Estimation of submarine groundwater discharge and associated nutrient fluxes in the coastal area of Qi'ao island using 222Rn as a tracer

Key Points

• This research aims to estimate submarine groundwater discharge (SGD) and associated nutrient fluxes using tracer methods in the coastal area of Qi'ao Island.
• Establishment of 13 groundwater monitoring wells in tidal zones and intertidal areas.
• Collection of groundwater, river water, and seawater samples during wet and dry seasons.
• Quantitative estimation of SGD rates and nutrient fluxes using a radon mass balance model.
• The SGD rates in the northeastern sea area of Qi'ao Island are seasonal, ranging from 6.36 to 9.84 cm/d in wet season and 1.03 to 1.49 cm/d in dry season.
• Land-derived submarine fresh groundwater discharge constitutes 15.6% in the wet season and 8.2% in the dry season.
• Nutrient fluxes show significant increases in the wet season, with ammonium, nitrate, and dissolved inorganic nitrogen fluxes ranging from 383% to 901% of the dry season values.