou) and a remote high‐altitude background site (Qomolangma Station). By disentangling meteorological confounders, we reveal a fundamental divergence in the controls on atmospheric O 2 variability: the remote baseline is primarily controlled by meteorological variability, especially temperature‐pressure coupling, whereas urban O 2 variability in the valley reflects the interaction between local anthropogenic emissions and large‐scale weather patterns that regulate atmospheric stability and dispersion. Crucially, mechanistic analyses of urban atmospheric oxygen depletion reveal a regime‐dependent transition in its dominant controls: (a) Aerosol pollution is marked by “physical decoupling”, where external transport disrupts the linearity between local combustion and oxygen deficits; (b) Ozone pollution, conversely, exhibits “chemical synergy”, driven by temperature‐enhanced precursor oxidation and associated secondary transformations. These findings establish urban O 2 variability as an integrator of anthropogenic emissions and atmospheric oxidation capacity, underscoring the necessity of incorporating chemical‐meteorological feedbacks into assessments of urban ecosystem sustainability and carbon budgets.