Monitoring and Modeling of Metal Concentration Distributions in Anoxic Basins: Aitoliko Lagoon, Greece |
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| Authors: | Areti Gianni Miltiadis Zamparas Ioannis T Papadas George Kehayias Yiannis Deligiannakis Ierotheos Zacharias |
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| Institution: | 1. Department of Environmental and Natural Resources Management, University of Ioannina, 2 Seferi Str., 30100, Agrinio, Greece
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| Abstract: | The balance between physicochemical processes, influencing vertical and temporal distributions of metal compounds in one relatively isolated anoxic environment, constitutes the objective of the present work. Ion activity product (IAP) was calculated for manganese and iron sulfides, in order to define the metal sulfide forms that control Fe and Mn solubility in the bottom waters of anoxic lagoons. Iron solubility depended on amorphous FeS formation, while manganese sulfides were a minor component in a solid solution lowering its solid-phase activity. A theoretical physicochemical model was developed for the iron speciation, based on experimental pH and redox potential data. A very good match was achieved for the measured and the theoretical total dissolved iron, at all depths. The dominance of oxidant iron species Fe(OH) 3 ? in the surface waters and their sequence by FeSH+ and FeSaq in the deeper layers brings out the influence of physicochemical parameters (dissolved oxygen, sulfide, pH and Eh) in vertical distribution of dissolved metal species, in anoxic/hypoxic basins. Based on these findings, we can conclude that the distribution of manganese and iron is of special interest, not only because these are the indicators of redox conditions but also for the role of their oxidized/reduced forms in the formation of the biogeochemical structure of redox zone. |
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