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Past, present and future of the nutrients cascade in the Seine, Somme and Scheldt watersheds

Abstract : This PhD was carried out in the scope of a participative science program (AWARE) granted by the European Union. The aim of this program was to bring together scientists, citizens and stakeholders in order to think about how to improve the quality of European coastal zones, by studying three different cases study. Our case study is focused on the south part of the North Sea and its three contributing watersheds, the Seine, the Somme and the Scheldt basins. Through this dissertation, we aim to describe and to understand the cascade of nutrients along the land to sea aquatic continuum. The dissertation is organized following an upstream to downstream logic. In a first step, we outline the current quality of the continental and marine hydrosystems according to their past trajectory. This historical reconstruction covers a three centuries period for the well documented basin of the Zenne River, located within the Scheldt watershed. A more precise reconstruction covers the 24 last years for the Seine, Somme and Scheldt basins together. In a second step, we explore the role of the topography and of the riparian zones on the nitrogen cycle. First we explore this role at the scale of the Orgeval basin (sub-basin of the Seine), and then on the whole Seine catchment. In a third step, we explore the role of the stagnant waterbodies of the hydrographic network on the nitrogen, phosphorus and silica fluxes. This survey is composed of a retrospective approach based on the study of old maps, and of a prospective approach by the proposal of scenarios of ponds reintroduction within the hydrographic network. In a fourth step, we present the role played by estuaries of the Scheldt and of the Seine rivers on nutrients fluxes before they discharge into the coastal zone. Finally, a general conclusion summarizes the new knowledge we have gained about the cascade of nutrients. In this part, we also suggest a prioritization of some measures which could be taken in order to improve the quality of the continental and marine ecosystems.
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https://tel.archives-ouvertes.fr/tel-00789546
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Submitted on : Monday, February 18, 2013 - 2:30:24 PM
Last modification on : Tuesday, November 10, 2020 - 4:50:19 PM
Long-term archiving on: : Sunday, May 19, 2013 - 4:03:36 AM

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  • HAL Id : tel-00789546, version 1

Citation

Paul Passy. Past, present and future of the nutrients cascade in the Seine, Somme and Scheldt watersheds. Environmental and Society. Université Pierre et Marie Curie - Paris VI, 2012. English. ⟨tel-00789546⟩

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