scholarly journals Scaling oxygen microprofiles at the sediment interface of deep stratified waters

2017 ◽  
Vol 44 (3) ◽  
pp. 1340-1349 ◽  
Author(s):  
Robert Schwefel ◽  
Miki Hondzo ◽  
Alfred Wüest ◽  
Damien Bouffard
Keyword(s):  
Sediment Interface ◽  
Oxygen Microprofiles

scholarly journals Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 196
Author(s):  
Jiangbo Ren ◽  
Yan Liu ◽  
Fenlian Wang ◽  
Gaowen He ◽  
Xiguang Deng ◽  
...  
Keyword(s):  
Deep Sea ◽  
Research Progress ◽  
Bottom Current ◽  
Knowledge Map ◽  
P2o5 Content ◽  
Deep Sea Sediments ◽  
Potential Resource ◽  
And Migration ◽  
Adsorption Desorption ◽  
Sediment Interface

Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea sediments include aluminosilicate, Fe-Mn oxyhydroxides, and phosphate components. The ∑REY of the phosphate component is 1–2 orders of magnitude higher than those of the other two carriers, expressed as ∑REY = 0.001 × [Al2O3] − 0.002 × [MnO] + 0.056 × [P2O5] − 32. The sediment P2O5 content of 1.5% explains 89.1% of the total variance of the sediment ∑REY content. According to global data, P has a stronger positive correlation with ∑REY compared with Mn, Fe, Al, etc.; 45.5% of samples have a P2O5 content of less than 0.25%, and ∑REY of not higher than 400 ppm. The ∑REY of the phosphate component reaches n × 104 ppm, much higher than that of marine phosphorites and lower than that of REY-phosphate minerals, which are called REY-rich phosphates in this study. The results of microscopic observation and separation by grain size indicate that the REY-rich phosphate component is mainly composed of bioapatite. When ∑REY > 2000 ppm, the average CaO/P2O5 ratio of the samples is 1.55, indicating that the phosphate composition is between carbonate fluoroapatite and hydroxyfluorapatite. According to a knowledge map of sediment elements, the phosphate component is mainly composed of P, Ca, Sr, REY, Sc, U, and Th, and its chemical composition is relatively stable. The phosphate component has a negative Ce anomaly and positive Y anomaly, and a REY pattern similar to that of marine phosphorites and seawater. After the early diagenesis process (biogeochemistry, adsorption, desorption, transformation, and migration), the REY enrichment in the phosphate component is completed near the seawater/sediment interface. In the process of REY enrichment, the precipitation and enrichment of P is critical. According to current research progress, the REY enrichment is the result of comprehensive factors, including low sedimentation rate, high ∑REY of the bottom seawater, a non-carbonate depositional environment, oxidation conditions, and certain bottom current conditions.

scholarly journals Nitrogen removal processes in lakes of different trophic states from on-site measurements and historic data

2021 ◽  
Vol 83 (2) ◽  
Author(s):  
Beat Müller ◽  
Raoul Thoma ◽  
Kathrin B. L. Baumann ◽  
Cameron M. Callbeck ◽  
Carsten J. Schubert
Keyword(s):  
Eutrophic Lake ◽  
Oligotrophic Lake ◽  
Removal Rates ◽  
N Removal ◽  
Central Switzerland ◽  
Denitrification Activity ◽  
Historic Data ◽  
Anthropogenic Nitrogen ◽  
Removal Processes ◽  
Sediment Interface

AbstractFreshwater lakes are essential hotspots for the removal of excessive anthropogenic nitrogen (N) loads transported from the land to coastal oceans. The biogeochemical processes responsible for N removal, the corresponding transformation rates and overall removal efficiencies differ between lakes, however, it is unclear what the main controlling factors are. Here, we investigated the factors that moderate the rates of N removal under contrasting trophic states in two lakes located in central Switzerland. In the eutrophic Lake Baldegg and the oligotrophic Lake Sarnen, we specifically examined seasonal sediment porewater chemistry, organic matter sedimentation rates, as well as 33-year of historic water column data. We find that the eutrophic Lake Baldegg, which contributed to the removal of 20 ± 6.6 gN m−2 year−1, effectively removed two-thirds of the total areal N load. In stark contrast, the more oligotrophic Lake Sarnen contributed to 3.2 ± 4.2 gN m−2 year−1, and had removed only one-third of the areal N load. The historic dataset of the eutrophic lake revealed a close linkage between annual loads of dissolved N (DN) and removal rates (NRR = 0.63 × DN load) and a significant correlation of the concentration of bottom water nitrate and removal rates. We further show that the seasonal increase in N removal rates of the eutrophic lake correlated significantly with seasonal oxygen fluxes measured across the water–sediment interface (R2 = 0.75). We suggest that increasing oxygen enhances sediment mineralization and stimulates nitrification, indirectly enhancing denitrification activity.

Direct measurements of oxygen microprofiles and distribution of phospholipid-P in a two-phase soil—manure system

Geoderma ◽  
1993 ◽  
Vol 56 (1-4) ◽  
pp. 549-559 ◽  
Author(s):  
Søren O. Petersen ◽  
Tommy Harder Nielsen ◽  
Kaj Henriksen
Keyword(s):  
Two Phase ◽  
Direct Measurements ◽  
Oxygen Microprofiles

Evidence for toxic cyanobacteria in sediments and the water-sediment interface of a tropical drinking water reservoir

Limnologica ◽  
2021 ◽  
pp. 125924
Author(s):  
Lina Arismendi-González ◽  
Marisol Sepúlveda-Sánchez ◽  
Clara María Arboleda-Baena ◽  
Hilda Palacio-Betancur ◽  
Enderson Murillo Ramos ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Reservoir ◽  
Drinking Water Reservoir ◽  
Toxic Cyanobacteria ◽  
Sediment Interface

scholarly journals Dynamics of microalgal communities in the water-column/sediment interface of the inner shelf off Parana State, Southern Brazil

2004 ◽  
Vol 52 (3-4) ◽  
pp. 183-194 ◽  
Author(s):  
Ricardo Luiz Queiroz ◽  
Frederico Pereira Brandini ◽  
Franciane Maria Pellizzari
Keyword(s):  
Water Column ◽  
Cyanobacterial Bloom ◽  
Interface Layer ◽  
Benthic Diatoms ◽  
Southern Brazil ◽  
Planktonic Diatoms ◽  
Cell Densities ◽  
Sediment Interface ◽  
Microalgal Community

The composition and biomass of the microalgal community at the water-column/sediment interface on the continental shelf off Parana State (Brazil) were studied every 2 months during 1999. Samples for cell identification and determination of chlorophyll a were taken from the interface layer and at discrete depths up to 4 m above the sediment. Results showed a community mainly formed by benthic and planktonic diatoms >30 µm, benthic diatoms <30 µm and cyanobacteria. Cell densities were generally higher at the interface layer. Resuspension and sedimentation events seemed to be a paramount factor regulating the composition and biomass of these communities, and affected differently cells of different size classes. Cells >30 µm, which accounted for most of the pigment biomass, were resuspended from the interface after turbulent periods, and may take advantage of calm periods to stay and grow at the interface. Small benthic diatoms were more susceptible to wind-induced turbulence occurring in higher densities in the water column just above the water-sediment interface. A cyanobacterial bloom (Trichodesmiun) was observed at these bottom layers in the spring-summer periods.

Exceptional preservation in the Jurassic of Osteno

1985 ◽  
Vol 311 (1148) ◽  
pp. 171-180 ◽  
Keyword(s):  
Calcium Phosphate ◽  
Organic Material ◽  
Soft Tissues ◽  
Taxonomic Diversity ◽  
Cellular Level ◽  
Metasomatic Process ◽  
Exceptional Preservation ◽  
Sea Bottom ◽  
Colloidal Calcium Phosphate ◽  
Sediment Interface

The Sinemurian deposit of Osteno, discovered in 1964, is remarkable for the exceptional preservation of its fossils. They are almost exclusively non-calcareous organisms such as fishes, crustaceans, polychaetes and nematodes. Their exceptional fossilization is due to a metasomatic process implying a molecule-for-molecule replacement of the organic material by colloidal calcium phosphate, a process that has permitted the preservation of the soft tissues of the organisms in some cases even to cellular level. The Osteno deposit formed on a poorly oxygenated sea bottom inhabited by fauna with a low taxonomic diversity, in some cases monotypic. Infaunal organisms are not found in the deposit since the H 2 S-O 2 boundary was probably situated slightly below the water-sediment interface.

The nature and pollutant role of solids at the water-sediment interface in combined sewer networks

2003 ◽  
Vol 47 (4) ◽  
pp. 1-10 ◽  
Author(s):  
G. Chebbo ◽  
R. Ashley ◽  
M.-C. Gromaire
Keyword(s):  
Current Knowledge ◽  
Pollution Potential ◽  
Combined Sewer ◽  
New Ideas ◽  
Transport Modes ◽  
Sediment Interface ◽  
Sewer Networks

Solids at the water-sediment interface in combined sewers are known to be important for pollution potential during storm washout via CSOs. They have been investigated in several studies, but nonetheless, little is known about the origins, build-up, transport and nature of these solids. From a review of current knowledge, it is apparent that whilst there is general agreement that these solids are largely organic and have high polluting potential, their modes of transport and definition are not generally agreed upon. It is possible that there may be several “types” of these solids, defined as either: “near bed solids” or “fluid sediments/dense undercurrents”, possibly representing transport modes in flows with different ranges of ambient (dry weather) velocities and with differing sewerage layouts. Current knowledge is presented and new ideas for resolving the uncertainties regarding the nature, movement and effects of this material are outlined.

scholarly journals Erratum to: Assessment of nitrogen and phosphate balance and the roles of bacteria and viruses at the water-sediment interface in the Allal El Fassi reservoir (Morocco)

2014 ◽  
Vol 186 (12) ◽  
pp. 9117-9118
Author(s):  
Mohamed Alaoui-Mhamdi ◽  
Amel Dhib ◽  
Abderrahim Bouhaddioui ◽  
Boutheina Ziadi ◽  
Souad Turki ◽  
...  
Keyword(s):  
Sediment Interface
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