Measurement and modeling of mercury complexation by dissolved organic matter isolates from freshwater and effluents of a major wastewater treatment plant |
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| Authors: | Bogdan Muresan Benoît Pernet-Coudrier Daniel Cossa Gilles Varrault |
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| Institution: | aUniversité Paris-Est, LEESU, UMR MA 102, AgroParisTech, Univ. Paris Est Créteil, 61 Av. du Gal de Gaulle, 94010 Créteil Cedex, France;bIFREMER Centre de Méditerranée, Lab. de Biogéochimie des Contaminants Métalliques, BP 330, Zone Portuaire de Brégaillon, F.83507 La Seyne-sur-mer, France |
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| Abstract: | Dissolved organic matter (DOM) samples were obtained from a low-density urbanized area located upstream of Paris (along the Marne River, France) and from the treated effluents at the Paris main wastewater treatment plant. These samples were then fractionated according to their hydrophobicity. DOM fractions consisted of nanomolar to sub-micromolar fresh organic substances with extremely strong Hg-complexing ligands. The conditional stability constants (i.e.  ; pH ∼ 6.8, INaCl = 0.5 M, T = 25 °C) of the Hg-DOM complexes formed were greater than 1024 M−1, for the reaction Hg2+ + L = HgL (with L as ligand). For upstream of Paris, thermodynamic calculations indicated that the vast majority of Hg-DOM was associated with hydrophobic DOM. In contrast, in the Paris main wastewater treatment plant effluents, Hg-DOM was mainly bound to hydrophilic DOM. Simple dilution calculations highlighted that due to the large DOM loading of urban discharges, the hydrophilic urban DOM ligands may commonly dominate Hg-DOM speciation in the downstream Seine River, except under extreme dilution (i.e. high water episodes or floods). |
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