A theoretical and experimental physicochemical study of sulfur species in the anoxic lagoon of Aitoliko-Greece

The spatiotemporal changes of metals, inorganic ions and physiochemical parameters of Aitoliko lagoon, an anoxic wetland in Western Greece, were studied with special emphasis in sulfur species. Theoretical physicochemical modeling was performed for the sulfur speciation, based on experimental pH and...

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Bibliographic Details
Published in:Chemosphere (Oxford) 2009-02, Vol.74 (8), p.1011-1017
Main Authors: Papadas, Ioannis T., Katerinopoulos, Lambros, Gianni, Areti, Zacharias, Ierotheos, Deligiannakis, Yiannis
Format: Article
Language:English
Subjects:
Anoxic
Applied sciences
Exact sciences and technology
Greece
Hydrogen-Ion Concentration
Iron - analysis
Lagoon
Models, Chemical
Oxidation-Reduction
Oxygen - analysis
Oxygen - metabolism
pe-pH
Pollution
Speciation
Sulfate
Sulfide
Sulfur Compounds - analysis
Sulfur Compounds - chemistry
Time Factors
Wetlands
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Summary:The spatiotemporal changes of metals, inorganic ions and physiochemical parameters of Aitoliko lagoon, an anoxic wetland in Western Greece, were studied with special emphasis in sulfur species. Theoretical physicochemical modeling was performed for the sulfur speciation, based on experimental pH and redox potential data. Accordingly, the speciation of sulfur in the lagoon can be operationally divided in two domains: (a) for depths d = 0–10 m below the surface, the sulfur speciation can be described by equilibrium reactions between the aqueous species. (b) At depths d > 10 m a progressive decline for SO 4 2 - concentration is observed between theory and experiment. At the lagoon-bottom an elevated concentration of 19 ± 2 mM SO 4 2 - was measured, which cannot be described by physicochemical equilibrium based on the pH, E h, O 2 concentrations measured in situ. Accordingly, we suggest that additional biogeochemical processes, such as sulfur bacteria activity, have to be invoked. Of particular importance is that the experimental pH-pe values cross the critical region where the interplay of SO 4 2 - / S 2 - /H 2S occurs. This explains why a relatively small fluctuation of pH, pe values may result in a shift of the equilibrium over one sulfur species. This explains the, otherwise accidental, previously reported releases of H 2S in the air over the lagoon.
ISSN:0045-6535
1879-1298
DOI:10.1016/j.chemosphere.2008.11.009