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Influence du réseau hydraulique sur la qualité des eaux de surface dans un marais littoral agricole : Rôle des processus géochimiques à l’interface eau-sédiment

Abstract : In the context of new policy development concerning the management of surface waters in french atlantic coastal wetlands, agricultural runoff are studied at the scale of a 2500 ha hydraulic network unit model. Controlling the risks emerging from drainage agricultural practices toward other activities like shellfish culture and natural resources preservation is the principal aim of this work. The hydraulic ditch network is the main focus since it is the principal collective water management tool which allows quality improvements. Fluxes measurements are done at three levels : nearby contamination sources (drainage pumps), along a channel and at the wetland outlet in the sea. This work underlines the major action of water-sediment interface in the solutes recycling of nitrogen and atrazin in particular. The nitrate removal rate potential in the ditches network varies from 0,6 to 30 mg.m-2.j-1 ; atrazine adsorption and biodegradation is evaluated at ca. -25 % in fifteen days (with 30 μg.l-1 of atrazine) and ca. -30 % in sixty days (with 2 μg.l-1 of atrazine). The contamination levels of water discharges at sea are fairly high (water average concentrations are below 20 mg.l-1 for nitrates and 1 μg.l-1 for atrazine) and are not insignificant at the scale of Marennes Oleron Basin (7 to 12 tons of nitrates, 3 kg of triazine during the complete discharge period). The completion of this work was achieved through the development of special equipments such as current meter, benthic chambers and bioreactor. The results of this work should permit to promote natural degradation processes before water discharge at sea in the global policy project of the wetlands. In an integrative approach, the question of water levels management and hydraulics should be addressed through a better management of water volume stocked within the network, network mesh density and contaminated water residence time adjustments for a better exploitation of the characteristics of this particular ecosystem.
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Contributor : Loïc Anras <>
Submitted on : Monday, March 19, 2018 - 12:57:09 PM
Last modification on : Friday, March 20, 2020 - 1:01:07 AM
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Loïc Anras. Influence du réseau hydraulique sur la qualité des eaux de surface dans un marais littoral agricole : Rôle des processus géochimiques à l’interface eau-sédiment. Sciences de l'environnement. Université de Poitiers, 1997. Français. ⟨tel-01737226⟩

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