Mercury speciation and exchanges at the air-water interface of a tropical artificial reservoir, French Guiana

Type Article
Date 2007-10
Language English
Author(s) Muresan Paslaru Bogdan1, Cossa Daniel1, Richard S2, Burban B2
Affiliation(s) 1 : IFREMER, F-44311 Nantes 3, France.
2 : HYDRECO, Lab Petit Saut, F-97388 Kourou, French Guiana, France.
Source Science of The Total Environment (0048-9697) (Elsevier), 2007-10 , Vol. 385 , N. 1-3 , P. 132-145
DOI 10.1016/j.scitotenv.2007.06.013
WOS© Times Cited 16
Keyword(s) Fluxes, Speciation, Mercury, Artificial reservoir, Atmosphere
Abstract The distribution and speciation of mercury (Hg) in air, rain, and surface waters from the artificial tropical lake of Petit-Saut in French Guiana were investigated during the 2003/04 period. In the air, total gaseous mercury (TGM) at the dam station averaged 12 +/- 2 pmol m(-3) of which > 98% was gaseous elemental mercury (GEM). GEM distribution depicted a day-night cycling with high concentrations (up to 15 pmol m(-3)) at dawn and low concentrations (down to 5 pmol m(-3)) at nightfall. Reactive gaseous mercury (RGM) represented < 1% of the GEM with a mean concentration of 4 3 fmol m(-3). Diel RGM variations were negatively related to GEM. In the rain, the sum of all Hg species in the unfiltered (HgTUNF) averaged 16 +/- 112 pmol L-1. Temporal distribution of HgTUNF exhibited a pattern of high concentrations during the late dry seasons (up to 57.5 pmol L-1) and low concentrations (down to 2.7 pmol L-1) in the course of the wet seasons. Unfiltered reactive (HgRUNF), dissolved gaseous (DGM) and monomethyl (MMHgUNF.) Hg constituted 20, 5 and 5% of HgTUNF, respectively. All measured Hg species were positively related and displayed negative relationships with the pH of the rain. In the reservoir surface waters, dissolved total mercury (HgTD) averaged 3.4 +/- 1.2 pmol L-1 of which 10% consisted of DGM. DGM showed a trend of high concentrations during the dry seasons (480 +/- 270 finol L-1 and lower (230 +/- 130 finol L-1) in the course of the wet seasons. Diel variations included diurnal photo-induced DGM production (of about 60 firiol L-1 h(-1)) coupled to minute to hour oxidation/ reduction cycles (of > 100 firiol L-1 amplitude). Finally, calculated atmospheric Hg inputs to the Petit-Saut reservoir represented 14 mot yr(-1) whereas DGM evasion reached 23 mol yr(-1). Apportionment among forms of Hg deposition indicated that up to 75% of the total Hg invasive flux follows the rainfall pathway. (C) 2007 Elsevier B.V. All rights reserved.
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