title: Investigations into the differential reactivity of endogenous and exogenous mercury species in coastal sediments.
abstract: Stable isotopic tracer methodologies now allow the evaluation of the reactivity of the endogenous (ambient) and exogenous (added) Hg to further predict the potential effect of Hg inputs in ecosystems. The differential reactivity of endogenous and exogenous Hg was compared in superficial sediments collected in a coastal lagoon (Arcachon Bay) and in an estuary (Adour River) from the Bay of Biscay (SW France). All Hg species (gaseous, aqueous, and solid fraction) and ancillary data were measured during time course slurry experiments under variable redox conditions. The average endogenous methylation yield was higher in the estuarine (1.2 %) than in the lagoonal sediment (0.5 %), although both methylation and demethylation rates were higher in the lagoonal sediment in relation with a higher sulfate-reducing activity. Demethylation was overall more consistent than methylation in both sediments. The endogenous and exogenous Hg behaviors were always correlated but the exogenous inorganic Hg (IHg) partitioning into water was 2.0-4.3 times higher than the endogenous one. Its methylation was just slightly higher (1.4) in the estuarine sediment while the difference in the lagoonal sediment was much larger (3.6). The relative endogenous and exogenous methylation yields were not correlated to IHg partitioning, demonstrating that the bioavailable species distributions were different for the two IHg pools. In both sediments, the exogenous IHg partitioning equaled the endogenous one within a week, while its higher methylation lasted for months. Such results provide an original assessment approach to compare coastal sediment response to Hg inputs.
authors: Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, UMR 5254 CNRS-Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2, av. P. Angot, 64053, Pau cedex 9, France.
authors: S
authors: S
authors: Bouchet
authors: P
authors: P
authors: Rodriguez-Gonzalez
authors: R
authors: R
authors: Bridou
authors: M
authors: M
authors: Monperrus
authors: E
authors: E
authors: Tessier
authors: P
authors: P
authors: Anschutz
authors: R
authors: R
authors: Guyoneaud
authors: D
authors: D
authors: Amouroux
mesh_terms: D001673:Biodegradation, Environmental; D063366:Estuaries; D005602:France; D019015:Geologic Sediments / Q000032:analysis*; D017669:Mercury Compounds / Q000032:analysis* / Q000378:metabolism; D008629:Mercury Isotopes / Q000032:analysis; D008745:Methylation; D010084:Oxidation-Reduction; D013054:Spectrophotometry, Atomic; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D017669:Mercury Compounds; D008629:Mercury Isotopes; D014874:Water Pollutants, Chemical