Mercury contamination in Marano Lagoon (Northern Adriatic sea,Italy): Source identification by analyses of Hg phases |
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| Institution: | 1. Department of Geological, Marine and Environmental Sciences, University of Trieste, Via Weiss, 2, 34127 Trieste, Italy;2. Institute of Environmental Geochemistry, INF 236, University of Heidelberg, 69120 Heidelberg, Germany;1. School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, Hampshire PO1 3QL, UK;2. School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michael’s Building, White Swan Road, Portsmouth, Hampshire PO1 2DT, UK;3. AWE Aldermaston, Reading, Berkshire RG7 4PR, UK;1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, People’s Republic of China;2. Agro-Environmental Protection Institute Ministry of Agriculture, Tianjin 300191, People’s Republic of China;3. Center for Advances in Water and Air Quality, Lamar University, Beaumont, TX, USA;4. Department of Civil & Environmental Engineering, Lamar University, Beaumont, TX, USA;1. Department of Biology, Research Centre of Excellence of Plant and Vegetation Ecology, University of Antwerp, B-2610 Wilrijk, Belgium;2. Global Change Research Center AS CR, v.v.i., Bělidla 986/4a, 603 00 Brno, Czech Republic;3. Department of Animal and Plant Sciences, University of Sheffield, United Kingdom;1. Department of Soil Science, North Dakota State University, Fargo, ND 58108-6050, USA;2. Biosciences Research Laboratory, USDA-ARS, Fargo, ND 58102-2765, USA;3. Department of Geosciences, North Dakota State University, Fargo, ND 58108-6050, USA;4. Department of Civil Engineering, North Dakota State University, Fargo, ND 58108-6050, USA;1. Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA;2. Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, USA;3. Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA |
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| Abstract: | Total Hg concentrations and Hg speciation were determined in bottom sediments of Marano lagoon to investigate the consequences of Hg phases on fish farms and shellfish cultivation areas. Mercury phases were separated into cinnabar (HgS) and non-cinnabar compounds, via a thermo-desorption technique, in surface and core sediments; both of which had been contaminated by industrial wastes and mining activity residues. The former are due to an industrial complex, which has been producing cellulose, chlor-alkali and textile artificial fibres since 1940. Processing and seepage wastewaters, which were historically discharged into the Aussa-Corno river system and therefore into the lagoon, have been significantly reduced since 1984 due to the construction of wastewater treatment facilities. The second source is the Isonzo River, which has been the largest contributor of Hg into the northern Adriatic Sea since the 16th century due to Hg mining at the Idrija mine (western Slovenia). Red cinnabar (HgS) derived from the mining area is mostly stable and insoluble under current environmental conditions. In contrast, organically bound Hg, such as Hg bound to humic acids, has the potential to be transformed into bioavailable Hg compounds (for example, methylmercury). The presence of the two Hg forms permitted each Hg source to be quantified. It also allowed the areas with the highest risk of Hg contamination from Hg-rich sediment to be identified; thus potentially avoiding the transfer of Hg from the sediment into the water column and eventually into living biota. The results show that Hg Enrichment Factors in bottom sediments exceed values of 10 and cinnabar dominates the central sector near the main tidal channel where tidal flux is more effective. Non-cinnabar compounds were found to be enriched in fine grained material and organic matter. In fact, up to 98% of total Hg at the Aussa-Corno river mouth and in the inner margin of the basin occurred in an organic form. This evidence, combined with the high contents of total Hg (4.1–6.6 μg g−1 and EF > 10) measured in surface sediments, suggest that Hg in Marano lagoon is involved in biogeochemical transformations (e.g., methylation). |
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