Biogeochemical processes during the infiltration of river water into an alluvial aquifer
| Autor: | Alain C.M. Bourg, Clotilde Bertin |
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| Rok vydání: | 1993 |
| Předmět: | |
| Zdroj: | Environmental Science & Technology. 27:661-666 |
| ISSN: | 1520-5851 0013-936X |
| DOI: | 10.1021/es00041a009 |
| Popis: | Summary and Conclusions The chemical changes in the infiltration flow path from the Lot River to an adjacent aquifer were followed using chloride as an indicator of physical mixing of the river water with groundwater. The chemical reactivity close to the river is very significant with respect to the aquifer water composition (Figure 7). Two types of processes occur. A first series leads to irreversible reactions: weathering produces enriched Ca, Mg, bicarbonate, and Si concentrations, reductive reactions lead to denitrifi- cation, and adsorption reactions remove zinc from solution (11,22). A second series comprises processes which lead to the formation of the so-called reduced zone, and most of them are reversible. As long as microbial activity, which is very intense in the river sediments, consumes more oxygen than what is brought by the water coming from the river, the environment becomes reduced. This leads to dissolution of manganese oxides. Further along, when the microbial activity decreases, and when additional oxygen can be supplied by the permeable unsaturated zone, the water environment becomes oxidized again. Manga- nese is removed from solution by a combination of adsorption and surface oxidation reactions. |
| Databáze: | OpenAIRE |
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