Rapid nitrogen removal in sandy beaches driven by periodic tidal inundations

Sandy beaches are hotspots of nitrogen loss in coastal ecosystems. Our initial dataset included the following measurements: total ²²⁴Ra and ²²⁸Th in bulk sediments; and dissolved ²²⁴Ra activity, DO, DIC, NOₓ⁻, and NH₄⁺ concentrations in seawater and porewater. Applying the ²²⁴Ra/²²⁸Th disequilibrium approach to these data, we estimated the export fluxes of DIC and DIN, as well as nitrogen removal rates, at three intertidal sandy beaches with distinct slopes along the southeast China coast.