Dataset: 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 were collected during August 2019 from a sandy subterranean estuary (STE) located in Gloucester Point, Virginia, USA. Porewater was collected from surface water and piezometers placed at 40, 50, and 60cm. Prior to the injection, porewater was collected from replicate 50cm piezometers and amended with 15N-labeled ammonium, sulfur hexaflouride, and bromide. The amended porewater was then reintroduced into the STE through the 50cm injection piezometers.

After injection porewater was collected overtime from both the injection piezometers and other piezometers surrounding the injection well. At each time point, porewater was collected in serum bottles prepared with potassium hydroxide and were equlibrated by shaking before being run on a gas chromatograph with electron capture detection (GC-ECD, Shimadzu) in order to determine the sulfur hexaflouride concentration. Porewater was also collected for inorganic nutrients and ions, filtered with a 0.45 µm syringe filter (Whatman GE) and were frozen (-20 °C) until analysis.