Global integrated modeling framework of riverine dissolved inorganic nitrogen with seasonal variation

Abstract

: Understanding patterns and seasonal variations of exces‐ sive nutrients in surface water from anthropogenic activi‐ ties is important for pollution control. In this study, we developed an integrated biogeochemical modeling frame‐ work for nitrogen exchanges among the atmosphere, terres‐ trial, and aquatic ecosystems. A land surface model, a ter‐ restrial nitrogen cycle model, and a riverine hydrodynamics model incorporated with a river temperature model were consolidated and driven by multiple nitrogen sources related to anthropogenic activities. We estimated the global nitrogen loading and transporting in global rivers, with con‐ sideration of seasonal variations, and the validation demon‐ strates the reliability of the proposed model. The total dis‐ solved inorganic nitrogen (DIN) flow rate is accumulated following rivers and it has high total DIN loads even in regions with low population density but large basin area, such as those at high latitudes. This study successfully improves estimation of nitrogen loading on global scale with consideration of seasonal variation. Our results show consistent trends with the observed data of DIN concentra‐ tions in global rivers, where all above variables are greatly affected by seasonal variations. The results also reflect the monthly-variant nitrogen inputs help produce closer DIN concentration estimates to observations, which will possi‐ bly stress the need for further study on seasonal variability of anthropogenic emissions.