A sequential procedure for the extraction of iron hydroxides and the associated phosphate in estuarine seston is proposed. The procedure which uses a citrate-dithionite-bicarbonate (CDB) reagent has been chosen among five commonly used methods. It makes it possible to distinguish four statistically different modes of association between P and Fe based on the (Fe/P)$ sb{ rm CDB}$ values. The extraction sequence is applied to suspend particulate matter and to surface sediments of the Saint-Lawrence Upper Estuary. The intensity and the position of the core of its maximum turbidity zone is determined by sediment exchanges between the channel and large intertidal flats. These exchanges are controlling seasonal fluctuations observed in the estuarine phosphorus geochemistry: The fresh to salt water early transition zone is the main site for the flocculation and deposition of river derived colloids, mainly as surface coating on particle, a process which results in phosphate adsorption on the suspended matter; After this process has reached equilibrium in the water column, partial desorption occurs on the flats as the particles settle temporarily in spring and summer. The P-depleted solids are returned to the estuary when the marsh vegetation is destroyed in the fall by migrating snow geese. Laboratory experiments with natural materials confirm the equilibrium level of P-adsorption observed in situ, and evidence its reversibility under the low reducing conditions typical of marsh surface sediments.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75436 |
| Date | January 1987 |
| Creators | Lucotte, Marc |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Institute of Oceanography.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000550438, proquestno: AAINL44312, Theses scanned by UMI/ProQuest. |
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