Sediment nitrogen, iron and phosphorus species and fluxes in Pinqing Lagoon, South China Sea

We collected water and sediment samples from the Pinqing Lagoon in southern China and measured dissolved oxygen, dissolved Fe (dFe; Fe2+ and Fe3+), ammonium (NH4+), nitrate (NO3-), phosphate (PO43-), sulfate (SO42-), and sulfide (H2S) in the porewaters, as well as solid-phase iron and phosphorus species, particulate organic carbon (POC), the carbon stable isotope ratios of POC (δ13CPOC), and particulate nitrogen (PN) in the sediments. We estimate the sediment diffusive flux of oxygen, NH4+, NO3-, dFe, and PO43- using Fick’s law of diffusion. We measured the total flux of oxygen using a whole-core incubation technique, then use the difference between diffusive and total fluxes of oxygen to calculate the sediment irrigation coefficients for estimation of the total flux of other dissolved species.