资源环境科技发展态势分析平台

Air‐water gas transfer influences fundamental processes of aquatic systems such as photosynthesis, respiration, and greenhouse gas emission. Previous predictive models for gas transfer velocity (K_L) often only apply to a small range of streams and rivers. Two ‘universal’ scalings, K_L ∼ ¼ power of turbulent dissipation rate (ε^1/4) and K_L ∼ shear velocity (U*), deduced from classic thin‐film theory and surface renewal theory, have been reported for lake and marine systems, but have not been adequately tested for streams or rivers. To test the two scalings and understand how K_L varies across systems, we compiled 588 field measurements of K_L, and used inverse modeling based on long‐term high‐frequency dissolved oxygen time series to estimate K_L of 35 streams and rivers capturing a wide range of discharge (0 – 221 m³/s). We found that the two scalings held for both the K_L estimated by inverse modeling and the K_L from measurements, and outperformed 23 previous models in predicting K_L. Furthermore, the main driver of K_L variation shifts from bottom friction to other factors with increasing stream/river size. In most streams and a few rivers, correlation between U* and K_L is high, and discharge–K_L relationships are strongly positive, indicating that turbulence generated by bottom friction dominates near‐surface turbulence, a fundamental control of K_L, thus, the two scaling models are applicable to these systems. However, most rivers (mean discharge > 10 m³/s) show low correlations between U* and K_L, suggesting biochemical factors and winds likely override bottom friction in driving near‐surface turbulence and K_L.