Abstract:

With the coupled influence of multiple factors, such as climate change and human activity, the excessive input of reactive nitrogen has exacerbated the loss of nitrogen from terrestrial ecosystems to aquatic ecosystems, which has seriously affected the quality of water in the basin. Identifying the spatiotemporal variation characteristics of nitrogen sources and their transformation processes within the watershed system has become a primary objective for preventing and controlling the loss of pollutants and improving regional ecological quality. Understanding the nitrogen cycle in the watershed system faces challenges owing to the diversity of nitrogen sources, complexity of biogeochemical processes, and coupled influence of many factors in the watershed. Among the research approaches, model simulation has become an important tool to reveal the nitrogen transport, transformation and dynamic change processes at the watershed scale owing to its high flexibility, high systematicity, and the ability to simulate and analyze multiple scenarios. This review summarized the characteristics of watershed hydrological models and nitrogen transport models for soil, surface water, and groundwater in watershed, as well as research examples of various models. The models were compared based on their principles, characteristics. Among the many factors affecting the nitrogen cycle, it is analyzed that uncontrolled anthropogenic disturbances and extreme climate change have become important factors disturbing the nitrogen cycle in watersheds. Hydrological process-driven processes and mechanistic studies of water and nitrogen are particularly important. Hydrological biogeochemical models (e.g., CNMM-DNDC, PIHM) constructed based on these models have become an important for obtaining high-precision spatial and temporal distribution patterns of nitrogen in the watershed system and its prediction and analysis. In addition, the combination of big datasets and processes modeling has become an important way to reveal the complexity of the nitrogen cycle process. By synthesizing the applicability of many models to the spatial pattern and intensity of anthropogenic impacts, we sorted the applicable models of nitrogen cycling in the river network area of the coastal plain, which is subjected to strong anthropogenic disturbances. These models may deepen the scientific knowledge of nitrogen cycling under the interactions of surface water, groundwater, and seawater in coastal watersheds of the intertwined zone of sea and land, and assess the quality of the water environment and the environmental effects of the river system of the coastal plain in a more comprehensive and scientific way.

Key words: nitrogen cycle, watershed, model, coastal catchment, processes modelling