Search results for "Sediment"
showing 10 items of 1648 documents
Early diagenetic processes during Mn-carbonate formation: evidence from the isotopic composition of authigenic Ca-rhodochrosites of the Baltic Sea
2002
The formation of authigenic Ca-rich rhodochrosite (ACR) in sapropelic sediments of the Gotland Basin, Baltic Sea, is governed by deepwater renewal processes whereby saline water from the North Atlantic flushes the brackish anoxic Baltic Deeps. The carbon and oxygen isotopic compositions of these Mn- carbonates suggest that ACR formation takes place just below the sediment surface and that dissolved compounds from the deepwater column, such as water and bicarbonate molecules, were incorporated in ACR during authigenesis. Porewaters near the sediment surface display 18 O values of 5.4‰ (VSMOW) and are generally depleted in 18 O, compared to the oxygen isotopic composition of water in equilibr…
Seismic and sedimentologic features of Oxfordian-Kimmeridgian syn-rift sediments on the eastern margin of the Lusitanian Basin
1989
Following deposition of widespread middle Oxfordian lacustrine carbonates and evaporites, the Lusitanian Basin was differentiated into a number of sub-basins. The Arruda sub-basin is a half graben basin situated some 30 km north of Lisbon. It accumulated over 2.5 km of Kimmeridgian siliciclastic sediments, and is bounded to the east by the Vila Franca de Xira fault zone. Carbonate deposition persisted over horsts along the fault zone from the Oxfordian to the early Kimmeridgian, and in places to the late Kimmeridgian, and shows a pronounced west-east facies zonation, with higher energy framestones and grainstones accumulating along the exposed western margins. Seismic data indicate a major …
Devona Stipinu svītas dolomītu fācijas un veidošanās apstākļi
2020
Bakalaura darba mērķis ir veikt Stipinu svītas nogulumiežu fāciju analīzi un sedimentācijas apstākļu interpretāciju, pamatojoties uz lauka darbiem un apskatīto literatūru. Pētījuma ietvaros ir dokumentēti 10 atsegumi, kuri atrodas Kurzemē un Zemgalē. Nogulumiežu fāciju nodalīšana tika balstīta uz lauku darbos veiktajiem mērījumiem un to pēcapstrādi. Darba rezultātā ir nodalītas 10 fācijas un 2 fāciju asociācijas – vidējā līdz augšējā plūdmaiņu zona ar mālaini karbonātisko nogulu sedimentāciju, kā arī apakšējā plūdmaiņu zona līdz atklātam šelfam ar karbonātu sedimentāciju.
Zr, Hf and REE distribution in river water under different ionic strength conditions
2018
International audience; The Platani River flowing in south-central Sicily, interacting with evaporite rocks, generates a wide range of ionic strength in the water catchment from 0.1 to 5.0 mol kg−1. We sampled 38 river sites and analysed the composition for the dissolved fraction filtered through 0.45 μm, the truly dissolved fraction obtained through ultrafiltration (10 kDa) and the relative included colloidal fraction.This study was focused on the recognition of Zr, Hf and REE behaviour under changing ionic strength conditions, since this is one of parameters responsible for colloid stability in natural waters. In turn, this phenomenon leads to REE release from the colloidal fraction and t…
Flash-Floods Influence Macroinvertebrate Communities Distribution in Lotic Ecosystems
2019
Abstract Stream dwelling invertebrate populations are facing an ample array of stressors including the habitat imbalance caused by important floods. In this research we used a novel way to estimate the impact of floods upon the substrate, by utilising a remote variable named “flash-flood potential” (FFP), which accounts for the site slope and the average slope of the upstream catchment. The results showed that certain groups are sensitive to the influence of the FFP whereas other are not. We propose this remote variable as a surrogate for assessing stress imposed by floods and sediment scouring for lotic macroinvertebrates.
Experimental observation of horizontal coherent turbulent structures in a straight flume
2009
The present paper describes results of laboratory experiments carried out to investigate the evolution of horizontal coherent turbulent structures for different roughness conditions of channel walls. The occurrence of turbulent events (inward interaction, ejection, sweep and burst) is identified through the conditioned quadrant analysis. The filtered data set is used to determine the probability density distribution of each turbulent event. Particular attention is focused on sweep and ejection events and peculiar maps showing the distributions of the horizontal Reynolds shear stress, for each examined experimental condition, are also presented and discussed.
Studio integrato di rocce sedimentarie da cave siciliane di interesse storico-artistico
2005
Evidence de l'adaptation des communautés microbiennes sédimentaires de rivière à la minéralisation du diuron: influence du ruissellement et de l'éros…
2010
International audience; Purpose Surface runoff and erosion are major drivers of pesticide transport from soils to rivers draining vineyard watersheds. A recent study showed that applications of diuron on vineyards and diuron dispersal could lead to microbial adaptation to diuron biodegradation from treated soils to the receiving hydrosystem. Given the limited knowledge on microbial adaptation to pesticide degradation in aquatic environments, we conducted a microcosm study designed to assess the impact of runoff and erosion processes on the adaptation of riverine-sediment microbial communities to diuron mineralization. Materials and methods The experimental laboratory set-up consisted in aqu…
I reattori aerobici granulari: esperienze con refluo reale e sintetico
2008
La granulazione aerobica può essere ottenuta nei sistemi con alimentazione discontinua in due differenti configurazioni impiantistiche, che permettono di realizzare i necessari sforzi tangenziali per la formazione dei granuli: il Sequencing Batch Bubble Column Reactor (SBBC) e il Sequencing Batch Airlift Reactor (SBAR). Lo scopo di questo studio è stato quello di osservare il fenomeno della granulazione aerobica e valutare il ruolo del tempo di sedimentazione durante la fase di selezione e formazione dei granuli. L’intera sperimentazione è stata suddivisa in due diverse campagne sperimentali in cui è stato utilizzato refluo sintetico, nella prima, e refluo reale, nella seconda. Al fine di e…