In situ tracer injection experiment conducted with 15N-labeled ammonium in a shallow, sandy subterranean estuary in Gloucester Point, USA in August 2019.

These data are the result of an in situ tracer injection experiment conducted with 15N-labeled ammonium to determine the fate and transport rates of ammonium within a shallow, sandy subterranean estuary in Gloucester Point, VA, USA.

Replicate injections of 15N-labeled ammonium, sulfur hexaflouride, and bromide amended porewater were injected into piezometers at 50cm. Porewater was then collected overtime from the injection piezometers and tracer piezometers surrounding the injection site ranging in depth from 40-60cm. At each time point, samples were collected to analyze dissolved inorganic nitrogen (nitrate, nitrite, and ammonium) concentrations, sulfur hexaflouride, bromide, chloride. Nitrate and nitrite samples from porewater were analyzed with an isotope ratio mass spectrometer in order to assess the 15N enrichment of the nitrate in each sample resulting in a delta value (d15N) that allows for the calculation of the mole fraction of 15N-labeled nitrite and nitrate in porewater at each time point. The production or consumption over time constitutes subterranean estuary nitrogen cycling rates (e.g. nitrification, denitrification, etc.).