Diagenetic production, accumulation and sediment-water exchanges of methylmercury in contrasted sediment facies of Lake Titicaca (Bolivia)
| Type | Article | ||||||||||||||||
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| Date | 2020-06 | ||||||||||||||||
| Language | English | ||||||||||||||||
| Author(s) | Guédron S.1, 2, Audry S.3, Acha D.4, Bouchet S.5, Point D.3, Condom T.6, Heredia C.1, 4, Campillo S.1, Baya A.3, Groleau A.7, Amice Erwan8, Amouroux D.4, 5 | ||||||||||||||||
| Affiliation(s) | 1 : Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France 2 : Laboratorio de Hidroquímica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andres, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia 3 : Géosciences Environnement Toulouse, UMR5563, IRD UR 154, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400 Toulouse, France 4 : Unidad de Calidad Ambiental (UCA), Instituto de Ecología, Universidad Mayor de San Andrés, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia 5 : Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les matériaux, Pau, France 6 : Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, Institut des Géosciences de l'Environnement (IGE), UMR 5001, F-38000 Grenoble, France 7 : Institut de Physique du Globe de Paris (IPGP), 1, rue Jussieu, 75238 Paris Cedex 05, France 8 : LEMAR- Laboratoire des sciences de l'environnement marin, Institut Universitaire Européen de la Mer - Technopôle Brest-Iroise, Rue Dumont d'Urville, 29280 Plouzané, France |
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| Source | Science Of The Total Environment (0048-9697) (Elsevier BV), 2020-06 , Vol. 723 , P. 138088 (14p.) | ||||||||||||||||
| DOI | 10.1016/j.scitotenv.2020.138088 | ||||||||||||||||
| WOS© Times Cited | 18 | ||||||||||||||||
| Keyword(s) | Methylmercury, Lake sediment, Early diagenesis, High altitude ecosystem, Diffusive fluxes | ||||||||||||||||
| Abstract | Monomethylmercury (MMHg) concentrations in aquatic biota from Lake Titicaca are elevated although the mercury (Hg) contamination level of the lake is low. The contribution of sediments to the lake MMHg pool remained however unclear. In this work, seven cores representative of the contrasted sediments and aquatic ecotopes of Lake Titicaca were sliced and analyzed for Hg and redox-sensitive elements (Mn, Fe, N and S) speciation in pore-water (PW) and sediment to document early diagenetic processes responsible for MMHg production and accumulation in PW during organic matter (OM) oxidation. The highest MMHg concentrations (up to 12.2 ng L−1 and 90% of THg) were found in subsurface PWs of the carbonate-rich sediments which cover 75% of the small basin and 20% of the large one. In other sediment facies, the larger content of OM restricted MMHg production and accumulation in PW by sequestering Hg in the solid phase and potentially also by decreasing its bioavailability in the PW. Diagenetically reduced S and Fe played a dual role either favoring or restricting the availability of Hg for biomethylation. The calculation of theoretical diffusive fluxes suggests that Lake Titicaca bottom sediments are a net source of MMHg, accounting for more than one third of the daily MMHg accumulated in the water column of the Lago Menor. We suggest that in the context of rising anthropogenic pressure, the enhancement of eutrophication in high altitude Altiplano lakes may increase these MMHg effluxes into the water column and favor its accumulation in water and biota. |
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