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

Redox conditions and organic matter control marine methylmercury (MeHg) production. The Black Sea is the world's largest and deepest anoxic basin and is thus ideal to study Hg species along the extended redox gradient. Here we present new dissolved Hg and MeHg data from the 2013 GEOTRACES MEDBlack cruise (GN04_leg2) that we integrated into a numerical 1-D model, to track the fate and dynamics of Hg and MeHg. Contrary to a previous study, our new data show highest MeHg concentrations in the permanently anoxic waters. Observed MeHg/Hg percentage (range 9-57%) in the anoxic waters is comparable to other subsurface maxima in oxic open-ocean waters. With the modeling we tested for various Hg methylation and demethylation scenarios along the redox gradient. The results show that Hg methylation must occur in the anoxic waters. The model was then used to simulate the time evolution (1850-2050) of Hg species in the Black Sea. Our findings quantify (1) inputs and outputs of Hg-T (similar to 31 and similar to 28 kmol yr(-1)) and MeHgT (similar to 5 and similar to 4 kmol yr(-1)) to the basin, (2) the extent of net demethylation occurring in oxic (similar to 1 kmol yr(-1)) and suboxic water (similar to 6 kmol yr(-1)), (3) and the net Hg methylation in the anoxic waters of the Black Sea (similar to 11 kmol yr(-1)). The model was also used to estimate the amount of anthropogenic Hg (85-93%) in the Black Sea

Un modello integrato per la gestione della venericoltura nella laguna di Venezia

Questo volume consente la valutazione della sostenibilit\ue0 ambientale e tecnico-economica dell'attivit\ue0 di allevamento e di pesca della vongola in significative aree produttive del Nord Adriatico. Le specie indagate, Chamelea gallina e Tapes philippinarum , si possono ritenere le pi\uf9 rilevanti, per quanto riguarda le quantit\ue0 prodotte, i risvolti commerciali, l'indotto: costituiscono un bene estremamente diffuso nei mercati al consumo e sensibile da un punto di vista ecologicoambientale. Il volume riporta i risultati dell'indagine sugli aspetti biologici, ecologici e ambientali legati alla pesca e/o allevamento di vongole, analizza l'offerta del prodotto e le dinamiche della domanda. Oltre alla produttivit\ue0 economica dell'impresa, vengono analizzati i costi di produzione, aspetti legati alla forza lavoro, alla dotazione meccanica, i sistemi organizzativi e i rapporti con il mondo esterno. Si riportano gli esiti di un modello integrato ecologico, sociale ed economico per la valutazione di diversi scenari di gestione. Infine, riguardo al consumo del prodotto, si presenta il risultato di un'indagine volta a conoscere l'interesse degli acquirenti verso una certificazione di qualit\ue0. Nel complesso si pu\uf2 considerare originale lo studio, in particolare riguardo all'analisi economo-aziendale di un comparto, quale quello della venericoltura, tutt'oggi ancora poco conosciuto

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

International audienceRedox conditions and organic matter control marine methylmercury (MeHg) production. The Black Sea is the world's largest and deepest anoxic basin and is thus ideal to study Hg species along the extended redox gradient. Here we present new dissolved Hg and MeHg data from the 2013 GEOTRACES MEDBlack cruise (GN04_leg2) that we integrated into a numerical 1-D model, to track the fate and dynamics of Hg and MeHg. Contrary to a previous study, our new data show highest MeHg concentrations in the permanently anoxic waters. Observed MeHg/Hg percentage (range 9-57%) in the anoxic waters is comparable to other subsurface maxima in oxic open-ocean waters. With the modeling we tested for various Hg methylation and demethylation scenarios along the redox gradient. The results show that Hg methylation must occur in the anoxic waters. The model was then used to simulate the time evolution (1850-2050) of Hg species in the Black Sea. Our findings quantify (1) inputs and outputs of Hg T (~31 and ~28 kmol yr À1) and MeHg T (~5 and ~4 kmol yr À1) to the basin, (2) the extent of net demethylation occurring in oxic (~1 kmol yr À1) and suboxic water (~6 kmol yr À1), (3) and the net Hg methylation in the anoxic waters of the Black Sea (~11 kmol yr À1). The model was also used to estimate the amount of anthropogenic Hg (85-93%) in the Black Sea