Modelling agricultural nitrogen contributions to the Jiulong River estuary and coastal water

Abstract: The geographical setting of the Jiulong River estuary determines that the estuary receives wastes from both riverine input and adjacent urban sewage. However, the dominant nitrogen (N) source remains unclear. A nutrient mass-balance model and a preliminary LOICZ (Land–Ocean Interactions in the Coastal Zone) biogeochemical model were linked to evaluate agricultural N contributions from the Jiulong River catchment to the estuary and coastal water. Results showed that agricultural N surplus was the largest N source in the catchment, contributing 60.87% of the total Nitrogen (N) and 68.63% of the dissolved inorganic nitrogen (DIN). Household wastes and other sources followed. Riverine DIN fluxes were about 20.3% of exportable DIN and 14.4% of exportable total N, but approximately 9.7% of DIN inputs, and 7.3% of total N inputs to the Jiulong River catchment. The model system clearly showed that agricultural and anthropogenic activities in the catchment were the major N sources of the estuary and coastal water, and riverine N fluxes from these sources substantially impacted the estuary and coastal water quality and biogeochemical processes. [Copyright &y& Elsevier]