GEOSCAN, résultats de la recherche


TitreMeasuring particle dynamics in Arctic and mussel aquaculture environments
AuteurWalker, T R; Grant, J; Hill, P S; Cranford, P; Lintern, G; Scofield, B
SourceProceedings of the 12th Canadian Coastal Conference/Comptes-rendus, Conférence canadienne sur le littoral 2005; 2005 p. 1-11
Séries alt.Secteur des sciences de la Terre, Contribution externe 20080318
Réunion12th Canadian Coastal Conference 2005; Dartmouth, NS; CA; Novembre 6-9, 2005
Mediapapier; en ligne; numérique
ProvinceÎle-du-Prince-Édouard; Québec; Territoires du Nord-Ouest
SNRC107B; 107C; 117A; 117D; 11L/07; 11N/12
Lat/Long OENS -61.7500 -61.2500 47.7500 47.5000
Lat/Long OENS-624.0000 -63.0000 46.5000 46.2500
Lat/Long OENS-140.0000 -132.0000 70.0000 68.0000
Sujetssedimentation; débit de sedimentation; suspension des sédiments; érosion; analyses granulométriques; milieu côtièr; études côtières; carottes; repartition granulométrique; carbone; salinité; aquaculture; sédimentologie; géologie marine
Illustrationsphotographs; sketch maps; analyses
Résumé(disponible en anglais seulement)
Resuspension of bottom sediments, particle settling rates and particle sizes were assessed at coastal locations around Canada. Sediment erosion was measured using a recently calibrated field instrument called the BEAST. The BEAST (Benthic Environmental Assessment Sediment Tool) is a portable device, designed for measuring sediment resuspension and calibrated to yield sediment bed shear velocity (u*). Sediment cores were placed beneath an oscillating grid, which penetrates down to the sediment-water interface creating turbulence, and causes resuspension. Resuspended material is proportional to the frequency of the grid oscillation and shear velocity. Equivalent shear stresses created by the oscillating grid were determined by comparing results from a calibrated shear stress probe with known shear velocity values from fluid flow experiments performed in a laboratory flume. The BEAST allows for estimates of erosion rates, critical shear stress and particle size distributions on resuspended sediment particles in cores from fresh, undisturbed sediment. Using the BEAST, settling chambers, sediment traps and water samples, particle dynamics were investigated around several coastal sites in Canada, including mussel culture sites in the Magdalen Islands and PEI and also in the Arctic on the Mackenzie Delta and Beaufort Sea. Comparisons of sediment erosion were made between cores collected by divers and grabs at Tracadie Bay, PEI. There was no significant difference between erosion thresholds, of bottom sediments in Tracadie Bay, using both methods of collection. The slopes of curves for all erosion sequences at this site were highly correlated with each other (correlation coefficient = 0.99). In the Magdalen Islands resuspension experiments were performed along a transect, beginning under a mussel line to a control site. Sediment resuspension decreased away from the mussel line, with u* values ranging from 3-5 cm s-1. Mean floc settling rates were 0.21 cm s-1 and mean particle sizes (Estimated Spherical Diameter, ESD) from a disturbed mussel line were 0.23 mm compared to a reference site, which were 0.09 mm. The Mackenzie River is an important source of sediment and organic carbon to the Arctic and horizontal fluxes of suspended sediment and timing of high turbidity were investigated. Suspended sediment concentrations reached over 5000 mg L-1 in summer and sediment turbidity from SPM analysis showed a strong relationship with wind speed (R2 = 0.71) in inner Kugmallit Bay. Particle size analysis and settling rates were also strongly related (R2 = 0.91) and mean ESD values of 0.9 mm with mean settling rates were less than 1.0 cm s-1. Erosion thresholds for sediment collected in the Beaufort Sea varied between 4 to 5 cm s-1.