<b>Article: </b><b>Physical controls on dissolved N₂/Ar supersaturation in a windy estuary</b>

In high-wind estuaries, however, bubble-mediated exchange diverges markedly among gases due to differences in solubility and partial pressure. Using winter observations in the Changjiang Estuary and a size-fractionated bubble model, we quantified air–sea exchange of N₂, O₂, and Ar.

Small bubbles injected N₂ (1.92–14.45 mmol m⁻² d⁻¹) while large bubbles drove degassing (−24.06 to −4.21 mmol m⁻² d⁻¹). After correction, surface ΔN₂′ remained positive (10.38–18.64 μM), ΔO₂′ was 3.15–5.96 μM, and Ar stayed near equilibrium. Bubble-induced concentration offsets represented cumulative physical states accounting for one-third to one-half of observed surface ΔN₂, whereas instantaneous net fluxes reflected N₂ efflux at sampling. δ¹⁵N-N₂ correlated weakly with ΔN₂′, indicating atmospheric dominance.