Aquatic Sciences Meeting, Albuquerque 2001
| SS08 Processes at the Benthic Interface (Environmental Connections) |
| Date: Wednesday, February 14, 2001, Time: 11:30:00 AM |
| Location: Ruidoso/Pecos |
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| Rocha, C, S, University of Algrave, Faro, Portugal, crocha@ualg.pt |
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| OXYGEN PORE WATER PROFILES IN PERMEABLE SANDY SEDIMENTS: AN APPROACH TO MODEL AND RESOLVE THE ROLE OF ENHANCED TRANSPORT AT THE SEDIMENT-WATER INTERFACE. |
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| The present work proposes an approach to describe oxygen pore water profiles in sandy sediments influenced by boundary-layer flow (advection). Results indicate that this type of solute behavior can be described by two-layer, 1-D advection-diffusion reaction modeling, and that relevant biogeochemical parameters, such as the advective mixing coefficient and the volumetric benthic oxygen consumption, can be independently estimated from real data through the calculation of adimensional parameter groupings called Damkohler numbers. Robustness of the approach was demonstrated in a study of benthic O2 dynamics in sandy sediments of the Ria Formosa (Southern Portugal), using mini-flumes with artificially imposed tidal currents, and by recalculating benthic uptake rates and mixing coefficients for North Sea continental shelf sandy sediments from published profiles. Estimated benthic uptake rates for intertidal sandy sediments of the Ria Formosa ranged from 1.76 to 5.12 mmol.m-2.d-1 in undisturbed sediments, from 3.76 to 9.17 mmol.m-2.d-1 in artificially disturbed sediment, and from 0.23 to 10.12 mmol O2.m-2.d-1 for the North Sea continental shelf sands. These are shown to be of the same magnitude as those measured in-situ for muddy sediments in several marine environments. It is argued that the present approach could aid in shortening the reported gap of 0-80 % between diffusion-based estimates and actual measurements in-situ of O2 flux and benthic uptake, therefore supporting more accurate estimates of organic matter turnover in continental shelf sands. |
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