Sediment nitrogen fluxes and rates in the Pearl River Estuary region

We collected water and sediment samples from the Pearl River Estuary and its adjacent coastal shelf. We measured dissolved oxygen, ammonium, and nitrate in the porewaters and particulate organic carbon and nitrogen. We estimate the sediment oxygen uptake using whole core incubations and estimate the diffusive fluxes of oxygen, ammonium and nitrate using Fick’s law of diffusion. The bioirrigated fluxes of ammonium and nitrate are calculated using total sediment uptake and diffusive oxygen flux, considering proportional bioirrigation and molecular diffusion coefficients. The rates of nitrification and N2 production were estimated using mass-balance model calculations. Data from the literature were also compiled for comparison. The compiled data include those from the Changjiang Estuary region (Song et al. 2021), the Northern Gulf of Mexico (Lehrter et al. 2012, MaCarthy et al. 2013 and 2015), the Gulf of St Lawrence Alkhatib et al. 2012, Thibodeau et al. 2010, Mazur et al. 2021), and the Chesapeake Bay (Boynton et al. 2018, 2019, and 2022). Details of the samples and methods are described in the metadata file.

In this version, we calculated the bioirrigation flux of nitrate and ammonium, and the burial flux of ammonium. These fluxes are included in the mass-balance calculation of the rates. In the previous version, only molecular diffusive fluxes were considered.