Scale Dependent Relationships Between Precipitation and Atmospheric Source Nitrate: Insights From the Yarlung Tsangpo River Basin

Abstract Precipitation can increase the fluxes of both atmospheric‐source and biological‐source nitrate to rivers simultaneously, making it unclear whether precipitation increases the relative contribution of atmospheric‐source nitrate in rivers. To gain a deeper insight into this issue, this study leveraged the significant precipitation gradient of the Yarlung Tsangpo River Basin, which spans the entire southern Tibetan Plateau, to explore the impact of precipitation on the relative contribution of atmospheric‐source nitrate ( f atm ) in rivers using the Δ 17 O–NO 3 − approach. The results showed that f atm can be as high as 20% particularly in areas with substantial precipitation, glacier and permanent snow coverage and lower nitrogen concentrations. f atm exhibited a strong positive correlation with precipitation in the Yarlung Tsangpo River Basin, although this relationship varied across individual rivers. Predictive models were developed to estimate the f atm in unsampled rivers, which could be valuable for watershed management and nitrogen budget calculations.