Cross-Media Cycling of Tropospheric Reactive Nitrogen and Its Implications for Sulfur Chemistry

Reactive nitrogen (Nr) species serve as a pivotal catalytic engine in tropospheric oxidation processes. Furthermore, their multiphase transport and interfacial conversions can also perturb biogeochemical equilibria across marine, terrestrial, and atmospheric systems. This review integrates groundbreaking advances in the cycling and conversion of Nr at multimedia surfaces (gas-aqueous, gas-particle, and gas-soil interfaces), revealing their key role in driving the formation of atmospheric fine particulate matter and enhancing atmospheric oxidizing capacity. The critical environmental factors affecting the cycle at each active interface were also systematically investigated and comprehensively analyzed. By integrating laboratory studies, field campaigns, and modeling simulations, we reveal how aerosol-mediated Nr-S chemistry creates self-amplifying positive feedback that exacerbates haze formation. These mechanisms partly explain why the advanced model often underestimates sulfate concentrations in megacities, providing direct support for pollution control strategies. Our analysis bridges molecular-scale interfacial processes with the fast increase in regional fine particles, offering actionable insights for scientists, policymakers, and engineers combating atmospheric complex pollution, particularly in developing countries.