Water Sodium Concentration Research Articles

THE EFFECT OF EXCESSIVE SODIUM-CONTAINING IRRIGATION WATERS ON SOIL INFILTRATION RATE

Due to increasing demand for limited water resources, the pressure on irrigation water used in agricultural production is also increasing. One of the alternative solutions to meet the irrigation water needed in agricultural production is to use low-quality water resources. However, use of these waters can cause serious problems for the environment, especially for soil and plants, in the short, medium and long term. The sodium concentration of the irrigation water affects the structure of the soil, infiltration rate and hydraulic conductivity properties, as well as negatively affects the nutrient uptake of the plants. In this study, the effect of irrigation water with excess sodium content on the infiltration rate, which is one of the important parameters for the design and operation of irrigation systems and sustainable agricultural production, was researched. The infiltration rate was measured by the double-ring infiltrometer method. In this study, irrigation water with four different Electrical Conductivity (ECi = 0.6 [control], 5, 10 and 15 dS m-1) and Sodium Adsorption Ratio (SAR) (1, 20, 40 and 50) were used. Cumulative infiltration values varied between 360-446 mm, and a 9-19% reduction was determined as compared to the control treatments, depending on the increasing ECi and SAR ratios. The steady-state infiltration rate of the treatments varied between 24.5-36.5 mm h-1 and decreased by 24-34%. In response to increased EC and SAR in irrigation water, the infiltration rates and cumulative infiltration values of soils decreased.

Evolution of Alkali Release by an Illitic Rock for Use as Supplementary Cementitious Material

AbstractThe levels of CO2 emissions generated by the cement industry and the growth in demand for its products have led to a search for ways to reduce these emissions. The use of supplementary cementitious materials has become one of the solutions proposed for this problem. Illite, which is found all over the world, is a possible supplementary cementitious material. Before illite can be used, it must be milled and treated thermally in order to activate it, so that the alkalis (Na+ and K+) are free and available to react. Alkalis in cement participate in deleterious reactions (alkali-silica reaction) or have a beneficial effect (alkaline activation). The alkalis present in the rocks can play an active role in these phenomena, however. In addition, the material could be influenced by the alkaline environment produced by the cement. The current study was aimed at analyzing whether an alkali release occurs and if so, how it is affected when a milled and thermally treated illitic rock is in contact with water or an alkaline solution. The material was characterized by X-ray fluorescence, polarizing microscopy, and X-ray diffraction (XRD). The sample was treated thermally at 300, 600, and 900°C, and the thermal activation was evaluated through XRD, density, and Atterberg limits. The evolution of alkali release was studied by determining the sodium and potassium concentration of contact water obtained by mixing the samples with different pH solutions for various lengths of time. In addition, the calcium concentration was determined. The concentrations of sodium and potassium in the contact water were determined by flame photometry, and of calcium by EDTA (ethylenediaminetetraacetic acid) titration. The results showed that with increasing age, increasing solution pH, and higher treatment temperatures, alkali release occurred and increased, whereas Ca2+ concentration decreased.

Does the mineral content of tap water correlate with urinary calculus composition?

The association between the mineral content of drinking water and urolithiasis remains elusive. The aim of this study is to investigate whether the mineral composition of tap water correlates with urinary calculus composition. Patients with calculi that underwent biochemical analysis at two urological centres in the North-West of England between November 2015 and December 2020 were included. Calculus composition was reviewed with respect to patient demographics, serum biochemical variables, and water mineral composition data obtained from the local water supply company using patient postcodes. 1711 urinary tract calculi from 1518 patients, living in 87 water supply zones were included. Water sodium concentration was an independent predictor of mixed calcium oxalate/uric acid calculi (OR 1.157, p < 0.001) and a negative independent predictor of calcium oxalate monohydrate (OR 0.896, p = 0.001) and dihydrate (OR 0.742, p = 0.034) calculi. Moreover, the magnesium-to-calcium ratio of tap water was a negative independent predictor of calcium oxalate monohydrate calculi (OR < 0.001, p = < 0.001), while tap water magnesium concentration inversely correlated with the percentage of calcium oxalate within calculi (rs = -0.054, p = 0.026). Total water hardness did not independently predict calculus type. Many factors are implicated in the formation of urinary calculi. This study is the first to assess calculus composition in relation to tap water mineral content using postcode data on a case-by-case basis. Though total water hardness did not independently predict calculus composition, the interesting findings relating to water sodium and magnesium concentrations are in need of closer scrutiny in larger scale studies.

Surface water sodium (Na+) concentration prediction using hybrid weighted exponential regression model with gradient-based optimization.

Undeniably, there is a link between water resources and people's lives and, consequently, economic development, which makes them vital in health and the environment. Proper water quality forecasting time series has a crucial role in giving on-time warnings for water pollution and supporting the decision-making of water resource management. The principal aim of this study is to develop a novel and cutting-edge ensemble data intelligence model named the weighted exponential regression and hybridized by gradient-based optimization (WER-GBO). Indeed, this is to reach more meticulous sodium (Na+) prediction monthly at Maroon River in the southwest of Iran. This developed model has advantages over other previous methodologies thanks to the following merits: (i) it can improve the performance and ability by mixing the outputs of four distinct data intelligence (DI) models, i.e., adaptive neuro-fuzzy inference system (ANFIS), least square support vector regression (LSSVM), Bayesian linear regression (BLR), and response surface regression (RSR); (ii) the proposed model can employ a Cauchy weighted function combined with an exponential-based regression model being optimized by GBO algorithm. To evaluate the performance of these models, diverse statistical indices and graphical assessment including error distributions, box plots, scatter-plots with confidence bounds and Taylor diagrams were conducted. According to obtained statistical metrics and verified validation procedures, the proposed WER-GBO resulted in promising accuracy compared to other models. Furthermore, the outcomes revealed the WER-GBO (R = 0.9712, RMSE = 0.639, and KGE = 0.948) reached more accurate and reliable results than other methods such as the ANFIS, LSSVM, BLR, and RSR for Na prediction in this study. Hence, the WER-GBO model can be considered a constructive technique to forecast the water quality parameters.

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia.

In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

Determination of concentration of total sodium and potassium in surface and ground water using a flame photometer

In this paper, we have investigated 18 water samples collected from various sources, e.g., surface, underground and river water, as specimens for their sodium and potassium ions content in and around Dhanbad, a mining town, using the flame photometry. We have plotted the contour maps to show the spatial distributions of the dissolved sodium and potassium cations in the groundwater and surface water sources in and around the Dhanbad city to identify the relative contributions of human and natural phenomena to it. Along with it, water quality index (WQI) is calculated to evaluate whether the collected surface, ground and river water samples are fit for human consumption for the residents of those areas. The water of Maithan Dam has been observed to have the least sodium and potassium concentrations of 16 mg/l and 7 mg/l, respectively, which make it most suitable for human consumption. The water of Rani Talab Pond has the highest sodium and potassium contents of 49 mg/l and 24 mg/l. WQI values of all the samples are found to be less than 50, which indicates they are safe to consume by the humans. Reduction in the use of pesticides, potassium permanganate and water softeners is recommended to maintain WQI of the Dhanbad city within safe limit.

Sodium transport and attenuation in soil cover materials for oil sands mine reclamation

Reclamation soil covers are used in oil sands mine closure to support vegetative growth over tailings. Geochemical processes within these covers may impact solute transport during upward migration of oil sands process-affected water (OSPW) from the underlying tailings. In this study, we examined the geochemical processes controlling Na transport and attenuation within the peat and clay-till cover soils at Sandhill Fen in northern Alberta, Canada. We analyzed soil core samples collected along transects of this 54-ha pilot-scale oil sands mine reclamation wetland. The geochemical (Na, Ca, Mg, K, Cl, SO4, HCO3) and isotopic (δ2H, δ18O) compositions of extracted pore water were analyzed statistically to identify OSPW and fresh surface water within the cover. Depth-dependent trends in pore water sodium concentrations were not apparent, suggesting that the soil cover had been fully flushed by a mixture of OSPW and fresh surface water used to flood the fen. Relative concentrations of Na, Ca and Mg were used to define the extent of cation exchange within the clay cover. Complementary laboratory column experiments showed that cation exchange removed up to 50% of dissolved Na as the first pore volume of simulated OSPW passed through the peat and till. However, Na attenuation by these materials declined rapidly and was limited after 4 (peat) to 7 (till) pore volumes of OSPW flushing. Reactive transport modeling confirmed that cation exchange was the dominant control on Na attenuation and corresponding Ca and Mg release within the till and peat columns. Mineral precipitation-dissolution reactions also influenced dissolved Ca and Mg concentrations and, therefore, indirectly impacted Na attenuation. Overall, this study helps constrain the geochemical processes controlling Na transport and attenuation in oil sands reclamation soil covers exposed to OSPW, and indicates that the attenuation of Na from OSPW by these covers is short-lived.

Activity changes in gill ion transporter enzymes in response to salinity and temperature in fathead minnows (Pimephales promelas)

Fathead minnows, Pimephales promelas, are found throughout the continental United States in waters in which salinity can change with tides and temperatures vary seasonally. They have been used extensively in studies of environmental toxicology and are commercially important. In a very recent study in our labs RNA Seq was used to assemble transcriptomes from the gills of fatheads acclimated to either 5° or 22 °C. By comparison with published genomes, transcripts were identified for a number of ion transporters, ion channels, and signal molecule receptors, as well as enzymes that generate ammonia. H-ATPase and Na/K-ATPase activities were measured in supernatants of gill homogenates from fish acclimated to water sodium concentrations of 1.6, 3.1 or 124 mM sodium. As the water sodium concentration increased, in vitro activities of Na/K-ATPase activity and gill glutamate dehydrogenase activity decreased while H-ATPase activity increased. In a second series of experiments minnows were acclimated to 5 °C, 12.5 °C or 22 °C. In vitro activity of Na/K-ATPase decreased but activities of H-ATPase and glutamate dehydrogenase increased as temperature increased in gill membranes. These data do not support a primary role for apical H-ATPase in sodium influx under all conditions but do suggest a role for glutamate dehydrogenase production of ammonium to act as a counter-ion for sodium uptake by NHE-3.

Climatic and watershed controls of dissolved organic matter variation in streams across a gradient of agricultural land use

Human land use has led to significant changes in the character of dissolved organic matter (DOM) in lotic ecosystems. These changes are expected to have important environmental and ecological consequences. However, high spatiotemporal variability has been reported in previous studies, and the underlying mechanisms remain inadequately understood. This study assessed variation in the properties of stream water DOM within watersheds across a gradient of agricultural land use with grazing pasture lands as the dominant agricultural type in the southeastern United States. We collected water samples under baseflow conditions five times over eight months from a regional group of first- to fourth-order streams. Samples were analyzed for dissolved organic carbon (DOC) concentration, DOM quality based on absorbance and fluorescence properties, as well as DOM biodegradability. We found that air temperature and antecedent hydrological conditions (indicated by antecedent precipitation index and stream water sodium concentrations) positively influenced stream water DOC concentration, DOM fluorescence index, and the proportion of soil-derived, microbial humic fluorescence. This observation suggests that elevated production and release of microbial DOM in soils facilitated by high temperature, in conjunction with strong soil-stream hydrological connectivity, were important drivers for changes in the concentration and composition of stream water DOM. By comparison, watersheds with a high percentage of agricultural land use showed higher DOC concentration, larger proportion of soil-derived, humic-like DOM compounds, and higher DOC biodegradability. These observations reflect preferential mobilization of humic DOM compounds from shallow organic matter-rich soils in agricultural watersheds, likely due to enhanced soil erosion, organic matter oxidation and relatively shallow soil-to-stream flow paths.

Hillslope soil water flowpaths and the dynamics of roadside soil cation pools influenced by road deicers

AbstractOver the past 60 years, road deicers (i.e. road salt) have been applied to roadways in high latitudes to improve road conditions in winter weather. However, the dissolution of road deicers in highway runoff creates waters with high concentrations of sodium, which can mobilize soil metals via soil cation‐exchange reactions. While several studies have detailed the interactions of road salt‐rich solutions and surface and ground waters, less attention has been given to how local hydrologic flowpaths can impact the delivery of these solutions to near‐road soils. Between 2013 and 2014, soil water samples were collected from a roadside transect of lysimeter nests in Pittsburgh, Pennsylvania (USA). Soil water samples were analysed for metal concentrations and resulting data used to examine cation dynamics. While patterns in soil water calcium and magnesium concentrations follow patterns in soil water sodium concentrations, additional processes influence patterns in soil water potassium concentrations. Specifically, we observe the highest calcium and magnesium concentrations in the deepest lysimeters, suggesting divalent cations are mobilized to, and potentially accumulate in, deeper soil horizons. In contrast, soil water potassium concentrations do not follow this pattern. Additionally, in all examined elements (Ca, Mg, K, Na, and Cl), the timing of concentration peaks appears be influenced by a combination of both distance from the roadside and sampling depth. These relationships not only suggest that multiple soil water flowpaths interact with our study transect but also confirm that road salt plumes persist and migrate following the road salting season. Characterizing the interactions of sodium‐rich solutions and roadside soil cation pools clarifies our understanding of metal dynamics in the roadside environment. A deeper understanding of these processes is necessary to effectively restore and manage watersheds as high total dissolved solid solutions (e.g. road deicing melt, unconventional natural gas brines, and marginal irrigation water) continue to influence hydrological systems. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Osmotically inactive sodium and potassium storage: lessons learned from the Edelman and Boling data.

Because changes in the plasma water sodium concentration ([Na(+)]pw) are clinically due to changes in the mass balance of Na(+), K(+), and H2O, the analysis and treatment of the dysnatremias are dependent on the validity of the Edelman equation in defining the quantitative interrelationship between the [Na(+)]pw and the total exchangeable sodium (Nae), total exchangeable potassium (Ke), and total body water (TBW) (Edelman IS, Leibman J, O'Meara MP, Birkenfeld LW. J Clin Invest 37: 1236-1256, 1958): [Na(+)]pw = 1.11(Nae + Ke)/TBW - 25.6. The interrelationship between [Na(+)]pw and Nae, Ke, and TBW in the Edelman equation is empirically determined by accounting for measurement errors in all of these variables. In contrast, linear regression analysis of the same data set using [Na(+)]pw as the dependent variable yields the following equation: [Na(+)]pw = 0.93(Nae + Ke)/TBW + 1.37. Moreover, based on the study by Boling et al. (Boling EA, Lipkind JB. 18: 943-949, 1963), the [Na(+)]pw is related to the Nae, Ke, and TBW by the following linear regression equation: [Na(+)]pw = 0.487(Nae + Ke)/TBW + 71.54. The disparities between the slope and y-intercept of these three equations are unknown. In this mathematical analysis, we demonstrate that the disparities between the slope and y-intercept in these three equations can be explained by how the osmotically inactive Na(+) and K(+) storage pool is quantitatively accounted for. Our analysis also indicates that the osmotically inactive Na(+) and K(+) storage pool is dynamically regulated and that changes in the [Na(+)]pw can be predicted based on changes in the Nae, Ke, and TBW despite dynamic changes in the osmotically inactive Na(+) and K(+) storage pool.

Upper Pleistocene interstratal piping-cave speleogenesis: The Seso Cave System (Central Pyrenees, Northern Spain)

The Seso Cave System (SCS, South Central Pyrenees, Northeastern Spain) develops in poorly soluble marly interstratum between limestone beds of Eocene age. We propose an innovative and singular pseudokarstic speleogenetic model under vadose conditions based on cave morphological evidence, physicochemical and mineralogical characteristics of the Eocene marly host rock, U–Th dating of cave deposits, and local geological and geomorphological information. Eocene marls are shown to be sensitive to dispersion processes supported by their high clay content and the high concentration of sodium and low electrical conductivity in the seepage water. Runoff inside the cave results from water that infiltrates through joints and seepage water in cave walls. Thereby piping processes become very active, triggering mechanical scouring and outwashing mechanisms. The hydraulic gradient required to develop piping activity is determined by regional fluvial incision. The base level controlling water discharge during opening of the SCS coincides with a terrace of the Ara River dated at 65kaBP. Considering this age, as well as the U–Th age of the oldest speleothems dated in the cave at 38kaBP, the timing of the SCS interstratal piping-cave speleogenesis is constrained to the Upper Pleistocene; very likely at the end of Marine Isotope Stage 4 during a period characterized by high water availability following glacial retreat in northern Iberian mountains.

Defining the role of albumin infusion in cirrhosis-associated hyponatremia.

The presence of negatively charged, impermeant proteins in the plasma space alters the distribution of diffusible ions in the plasma and interstitial fluid (ISF) compartments to preserve electroneutrality and is known as Gibbs-Donnan equilibrium. In patients with hypoalbuminemia due to underlying cirrhosis, the decrease in the plasma water albumin concentration ([Alb-]pw) would be expected to result in a decrease in the plasma water sodium concentration ([Na+]pw) due to an alteration in the distribution of Na+ between the plasma and ISF. In addition, cirrhosis-associated hyponatremia may be due to the renal diluting defect resulting from the intravascular volume depletion due to gastrointestinal losses and overdiuresis and/or decreased effective circulatory volume secondary to splanchnic vasodilatation. Therefore, albumin infusion may result in correction of the hyponatremia in cirrhotic patients either by modulating the Gibbs-Donnan effect due to hypoalbuminemia or by restoring intravascular volume in patients with intravascular volume depletion due to gastrointestinal losses and overdiuresis. However, the differential role of albumin infusion in modulating the [Na+]pw in these patients has not previously been analyzed quantitatively. In the present study, we developed an in vitro assay system to examine for the first time the quantitative effect of changes in albumin concentration on the distribution of Na+ between two compartments separated by a membrane that allows the free diffusion of Na+. Our findings demonstrated that changes in [Alb-]pw are linearly related to changes in [Na+]pw as predicted by Gibbs-Donnan equilibrium. However, based on our findings, we predict that the improvement in cirrhosis-associated hyponatremia due to intravascular volume depletion results predominantly from the restoration of intravascular volume rather than alterations in Gibbs-Donnan equilibrium.

EFFECT OF ORAL REHYDRATION SOLUTION ON HYDRATION STATE DURING ‘SUMO’ TRAINING

BackgroundExercise in a hot environment can cause loss of water and electrolytes, which conveys tress on homeostasis.ObjectiveTo maintain appropriate hydration status in such situation, it expects to be suitable for...

A geographical approach to tracking Escherichia coli and other water quality constituents in a Texas coastal plains watershed

Diffuse sources of surface water pathogens and nutrients can be difficult to isolate in larger river basins. This study used a geographical or nested approach to isolate diffuse sources of Escherichia coli and other water quality constituents in a 145.7-km(2) river basin in south central Texas, USA. Average numbers of E. coli ranged from 49 to 64,000 colony forming units (CFU) per 100 mL depending upon season and stream flow over the 1-year sampling period. Nitrate-N concentrations ranged from 48 to 14,041 μg L(-1) and orthophosphate-P from 27 to 2,721 μg L(-1). High concentrations of nitrate-N, dissolved organic nitrogen, and orthophosphate-P were observed downstream of waste water treatment plants but E. coli values were higher in a watershed draining an older part of the city. Total urban land use explained between 56 and 72 % of the variance in mean annual E. coli values (p < 0.05) in nine hydrologically disconnected creeks. Of the types of urban land use, commercial land use explained most of the variance in E. coli values in the fall and winter. Surface water sodium, alkalinity, and potassium concentrations in surface water were best described by the proportion of commercial land use in the watershed. Based on our nested approach in examining surface water, city officials are able to direct funding to specific areas of the basin in order to mitigate high surface water E. coli numbers and nutrient concentrations.

A Clinical Approach to the Treatment of Chronic Hypernatremia

Hypernatremia is a commonly encountered electrolyte disorder occurring in both the inpatient and outpatient settings. Community-acquired hypernatremia typically occurs at the extremes of age, whereas hospital-acquired hypernatremia affects patients of all age groups. Serum sodium concentration is linked to water homeostasis, which is dependent on the thirst mechanism, arginine vasopressin, and kidney function. Because both hypernatremia and the rate of correction of hypernatremia are associated with significant morbidity and mortality, prompt effective treatment is crucial. Chronic hypernatremia can be classified into 3 broad categories, hypovolemic, euvolemic, and hypervolemic forms, with each form having unique treatment considerations. In this teaching case, we provide a clinically based quantitative approach to the treatment of both hypervolemic and hypovolemic hypernatremia, which occurred in the same patient during the course of a prolonged illness.

The effects of salinity and osmotic stress on barley germination rate: sodium as an osmotic regulator

Seed germination is negatively affected by salinity, which is thought to be due to both osmotic and ion-toxicity effects. We hypothesize that salt is absorbed by seeds, allowing them to generate additional osmotic potential, and to germinate in conditions under which they would otherwise not be able to germinate. Seeds of barley, Hordeum vulgare, were germinated in the presence of either pure water or one of five iso-osmotic solutions of polyethylene-glycol (PEG) or NaCl at 5, 12, 20 or 27 °C. Germination time courses were recorded and germination indices were calculated. Dry mass, water content and sodium concentration of germinating and non-germinating seeds in the NaCl treatments at 12 °C were measured. Fifty supplemental seeds were used to evaluate the changes in seed properties with time. Seeds incubated in saline conditions were able to germinate at lower osmotic potentials than those incubated in iso-osmotic PEG solutions and generally germinated faster. A positive correlation existed between external salinity and seed salt content in the saline-incubated seeds. Water content and sodium concentration increased with time for seeds incubated in NaCl. At higher temperatures, germination percentage and dry mass decreased whereas germination index and sodium concentration increased. The results suggest that barley seeds can take up sodium, allowing them to generate additional osmotic potential, absorb more water and germinate more rapidly in environments of lower water potential. This may have ecological implications, allowing halophytic species and varieties to out-compete glycophytes in saline soils.

The Origin and Fate of Arsenic in Coalbed Natural Gas–Produced Water Ponds

Coalbed natural gas (CBNG)-produced water contains small amounts of trace metals that can accumulate over time in produced water retention ponds. Within the Powder River Basin (PRB) of Wyoming, high concentrations of trace metals in pond water and their effect on shallow groundwater are potential concerns. A pond with a maximum As concentration of 146 microg L(-1) was studied in detail to determine the potential for groundwater pollution and to explain the cause for the high concentration of As. Infiltration characteristics, subsurface hydrology, our fall and pond water quality, isotope signatures, and trace metal balances were examined to assess the hydrology and geochemistry of the pond. The results indicated minimum or no infiltration of pond water and no measurable contamination of the shallow groundwater. The high As concentrations in the pond were determined to be the result of semi-continuous inputs of CBNG-produced water with low As concentrations (0.20-0.48 microg L(-1)), exasperated by low pond volumes during drought conditions. Because of reduced infiltration and high evaporation rates, As became concentrated over time. Reduced infiltration was most likely caused by the high sodium concentration and high sodium adsorption ratio of the CBNG-produced water, which disrupt soil structure. The findings for the pond and the techniques used may serve as a template for future impact assessments of other CBNG-produced water ponds and are relevant for the approximately 4000 ponds currently permitted in the PRB and for future ponds. Further studies are recommended in the use of playa landforms to store marginal-quality produced water.

Can Changes in Body Mass and Total Body Water Accurately Predict Hyponatremia After a 161-km Running Race?

To relate changes in body mass, total body water (TBW), extracellular fluid (ECF), and serum sodium concentration ([Na]) from a 161-km ultramarathon to finish time and incidence of hyponatremia. Observational. : The 2008 Rio Del Lago 100-Mile (161-km) Endurance Run in Granite Bay, California. Forty-five runners. Pre-race and post-race body mass, TBW, ECF, and serum [Na]. Body mass and serum [Na] significantly decreased 2% to 3% (P < 0.001) from pre-race to post-race, but TBW and ECF were unchanged. Significant relationships were observed between finish time and percentage change in body mass (r = 0.36; P = 0.01), TBW (r = 0.50; P = 0.007), and ECF (r = 0.61; P = 0.003). No associations were found between post-race serum [Na] and percentage change in body mass (r = -0.04; P = 0.94) or finish time (r = 0.5; P = 0.77). Hyponatremia (serum [Na] < 135 mmol/L) was present among 51.2% of finishers. Logistic regression prediction equation including pre-race TBW and percentage changes in TBW and ECF had an 87.5% concordance with the classification of hyponatremia. Hyponatremia occurred in over half of the 161-km ultramarathon finishers but was not predicted by change in body mass. The combination of pre-race TBW and percentage changes in TBW and ECF explained 87.5% of the variation in the incidence of hyponatremia. Exercise-associated hyponatremia can occur simultaneously with dehydration and cannot be predicted by weight checks at races.

Turbulent mixing in the Amazon River: The isotopic memory of confluences

Rivers continuously discharge dissolved material to the oceans. Dissolved compounds partially result from water–rock interactions, which produce a large range of water chemical and isotopic compositions. These waters are collected by rivers, that are commonly assumed to be well-mixed with regard to their different tributaries, as a result of turbulent dispersion. In this paper, we test this hypothesis on the Solimões River (at Manacapuru), the largest tributary of the Amazon River, by analyzing the sodium concentration and strontium isotopic composition of river water on a transverse section at different depths. High-precision measurements reveal lateral heterogeneities. This reflects poor mixing between two main river masses, that have distinct chemical and isotopic signatures, a hundred kilometers downstream from their confluence: the Solimões mainstream and the Purús River. Using sodium concentration data, the transverse dispersion coefficient is estimated for the studied Solimões reach (the Earth's largest river on which such an estimate now exists), and is found to be 1.8 ± 0.2 m 2/s. Comparison with previously reported data highlights the potential role of bed morphology and islands in the efficiency of lateral mixing in large rivers. We finally demonstrate that the characteristic length of lateral mixing downstream from confluences in large rivers is at least of several tens of kilometers.