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Mobilité des éléments selon les alternances aérobie-anaérobie dans un écosystème rizicole en Camargue

Abstract : In natural or cultivated soils from wet areas, the oxido-reductive conditions influence the mechanisms of element mobilisation or immobilisation. The mobility of elements is studied in paddy soils in Camargue. Soils are originally constituted of sediments which filled a Rhône paleochannel. Processes controlling the soil solution are analysed through continuously in situ recordings of physicochemical parameters. The impact of aerobic-anaerobic alternances, linked to annual irrigation cycle or to stormy precipitations, is studied at high frequency both in ground waters and in irrigation waters. In the waterlogged soil area, these perturbations generate mineral precipitation or dissolution. Thirty years of irrigation are enough for the annual dynamics to create an enriched horizon containing an oxido-reduction front. A year without irrigation initiates the dissolution of neoformed carbonates and oxides phases from this horizon. In the cultivated horizon, silicon, iron and lead are submitted to seasonal fluctuations linked to reductive conditions and plant activity. The amounts of dissolved iron, manganese and magnesium in waters are not controlled by known mineralogical phases. The acidification at pH 4 during the fourteen days of the pre-reproductive period allows the supply of nutrients from the dissolution of solid phases. Poor-crystallized clays and phytoliths are dissolved and provide silicon to rice.
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https://tel.archives-ouvertes.fr/tel-00186875
Contributor : Lise Cary <>
Submitted on : Monday, November 12, 2007 - 4:58:35 PM
Last modification on : Wednesday, October 14, 2020 - 3:50:32 AM
Long-term archiving on: : Monday, April 12, 2010 - 1:58:25 AM

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  • HAL Id : tel-00186875, version 1

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Lise Cary. Mobilité des éléments selon les alternances aérobie-anaérobie dans un écosystème rizicole en Camargue. Géochimie. Université de droit, d'économie et des sciences - Aix-Marseille III, 2005. Français. ⟨tel-00186875⟩

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