High metal inputs to closed seas: the New Caledonian lagoon |
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| Institution: | 1. URA CNRS 132, Géochimie Isotopique, Parc Valrose, Université de Nice, F-06108 Nice cedex 2, France;2. URA CNRS 132, Géosciences de l''Environnement. Faculté des Sciences de St Jérôme, Univ., F-13397 Marseille, France;3. O.R.S.T.O.M., 70 Route d''Aulnay, F-93140 Bondy, France;1. South African Sugarcane Research Institute, Private Bag X02, Mount Edgecombe, Durban, South Africa;2. School of Agricultural, Earth and Environmental Sciences, University of Kwazulu-Natal, Pietermaritzburg, South Africa;3. Division of Plant Breeding, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein, South Africa;1. Department of Environmental Studies and Agriculture, Beit Berl College, Doar beit Berl, Israel;2. Dipartimento di Agricoltura, Ambiente e Alimenti, Università degli Studi del Molise, Via Francesco De Sanctis, 86100 Campobasso, Italy;3. Dipartimento di Scienze delle Produzioni Agroalimentari e dell''Ambiente (DISPAA), Università degli Studi di Firenze, P.le delle Cascine 28, 50144 Firenze, Italy;4. Istituto di Bioscienze e Biorisorse – C.N.R., via Madonna del Piano 10, 50019 Sesto F.no, Firenze, Italy;1. State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China;2. College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China;3. Postgraduate School, Chinese Academy of Forestry, Beijing 100091, China;4. Büsgen-Institut, Department of Forest Botany and Tree Physiology, Georg-August Universität, Büsgenweg 2, 37077 Göttingen, Germany;1. Department of Plant Physiology, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland;2. Department of Agricultural and Environmental Chemistry, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland;3. Department of Botany, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland;1. AP–HP, DHU Authors, Centre de référence national pour les maladies systémiques auto-immunes rares, hôpital Cochin, service de médecine interne, Paris, France;2. Université Paris Descartes, institut Cochin, CNRS UMR 8104, Inserm U1016, 22, rue Méchain, 75014 Paris, France;1. Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China;2. Bio-Innovation Center of DR PLANT, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China |
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| Abstract: | The islands of New Caledonia are largely composed of ultrabasic rocks (peridotites). severily weathered, rich in Fe, Mn and Co, and where several ore deposits of Ni and Cr are extensively mined. Sediment cores from the bay of Dumbea, in the south of the main island, and from the northern part of the lagoon (Belep Islands), less affected by the mining activities, were analyzed for their mineral composition and metal concentrations. In the surficial sediments, oxides and silicates, including Fe serpentine and smectites, undergo rapid transformation or neoformation in a short time, in particular in the confined bay of Dumbea. Fe is largely present as goethite, and in deeper layers (60–100 cm) as hematite and magnetite. Chromite can be identified at each horizon. The metal concentrations decrease from the near shore areas, in particular the vicinity of the Dumbea river mouth to the open part of the lagoon. This trend is more important for Ni than for Fe or Cr. Fe ranges from 3.5 to 9% (dry weight), Ni from 200 to 2000 μg/g, Cr from 700 to 2000 μg/g, Co from 20 to 150 μg/g and Mn from 130 to 900 μg/g; yet the concentrations are lower than concentrations found in the ultrabasic rocks or laterites of the watershed. To try to understand the behavior of metals during the sedimentation-diagenesis events, we evaluated the sediment accumulation rate, and used different sequential leaching procedures. Fe, Mn, Ni, Cr and Co are mainly present as, or bound to, oxides or oxyhydroxides, even in the deeper layers ( > 100 cm) where the organic content is relatively high (about 6% of organic C). Metals are mainly transported from the land to the lagoon as oxides and dispersed in the lagoon sediments, where they are diluted with a large amount of carbonaceous sediment. During diagenesis, a significant part of Mn, Co and Ni are dissolved; but, unlike Mn and Co, which seem to coprecipitate with carbonate, most of the Ni is released into the waters of the lagoon. Apparently no horizon of the sediment has undergone significant in-situ metal enrichment. |
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