HR3DHG version 1: modeling the spatiotemporal dynamics of mercury in the Augusta Bay (southern Italy)

The biogeochemical dynamics of inline-formulaHg, and specifically of its three species inline-formulaHg⁰, inline-formulaHg^II, and inline-formulaMeHg (elemental, inorganic, and organic, respectively), in the marine coastal area of Augusta Bay (southern Italy) have been explored by the high-resolution 3D Hg (HR3DHG) model, namely an advection–diffusion–reaction model for dissolved mercury in the seawater compartment coupled with a diffusion–reaction model for dissolved mercury in the pore water of sediments in which the desorption process for the sediment total mercury is taken into account. The spatiotemporal variability of the mercury concentration in both seawater (inline-formula[Hg_D]) and the first layers of bottom sediments (inline-formula $M6inlinescrollmathml\left[chem{\mathrm{normal\; Hg}}_{\mathrm{normal\; D}}^{\mathrm{normal\; sed}}\right]$ 36pt17ptsvg-formulamathimg83df6d55867198ef1d50b6446f0a32a0 gmd-13-2073-2020-ie00001.svg36pt17ptgmd-13-2073-2020-ie00001.png and inline-formula $M7inlinescrollmathml\left[chem{\mathrm{normal\; Hg}}_{\mathrm{normal\; T}}^{\mathrm{normal\; sed}}\right]$ 36pt17ptsvg-formulamathimgc593301064c5a3361af123dabcd8c770 gmd-13-2073-2020-ie00002.svg36pt17ptgmd-13-2073-2020-ie00002.png ), as well as the inline-formulaHg fluxes at the boundaries of the 3D model domain, have been theoretically reproduced, showing acceptable agreement with the experimental data collected in multiple field observations during six different oceanographic cruises. Also, the spatiotemporal dynamics of the total mercury concentration in seawater have been obtained by using both model results and field observations. The mass balance of the total inline-formulaHg species in seawater has been calculated for the Augusta Harbour, improving previous estimations. The HR3DHG model could be used as an effective tool to predict the spatiotemporal distributions of dissolved and total mercury concentrations, while contributing to better assessing hazards for the environment and therefore for human health in highly polluted areas.