scholarly journals EFFECTS OF THERMODYNAMICAL PROCESSES ON RADIOCESIUM BEHAVIOR IN LAKE TAPELIAI / TERMODINAMINIŲ PROCESŲ ĮTAKA RADIOCEZIO ELGSENAI TAPELIŲ EŽERE

2012 ◽  
Vol 3 (6) ◽  
pp. 95-100
Author(s):  
Anastasija Moisejenkova ◽  
Aloyzas Girgždys ◽  
Nikolaj Tarasiuk
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Lake Water ◽  
Sediment Surface ◽  
Main Process ◽  
Complex Data ◽  
Data Set ◽  
Activity Concentrations ◽  
Lake Bottom ◽  
Integrated Study

The article presents the results of the integrated study of radiocesium behavior in Lake Tapeliai using not only conventional data on radiocesium activity concentrations in lake water and sediments but also a complex data set on seasonal variations and vertical profiles of standard water variables. Radiocesium activity concentrations in lake water as well as the vertical structure of the water column considerably depend on the inflows of the colored waters from the swampy watershed of the lake enriched in radiocesium. The global fallouts are mainly responsible for radiocesium inventory in lake sediments, which reaches maximum in the upper part of the water column above the ~5.4-m depth. The maximum values of radiocesium inventories in lake sediments are consistent with the respective densities of its deposits in the nearest forest soils. The main process of sediment activation is the direct sorption of radiocesium onto the sediment surface. Sedimentation rates in the lake vary mainly in the range of 3.5–5 mm·a–1. Lake bottom feeding sources located mainly on the southern terrace as well as their related near-bottom flows reduce respective sedimentation and radiocesium inventories in the sediments. Santrauka Straipsnyje nagrinėjama radiocezio elgsena Tapelių ežere, naudojant ne tik radiocezio savitojo ir tūrinio aktyvumų duomenis, bet ir standartinius vertikaliuosius parametrus, tokius kaip temperatūra, elektros laidumai ir oksiduoto sluoksnio storis. Radiocezio aktyvumas ežero vandenyje priklauso nuo spalvoto pelkinio vandens, kuriame yra radiocezio, patekimo į ežerą. Radiocezio apkrova dugno nuosėdose yra didžiausia viršutinėje ežero dalyje, t. y. iki 5,4 m gylio. Sedimentacijos greitis svyruoja 3,5–5 mm·m–1. Ežero priedugniniai vandens šaltiniai daugiausia išsidėstę pietinėje ežero terasoje, jų srovės sumažina sedimentaciją ir radiocezio apkrovą dugno nuosėdose.

Radioactivity measurements in the atmosphere and water column of Rogoznica Lake (central Adriatic)

2021 ◽  
Author(s):  
Ivana Tucaković ◽  
Sarah Mateša ◽  
Ivana Coha ◽  
Marija Marguš ◽  
Milan Čanković ◽  
...  
Keyword(s):  
Water Column ◽  
Long Range ◽  
Lake Water ◽  
Dry Deposition ◽  
Long Range Transport ◽  
Atmospheric Input ◽  
Air Masses ◽  
Activity Concentrations ◽  
Range Transport ◽  
Radionuclide Activity

<p>Croatian Science Foundation MARRES project (MARine lake (Rogoznica) as a model for EcoSystem functioning in a changing environment) aims to investigate the unique environment (slow exchange of seawater with the sea; atmospheric input is the only source of freshwater) of the marine lake which is an example of highly stratified (permanent anoxia bellow 9 m depth), and by climate changes affected marine system in the middle of the eastern Adriatic coast (43.53° N, 15.95° E). The area of the lake is characterized by the extensive tourism and mariculture, and the low impact of local industrial activities. It is also affected by the combined influence of long-range transport of air masses and local emissions (open-fire events).</p><p>An important part of the project is focused on the exchange and interaction between atmosphere, water column and sediment by measuring the atmospheric input (wet and dry deposition) of sulphur compounds, organic carbon, trace metals and radionuclides (Be-7, Pb-210).</p><p>This work for the first time will present the current state of the measurements of radioactivity in the Rogoznica lake area, including samples of aerosol particulate matter, PM2.5 < 2.5 um, rainwater and lake water column. Namely, the concentrations of Be-7 and Pb-210 in PM2.5 are measured to determine and correlate the dynamics of particle transport, meteorological information, especially origin of air masses and seasonal variation of PM2.5. While presence of Be-7 indicates the recent wet or dry deposition from the upper parts of the atmosphere, Pb-210 may be used as a tracer for continental air masses. Therefore, it can also indicate the influence of the pollution induced by human activity. Regarding that, special attention will be paid to compare results before and during the Covid-19 lockdown periods.</p><p>So far, preliminary results do not show significant difference in PM2.5 masses and measured radionuclide activity concentrations for the lockdown period. Be-7 and Pb-210 were regularly detected in aerosols collected on a glass fiber filters during a one-week sampling periods with the air flow rate of 2.3 m<sup>3</sup>/h. Their activity concentrations are determined by gamma spectrometry using High Purity Germanium detectors. The results are found to be correlated with PM2.5 masses, ranging from 2.9 to 12.2 Bq/m<sup>3</sup> for Be-7 and from 0.5 to 2.5 Bq/m<sup>3</sup> for Pb-210. First analyses show that the highest values can be related to the long-range transport of air masses and to the recorded near open-fire event. As expected, Be-7 is also detected in almost every rainwater sample (event), with the activity concentration up to 5.6 Bq/L, while low activities of Pb-210 are detected only sporadically. Related to that, Be-7 is detected in lake water column as well, but only in the surface layer and in samples collected during, or immediately after the rain events. </p><p>Dynamics and seasonal variation of radionuclide activity concentrations in here studied samples will be discussed, and the relationships with some meteorological parameters (temperature, wind speed, relative humidity, precipitation level) as well as local and long-range transport and physico-chemical conditions in the lake water column will be established.</p>

scholarly journals Scientific access into Mercer Subglacial Lake: scientific objectives, drilling operations and initial observations

2021 ◽  
pp. 1-13
Author(s):  
John C. Priscu ◽  
Jonas Kalin ◽  
John Winans ◽  
Timothy Campbell ◽  
Matthew R. Siegfried ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Lake Water ◽  
Sediment Cores ◽  
Hot Water ◽  
Water Ice ◽  
Subglacial Lake ◽  
Entry Models ◽  
Borehole Water ◽  
Ice Water

Abstract The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

Sedimentation of Pb-210 in Laurentian Shield Lakes

1984 ◽  
Vol 19 (2) ◽  
pp. 97-109 ◽  
Author(s):  
R.J. Cornett ◽  
L. Chant ◽  
D. Link
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Rate Constant ◽  
Bottom Sediments ◽  
Atmospheric Fallout ◽  
Small Lakes ◽  
Fractional Rate ◽  
Total Input ◽  
Shield Lakes ◽  
Annual Flux

Abstract The average annual flux of Pb-210 from the atmosphere to lake surfaces and to the bottom sediments was measured in seven small lakes located on the Laurentian Shield. Direct atmospheric fallout of Pb-210 was 136 ± 16 Bq m-2 a-1 Streams from the lakes' catchments input an additional 5 to 473 Bq m-2 a-1. Only 16 to 80 percent of the total input was found in the lake sediments. The fractional rate constant for Pb-210 sedimentation from the water column ranged from 0.25 to 5.3 per annum.

scholarly journals 136. Don’t Sweat the Small Stuff: Solutions for Large-Scale Stewardship Obstacles

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S79-S80
Author(s):  
Joanne Huang ◽  
Zahra Kassamali Escobar ◽  
Rupali Jain ◽  
Jeannie D Chan ◽  
John B Lynch ◽  
...  
Keyword(s):  
Urgent Care ◽  
Complex Data ◽  
Open Communication ◽  
University Of Washington ◽  
Data Set ◽  
Constructive Feedback ◽  
Diagnostic Coding ◽  
Icd 10 ◽  
Tract Infections ◽  
The University

Abstract Background In an effort to support stewardship endeavors, the MITIGATE (a Multifaceted Intervention to Improve Prescribing for Acute Respiratory Infection for Adult and Children in Emergency Department and Urgent Care Settings) Toolkit was published in 2018, aiming to reduce unnecessary antibiotics for viral respiratory tract infections (RTIs). At the University of Washington, we have incorporated strategies from this toolkit at our urgent care clinics. This study aims to address solutions to some of the challenges we experienced. Challenges and Solutions Methods This was a retrospective observational study conducted at Valley Medical Center (Sept 2019-Mar 2020) and the University of Washington (Jan 2019-Feb 2020) urgent care clinics. Patients were identified through ICD-10 diagnosis codes included in the MITIGATE toolkit. The primary outcome was identifying challenges and solutions developed during this process. Results We encountered five challenges during our roll-out of MITIGATE. First, using both ICD-9 and ICD-10 codes can lead to inaccurate data collection. Second, technical support for coding a complex data set is essential and should be accounted for prior to beginning stewardship interventions of this scale. Third, unintentional incorrect diagnosis selection was common and may require reeducation of prescribers on proper selection. Fourth, focusing on singular issues rather than multiple outcomes is more feasible and can offer several opportunities for stewardship interventions. Lastly, changing prescribing behavior can cause unintended tension during implementation. Modifying benchmarks measured, allowing for bi-directional feedback, and identifying provider champions can help maintain open communication. Conclusion Resources such as the MITIGATE toolkit are helpful to implement standardized data driven stewardship interventions. We have experienced some challenges including a complex data build, errors with diagnostic coding, providing constructive feedback while maintaining positive stewardship relationships, and choosing feasible outcomes to measure. We present solutions to these challenges with the aim to provide guidance to those who are considering using this toolkit for outpatient stewardship interventions. Disclosures All Authors: No reported disclosures

scholarly journals Traces of sunlight in the organic matter biogeochemistry of two shallow subarctic lakes

2021 ◽  
Author(s):  
Marttiina V. Rantala ◽  
Carsten Meyer-Jacob ◽  
E. Henriikka Kivilä ◽  
Tomi P. Luoto ◽  
Antti. E. K. Ojala ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Lake Sediments ◽  
Lake Water ◽  
Human Impacts ◽  
Global Environmental Change ◽  
Carbon Export ◽  
Subarctic Lakes ◽  
Carbon Regulation ◽  
In Situ Experiments

AbstractGlobal environmental change alters the production, terrestrial export, and photodegradation of organic carbon in northern lakes. Sedimentary biogeochemical records can provide a unique means to understand the nature of these changes over long time scales, where observational data fall short. We deployed in situ experiments on two shallow subarctic lakes with contrasting light regimes; a clear tundra lake and a dark woodland lake, to first investigate the photochemical transformation of carbon and nitrogen elemental (C/N ratio) and isotope (δ13C, δ15N) composition in lake water particulate organic matter (POM) for downcore inferences. We then explored elemental, isotopic, and spectral (inferred lake water total organic carbon [TOC] and sediment chlorophyll a [CHLa]) fingerprints in the lake sediments to trace changes in aquatic production, terrestrial inputs and photodegradation before and after profound human impacts on the global carbon cycle prompted by industrialization. POM pool in both lakes displayed tentative evidence of UV photoreactivity, reflected as increasing δ13C and decreasing C/N values. Through time, the tundra lake sediments traced subtle shifts in primary production, while the woodland lake carried signals of changing terrestrial contributions, indicating shifts in terrestrial carbon export but possibly also photodegradation rates. Under global human impact, both lakes irrespective of their distinct carbon regimes displayed evidence of increased productivity but no conspicuous signs of increased terrestrial influence. Overall, sediment biogeochemistry can integrate a wealth of information on carbon regulation in northern lakes, while our results also point to the importance of considering the entire spectrum of photobiogeochemical fingerprints in sedimentary studies.

scholarly journals DEELIG: A Deep Learning Approach to Predict Protein-Ligand Binding Affinity

2021 ◽  
Vol 15 ◽  
pp. 117793222110303
Author(s):  
Asad Ahmed ◽  
Bhavika Mam ◽  
Ramanathan Sowdhamini
Keyword(s):  
Deep Learning ◽  
Ligand Binding ◽  
Binding Affinity ◽  
Chemical Space ◽  
Biological Significance ◽  
Protein Crystal ◽  
Ligand Docking ◽  
Complex Data ◽  
Binding Prediction ◽  
Data Set

Protein-ligand binding prediction has extensive biological significance. Binding affinity helps in understanding the degree of protein-ligand interactions and is a useful measure in drug design. Protein-ligand docking using virtual screening and molecular dynamic simulations are required to predict the binding affinity of a ligand to its cognate receptor. Performing such analyses to cover the entire chemical space of small molecules requires intense computational power. Recent developments using deep learning have enabled us to make sense of massive amounts of complex data sets where the ability of the model to “learn” intrinsic patterns in a complex plane of data is the strength of the approach. Here, we have incorporated convolutional neural networks to find spatial relationships among data to help us predict affinity of binding of proteins in whole superfamilies toward a diverse set of ligands without the need of a docked pose or complex as user input. The models were trained and validated using a stringent methodology for feature extraction. Our model performs better in comparison to some existing methods used widely and is suitable for predictions on high-resolution protein crystal (⩽2.5 Å) and nonpeptide ligand as individual inputs. Our approach to network construction and training on protein-ligand data set prepared in-house has yielded significant insights. We have also tested DEELIG on few COVID-19 main protease-inhibitor complexes relevant to the current public health scenario. DEELIG-based predictions can be incorporated in existing databases including RSCB PDB, PDBMoad, and PDBbind in filling missing binding affinity data for protein-ligand complexes.

scholarly journals Occurrence and distribution of ladderane oxidation products in different oceanic regimes

2012 ◽  
Vol 9 (7) ◽  
pp. 2407-2418 ◽  
Author(s):  
D. Rush ◽  
E. C. Hopmans ◽  
S. G. Wakeham ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Fatty Acids ◽  
Water Column ◽  
Arabian Sea ◽  
Degradation Products ◽  
Oxidation Products ◽  
Short Chain ◽  
Sediment Surface ◽  
Ammonium Oxidation ◽  
Anammox Activity ◽  
Sediment Matrix

Abstract. Ladderane fatty acids are commonly used as biomarkers for bacteria involved in anaerobic ammonium oxidation (anammox). These lipids have been experimentally shown to undergo aerobic microbial degradation to form short chain ladderane fatty acids. However, nothing is known of the production or the distribution of these oxic biodegradation products in the natural environment. In this study, we analysed marine water column particulate matter and sediment from three different oceanic regimes for the presence of ladderane oxidation products (C14 ladderane fatty acids) and of original ladderane fatty acids (C18 and C20 ladderane fatty acids). We found that ladderane oxidation products, i.e. C14 ladderane fatty acids, are already produced within the water column of the Arabian Sea oxygen minimum zone (OMZ) and thus only low amounts of oxygen (< 3 μM) are needed for the β-oxidation of original ladderane fatty acids to proceed. However, no short chain ladderane fatty acids were detected in the Cariaco Basin water column, where oxygen concentrations were below detection limit, suggesting that the β-oxidation pathway is inhibited by the absence of molecular oxygen, or that the microbes performing the degradation are not proliferating under these conditions. Comparison of distributions of ladderane fatty acids indicates that short chain ladderane fatty acids are mostly produced in the water column and at the sediment surface, before being preserved deeper in the sediments. Short chain ladderane fatty acids were abundant in Arabian Sea and Peru Margin sediments (ODP Leg 201), often in higher concentrations than the original ladderane fatty acids. In a sediment core taken from within the Arabian Sea OMZ, short chain ladderanes made up more than 90% of the total ladderanes at depths greater than 5 cm below sea floor. We also found short chain ladderanes in higher concentrations in hydrolysed sediment residues compared to those freely occurring in lipid extracts, suggesting that they had become bound to the sediment matrix. Furthermore, these matrix-bound short chain ladderanes were found at greater sediment depths than short chain ladderanes in the lipid extract, suggesting that binding to the sediment matrix aids the preservation of these lipids. Though sedimentary degradation of short chain ladderane fatty acids did occur, it appeared to be at a slower rate than that of the original ladderane fatty acids, and short chain ladderane fatty acids were found in sediments from the Late Pleistocene (~ 100 kyr). Together these results suggest that the oxic degradation products of ladderane fatty acids may be suitable biomarkers for past anammox activity in OMZs.

scholarly journals Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic

2014 ◽  
Vol 11 (8) ◽  
pp. 2211-2224 ◽  
Author(s):  
E. Metzger ◽  
D. Langlet ◽  
E. Viollier ◽  
N. Koron ◽  
B. Riedel ◽  
...  
Keyword(s):  
Water Column ◽  
Experimental Studies ◽  
Geochemical Evolution ◽  
Sediment Surface ◽  
Pore Waters ◽  
In Situ Experiment ◽  
Solid Oxides ◽  
Northern Adriatic ◽  
Entire Height ◽  
Benthic Chambers

Abstract. Long-term experimental studies suggest that, under transient anoxic conditions, redox fronts within the sediment shift upwards, causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) and S(-II)). Infaunal benthic organisms are associated with different redox fronts as micro-habitats and must be affected by such changes during natural hypoxia events. In order to document the geochemical evolution of the sediment during prolonged anoxia in the framework of an in situ experiment designed to mimic natural conditions, benthic chambers were deployed on the seafloor of the Northern Adriatic and sampled after 9, 30 and 315 days of incubation. Oxygen and sulfide were measured continuously in the early stages (9 days) of the experiment. High-resolution pore water profiles were sampled by DET probes and redox-sensitive species (S(VI), Mn(II) and Fe(II)) and alkalinity were measured. Starting oxygen saturation was about 80% within the chamber. After 7 days, anoxia was established in the bottom waters within the chambers. Mn(II) and Fe(II) started diffusing towards the anoxic water column until they reached the surficial sediment. Being reoxidized there, Mn and Fe reprecipitated, giving a rusty coloration to the seafloor. Infaunal species appeared at the sediment surface. After 20 days, all macro-organisms were dead. Decomposition of macro-organisms at the sediment–water interface generated S(-II) within the entire height of the chamber, leading to a downward flux of sulfides into the sediment, where they were quickly oxidized by metallic oxides or precipitated as FeS. S(-II) was below detection in the water column and pore waters at the end of the experiment. Our results suggest that S(-II) enrichment in the water column of coastal systems, which are episodically anoxic, is strongly controlled by the biomass of benthic macrofauna and its decay during anoxia, whereas its residence time in the water column is controlled by iron availability (as solid oxides or as dissolved reduced cations) within the sediment, even without water circulation.

Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor

1990 ◽  
Vol 36 (12) ◽  
pp. 859-863 ◽  
Author(s):  
James A. Novitsky
Keyword(s):  
Bacterial Community ◽  
Water Column ◽  
Sediment Surface ◽  
Metabolic Inhibitor ◽  
Optimum Conditions ◽  
Bacterial Populations ◽  
Protozoan Grazing ◽  
Large Numbers ◽  
Doubling Times

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.

scholarly journals Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

2015 ◽  
Vol 12 (5) ◽  
pp. 1561-1583 ◽  
Author(s):  
M. Hagens ◽  
C. P. Slomp ◽  
F. J. R. Meysman ◽  
D. Seitaj ◽  
J. Harlay ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Primary Production ◽  
Water Column ◽  
Bottom Water ◽  
Substantial Reduction ◽  
Buffering Capacity ◽  
Total Alkalinity ◽  
Acid Base ◽  
Data Set ◽  
Ph Fluctuations

Abstract. Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light–dark incubations, in addition to sediment–water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air–sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment–water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid–base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid–base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

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