One of the most recognised values of tidal salt marshes is the ecosystem service they provide as natural sinks for contaminants such as metals. This study examines net accumulation of metals (As, Cr, Cu, Hg, Ni, Pb, Zn and V) over a 5-yr period, from 1997 to 2002, in surface sediments of salt marshes in the Bay of Fundy, Canada. Metal accumulation has been measured in seven sites that extend from outer to inner Bay and in low and high marsh areas within each site. Overall, sediment metal concentrations are at or near their natural levels. Concentrations of metals show variability among marshes but are not significantly different between low and high marsh. Concentrations of As, Hg, Pb and V appear to be influenced by anthropogenic inputs. Calculated sediment loading rates for these metals generally showed gradients of increased loading from outer to inner Bay. Variability in sediment deposition rate is the driving force behind this spatial pattern. Results of this study suggest that the value of salt marshes as a sink for metals may be enhanced by high sedimentation rates.

No description available.

The influence of sedimentary variables on the structure and function of infaunal estuarine and marine communities is well studied but less is known of the influence of biota on sediment properties. Feeding and burrowing activity, locomotion, the production of faecal pellets and biological secretions (bioturbation) have important implications for sediment structure, chemistry, transport characteristics and the flux of nutrients and contaminants. Although spatial and temporal patterns in bioturbation have been studied to some extent, little attention has been given to the effects of pollution. The present study examines the effects of an intertidal petrochemical discharge into the Humber estuary (UK), from BP chemicals (Saltend) Ltd on the structure and function of the communities. Field and laboratory techniques were used to determine the effects of community change on bioturbation potential. In addition, a laboratory flume was constructed to measure sediment erosion potential with field measurements being taken using a Cohesive Strength Meter (CSM). The physico-chemical properties of the sediment, changes to the infaunal community structure, bioturbation potential and the interaction of these variables were used to explain differences between the erosion potential of sediments subject to varying levels of contamination. The main study was carried out on the Saltend mudflats near Hull, with sites at various distances from the outfall being used. A further set of control sites on the adjacent, and largely unaffected, mudflat at Paull were also used. In terms of the sediment properties, sites closest to the outfall showed the greatest degree of anoxia and the highest chlorophyll-a and carbohydrate concentrations, with all three parameters being seasonally influenced. No consistent spatial or temporal patterns were found for any of the other parameters (water and organic content, particle size). Whilst the infaunal communities were characteristic of estuarine areas, macrobenthic community response followed the Pearson & Rosenberg (1978) model for organic discharges with high abundance and low species diversity being associated with the more polluted sediments. Close to the discharge, there was an impoverished community consisting predominantly of highly abundant oligochate worms. With increasing distance from the outfall, species diversity and biomass increased with Hediste diversicolor becoming increasingly dominant and the appearance of Corophium volutator, Streblospio shrubsolii and Macoma balthica. Bioturbation potential was significantly reduced (in terms of depth and burrow volume and density) by increasing effiuent concentrations and with proximity to the discharge. The diversity of both feeding and sediment modification guilds was also reduced as a result of the discharge. Both field and laboratory studies indicated a stabilising effect of this type of pollution. Using the CSM, critical shear stress values were found to be significantly lower from unpolluted sites, indicating higher erosion potential, than those from sites close to the discharge. As a result of this, the total mass of sediment eroded from unpolluted sites was significantly higher than that from polluted areas. A similar trend was observed in the laboratory with sediments treated with an effluent concentration of 32% being considerably more stable than untreated sediments. Flume studies also indicated the stabilising effect of pollution with suspended particulate matter (SPM) concentrations and mass of sediment being transported as bedload being significantly higher for unpolluted sediments. These differences in erosion potential were attributed to the direct effects of the effiuent on the physico-chemical properties of the sediment, the effects of the effiuent and sediment type on macrofaunal community structure and function and the differences in bioturbation potential between sites. The implications of these findings in the wider context of coastal management are discussed.

During 1973 data was collected to analyze the seasonal variations of the tidal dynamics, water quality and sediments of the Alsea Estuary. A summary of historical information with a list of all known alterations to the estuary was made. A complete physical description, including the geographical setting and mixing classification of the estuary, was done. Times of high and low water and tidal ranges at three locations were measured. Tide measurements made at Waldport indicated that the published tide predictions for that location were reliable. At a location upstream of the estuary embayment noticeable damping of the tidal wave amplitude was detected during periods of high river flow and high tidal range. High water lag times were found to decrease during periods of high river flow, but low water lag times were unaffected by river flow. The tide motion was found to be a damped, partially standing wave, which altered its behavior according to the volume of water in the estuary. The high and low tide water quality parameters of salinity, temperature, dissolved oxygen, turbidity and pH were measured at 10 to 18 locations during each season to determine any seasonal changes in them. The parameters at a given location were found to be a function of river flow and tidal range. Winter and summer sediment samples were analyzed for grain size distribution, volatile solids and porosity. The sediments from the main channel exhibited characteristics of a high velocity regime and those of the north channel, a low velocity regime. / Graduation date: 1975

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (October 20, 2008) Includes bibliographical references (p. 101-106)

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [74]-79)

Thesis (Ph. D.)--Université de Nantes, L'U.E.R. des Sciences de la Nature, 1979. / Accompanying map: "Carte des points de prélèvements éffectués dans l'estuaire de la Loire." Includes bibliographical references (p. 213-227).

Les estuaires sont généralement soumis à des phénomènes de comblement sédimentaires. Dans cette partie des systèmes fluviaux du territoire, l'accumulation des matériaux fins modifie radicalement la morphologie de l'estuaire, et conditionne la présence des espèces animales et végétales et on distingue un impact fort sur le plan économique, social et industriel. Les comblements compliquent la circulation dans les estuaires, compliquent les activités de pêches, de loisirs, modifient les propriétés des écoulements et constituent un facteur risque sur les zones d'habitations voisines. Des solutions temporaires consistent à curer les estuaires et des solutions d'aménagement des estuaires peuvent être envisagées. Néanmoins, il ressort de la littérature un manque important sur la caractérisation des mélanges liquides-solides et sur les mécanismes de structuration. Ce travail s'inscrit dans le contexte de l'étude des mécanismes de structuration des matériaux sédimentaires dans les estuaires afin de mieux comprendre les remplissages des zones estuariennes et surtout d'envisager des solutions durables de « nettoyage » de ces zones. L'estuaire de la Rance est particulièrement ciblé par notre étude. Le but est de donner des éléments de réponse sur le comportement rhéologique des vases naturelles en distinguant les échelles les plus significatives afin de détecter les facteurs structurants qui influencent les paramètres rhéologiques. La rhéologie des sédiments est ainsi étudiée à l'aide du rhéomètre Kinexus, géométrie plan-plan. On a pu alors détecter un comportement visco-plastique Bighamien. L'influence du diamètre moyens et de la fraction volumique solide sur la viscosité et le seuil de la contrainte de cisaillement dynamique du modèle de Bingham sont ainsi analysés. Ensuite, nous avons étudié grâce à des sédiments sans sel et sans matière organique, l'influence de ces deux composés chimiques sur le comportement rhéologiques des sédiments et puis leurs influences sur le vieillissement des sédiments. Une étude statique est également réalisée à l'aide du Va ne test permettant le calcul de la contrainte de cisaillement seuil. •Enfin, une assimilation du piège du Lyvet est réalisée grâce à des colonnes de sédimentation dans des conditions assez proches des conditions naturelles. Un processus de sédimentation-tassement-consolidation sous poids propre est recréé en laboratoire. Les sédiments sont amenés à vieillir cette fois pour des longues durées allant jusqu'à 9 mois. Au terme de périodes de vieillissement retenues, le massif créé est caractérisé depuis l'interface fluide-sédiments. Cela nous a permis d'étudier la répartition granulaire des sédiments après structuration et la variation de la contrainte de cisaillement seuil selon la profondeur de la colonne et la durée du vieillissement. Ce type d'essai est aussi réalisé pour les sédiments sans sel et sans matières organiques. / Estuaries are generally subject of sedimentary filling phenomena that alter their morphology and affect subsequently the economic, social and industrial plans. In this part of the fluvial systems of the territory, the accumulation of fine materials radically modifies the morphology of the estuary, and conditions the presence of animal and plant species and cause a strong impact on the economic, social and industrial. Filling complicates navigation in estuaries, fishing, recreational activities and modifies flow properties and is a risk factor in neighboring housing areas. Temporary solutions consist of cleaning estuaries and estuarine management solutions can be considered. Nevertheless, the literature shows a significant lack of characterization of liquid-solid mixtures and structuring mechanisms. This work is in the context of the study of structuring mechanisms of sedimentary materials in estuaries to better understand the fillings estuarine areas and specially to consider sustainable solutions of "cleansing" of these areas. The Rance estuary is particularly targeted by the study. The aim is to provide answers on the rheological behavior of natural vessels by distinguishing the most significant scales to detect structural factors influencing the rheological parameters. The rheology of the sediments is studied using the Kinexus rheometer, plan-plan geometry. A Bighamien visco-plastic behavior was then detected. The influence of the mean diameter and the solid volume fraction on the viscosity and the threshold of the dynamic shear stress of the Bingham model are thus analyzed. Then, using sediments without salt and organic matter, we studied the influence of these two chemical compounds on the rheological behavior of the sediments and their influence on the aging of the sediments. A static study is also carried out using the Vane test allowing the calculation of the threshold shear stress. Finally, an assimilation of the natural filling phenomenon is achieved in columns under conditions similar to natural conditions. These columns are then filled with natural sediments, washed sediments and sediments free of organic material and left for ages ranging from one week to 9 months. Then, the columns will be disassembled and rheological tests with the Brookfield Rheometer will be performed throughout the depth of the columns as well as measurements of water content and grain size. These tests allow us to study sediment structuring in the long term and also to identify the effect of salt and organic matter on sedimentation.

A geochemical study of the composition of natural sediments and contaminating mine tailings in Hastings and Alice Arms has been carried out. Apart from the geochemical investigation on the solid fraction, pore waters from six sediment cores have been analyzed to evaluate the diagenetic processes in the sediments of these two inlets. Differences in the mineralogy as well as in the chemical composition of the sediments were used to distinguish the natural sediments from contaminated sediments and pure tailings. In Alice Arm, two types of tailings could be differentiated with these methods. The first tailings type originated from the Kitsault Mo-deposit, which was mined in the past two decades by the B.C. Molybdenum Corporation and AMAX/Canada. These tailings are characterized by a number of features which make them distinguishable from natural sediments. The K-feldspar content of the tailings is significantly increased, mainly at the expense of plagioclase, which is the main characteristic for the mineralogical identification of this tailings type. The enhanced K-feldspar content is the cause for increased K and Rb values in the Mo-mine tailings. Another indicator specific to these recent tailings is an increased Mo content. The second tailings type is derived from an older mining operation in the Kitsault Valley, most likely the Dolly Varden Silver Mine. A specific indicator for these tailings is their high Ba content which is due to large amounts of barite. This mineral phase could be identified by X-ray diffraction methods in a heavy mineral fraction of the relevant sediment layers. Both tailings types show enrichment in their Pb, Zn and S concentrations, caused by an increased amount of metal-sulphides in the ore materials. In this area, these elements can therefore serve as a general indicator for the contamination of natural sediment with either tailings type. The interstitial water analyses indicated that the sediments in both inlets become reducing at a fairly shallow depth (10-15 cm), resulting in the mobilization of Mn, Fe and Mo from the solid phase. In the deeper parts of the cores, consumption of these metals could usually be observed which is likely due to precipitation of authigenic components. The dissolved Mo concentrations in the sediments contaminated with the modern tailings were much higher than in the natural sediments. In the pore water of the pure tailings the concentration reaches some 300 times that of the overlying water, which is the highest value ever reported for saline pore waters. These high Mo concentrations must support a flux of Mo from the sediment into the overlying water, and it is shown that such a flux could increase the inventory of naturally occurring dissolved Mo in the deep waters of Alice Arm by up to 4%. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.