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Abstract Title: Investigating Hg Cycling and Bioaccumulation in a Temperate Macro-tidal Lagoon Impacted by Legacy Pollution, the Venice Lagoon Case Study
Presenter Name: Ginevra Rosati
Company/Institution: National Institute of Oceanography and Applied Geophysics - OGS
Session: Mercury in Contaminated Sites
Day and Session: Thursday 28th July - Session Two
Start Time: 10:00 UTC
Co-Authors: Ginevra Rosati,C‚lia Laurent,Leslie Aveytua-Alcazar,Cosimo Solidoro,Donata Canu

Abstract Information :

Coastal bays and lagoons are impacted by multiple anthropogenic pressures and are often repositories for land-based chemical pollution, which can compromise their capability to provide ecosystem services such as fisheries in case of bioaccumulation levels exceeding thresholds for safe human consumption and commercialization. We integrate different modeling tools to investigate the spatial and temporal variability of Hg fate and transport in a well-studied temperate macro-tidal lagoon (The Venice Lagoon) impacted by legacy Hg, and its effects on bioaccumulation in the clam T. Philippinarum, representing an important economic resource to the area.
Previous field and modeling works pointed out the importance of hydrodynamics and dynamics of organic and inorganic sediment in controlling the fate of Hg and MeHg in shallow coastal environments like the Venice lagoon. The impact of sediment dynamics on Hg fluxes increases with elevated hydrodynamics and/or high concentrations of Hg in sediments due to accumulation from past pollution. We developed a model to simulate the biogeochemistry of Hg species and sediment dynamics and coupled it into the hydrodynamic finite element model SHYFEM. The variable-size elements constituting the model domain allow a good approximation of the bathymetry, also accounting for wetting and drying in the shallowest areas. This, along with the inclusion of the benthic-pelagic exchanges of Hg and particles driven by sediment resuspension and deposition, make the SHYFEM-Hg model particularly suitable to simulate the Hg cycling in coastal and shallow water environments at a fine spatial resolution. The plankton component is approximated through a ?labile POM? state variable, differentiated from the refractory phase of organic matter delivered from the watershed. The model was calibrated against available data for the Venice Lagoon and used to assess spatial and seasonal dynamics, as well as climate change scenarios under RCP8.5 forcings estimated for the area.
Modeled concentrations of MeHg in labile POM at clam-farming sites extracted from the Shyfem-Hg model will be used to force a bioenergetic-bioaccumulation model for T. Philippinarum.

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