scholarly journals Remobilisation of uranium from contaminated freshwater sediments by bioturbation

2014 ◽  
Vol 11 (12) ◽  
pp. 3381-3396 ◽  
Author(s):  
S. Lagauzère ◽  
M. Motelica-Heino ◽  
E. Viollier ◽  
G. Stora ◽  
J. M. Bonzom
Keyword(s):  
Water Column ◽  
Current Knowledge ◽  
Chemical Species ◽  
Iron Sulfate ◽  
Tubifex Tubifex ◽  
Negative Effects ◽  
Freshwater Sediments ◽  
Overlying Water ◽  
U Contamination ◽  
Nitrate And Nitrite

Abstract. Benthic macro-invertebrate bioturbation can influence the remobilisation of uranium (U) initially associated with freshwater sediments, resulting in a high release of this pollutant through the overlying water column. Given the potential negative effects on aquatic biocenosis and the global ecological risk, it appears crucial to improve our current knowledge concerning the biogeochemical behaviour of U in sediments. The present study aimed to assess the biogeochemical modifications induced by Tubifex tubifex (Annelida, Clitellata, Tubificidae) bioturbation within the sediment in order to explain such a release of U. To reach this goal, U distribution between solid and solute phases of a reconstructed benthic system (i.e. in mesocosms) inhabited or not by T. tubifex worms was assessed in a 12-day laboratory experiment. Thanks notably to fine-resolution (mm-scale) measurements (e.g. "diffusive equilibrium in thin-films" DET gel probes for porewater, bioaccumulation in worms) of U and main chemical species (iron, sulfate, nitrate and nitrite), this work (i) confirmed that the removal of bottom sediment particles to the surface through the digestive tract of worms greatly favoured oxidative loss of U in the water column, and (ii) demonstrated that both U contamination and bioturbation of T. tubifex substantially influenced major microbial-driven biogeochemical reactions in sediments (e.g. stimulation of denitrification, sulfate reduction and iron dissolutive reduction). This study provides the first demonstration of biogeochemical modifications induced by bioturbation in freshwater U-contaminated sediments.

scholarly journals Remobilisation of uranium from contaminated freshwater sediments by bioturbation

2013 ◽  
Vol 10 (10) ◽  
pp. 17001-17041 ◽  
Author(s):  
S. Lagauzère ◽  
M. Motelica-Heino ◽  
E. Viollier ◽  
G. Stora ◽  
J. M. Bonzom
Keyword(s):  
Water Column ◽  
Current Knowledge ◽  
Chemical Species ◽  
Iron Sulfate ◽  
Tubifex Tubifex ◽  
Negative Effects ◽  
Freshwater Sediments ◽  
Overlying Water ◽  
Uranium Distribution ◽  
Fine Resolution

Abstract. Previous studies have demonstrated that benthic macro-invertebrate bioturbation can influence the remobilization of uranium initially associated with freshwater sediments resulting in a high release of this pollutant through the overlying water column. Giving the potential negative effects on aquatic biocenosis and the global ecological risk, it appeared crucial to improve our current knowledge concerning the uranium biogeochemical behaviour in sediments. The present study aimed to assess the biogeochemical modifications induced by Tubifex tubifex (Annelida, Clitellata, Tubificidae) bioturbation within the sediment permitting to explain such a release of uranium. To reach this goal, uranium distribution between solid and solute phases of a reconstructed benthic system (i.e. in mesocosms) inhabited or not by T. tubifex worms was assessed in a 12 day laboratory experiment. Thanks notably to fine resolution (mm-scale) measurements (e.g. DET gels probes for porewater, bioaccumulation in worms) of uranium and main chemical species (iron, sulfate, nitrate, nitrite), this work permitted (i) to confirm that the removal of bottom sediment particles to the surface through the digestive tract of worms greatly favours the oxidative loss of uranium in the water column, and (ii) to demonstrate that both uranium contamination and bioturbation of T. tubifex substantially influence major microbial-driven biogeochemical reactions in sediments (e.g. stimulation of denitrification, sulfate-reduction and iron dissolutive reduction). This study provides the first demonstration of biogeochemical modifications induced by bioturbation in freshwater uranium-contaminated sediments.

scholarly journals Glucocorticoid Receptor β (GRβ): Beyond Its Dominant-Negative Function

2021 ◽  
Vol 22 (7) ◽  
pp. 3649
Author(s):  
Patricia Ramos-Ramírez ◽  
Omar Tliba
Keyword(s):  
Current Knowledge ◽  
Inflammatory Diseases ◽  
Cell Communication ◽  
Cell Types ◽  
The Body ◽  
Dominant Negative ◽  
Negative Effects ◽  
Independent Manner ◽  
Distinct Cell ◽  
Induced Apoptosis

Glucocorticoids (GCs) act via the GC receptor (GR), a receptor ubiquitously expressed in the body where it drives a broad spectrum of responses within distinct cell types and tissues, which vary in strength and specificity. The variability of GR-mediated cell responses is further extended by the existence of GR isoforms, such as GRα and GRβ, generated through alternative splicing mechanisms. While GRα is the classic receptor responsible for GC actions, GRβ has been implicated in the impairment of GRα-mediated activities. Interestingly, in contrast to the popular belief that GRβ actions are restricted to its dominant-negative effects on GRα-mediated responses, GRβ has been shown to have intrinsic activities and “directly” regulates a plethora of genes related to inflammatory process, cell communication, migration, and malignancy, each in a GRα-independent manner. Furthermore, GRβ has been associated with increased cell migration, growth, and reduced sensitivity to GC-induced apoptosis. We will summarize the current knowledge of GRβ-mediated responses, with a focus on the GRα-independent/intrinsic effects of GRβ and the associated non-canonical signaling pathways. Where appropriate, potential links to airway inflammatory diseases will be highlighted.

scholarly journals Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

2018 ◽  
Vol 15 (20) ◽  
pp. 6127-6138 ◽  
Author(s):  
Qixing Ji ◽  
Claudia Frey ◽  
Xin Sun ◽  
Melanie Jackson ◽  
Yea-Shine Lee ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Chesapeake Bay ◽  
Water Column ◽  
N2o Emissions ◽  
N2o Production ◽  
Isotope Tracer ◽  
Relative Contribution ◽  
Environmental Controls ◽  
Long Run ◽  
Nitrate And Nitrite

Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.

scholarly journals Sediment-water column fluxes of carbon, oxygen and nutrients in Bedford Basin, Nova Scotia, inferred from <sup>224</sup>Ra measurements

2013 ◽  
Vol 10 (1) ◽  
pp. 53-66 ◽  
Author(s):  
W. J. Burt ◽  
H. Thomas ◽  
K. Fennel ◽  
E. Horne
Keyword(s):  
Organic Matter ◽  
Nova Scotia ◽  
Water Column ◽  
Explicit Knowledge ◽  
Dissolved Inorganic Carbon ◽  
Chemical Constituents ◽  
Water Interface ◽  
Benthic Fluxes ◽  
Pore Waters ◽  
Overlying Water

Abstract. Exchanges between sediment pore waters and the overlying water column play a significant role in the chemical budgets of many important chemical constituents. Direct quantification of such benthic fluxes requires explicit knowledge of the sediment properties and biogeochemistry. Alternatively, changes in water-column properties near the sediment-water interface can be exploited to gain insight into the sediment biogeochemistry and benthic fluxes. Here, we apply a 1-D diffusive mixing model to near-bottom water-column profiles of 224Ra activity in order to yield vertical eddy diffusivities (KZ), based upon which we assess the diffusive exchange of dissolved inorganic carbon (DIC), nutrients and oxygen (O2), across the sediment-water interface in a coastal inlet, Bedford Basin, Nova Scotia, Canada. Numerical model results are consistent with the assumptions regarding a constant, single benthic source of 224Ra, the lack of mixing by advective processes, and a predominantly benthic source and sink of DIC and O2, respectively, with minimal water-column respiration in the deep waters of Bedford Basin. Near-bottom observations of DIC, O2 and nutrients provide flux ratios similar to Redfield values, suggesting that benthic respiration of primarily marine organic matter is the dominant driver. Furthermore, a relative deficit of nitrate in the observed flux ratios indicates that denitrification also plays a role in the oxidation of organic matter, although its occurrence was not strong enough to allow us to detect the corresponding AT fluxes out of the sediment. Finally, comparison with other carbon sources reveal the observed benthic DIC release as a significant contributor to the Bedford Basin carbon system.

Mixed bottom-friction–Kelvin–Helmholtz destabilization of source-driven abyssal overflows in the ocean

2009 ◽  
Vol 626 ◽  
pp. 33-66 ◽  
Author(s):  
GORDON E. SWATERS
Keyword(s):  
Water Column ◽  
Thermohaline Circulation ◽  
Unstable Mode ◽  
Stability Boundary ◽  
Phase Speed ◽  
Bottom Friction ◽  
Marginal Stability ◽  
Time Variability ◽  
Gravitational Acceleration ◽  
Overlying Water

Source-driven ocean currents that flow over topographic sills are important initiation sites for the abyssal component of the thermohaline circulation. These overflows exhibit vigorous space and time variability over many scales as they progress from a predominately gravity-driven downslope flow to a geostrophic along-slope current. Observations show that in the immediate vicinity of a sill, grounded abyssal ocean overflows can possess current speeds greater than the local long internal gravity wave speed with bottom friction and downslope gravitational acceleration dominating the flow evolution. It is shown that these dynamics lead to the mixed frictionally induced and Kelvin–Helmholtz instability of grounded abyssal overflows. Within the overflow, the linearized instabilities correspond to bottom-intensified baroclinic roll waves, and in the overlying water column amplifying internal gravity waves are generated. The stability characteristics are described as functions of the bottom drag coefficient and slope, Froude, bulk Richardson and Reynolds numbers associated with the overflow and the fractional thickness of the abyssal current compared to the mean depth of the overlying water column. The marginal stability boundary and the boundary separating the parameter regimes in which the most unstable mode has a finite or infinite wavenumber are determined. When it exists, the high-wavenumber cutoff is obtained. Conditions for the possible development of an ultraviolet catastrophe are determined. In the infinite-Reynolds-number limit, an exact solution is obtained which fully includes the effects of mean depth variations in the overlying water column associated with a sloping bottom. For parameter values characteristic of the Denmark Strait overflow, the most unstable mode has a wavelength of about 19 km, a geostationary period of about 14 hours, an e-folding amplification time of about 2 hours and a downslope phase speed of about 74 cm s−1.

scholarly journals The Management Response to Wind Disturbances in European Forests

2021 ◽  
Author(s):  
Paula Sanginés de Cárcer ◽  
Piotr S. Mederski ◽  
Natascia Magagnotti ◽  
Raffaele Spinelli ◽  
Benjamin Engler ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Economic Losses ◽  
Future Research ◽  
Forest Site ◽  
Negative Effects ◽  
Salvage Logging ◽  
Forest Ownership ◽  
Forest Ecosystem Services ◽  
Disturbance Management ◽  
Timber Market

Abstract Purpose of the Review The review synthesises the current knowledge of post-windstorm management in selected European countries in order to identify knowledge gaps and guide future research. Recent Findings Despite the differences in forest ownership and national regulations, management experiences in Europe converge at (1) the need for mechanization of post-windthrow management to ensure operator safety, (2) the importance to promote operator training and optimise the coordination between all the actors involved in disturbance management and (3) the need to implement measures to consolidate the timber market while restoring forest ecosystem services and maintain biodiversity. Summary Windstorms are natural disturbances that drive forest dynamics but also result in socio-economic losses. As the frequency and magnitude of wind disturbances will likely increase in the future, improved disturbance management is needed. We here highlight the best practices and remaining challenges regarding the strategic, operational, economic and environmental dimensions of post-windthrow management in Europe. Our literature review underlined that post-disturbance management needs to be tailored to each individual situation, taking into account the type of forest, site conditions, available resources and respective legislations. The perspectives on windthrown timber differ throughout Europe, ranging from leaving trees on site to storing them in sophisticated wet storage facilities. Salvage logging is considered important in forests susceptible to bark beetle outbreaks, while no salvage logging is recommended in forests protecting against natural hazards. Remaining research gaps include questions of balancing between the positive and negative effects of salvage logging and integrating climate change considerations more explicitly in post-windthrow management.

scholarly journals Fleshy Red Algae Mats Influence Their Environment in the Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Neele Schmidt ◽  
Yusuf C. El-Khaled ◽  
Felix I. Roßbach ◽  
Christian Wild
Keyword(s):  
Environmental Factors ◽  
Light Intensity ◽  
Water Temperature ◽  
Mediterranean Sea ◽  
Water Column ◽  
Red Algae ◽  
Water Movement ◽  
Ecosystem Engineer ◽  
Overlying Water ◽  
The Mediterranean

In the Mediterranean Sea, the fleshy red alga Phyllophora crispa forms dense mats of up to 15 cm thickness, mainly located on rocky substrates in water depths below 20 m. Because of the observed density of these mats and some first observations, we hypothesize that P. crispa is a yet undescribed ecosystem engineer that provides a multitude of ecological niches for associated organisms along small-scale environmental gradients. Therefore, we conducted an in-situ pilot study in the Western Mediterranean Sea to assess potential influence of the algae mats on the key environmental factors water movement, temperature and light intensity. We comparatively and simultaneously measured in P. crispa mats, in neighboring Posidonia oceanica seagrass meadows, on neighboring bare rocky substrates without algae mats, and in the directly overlying water column. We used several underwater logging sensors and gypsum clod cards. Findings revealed that P. crispa significantly reduced water movement by 41% compared to the overlying water column, whereas water movement was not affected by P. oceanica meadows and bare rocky substrates. Surprisingly, P. crispa increased the water temperature by 0.3°C relative to the water column, while the water temperature in P. oceanica and on bare rocky substrates was reduced by 0.5°C. Light intensity inside the red algae mats was reduced significantly by 69% compared to the water column. This was similar to measured light reduction of 77% by P. oceanica. These findings highlight the strong influence of the dense red algae mats on some key environmental factors. Their influence is obviously similar or even higher than for the well-known seagrass ecosystem engineer. This may be a factor that facilitates associated biodiversity similarly as described for P. oceanica.

scholarly journals Challenges Hindering the Resourcing for Post-Disaster Housing Reconstruction in Gaza

2021 ◽  
Vol 26 (2) ◽  
pp. 183-210
Author(s):  
Nour Saleh ◽  
Adnan Enshassi ◽  
Matthias Sundermeier
Keyword(s):  
Current Knowledge ◽  
Gaza Strip ◽  
Rank Test ◽  
Negative Effects ◽  
Political Issues ◽  
Signed Rank Test ◽  
The Gaza Strip ◽  
Housing Reconstruction ◽  
Post Disaster ◽  
Implementing Agencies

Resourcing post-disaster housing reconstruction (PDHR) entails many drawbacks creating bottlenecks to reconstruction projects. Understanding these vulnerable issues is of utmost to identify the appropriate interventions to mitigate their effects. The devastating aggression in 2014 in Gaza Strip served as a typical example of resources hampers. Based on the quantitative approach, the research employed a self-administrated questionnaire survey to identify the most significant challenges hindering the resourcing for post-2014 aggression housing reconstruction. The questionnaire targeted 55 of the key people in the implementing agencies of post-2014 aggression housing reconstruction. The data collected was analysed using descriptive statistics, through frequency distribution and effect index (EI); and using inferential statistics through one sample Wilcoxon signed rank test. Findings indicated that the challenges related to political issues have the most significant effect on resourcing the PDHR. The main key challenges are: (1) Difficulties to obtain permits from the Israeli side to flow the reconstruction materials into the Gaza Strip, (2) Insufficient funds for reconstruction efforts and (3) Refusal of the international community to contact the local de facto government. This research fills the knowledge gap relating to Gaza and provides the basis for more research on resourcing problems. This research has also extended, updated and confirmed the current knowledge regarding challenges hindering the resourcing for PDHR. The results draw attention of the implementing agencies in Gaza to the factors that creating bottlenecks to resource the reconstruction projects in order to overcome them and to mitigate their negative effects.

Introduction

2019 ◽  
pp. 1-8
Author(s):  
Eileen A. Dombo ◽  
Christine Anlauf Sabatino
Keyword(s):  
Social Workers ◽  
Current Knowledge ◽  
School Social Workers ◽  
School Outcomes ◽  
Negative Effects ◽  
Knowledge And Skills ◽  
Poor Academic Performance ◽  
Trauma Informed ◽  
Outcomes For Children

Chapter 1 explains the basic assumption of the book: that school social workers are in a position to provide leadership, knowledge, and skills to create trauma-informed schools and foster resilience in schoolchildren. Trauma-informed schools aim to address students’ dysfunctional academic and behavioral performance driven by affective and physiological arousal. The correlation between high rates of trauma exposure and poor academic performance is established in the scholarly literature, as is the need for trauma-informed schools and communities. However, researchers are now finding negative effects on school outcomes for children who have not directly experienced trauma, but whose classmates have. This means that all children benefit from trauma-informed schools. School social workers are in a prime position to prevent and address trauma, and this book provides current knowledge and concrete skills to guide development of trauma-informed schools, helping students succeed in school.

scholarly journals Missing links in the study of solute and particle exchange between the sea floor and water column

2020 ◽  
Vol 77 (5) ◽  
pp. 1602-1616 ◽  
Author(s):  
Saskia Rühl ◽  
Charlie Thompson ◽  
Ana M Queirós ◽  
Stephen Widdicombe
Keyword(s):  
Water Column ◽  
Current Knowledge ◽  
Anthropogenic Impacts ◽  
Future Research ◽  
Sea Floor ◽  
Marine Habitats ◽  
Exchange Processes ◽  
Ecosystem Level ◽  
Particle Exchange

Abstract Exchanges of solutes and solids between the sea floor and water column are a vital component of ecosystem functioning in marine habitats around the globe. This review explores particle and solute exchange processes, the different mechanisms through which they interact at the ecosystem level, as well as their interdependencies. Solute and particle exchange processes are highly dependent on the characteristics of the environment within which they takes place. Exchange is driven directly by a number of factors, such as currents, granulometry, nutrient, and matter inputs, as well as living organisms. In turn, the occurrence of exchanges can influence adjacent environments and organisms. Major gaps in the present knowledge include the temporal and spatial variation in many of the processes driving benthic/pelagic exchange processes and the variability in the relative importance of individual processes caused by this variation. Furthermore, the accurate assessment of some anthropogenic impacts is deemed questionable due to a lack of baseline data and long-term effects of anthropogenic actions are often unknown. It is suggested that future research should be transdisciplinary and at ecosystem level wherever possible and that baseline surveys should be implemented and long-term observatories established to fill the current knowledge gaps.

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