title: Mercury dilution by autochthonous organic matter in a fertilized mangrove wetland.
abstract: A dated sediment core from a highly-fertilized mangrove wetland located in Cubatão (SE Brazil) presented a negative correlation between mercury (Hg) and organic carbon contents. This is an unusual result for a metal with well-known affinity to organic matter. A dilution of Hg concentrations by autochthonous organic matter explained this observation, as revealed by carbon stable isotopes signatures (δ(13)C). Mercury dilution by the predominant mangrove-derived organic matter counterbalanced the positive influences of algal-derived organic matter and clay contents on Hg levels, suggesting that deleterious effects of Hg may be attenuated. Considering the current paradigm on the positive effect of organic matter on Hg concentrations in coastal sediments and the expected increase in mangrove organic matter burial due to natural and anthropogenic stimulations of primary production, predictions on the influences of organic matter on Hg accumulation in mangrove wetlands deserve caution.
authors.affiliation: Departamento de Geoquímica, Instituto de Química, Universidade Federal Fluminense, Niterói, RJ, 24020-150, Brazil. Electronic address: wmachado@geoq.uff.br.
authors.forename: Wilson
authors.initials: W
authors.lastname: Machado
authors.affiliation: National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW, 2540, Australia.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Sanders
authors.affiliation: National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW, 2540, Australia.
authors.forename: Isaac R
authors.initials: IR
authors.lastname: Santos
authors.affiliation: Southern Cross Geoscience, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia.
authors.forename: Luciana M
authors.initials: LM
authors.lastname: Sanders
authors.affiliation: Departamento de Geoquímica, Instituto de Química, Universidade Federal Fluminense, Niterói, RJ, 24020-150, Brazil.
authors.forename: Emmanoel V
authors.initials: EV
authors.lastname: Silva-Filho
authors.affiliation: Instituto de Geociências, Universidade Estadual de Campinas, Campinas, SP, 13083-970, Brazil.
authors.forename: Wanilson
authors.initials: W
authors.lastname: Luiz-Silva
mesh_terms: D001938:Brazil; D002247:Carbon Isotopes; D019015:Geologic Sediments / Q000032:analysis*; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D043982:Rhizophoraceae / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D002247:Carbon Isotopes; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Contamination history; Mangrove wetlands; Mercury dilution effect; Organic matter sources; Rhizosphere processes