title: Seasonal variation of methylmercury in sediment cores from the Tagus Estuary (Portugal).
abstract: Seasonal and spatial variations of dissolved and particulate methylmercury were evaluated for the first time in sediment cores from the Tagus Estuary. Results showed the highest MeHg concentrations in summer months indicating that the "seasonally" methylation process occurs not only at the topmost layers of the sediments but also in the deeper layers of the sediment column. The proportion of MeHg (up to 92%) in some of our pore water samples was higher than values reported in the literature for other estuaries suggesting that the sedimentary environment in the Tagus tends to favour Hg methylation. This work points to the importance of seasonal variation of the MeHg production in sediment cores. In physically dominated estuaries this enhances seasonal MeHg production in deeper sediments that can have serious ecological impacts due to resuspension or advection processes under extreme events by the increase of MeHg transported to the water column.
authors: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa, Portugal; Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisboa, Portugal.
authors: Carlos Eduardo
authors: CE
authors: Monteiro
authors: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa, Portugal; Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisboa, Portugal.
authors: Rute
authors: R
authors: Cesário
authors: Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia, Canada.
authors: Nelson J
authors: NJ
authors: O'Driscoll
authors: Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisboa, Portugal.
authors: Marta
authors: M
authors: Nogueira
authors: Departamento de Química, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors: Mónica
authors: M
authors: Válega
authors: Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisboa, Portugal.
authors: Miguel
authors: M
authors: Caetano
authors: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa, Portugal. Electronic address: joao.canario@tecnico.ulisboa.pt.
authors: João
authors: J
authors: Canário
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D063366:Estuaries; D019015:Geologic Sediments / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis; D008628:Mercury / Q000032:analysis; D008767:Methylmercury Compounds / Q000032:analysis*; D011174:Portugal; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Methylmercury; Pore waters; Seasonal variation; Sediments; Tagus Estuary