The biogeochemistry of mercury at the sediment water interface in the Thau lagoon. 1. Partition and speciation

Type Article
Date 2007-04
Language English
Author(s) Muresan Paslaru Bogdan1, Cossa Daniel1, Jezequel D2, 3, Prevot F2, 3, Kerbellec S1
Affiliation(s) 1 : IFREMER, Ctr Nantes, F-44311 Nantes 03, France.
2 : Univ D Diderot, CNRS, UMR 7047, LGE, F-75251 Paris, France.
3 : IPGP, F-75251 Paris 05, France.
Source Estuarine and Coastal Marine Science (0272-7714) (Elsevier), 2007-04 , Vol. 72 , N. 3 , P. 472-484
DOI 10.1016/j.ecss.2006.11.015
WOS© Times Cited 54
Keyword(s) Fluxes, Partition, Sediment, Lagoon, Methylmercury, Mercury
Abstract Solid sediment, pore and epibenthic waters were collected from the Thau lagoon (France) in order to study the post depositional partition and mobility of mercury and monomethylmercury in an organic rich sediment. Total Hg (HgT) and monomethymercury (MMHg) profiles were produced in both dissolved and solid phases. The distribution of HgT in the solid appeared to be related to the historical changes in the Hg inputs into the lagoon. HgT was in equilibrium between solid and solution in the sulfidic part of the cores, with a mean log Kd of 4.9 +- 0.2. The solid appeared to be a source of HgT for pore water in the upper oxic to suboxic parts of the cores. The MMHg represented a small fraction of HgT: 3-15 % and 0.02-0.80 % in the dissolved and in the solid phases respectively. Its distribution was characterized by a main peak in the superficial sediments, and another deeper in the core within the sulfide-accumulating zone. In addition, high dissolved MMHg concentrations and methylated percentage were found in the epibenthic water. Ascorbate (pH 8) dissolution of the sediments and analyses of the soluble fraction suggest that the amorphous oxyhydroxides played a major role in controlling total and methylmercury mobility throughout the sediment water interface. These features are discussed in term of sources, transfer and transformations. Diffusive fluxes of HgT and MMHg from sediment to the water column for the warm period were estimated to be 40 +- 15 and 4 +- 2 pmol m-2 d-1 respectively.
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