Phase Deposition Research Articles

Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers

Pyrite oxidation plays a critical role in the relationship between weathering and climate, and its impact on the global carbon cycle has previously been constrained through inversion models utilizing observations of river sulfate (SO42−) and its 34S/32S isotope ratio (δ34SSO4). However, measurements from some rivers have suggested that δ34SSO4 can be substantially impacted by processes such as microbial sulfate reduction and/or sulfur assimilation and cycling, rather than simply reflecting a weighted mixture of lithologic sulfur sources. To study the prevalence and controls on SO42− transformations, we measured dissolved major element concentrations and δ34SSO4 in river water samples from throughout western Iceland. Our analyses focused on samples from a small catchment hosting the Efri Haukadalsá river, a system with relatively uniform and isotopically constrained basaltic bedrock. We also measured sediment δ34S and sulfur speciation using sulfur K-edge X-ray absorption spectroscopy on sediment and vegetation samples from this catchment. Values of dissolved δ34SSO4 in the Efri Haukadalsá ranged from 2.5‰ to 23.7‰ and had a linear relationship with Cl−/SO42− ratios, indicating that SO42− predominantly derived from basalt weathering and meteoric precipitation. The lower δ34SSO4 values were found in fluvial valleys with V-shaped cross sections, while higher values of δ34SSO4 occurred in U-shaped, glacially eroded valleys with thick alluvial fills blanketing the valley floor. Spectroscopic observations identified organic sulfur phases in suspended river sediment, floodplain deposits, and vegetation. Mass balance calculations quantified the organic sulfur flux as less than 10% of SO42− export, and sediment δ34S values were comparable to river δ34SSO4. We interpreted these isotopic and chemical patterns as reflecting differences in the availability of unweathered bedrock across the Efri Haukadalsá catchment, with V-shaped valleys having greater access to fresh sulfide-bearing minerals than alluviated U-shaped valleys; this interpretation is in contrast to one in which the elevated δ34SSO4 values reflect fractionation during sulfur transformations along alluvial reaches. These results validated the application of river inversion models for constraining weathering fluxes and affirmed that pyrite oxidation globally, even in the presence of river sulfur cycling, modulates the abundance of atmospheric carbon dioxide.

Efficient Extraction of Past Seawater Pb and Nd Isotope Signatures From Southern Ocean Sediments

AbstractRadiogenic lead (Pb) and neodymium (Nd) isotope compositions extracted from authigenic phases in marine sediments are sensitive tracers to reconstruct past ocean circulation and water mass mixing. Chemical reductive leaching of hydrogenetic ferromanganese oxyhydroxides from bulk sediments is the most practical way to recover past seawater Pb and Nd isotope signatures in the Southern Ocean, due to the scarcity of alternative archives. However, the leached signal could be compromised if substantial quantities of Pb and Nd were released from non‐hydrogenetic sediment fractions during chemical extraction. Here we developed a very short 10‐s leaching method to extract reliable seawater Pb and Nd isotope signals from sediments in the Atlantic sector of Southern Ocean. The effect of a previously recommended MgCl2pre‐wash, the role of chelate ligands in the leaching solution and length of leaching time were investigated. The results show that 10‐s exposure time of sediments to reductive leaching extracted sufficient and more reliable hydrogenetic Pb and Nd compared with the commonly used 30‐min leaching approaches. The robustness of our improved leaching method was validated via direct comparison of Pb and Nd isotope signatures with actual seawater, porewater, and corresponding sediment leachates from three stations in front of the Antarctic Filchner‐Rønne Ice Shelf. Our findings also indicate that in contrast previously studied sites on the West Antarctic continental shelf, the bottom seawater Nd concentration is less elevated through benthic fluxes in the area of the southern Weddell Sea shelf.

Assessing the Power of Intensity Interaction between the Solid and Fluid Phases in the Unconsolidated Water-Saturated Sandy Marine Sediments at Shear Wave Propagation

Purpose. Propagation of a shear wave in sandy marine sediments is considered. The acoustic properties of a shear wave are the phase velocity and the attenuation coefficient. It is known that in dry sandy sediments, the attenuation coefficient is directly proportional to frequency. In the saturated mediums, there are the deviations from this law that implies existence of two physical mechanisms of losses – the intergranular friction and viscous loss. The study is aimed at developing a two-phase theoretical model of the shear wave propagation in the unconsolidated marine sediments, and at identifying the dissipative effects caused by the fluid relative movement in the pore space. Methods and Results. The intergranular friction is modeled using a springpot, which represents an element combing conservative properties of a spring and dissipative ones of a dashpot. The equation of motion is applied, where a part of fluid is assumed to be associated with the media solid phase and another part is considered to be mobile. For a harmonic displacement, the equations of state and the equation of motion yield a new two-phase dispersion relation (the theory of Grain Shearing + Effective Density, or GS + EDs, for short). The results of the GS + EDs theory are compared with the data of the velocity and attenuation measurements taken from the open sources. It is shown that during propagation of the compressional and shear waves, the mechanisms of interaction between the granules, and between the granules and fluid are not similar. Character of the changes in the grain-to-grain friction parameters when the pore space is saturated with fluid, is analyzed. Conclusions. Manifestation of the dissipative effects resulting from the pore saturation with fluid depends on the density of the granules packing. In case of a dense packing, there are no conditions for the fluid relative movement, and the sandy sediments exhibit the property of constant Q-factor. If the packing is loose, the viscous losses make a significant contribution, and the attenuation frequency dependence is nonlinear. The effective pore sizes for the compression and shear waves do not coincide.

Mechanisms of sedimentation in lacustrine environment of Babouri-Figuil and Mayo Oulo-Lere basins deposits (North Cameroon) during the Southern Atlantic opening: sedimentary structures and geochemistry constraints

Sedimentary structures are very useful to characterize sedimentation environments. In this study, sedimentary structures are documented in the Lower Cretaceous Babouri-Figuil and Mayo Oulo-Lere intracontinental Basins whose genesis is linked to the opening of the Southern Atlantic Ocean. Geochemical data is also presented with the aim to discriminate the paleoenvironment. Field investigations and facies analyses revealed synsedimentary and postsedimentary structures related or not to tectonic. Synsedimentary structures not affected by tectonic are lamination or bedding (rhythmic), graded bedding, cross-stratification, loads casts, channels, and ripple marks. Those affected by tectonic are convolute bedding, slump (Slump sensus stricto and olistolith). Desiccation cracks and print marks are postsedimentary structures not related to tectonic; others are stratigraphic unconformity, oblique bedding, clastic injection, and volcanic veins. The bottom of the sequence in the two basins is fluvio-lacustrine deposits with oblique stratification and global positive graded bedding; sometimes there is alternation of positive and negative graded beddings related to progressive variation of energy of sedimentation from high to low and low to high. The intermediate level is lacustrine dominated by lamination or bedding that characterizes a calm sedimentation environment marked by regular seasonal fluctuation. The ripple marks, desiccation cracks, and dinosaur footprints indicate the emersion period, and their fossilization indicates slow phases of sedimentation. Channels and load casts correspond to a rapid sedimentation phase. Seismic shocks at time break the fragile stability of deposited materials causing gravitational flows of the sublacustrine avalanche type and give olistolith and convolute bedding to slumps. The clastic or chemical injections and volcanic veins are related to brittle tectonic that affects consolidated deposits. From the geochemical data, the high accumulation of LREE (average: 142.93 ppm) over HREE (average: 13.10 ppm); La/La* generally 2) and the slight to very slight negative Ce/Ce* (0.87–0.99) suggest the nonmarine deposition, and the Y/Ho ratios (< 45) and ratios indicate river condition or transportation. The Sr/Ba ratios, ranging from 0.55 to 6.41, suggest a freshwater environment with fluctuant salinity and sometimes hypersaline (Hypersaline Lake). Thus the synsedimentary structures were essentially formed in lacustrine milieu, and some structures such as graded bedding and cross-stratification affecting the basal deposit indicate a fluviatile to fluvio-lacustrine environment.

Distributions, temporal trends and ecological risks of polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in sediments of Jiaozhou Bay, China

Spatiotemporal distribution and ecological risk of the polyethylene terephthalate (PET) plastic polymer and plasticizer di-(2-ethylhexyl) phthalate (DEHP) were investigated using both surface and core sediments in Jiaozhou Bay, China. The concentrations of PET and DEHP ranged 210.6–1929.7 μg/kg and 0–591.2 μg/kg, respectively. The depth profiles of PET and DEHP in the sediment cores indicated that PET and DEHP pollution increased since the 1970s, which is in accord with the regional PET and DEHP consumption history. The levels of PET in Jiaozhou Bay was found to represent low ecological risk based on the assessment models for Potential Ecological Risk factor and Potential Ecological Risk. The amounts of DEHP also posed a low risk to the aquatic organisms in the sediment phase as indicated by the Risk Quotient method.

An experimental investigation of the acquisition of Nd by authigenic phases of marine sediments

The neodymium isotope composition (ɛNd) of authigenic phases in marine sediment is widely used to reconstruct the origin and mixing of water masses of overlying seawater through time. However, at some locations in the modern ocean, the ɛNd of authigenic phases in surface sediment is not consistent with that of local seawater, raising concerns about its current interpretation as a paleotracer of water masses. To further investigate this question, we conducted a laboratory-based incubation experiment with a Mn-oxide phase placed at the sediment–water interface of multicores to assess the extent to which the authigenic phase records seawater ɛNd.Multicores were collected from the Strait of Georgia (SoG), which is a relatively deep coastal waterway with high sedimentation rates, oxygenated surface sediments, and active macrofauna, separating the mainland coast of British Columbia and Vancouver Island. Manganese oxide-coated XAD resin beads were placed at the sediment surface and the cores were incubated for 6 months in a tank filled with SoG seawater spiked with 150Nd. While the ɛNd of the Mn-oxide coated resin (−4.0) was similar to that of SoG seawater used for the incubation (−3.7), the 150Nd/144Nd of the Mn-oxide phase measured after the incubation indicates that, under our experimental conditions, a minimum of 83% of the Nd associated with the Mn-oxide phase is not sourced from seawater, but from pore water. The 150Nd/144Nd ratio of the Mn-oxide resin is necessary to determine the predominant source of Nd to the resin because the ɛNd of SoG pore water (−3.9) is within analytical error of seawater (−3.7). Using field data and constraints from the Nd mass balance during the incubation, we conclude that the similarity of ɛNd in pore water and seawater in the SoG is fortuitous and not a result of a top-down or bottom-up control. Although the setting of our sediments is not directly comparable to open ocean locations, this study raises concerns about the use of ɛNd in paleocirculation studies, and points to the necessity of elucidating the factors controlling local lithogenic dissolution in pore waters as a prerequisite for the correct interpretation of ɛNd in the authigenic phases of marine sediments.

Removal of Antibiotics and Antibiotic Resistance Genes from Urban Rivers Using Artificial Ecosystems

Four antibiotics[azithromycin (AZM), sulfamethoxazole (SMZ), ciprofloxacin (CIP), and tetracycline (TCY)], and the antibiotic resistance genes (ARGs)[sulfonamides (sul1 and sul2), tetracyclines (tetX and tetM), quinolones (qnrS and qnrD), macrolides (ermB), and 16S rDNA] were selected as target compounds. Artificial ecosystems were constructed with combinations of two emergent plants and Microcystis aeruginosa (Acorus calamus+Cordyceps, algae+Cordyceps, algae+Acorus calamus, and algae+Acorus calamus+Cordyceps) in an indoor-simulated river system. Throughout the artificial ecosystems, changes in antibiotic concentrations and other pollution indicators (i.e., COD, NH4+-N, TP, and TN) were monitored in different media (the aqueous phase, sediment phase, and in plants), and the distribution and removal of ARGs in aqueous and sediment phases were explored. Removal of the target compounds was calculated based on mass balance, and the correlation between ARG abundance and environmental factors in the aqueous and sediment phases was analyzed. The results showed that the constructed artificial ecosystem achieved removal rates of COD, NH4+-N, TP, and TN ranging from 60.2% to 74.8%, 63.4% to 77.4%, 64.0% to 73.2%, and 46.8% to 54.8%, respectively. The antibiotics in the aqueous phase were notably removed and the artificial ecosystem 'algae+Acorus calamus+Cordyceps' achieved the best removal efficiency for the four antibiotics. Removal rates of the antibiotics in the sediment phase were ranked in the order TCY>CIP>AZM>SMZ; the removal efficiency of TCY in the 'algae+Acorus calamus+Cordyceps' system reached up to 53.5%. The total removal rates of antibiotics obtained by the ecosystems were ranked in the following order:algae+Acorus calamus+Cordyceps > algae+Cordyceps > algae+Acorus calamus > Acorus calamus+Cordyceps. Removal of the four ARGs was very efficient and was higher in the aqueous phase than in the sediment phase. Correlations between the ARGs, the other pollution indicators, and the antibiotics were variable; tetX and environmental factors were correlated in the aqueous phase, while AZM and its corresponding ARGs were not significantly correlated in the sediment phase. The results showed that ARGs can be targeted under corresponding antibiotic pressure and other types of environmental pressure. In the study system, the concentrations of antibiotics did not directly affect the transmission of ARGs. Overall, this study shows that artificial ecosystems constructed with emergent plants and Microcystis aeruginosa can be effective at purifying water and reducing the environmental risks of antibiotics in urban rivers.

A Numerical Study of Onshore Ripple Migration Using a Eulerian Two‐phase Model

AbstractA new modeling methodology for ripple dynamics driven by oscillatory flows using a Eulerian two‐phase flow approach is presented in order to bridge the research gap between near‐bed sediment transport via ripple migration and suspended load transport dictated by ripple induced vortices. Reynolds‐averaged Eulerian two‐phase equations for fluid phase and sediment phase are solved in a two‐dimensional vertical domain with a k‐ε closure for flow turbulence and particle stresses closures for short‐lived collision and enduring contact. The model can resolve full profiles of sediment transport without making conventional near‐bed load and suspended load assumptions. The model is validated with an oscillating tunnel experiment of orbital ripple driven by a Stokes second‐order (onshore velocity skewed) oscillatory flow with a good agreement in the flow velocity and sediment concentration. Although the suspended sediment concentration far from the ripple in the dilute region was underpredicted by the present model, the model predicts an onshore ripple migration rate that is in very good agreement with the measured value. Another orbital ripple case driven by symmetric sinusoidal oscillatory flow is also conducted to contrast the effect of velocity skewness. The model is able to capture a net offshore‐directed suspended load transport flux due to the asymmetric primary vortex consistent with laboratory observation. More importantly, the model can resolve the asymmetry of onshore‐directed near‐bed sediment flux associated with more intense boundary layer flow speed‐up during onshore flow cycle and sediment avalanching near the lee ripple flank which force the onshore ripple migration.

Onset of sedimentation near the Carnian/Norian boundary in the northwestern Sichuan Basin: New evidence from ammonoid biostratigraphy and zircon U[sbnd]Pb geochronology

Upper Triassic deposits formed at the onset of subsidence in the Sichuan foreland basin of South China, and may record a crisis of carbonate deposition related to the Carnian Pluvial Episode. However, there is no consensus yet on the precise age of these deposits in northwestern Sichuan. In this work, ammonoid biostratigraphy has been improved, and a U/Pb age from detrital zircons has been obtained from the Upper Triassic of northwestern Sichuan. New ammonoid taxa Sinotropites sichuanensis n. gen., n. sp. and Hadrothisbites hanwangensis n. sp. are described from the upper part of the Ma'antang Formation in Hanwang and Jushui area and are assigned to the uppermost Tuvalian (Anatropites spinosus Zone, Gonionotites italicus Subzone). Ammonoid and conodont biostratigraphy, combined with U/Pb concordant ages of 227.2 ± 1.1 Ma obtained from youngest detrital zircons, provide a robust constrain on the initial sedimentation phases of the foreland basin in northwestern Sichuan, and suggest that the terrigenous turnover was not related to the Carnian Pluvial Episode.

Evaluation of thiobencarb runoff from rice farming practices in a California watershed using an integrated RiceWQ-AnnAGNPS system

The development of modeling technology to adequately simulate water and pesticide movement within the rice paddy environment faces several challenges. These include: (1) adequately representing ponded conditions; (2) the collection/implementation of temporal/spatial pesticide application data at field scales; (3) the integration of various mixed-landuses simulation schemes. Currently available models do not fully consider these challenges and results may not be sufficiently accurate to represent fate and transport of rice pesticides at watershed scales. Therefore, in this study, an integrated simulation system, “RiceWQ-AnnAGNPS”, was developed to fully address these challenges and is illustrated in a California watershed with rice farming practices. The integrated system successfully extends field level simulations to watershed scales while considering the impact of mixed landuses on downstream loadings. Moreover, the system maintains the application information at fine spatial scales and handles varying treated paddy areas via the “split and adjust” approach. The new system was evaluated by investigating the fate and transport of thiobencarb residues in the Colusa Basin, California as a case study. Thiobencarb concentrations in both water and sediment phases were accurately captured by the calibrated RiceWQ model at the edge of field. After spatial upscaling, the integrated system successfully reflected both the seasonal pattern of surface runoff and the timing of monthly thiobencarb loadings. Incorporating future enhancements can further improve model performance by including more detailed water drainage schedules and management practices, improving the accuracy of summer runoff estimations, and incorporating a more sophisticated in-stream process module. This integrated system provides a framework for evaluating rice pesticide impacts as part of a basin level management approach to improve water quality, which can be extended to other rice agrochemicals, or other areas with fine-scale spatial information of pesticide applications.

Late Quaternary episodes of clastic sediment deposition in the Tarimba Cave, Central Brazil

The study presents three sedimentary profiles from Tarimba cave in central Brazil. The data allow constraining the late Quaternary sedimentary evolution of cave systems in the region. A multi-techniques approach was used to characterize sediment texture (grain size and circularity index), mineralogical composition (X-Ray Diffraction), chemical composition (ICP-OES) and deposition ages (Optically Stimulated Luminescence and radiocarbon). Eight sedimentary facies were identified, including a facies formed by autochthonous sediments (Guano) and seven facies formed by allochthonous siliciclastic sediments. The siliciclastic facies range from clayey to gravelly deposits that correspond to high-density gravity flows (Diamicton) and water laid traction process of varied deposition energy (Channel, Backswamp, and Slackwater). The studied deposits reflect an intense cave filing from the Middle to Late Pleistocene in the last 200 Ka. Subsequent depositional events formed three sedimentation phases: the first before 200 Ka corresponding to a larger granulometric interval, clay to gravel, identified through erosive surfaces; the second, after 197 Ka, is composed of sandy sediments and oscillations in the water flow energy. The third phase between 87 and 52 Ka (which covered the other stages) was responsible for the last fluvial deposition.

Distribution behavior and risk assessment of emerging perfluoroalkyl acids in multiple environmental media at Luoma Lake, East China

Perfluoroalkyl acids (PFAAs) are ubiquitous in various environments. This has caused great public concern, particularly in the shallow freshwater lake region, where the lake, rivers, and estuaries form a highly interconnected continuum. However, little is known about the environmental behaviors of PFAAs in the continuum. For the first time, a high-resolution monitoring framework covering the river-estuary-lake continuum of Luoma Lake was built, and the concentrations, sources, and environmental fates of PFAAs were identified and analyzed. The results revealed that the total concentration of PFAAs was at a moderate level in the water and at a high level in the sediment compared to global levels respectively. Perfluorooctanesulfonate (PFOS) was the most abundant PFAA in the continuum. In particular, the ∑PFAA concentration in the particle phase was much higher than that in the sediment phase. Distinct spatial heterogeneities were observed in the behaviors of distribution and the multiphase fate of PFAAs in the continuum, mainly driven by the turbulent mixing during transport, dilution of lake water, and spatial differences of hydrodynamic features and sedimentary properties among the sub-regions. Interestingly, the pH of the sediment and water had significant effects on the water-sediment portioning of PFAAs in contrasting ways. Furthermore, based on the composition of the sediments, four possible migration paths for PFAAs were deduced and the main sources of PFAAs were identified as sewage, domestic, and industrial effluents using the positive matrix factorization model. During the human health assessment, no risk was found under the median exposure scenario; however, under the high exposure scenario, PFAAs posed uncertain risks to human health, which cannot be ignored. This study provides basic information for simulating the fate and transport of PFAAs in the continuum and is significant for developing cost-effective control and remediation strategies in the near future.

Sedimentary micro-phase and reservoir display characteristics in shale Oil

Sedimentary microphilic and its exhibition feature is of great significance for identifying the distribution of remaining oil. This paper studies the development of geological characteristics of Zhidan Oil Zone, mineralogue and scanning electron microscopy experiments, and obtains the sedimentary micro-phase and reservoir display characteristics. The results show that combined with logging data, the core phase analysis, logging phase analysis, single well phase analysis, etc. Taking the leading edge of the Delta, the microphase type such as the river, the diversion bay and the underwater natural embankment is developed under water, due to the lifting of the lake, form a number of invested, plus, replenishment, in which water The downstream river is facilitating the advantages of the reservoir. The sedimentary phase and the angle effect of the zone are dominated by 4 + 5, chang 6 oil and gas, showing the characteristics of the rock sex reservoir. The type of reservoir is a rock sex reservoir. The main development of sandstone is impaired and the sandstone lens is a rock sex reservoir. The reservoir is an important influencing factor in the reservoir. The area has no uniform oil and water interface, lacking edge, bottom water.

In-silico research of the influence of gas injection into the subsea crude oil pipeline on the paraffin solid phase deposition

The aim of the article is presenting of the preliminary results of simulations showing behaviour of paraffin deposits in submarine pipelines. The described parameters for changing the deposition of the solid paraffin phase with the flow of crude oil through the submarine pipeline inside the subsea system: subsea wellhead – platform processing system. The research includes considerations of the behaviour of paraffins in the presence of the injected gas phase. Author recommends using of phenomenon as an alternative way of securing submarine pipelines operating on the Baltic Sea. This analyse informs that the paraffin’ deposit is possible to adjust of it’s thickness buy using agents other than purely chemical paraffin point temperature depressants. It is supposed here that main impact on paraffin deposition behaviour get decreasing of sediments thickness on the walls of the submarine pipeline in the analysed sections. The reservoir fluid composition used in the simulation was taken from B3 fluid PVT analysis owned by LOTOS Petrobaltic S.A. General composition was used in Leda Flow 2.5 computer analysis in courtesy of Kongsberg Company.

Mineral phases of metals in industrial sediments of St. Petersburg rivers with extreme pollution

The aim of the research was to determine the patterns of distribution of metals and their main mineral phases in technogenic bottom sediments of St. Petersburg watercourses in conditions of extreme pollution. The objects of research were the Yekaterinofka, Okhta, Krasnen'kaya, Smolenka, Karpovka and Chernaya Rechka Rivers. Bottom sediments of urbanized rivers are characterized by abnormally high concentrations of metals and metalloids (TMM). The maximum metal content established in river sediments corresponds to ore concentrations: Cu — 0.487 %, Pb — 5.54 %, Co — 0.129 %, Cd — 0.0439 % (0.01–5.0), Ba — 6.32 % and Zn — 0.818 %. According to the Geoaccumulation Index (Igeo), TMMs are characterized from moderate and severe pollution (Cr, Co, Ni, Zn, As) to extremely severe (Cu, Cd, Sb, Hg). The rivers have their own geochemical specialization of bottom sediments: the Okhta River is characterized by the highest concentrations of Ba, As, Sb, Zn and Hg; the Ekaterinofka River — Cr, Co, Mn, Pb, Cd; Smolenka River — Cu; Red — Fe, V, Sc; Chernaya Rechka River — Ni. Based on the method of the main components of factor analysis, paragenetic associations are identified that indicate the main sources of pollution: the production of batteries using Sb-Cd-Pb-Co-Mn (Yekaterinofka River) and Ni (Karpovka River), paints and varnishes using Ba-Hg-As-Zn (Okhta River) and metal processing Cu-Cr (Yekaterinofka, Smolenka and Chernaya Rechka Rivers). Scanning electron micrographs studies showed a variety of authigenic minerals, among which barite, hematite, magnetite, goethite are of primary importance. The amount of barite formed is proportional to the concentration of Ba in the sediments. There are metal sulfides, framboidal pyrite, sphalerite, chalcopyrite, galena. An important feature of early diagenetic changes in the composition of sediments under extreme pollution conditions of the studied rivers is shown — the formation of native metals (Fe, Pb) and aggregates of complex composition (Fe, Pb, Zn, Cu). This is probably one of the significant mechanisms of the flow of metals under conditions of sustainable technogenesis.

Trace Element’s Speciation in the Water and Bottom Sediments of the Pirogovo Reservoir

The composition and speciation of trace elements were studied in surface and interstitial waters along with solid phase of bottom sediments to characterize the abiotic segment of the Pirogovo Reservoir. It was found that the concentrations of metals in surface waters did not exceed the MACs for fishery basins, excluding Zn and Cu (2–9 and up to 2 MACs, respectively). According to thermodynamic calculations, the predominant metal speciation in water is free ions (Sr, Ba, Zn, Ni, Co, and Cd), as well as fulvate and carbonate complexes of Cu and Pb, respectively. Interstitial waters showed a regular increase of the fraction of the sulfate complexes of trace elements in loamy sediments. The solid phase of the latter as well was characterized by low anomalous concentrations of Zn, Cd, Co, and Ni. According to the data of extraction, the metals were either fixed in bottom sediments within crystal structure of silicates or bound to oxides and hydroxides of iron and manganese, excluding Cd and Mn, which are characterized by a considerable role of their exchangeable and bound to carbonates fraction in the particulate matter.

Insights into the climate-driven evolution of gas hydrate-bearing permafrost sediments: implications for prediction of environmental impacts and security of energy in cold regions.

The present study investigates the evolution of gas hydrate-bearing permafrost sediments against the environmental temperature change. The elastic wave velocities and effective thermal conductivity (ETC) of simulated gas hydrate-bearing sediment samples were measured at a typical range of temperature in permafrost and wide range of hydrate saturation. The experimental results reveal the influence of several complex and interdependent pore-scale factors on the elastic wave velocities and ETC. It was observed that the geophysical and geothermal properties of the system are essentially governed by the thermal state, saturation and more significantly, pore-scale distribution of the co-existing phases. In particular, unfrozen water content substantially controls the heat transfer at sub-zero temperatures close to the freezing point. A conceptual pore-scale model was also proposed to describe the pore-scale distribution of each phase in a typical gas hydrate-bearing permafrost sediment. This study underpins necessity of distinguishing ice from gas hydrates in frozen sediments, and its outcome is essential to be considered not only for development of large-scale permafrost monitoring systems, bus also accurate quantification of natural gas hydrate as a potential sustainable energy resource in cold regions.

ייעוד ושלבי התפתחות של קירות טרסות-ואדי ושדה בעמק נחל זנוח בשפלת יהודה

This study presents a new methodological approach by which to identify the function, relative age, and field relations between buried walls at two sites in the valley of Nahal (wadi) Zanoah along the morphological contact between the Judean Highland Hills and Foothills. Sedimentology and relative pulsed-photon stimulated luminescence (PPSL)-based chronology of fine-grained sediments beneath, within, above, and abutting the studied walls, reveal the sedimentation phases of the valley and the role of these walls. A wadi-terrace wall was revealed bordering alluvium of a buried and ancient course of Nahal Zanoah, reflecting a more energetic flow regime than that of today. On the palaeosurface of the infilled sediment behind the wadi-terrace wall and up-valley are low field walls, probably marking agricultural boundaries. The upvalley field wall upon colluvium is found to be slightly more mature than the field wall positioned in the wadi-terraceAn overlaying ~0.75 m of sediment originating from the slopes and soils of the drainage basin forms the current valley floor, which appears to have undergone significant deposition due to premodern and modern mechanical activities.

Persistence and fate of chlortetracycline in the aquatic environment under sub-tropical conditions: generation and dissipation of metabolites

The persistence of chlortetracycline in the aquatic environment, including the generation and dissipation of its metabolites, were investigated over a period of 90 days using microcosm experiments, with a view to establishing the metabolites generated and their persistence under conditions closely resembling the actual aquatic environment in terms of chemical and microbial composition. The concentrations of chlortetracycline and its metabolites were monitored in the water phase as well as the sediment phase. Data are presented showing that the degradation of chlortetracycline in each phase conforms to a triphasic linear rate law, confirming the existence of three speciation forms in each phase, attributed to one free dissolved form, and two colloidal particle adsorbed forms. Data are also presented showing that the two adsorbed forms are the most persistent, with life-times of 204.1 and 20.3 days respectively in the water phase, and 215.1 and 19.8 days respectively in the sediment phase. Life-times of 5.01 and 3.7 days respectively were obtained for the free dissolved forms in the water phase and sediment phase respectively. Data are further presented showing that of the several metabolites of chlortetracycline reported previously, only 4-epi-chlortetracycline and iso-chlortetracycline could be detected, and that these two degradation products undergo microbial mineralization without transformation to other intermediate degradation products in significant or detectable amounts.

Conservative Treatment in Calcifying Tendinitis of Shoulder

"ABSTRACT. Introduction: Calcium tendinopathy of the shoulder is a familiar, unpleasant situation distinguished by calcium buildups in rotating tendons. Current assumptions suggest that these calcifications might originate from a cellular-involved procedure in whom, following a calcium sedimentation phase, calcifications are suddenly re-orbited. Objectives: This paper aims to establish non-surgical therapeutic conduct of maximum efficiency in the case of calcified Tendinitis in the shoulder by combining methods of physiokinetotherapy. Methods: The research methods used by us were: bibliographic method, experimental method, case study method, observation method, test method, statistical-mathematical methods of data processing, graphic method of presentation of results, Shapiro-Wilk test, t-Student test, parametric test for unpaired data, respectively Mann-Whitney test, non-parametric test for unpaired data. Results: As a result, statistically, using the t-Student test, p&lt;0.05, we found a statistically significant difference between the averages of the abstraction values in weeks 8 and 12 in the two lots. Conclusions: Kinetic treatment ensures improvement of the algal component and functional parameters, thus ensuring the patient's quality of life by combating muscle contractions and increasing joint mobility."