Long-term scenarios of mercury budgeting and exports for a Mediterranean hot spot (Marano-Grado Lagoon, Adriatic Sea)

Abstract

The Marano-Grado Lagoon (MGL) is extensively contaminated by mercury (Hg) from local sources and long-term (500 years) tidally delivered inputs from the Idrija Hg mine (Slovenia) through Isonzo River suspended loads. A multibox WASP-7 (Water Analysis Simulation Program) model was used to simulate the long-term dynamics of the mercury cycle in the MGL. Scenario simulations were used to compute changes in the system over 100 years. Present and future Hg concentrations in water, sediment, and Hg budgets were compared, including evasion and MeHg inputs to the Mediterranean Sea, based on climate changes and mercury capping in tributary rivers. Using the Ref baseline scenario, the model computes a general decrease in HgT of 13% in the water column and of 80% in sediment and a strong MeHg increase in sediment (+73%). The net sea export of HgT decreases by 77% to up to 48 kg/y while MeHg increases by 10% to up to 0.63 kg/y. The lagoon sediment recovery time of HgT up to a target level of 0.3 mg/kg is computed over 570 years for surface sediments (1750 for subsurface sediments). When removing Hg from boundaries, the same target value for surface sediments is reached within 110 years

Mercury in the Black Sea: New Insights From Measurements and Numerical Modeling

“…The WASP7 Hg model/MERC7 submodel (Wool et al, 2001) is a dynamic process-based model designed to simulate the Hg cycle within a system of well-mixed discrete spatial units (layers) of water and sediment as well as the exchanges of the system with its boundaries. This model has been already adapted and successfully applied to a shallow environment in a 2D configuration (Canu & Rosati, 2017;Melaku Canu et al, 2015), and is here used in a 1D configuration to explore Hg dynamics along an extended redox gradient. Figure 3 shows the conceptual model of the processes that affect the evolution of the state variables (Table S2).…”

“…Global Biogeochemical Cycles 10.1002/2017GB005700 WASP7 Hg model /MERC7 sub-model (Wool et al, 2001) and already succefully applied in shallow waters (Canu & Rosati 2017;Melaku Canu et al, 2015). One-dimensional (1-D) modeling has widely been used to investigate the biogeochemical and ecological features of the basin (Grégoire & Soetaert, 2010;Konovalov et al, 2004;Lamborg et al, 2008;Oguz et al, 2000;Yakushev et al, 2007).…”

Unbounded boundaries and shifting baselines: Estuaries and coastal seas in a rapidly changing world

“…In addition, the contribution of organic matter and nutrient deposition to estuarine sediment via urban run-off during the monsoon season, resulted in a two-fold and five-fold increase in methanogenesis and denitrification respectively, increasing the production of the greenhouse gases nitrous oxide (N2O) and methane (CH4). Canu and Rosati (2016) modelled the long-term (100 yrs) dynamics of the mercury cycle in the Marano-Grado Lagoon (a Mediterranean mercury hotspot), and showed that a sea level rise (of 0.315 m) and temperature rise (+2.5°C) may increase sediment methylmercury (MeHg) by up to 87% and 95% of current levels. Mercury bioaccumulation in biota was projected to increase accordingly.…”

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

“…The investigation of the biogeochemical dynamics of Hg species in the marine environment addresses the need to accurately model sources and pathways of this priority contaminant within and among the different abiotic and biotic compartments of the aquatic ecosystem (Driscoll et al, 2013;Batrakova et al, 2014). Over the last few years some theo-retical studies have offered innovative tools to reproduce the mass balance and the dynamics of [Hg] in the marine environment by means of biogeochemical models based on interconnected zero-dimensional boxes representing water or sediment compartments: among these are the River MERLIN-Expo model (Ciffroy, 2015) and the WASP (Water Analysis Simulation Program) model (Melaku Canu et al, 2015;Canu and Rosati, 2017;Rosati et al, 2018). In particular, the River MERLIN-Expo model (Ciffroy, 2015) has been used to reproduce the spatiotemporal distribution of inorganic and organic contaminants in the 1D domain of rivers and to calculate the mass balance for each of them.…”

“…Over the last few years some theo-retical studies have offered innovative tools to reproduce the mass balance and the dynamics of [Hg] in the marine environment by means of biogeochemical models based on interconnected zero-dimensional boxes representing water or sediment compartments: among these are the River MERLIN-Expo model (Ciffroy, 2015) and the WASP (Water Analysis Simulation Program) model (Melaku Canu et al, 2015;Canu and Rosati, 2017;Rosati et al, 2018). In particular, the River MERLIN-Expo model (Ciffroy, 2015) has been used to reproduce the spatiotemporal distribution of inorganic and organic contaminants in the 1D domain of rivers and to calculate the mass balance for each of them. Although the model is able to describe many of the physical and chemical processes involved in fresh water and sediment, it specifically targets environments characterized by (i) nearly homogeneous water bodies and (ii) limited variations in landscape geometry.…”