Marine Sediment

The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500 km2 region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7 Mm3/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%). La plateforme Lowllands du Saint-Laurent, Québec, Canada, est une aire densément peuplée, dépendant grandement des ressources en eau souterraine. En 1999, le Service Géologique du Canada a initié une étude hydrogéologique à grande-échelle sur 1500 km2 au Nord-Ouest de Montréal. Le sobjectifs ont été de définir la dynamique de l’écoulement régional, et de donner des estimations quantitatives des paramètres dynamiques des ressources disponibles en eau souterraine. L’approche utilisée consista à définir le cadre hydrogéologique de travail, les propriétés hydrauliques des unités aquifères, et les composantes dynamiques des eaux souterraines. Les roches sédimentaires du Paléozoïque Inférieur représentent les unités aquifères régionales. Les sédiments marins fins confinent la plus grande partie des aquifères régionaux. Les informations de base, collectées dans un SIG, ont été synthétisées dans un modèle numérique aux éléments finis. L’écoulement permanent régional, en zone saturée, a été calibré en conditions de stress en assumant une approche de milieu poreu équivalent. Les calculs du bilan hydrologique montrent que l’écoulement total des eaux souterraines dans les aquifères régionaux atteind 97,7 Mm3/an. L’infiltration à partir des précipitations apporte 86.6% de l’eau souterraine exploitée; sachant que 9,6% proviennent d’écoulement de subsurfaces, et que les 3,8% restants proviennent de la recharge via les eaux de surface. Le débit pompé des aquifères régionaux apparaît à travers l’écoulement des cours d’eau, le rabattement des eaux souterraines (18.4%), et l’écoulement ascendant (4.7%). La plataforma de Tierras Bajas San Lorenzo, Quebec, Canadá, es un área densamente poblada que depende fuertemente de recursos de agua subterránea. En 1999 el Servicio Geológico de Canadá inició un estudio de evaluación hidrogeológica a gran escala sobre un área de 1,500 km2 en la región noroeste de Montreal. Los objetivos fueron definir el flujo regional de agua subterránea y aportar estimados cuantitativos de los parámetros dinámicos de agua subterráne y de los recursos disponibles de agua subterránea. El enfoque aplicado consistió en definir el marco hidrogeológico, propiedades hidráulicas de las unidades acuíferas, y los componentes dinámicos de agua subterránea. Rocas sedimentarias del Paleozoico Inferior representan unidades regionales de acuíferos. Sedimentos fluvio-glaciares Cuaternarios gruesos sobreyacen localmente la secuencia rocosa y constituyen una unidad acuífera interfacial. Sedimentos marinos finos confinan la mayoría de acuíferos regionales. Información colectada basada en SIG se sintetizó en un modelo numérico de elemento finito. El flujo regional saturado en régimen permanente se calibró bajo condiciones de stress asumiendo un enfoque de medio poroso equivalente. Los cálculos de balance hídrico muestran que el flujo total de agua subterránea en acuíferos regional alcanza 97.7 Mm3/año. Infiltración a partir de lluvia aporta el 86.6% del abastecimiento al agua subterránea, mientras que el 9.6% proviene de entradas subsuperficiales y el restante 3.8% consiste de recarga inducida a partir de aguas superficiales. La descarga proveniente de acuíferos regionales ocurre a través de flujo a ríos (76.9%), utilización de agua subterránea (18.4%), y salida subterránea (4.7%).

Two high performance flow atomic absorption (HPF-AAS) related techniques were chosen to assess their suitability for the determination of several trace elements in complex environmental and biological samples. The technique selected were the Hydraulic High Pressure Nebulization Atomic Absorption Spectrometry (HHPN-AAS), and the Hydraulic High Pressure Nebulization Flame Furnace Atomic Absorption Spectrometry (HHPN-FF-AAS), which were applied directly, or after using off line liquid-liquid separation-preconcentration-back extraction procedures. Analytical methodologies were developed for Be, Sr, Ba, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, Ag, Al, Tl, Pb, and Bi, for a variety of samples such as river and seawater, river and marine sediments, soft tissue of mussels, tunicate siphons, aquatic plants, and human samples of clinical interest such as placentas, umbilical cords, and cardiovascular tissues from surgical procedures. The analytical efficiency of the techniques was also proved in a proposed trace metal fractionation approach for river and seawater samples. All samples collected in this work were obtained from the North of Chile, where the most important economic activity is the mining industry.

Carbonates are important constituents of marine sediments and play a fundamental role in the recycling of carbon into the Earth's deep interior via subduction of oceanic crust and sediments. Study of the stability of carbonates under high pressure and temperature is thus important for modelling the carbon budget in the entire Earth system. Such studies, however, have rarely been performed under appropriate lower-mantle conditions and no experimental data exist at pressures greater than 80 GPa (refs 3-6). Here we report an in situ X-ray diffraction study of the stability of magnesite (MgCO(3)), which is the major component of subducted carbonates, at pressure and temperature conditions approaching those of the core-mantle boundary. We found that magnesite transforms to an unknown form at pressures above approximately 115 GPa and temperatures of 2,100-2,200 K (depths of approximately 2,600 km) without any dissociation, suggesting that magnesite and its high-pressure form may be the major hosts for carbon throughout most parts of the Earth's lower mantle.

... J. Germán Rodríguez and Adolfo Uriarte ... View larger version (15K), Table 1. Pearson product moment correlations between cumulative percentiles, measured by laser diffractometry and by dry sieving on sandy marine sediments (n = 68). View larger version (27K), ...

Dinoflagellate cysts and XRF core scanning data from two marine sediment cores from embayments north (Bonavista Bay) and south (Placentia Bay) of Newfoundland show significant changes in ocean and atmospheric conditions of the SW Labrador Sea region during the last 5700 years. Fresh and cold conditions, probably accompanied by seasonal sea ice, prevailed both north and south of Newfoundland from c. 5.7 to 4.0 cal. kyr BP. This may be linked to intensified Labrador Current export of cold meltwater and/or sea ice from the Arctic, presumably related to warmer conditions in the northernmost latitudes and the prevalence of strong (north)westerly winds. After c. 4.0 cal. kyr BP, sea-surface conditions warmed up and sea ice decreased northeast of Newfoundland, but conditions were still cold south of Newfoundland. This suggests a decrease in Arctic meltwater export and westerly wind strength. After 2.9—2.5 cal. kyr BP, only minor changes in sea-surface conditions affected the study sites. S...

Introduction The Oslofjord region in SE-Norway has been subject to steady glacio-isostatic uplift during the whole Holocene. The final retreat of the ice at the termination of the last glacial took place in this area between 13,900 (retreat from Hvaler ice-marginal ridge) and 11,500 years BP (retreat from Ski ice-marginal ridge). Since then, the area has been characterized by continuous

Focused ultrasonic-assisted extraction (FUSE) is a new and particular technique based on the cavitation effect. In this work, the focused ultrasound assisted extraction was studied and developed for the extraction of polycyclic aromatic hydrocarbons from marine sediments and mussel tissues. The variables influencing the extraction (amplitude of the ultrasound pulse, the extraction time and the solvent) were studied by a full factorial design and a central composite design. As a result, flat response surfaces were obtained and the most convenient conditions were 45% of ultrasound amplitude, 120 s of extraction time and 5 mL of acetone. Both accuracy and precision of the method were evaluated by means of two certified reference materials (marine sediment and mussel tissue) and the results were also compared to those obtained by microwave assisted extraction.

Purpose Plastic pollution in the world has led to an abundance of microplastics (MPs) and has been identified as a potential factor that can lead to serious environmental problems, especially in oceans and seas. Information on the current status of MPs pollution along the Montenegrin coast is insufficiently investigated. This study monitors the abundance, distribution, and sources of MPs, and identifies present polymers in the surface sediment of the Montenegrin coast, as well as comparison with previous research. Materials and methods Ten sampling sites along the Montenegrin coast were selected to collect surface sediment samples. The upper layer of sediment (0-5 cm) was collected by a Petite ponar grab. The samples were dried, and density separation was performed using a NaCl solution. The abundance and morphological characteristics of MPs were determined using an optical microscope (DP-Soft software), while FT-IR analysis was done to identify the polymer type. Results and discussion Microplastics were identified in all sediment samples with an average abundance of 307 ± 133 (SD) MPs/kg in dry sediment. The highest abundance of MPs was found in locations in the vicinity of highly populated areas, near wastewater discharges, and areas with high fishing and tourist activities. The most dominant shape types of MPs in all samples were filaments and fragments. The most common colors of MPs were blue and red, while the dominant MPs sizes were 0.1-0.5 mm and 0.5-1.0 mm. Of the eight identified polymers, PP, PE, and PET were the most common. Conclusion This study reveals MPs characteristics (abundance, distribution, shape type, colors, size, polymers type) in surface sediment along the Montenegrin coast, as well as the most significant sources of MPs pollution, and provides important data for further research on MPs to identify the effects of MPs pollution on the quality, health, and functionality of the marine environment.

A method for mercury (Hg) determination in soil, river sediment and marine sediment without sample digestion is investigated. Mercury determination is performed by cold vapour atomic absorption spectrometry (CV-AAS) using a flow injection system. Mercury quantitatively leaches out from the investigated marine sediment into 30% (v/v) HNO3 assisted by ultrasonic irradiation (during 90–120s) when sample particles size are ≤120μm. Similar

One-third of the population of Oman depends upon groundwater extracted from the alluvium of the Batinah Plain, on the coast of the Gulf of Oman. Deep geophysical exploration techniques were used to determine the depth and nature of the alluvium and the boundaries of the aquifer. The base and structural controls of the alluvial basin at its contact with Tertiary marine sediments and Cretaceous ophiolite were mapped with seismic reflection data, recorded originally for oil exploration. The base of the alluvium dips northward from the foothills of the Northern Oman Mountains, reaching a maximum depth of 2000m at the coast. The varying facies of the alluvium are grossly characterised by different, overlapping ranges of electrical resistivity, depending largely on the clay content and degree of cementation. Resistivities near the coast are reduced by saline intrusion. These variations of resistivity were mapped with time-domain electromagnetic sounding along 400km of profile, to distinguish among the three zones of the alluvial aquifer. The wedge of saline intrusion was also delineated, up to 10km from the coast. The thickness of the saturated gravel aquifer ranges from 20-160m in an area greater than 600km2. Résumé Un tiers de la population d'Oman est alimenté par de l'eau souterraine pompée dans les alluvions de la plaine de Batinah, sur la côte du golfe d'Oman. Des techniques d'exploration géophysique profonde ont été mises en oeuvre pour déterminer la profondeur et la nature des alluvions et les limites de l'aquifère. La base et les contrôles structuraux du bassin alluvial au contact des sédiments marins tertiaires et des ophiolites crétacées ont été cartographiés à partir des données de sismique réflexion obtenues à l'origine pour la recherche pétrolière. La base des alluvions plonge vers le nord à partir du piémont du massif septentrional d'Oman, pour atteindre une profondeur maximale de 2000m sur la côte. Les divers faciès alluviaux sont grossièrement caractérisés par des différentes gammes de résistivitéélectrique se recouvrant, dépendant surtout de la teneur en argiles et du degré de cimentation. Les résistivités près de la côte diminuent du fait de l'intrusion marine. Ces variations de résistivité ont été cartographiées à partir de 400km de profils électromagnétiques, dans le domaine temporel ; trois zones ont été distinguées dans l'aquifère alluvial. Le biseau salé a aussi été délimité, jusqu'à 10km de la côte. L'épaisseur de la partie saturée des graviers va de 20-160m sur une étendue supérieure à 600km2. Resumen Un tercio de la población de Omán depende de las aguas subterráneas extraídas del aluvial de la Llanura de Batinah, en la costa del Golfo de Omán. Para determinar la profundidad y naturaleza del aluvial, así como los límites del acuífero, se han usado técnicas de exploración geofísica profunda. El basamento y los límites estructurales del aluvial en su contacto con los sedimentos marinos del Terciario y la ofiolita cretácica se obtuvieron mediante sísmica de reflexión, registrada previamente en campañas de exploración petrolífera. La base del aluvial buza hacia el norte desde el pie de las Montañas del Norte de Omán, alcanzando una profundidad máxima de 2000m en la costa. Las distintas facies del aluvial están caracterizadas por rangos distintos, pero superpuestos, de resistividad eléctrica, dependiendo del contenido en arcillas y del grado de cementación. Las resistividades cerca de la costa se reducen por la intrusión salina. Estas variaciones de resistividad se obtuvieron con registros electromagnéticos a lo largo de un perfil de 400km, con el objetivo de distinguir las tres zonas del acuífero aluvial. También se pudo obtener la geometría de la cuña de intrusión, que llega hasta 10km de la costa. El espesor de las gravas saturadas que forman el acuífero oscila entre los 20-160m en un área superior a 600km2.