Dilute Waters Research Articles

Wind Effects on Small‐Scale River and Creek Plumes

AbstractIn contrast to large river plumes, Coriolis effects are weak, and inertia is quickly depleted so that the fate and structure of small‐scale plumes are more sensitive to tide and wind. Advected alongshore by reversing tidal currents in absence of wind forcing, small buoyant plumes are persistently deflected downwind in presence of alongshore winds and exhibit little tidal variability. The effect of different upwelling/downwelling winds on buoyant outflows ∼10 m3 s−1 is explored. With increasing wind, tidal variability decreases, as does asymmetry in plume characteristics—for strong winds upwelling/downwelling plume structure is similar as the plume is retained closer to the shore. Wind forcing is exerted directly by wind stress on the surface of the plume and indirectly by wind‐driven currents that deflect the upwind boundary of the plume. While inertia and buoyancy dominate the inner plume, and wind dominates the outer plume, the mid‐plume responds to an interaction of wind and buoyancy forcing that can be indexed by a Plume Wedderburn Number Wpl (wind stress vs. density gradients): for weaker winds (Wpl < 1) surface stress enhances stratification through straining, lengthening the reach of low‐salinity waters, whereas for stronger winds (Wpl > 1) surface stress mixes the plume vertically, shortening the reach of low‐salinity waters. However, dilute plume waters extend furthest in strong winds, passively advected several kilometers downwind. Shoreline exposure to outflow transitions from a quasi‐symmetrical tide‐averaged zone of impact under zero‐wind to a heavily skewed zone with persistent weak wind and a one‐sided zone for strong wind.

A hybrid conductometric/spectrophotometric method for determining ionic strength of dilute aqueous solutions

This work describes a novel conductometric/spectrophotometric method to determine the ionic strength (I) of dilute aqueous solutions (e.g., natural waters from rivers and lakes). Because I ≤ 0.01 mol kg−1 in such waters, precision as well as accuracy is of paramount importance. In current practice the ionic strength of natural waters is determined almost exclusively with conductometric measurements. We used solutions of artificial freshwater to assess the performance of two commonly used types of conductometric instruments and found that a conductivity probe systematically overestimated I while a salinometer systematically underestimated I. We therefore recommend here an empirical correction that can be easily implemented to improve the accuracy of both types of conductivity measurements. Additional improvement in measurements of I can be achieved by using that high-quality conductometric measurement as input to a hybrid conductometric/spectrophotometric procedure that makes use of robust quantitative characterizations of the influence of ionic strength on the dissociation characteristics of phosphate pH buffers and sulfonephthalein pH indicators. This approach mitigates systematic conductometric errors associated with solution composition, thus yielding measurements of ionic strength with substantially improved accuracy and precision. The method was validated by testing on a broad suite of artificial freshwaters (n = 64) with compositions that include the major ions present in dilute natural waters (Na+, K+, Mg2+, Ca2+, Cl−, HCO3−, and SO42−). This new hybrid method is applicable to waters of 0 ≤ I ≤ 0.01 mol kg−1 (i.e., electrical conductivity of up to 900 μS cm−1 at 25 °C), with an accuracy of ±0.0003 and a precision of ±0.0003.

Origin of Li brine-type deposits in the Cretaceous gypsum-bearing formation of the Jitai Basin, South China: Constraints from geochemistry and H, O, Li, B, and Sr isotopes

Li brine-type deposits have recently been discovered in the Upper Cretaceous gypsum-bearing formation of the Jitai Basin, South China. The source and enrichment mechanism of Li in brines, however, are still unclear. To define the origin of lithium and evaluate the water-rock interaction process, this work presents chemical and multi-isotope data for Li-rich brines from the Jitai Basin. Seven brine samples collected from Meigang boreholes contain high salinities of 190–339 g/L, lithium concentrations of 60.6–106.0 mg/L, and low magnesium/lithium ratios of ∼11. The good correlation between δD and δ18O values suggests that the primary brine has been diluted by meteoric water, while contributions from halite dissolution or secondary brines having dissolved solid halite are also indicated by the high Na/Cl (0.58–0.63) and Cl/Br (average of ∼26987) mass ratios, the Na deficit and Ca excess, and the fact that high-salinity brines have lower δD, δ18O and δ34SSO4 values. Among the chemical geothermometers commonly used in the literature, only the SiO2-chalcedony, Na/K/Ca and K/Mg thermometric relationships give concordant temperature values of 120 ± 15 °C for the deep reservoir of these brines, suggesting that the latter are not in full chemical equilibrium with the reservoir rocks (excess of sodium due to halite dissolution), but this temperature can be considered as representative of their deep reservoir. Moreover, most of the chemical geothermometers yield close temperature values of 115 ± 15 °C for the deep reservoir of three neighboring dilute thermal waters. The homogeneous 87Sr/86Sr ratios (0.713865–0.713915) and δ11B (+1.8‰–+3.4‰) and δ7Li (+13.1‰–+14.2‰) values show a close affinity to the continental crust, possibly implying a fluid signature involving the interactions between clastic host rocks and brines. X-ray diffraction and scanning electron microscopy analyses and Li contents of reservoir rocks reveal the presence of dominant lithian muscovites of clastic origin, probably originating from weathering of Li-enriched igneous rocks, which contribute to most of the lithium input in the hydrologic system of the basin. Thus, it is proposed that lithium enrichment in brines from the Upper Cretaceous gypsum-bearing clastic aquifers of the Jitai Basin was generated by water-rock interactions involving lithian muscovites.

АНАЛИЗ ЗАРУБЕЖНОГО ОПЫТА УТИЛИЗАЦИИ СБРОСНЫХ И ДРЕНАЖНЫХ ВОД В ОРОСИТЕЛЬНЫХ МЕЛИОРАЦИЯХ

Purpose: to review the practice of using drainage and waste water for irrigating agricul-tural crops as a priority for their utilization. Discussions. One of the priority strategies for sustainable management of available water resources is the reuse of drainage and waste water for irrigation reclamation, taking into account the hydrogeological and reclamation conditions of the area. The reducing of the degradation rate of water supply sources subject to the impact of drainage and waste water, is possible only with the creation of a system for regulating water distribution in irrigation systems of various levels, which would allow taking into account the resource of drainage and waste water for irrigation. Most often, drainage and waste water is used for irrigating salt-tolerant crops. The use of drai-nage and waste water with salinity from 1.5 to 10.0 g/dm³ for irrigating grain and fodder crops did not cause a reduction in yield. Conclusions. As the analysis of drainage and waste water utilization shows, their wide-spread use in irrigation reclamation is explained by the increased mineralization and technogenic impurities (pesticides, herbicides, trace elements, oil products, etc.). The measures taken to dilute such waters with fresh water from canals only partially solved the problem of their accumulation and reduction of discharges into water bodies. Also, there was still an increase in the irrigation water consumption for irrigating crops. In this regard, it is relevant to conduct exploratory research in the field of technologies preparation and purification of drainage and waste water for irrigation purposes.

Fluid–rock interactions along detachment faults during continental rifting and mantle exhumation: the case of the Urdach lherzolite body (North Pyrenees)

The North Pyrenean Zone corresponds to the palaeopassive margin of the North Iberia plate, at the foot of which subcontinental mantle was exhumed during Albian times. Rare bodies of exhumed mantle rocks associated with strongly sheared lenses of continental crust are scattered among the North Pyrenean Zone metasediments. Significant fluid flow occurred along a major décollement at the basement–Trias interface in the Urdach massif (Chaînons Béarnais). Fluids with a broad range of salinity (10–38 wt.% NaCl equiv.), indicative of mixing between brines and more dilute waters, produced strong silicification of breccias. The brines circulated at c. 240–280°C under lithostatic pressures at c. 6 ± 1 km depth. The fluids became increasingly saline towards the final stages. The syndeposition of Cenomano-Turonian flysch layers then progressively isolated the lower aquifers close to the décollement where Triassic brines were predominant. The release and migration of significant volumes of brines during stretching and squeezing of the Triassic evaporites played a crucial part in the mineralogical and rheological transformations that occurred during the Pyrenean Cretaceous rifting event.

Physiological and morphological correlates of extreme acid tolerance in larvae of the acidophilic amphibian Litoria cooloolensis.

The Cooloola sedgefrog (Litoria cooloolensis) is one of a number of frog species endemic to the coastal sandy lowlands of east Australia exhibiting remarkable tolerance to dilute waters of low pH (<pH 3.5). To investigate the physiological and morphological underpinnings of acid tolerance in L. cooloolensis larvae, we compared Na+ balance, uptake and efflux rates, and gill and skin morphology in larvae reared in circum-neutral (pH 6.5) and pH 3.5 water. We hypothesised that L. cooloolensis larvae would be more resistant to ionregulatory disturbance and epithelial damage at low pH relative to acid-sensitive species. Net Na+ flux rates were not significantly different from zero in L. cooloolensis larvae reared at pH 3.5 and in acid-naïve animals maintained in pH 6.5 water. Animals reared at pH 6.5 and acutely exposed to pH 3.5, however, exhibited a net loss of Na+ due to inhibition of Na+ uptake. In contrast, L. cooloolensis larvae reared at pH 3.5 maintained Na+ balance at pH 3.5 and did not exhibit inhibition of Na+ uptake at this pH. Investigation of Na+ transport kinetics and the morphology of the gills and integument suggests tolerance of L. cooloolensis larvae to low pH may be attributed to a high capacity for branchial Na+ uptake, increased tight junction length and elevated mucus production at the gills and integument. These factors confer resistance to acid damage and disruption of ionic homeostasis which would otherwise result in the death of amphibian larvae exposed to waters of pH 4.0 and less.

Reinterpreting Models of Slope-Front Recharge in a Desert Basin

Identification of recharge areas in arid basins is challenging due to spatial and temporal variability and complexity of the hydrogeology. This study re-evaluates recharge mechanism in a desert basin where isotopic and geologic data indicated that published conceptual models of recharge are not accurate. A new model of recharge is formulated that is consistent with the unique geologic framework in the basin. In the area of study, the Rio Grande flows across a broad alluvial floodplain, the “El Paso-Juarez Valley”, where the river has incised the surface of the Hueco Bolson. The modern Rio Grande floodplain overlies the older basin fill, or “Hueco Bolson deposits”, in the valley portion of the area. The lateral contact between the older bolson deposits and the recent alluvial floodplain deposits defines the “slope front”. The valley wall along the slope front is penetrated by many arroyos that incise the Hueco Bolson deposits and modern floodplain surface. The presence of a large lens of freshwater at the boundary between the older bolson fill and recent Rio Grande alluvium seemed to suggest to previous researchers that dilute water developed due to runoff drawn in by San Felipe Arroyo, a prominent arroyo at the slope front between the older Hueco Bolson deposits and the recent Rio Grande alluvium. Our follow-up verification work illustrates that this is demonstrably not the case. The testing of groundwater samples for stable water isotopes and radioisotopes showed that the deeper and more dilute waters near San Felipe Arroyo are actually pre-dam waters recharged from the shifting Rio Grande channel.

Hydrogeological constraints for the genesis of the extreme lithium enrichment in the Salar de Atacama (NE Chile): A thermohaline flow modelling approach

The Salar de Atacama (SdA) is the largest Li reserve globally. The origin of Li, together with the rest of solutes, has been object of debate. Thus, rock weathering at low temperature, hydrothermal leaching or magmatic origin together with subsequent evaporation has been hypothesized. However, the extreme Li enrichment (>4000 mg/L) and the location of the Li-Mg-rich brines around the Salar Fault System (SFS) that crosses the nucleus of the SdA in half remain unexplained. The objective of this work is to define the thermohaline groundwater flow in the SdA basin to account for the genesis of its extreme Li enrichment.Thermohaline flow modelling has demonstrated the critical effect of the minimum hydraulic head (MHH) of the regional water table on the groundwater flow of salt flats. The MHH divides the basin into two isolated hydrodynamic systems and constitutes the endpoint towards which the most evaporated brines converge. The spatial mismatch between the locations of the Li-Mg-rich brines in the central-western zone of the nucleus (in the SFS) and the MHH in the easternmost zone of the nucleus discards recent evaporative concentration of the recharge water as the main mechanism of Li enrichment. Moreover, the persistence of a saline interface surrounding the nucleus at depth, regardless of the temperature gradient, also precludes lateral recharge (predominantly from the east) to ascend along the SFS.On the other hand, the computed thermohaline flow is compatible with the remobilization of buried layers of Li-Mg-enriched salts and/or clays by dilute recharge waters coming from the west or southwest of the basin. Here, the role of faults and density-driven flow is key to allow efficient downward and upward flow rates that favour the remobilization of Li and Mg.

The relationship between the pH value of dilute effluent streams and system durability in the separate bed electrodeionization process

The successful application of electrodeionization (EDI) for the preparation of ultra-pure water has been encouraging researchers to explore its feasibility in the treatment of heavy metal electroplating wastewaters. Based on the separate bed membrane stack, the relationship between the pH of dilute effluent streams and its long-term operation stability was investigated. The pH, conductivity, electric current and voltage were recorded on-line with cupric ions contents measured off-line. The microstructure and morphology of ion exchange resins and membranes were studied with infrared spectroscopy and scanning electron microscopy. It is the adsorption saturation in the cation exchange resins-filled compartment (CR-cell) that results in the acidity of dilute effluent waters due to the consumption of hydroxide ions in the anion exchange resins-filled compartment (AR-cell). The periodic change of acidity and alkalinity of dilute effluents was caused by the alternative processes of adsorption saturation and hydrolysis regeneration in CR-cell. The conversion of quaternary amines into tertiary ones of the anion resins and membranes owing to hygro-thermal aging weakened alkaline and shortened the acid-base change period. Increasing stack voltage and intermittent leaching play an important role in prolonging the service life of EDI, and make it feasible to remove heavy metal ions from industrial wastewaters.

Hydrogeochemistry, stable isotope composition and geothermometry of CO2-bearing hydrothermal springs from Western Iran: Evidence for their origin, evolution and spatio-temporal variations

This study aims to hydrochemically characterise three CO2-bearing springs representing distinct hydrofacies in NW Gorveh (western Iran) and interpret them in the light of their geological setting. The results of laboratory measurements of elemental concentrations, stable oxygen, carbon and hydrogen isotopes, dissolved and particulate organic and inorganic carbon (DIC, DOC, POC, PIC) and alkalinity are combined with in situ measurements of pH and temperature. Parameters such as alkalinity, DIC, Ca2+ and pCO2 concentration display strong, positively correlated values, with systematic decrease from the spring vent in down-flow direction for the three spring systems. The inverse correlation of pH and δ13CDIC is caused by CO2 degassing. The δ18O and δD values show no significant variation, related to minor or no evaporation due to normal ambient temperatures. The low concentration of POC, PIC and DOC compared to that of DIC and the lack of correlation between them reflect predominant inorganic carbon in these fluids.Spring I is oversaturated in calcite with additional dissolution of CO2, and despite high concentrations of Na+ and Cl−, undersaturated in halite, indicating a fluid of geothermal origin and/or reflecting steady state dissolution. This is related to water-rock interaction processes with carbonate and evaporitic rocks, that affected the isotopic signature of δ18O, which is shifted to the right of the global meteoric water line. Spring I also represents a partially equilibrated and mature (deep) chloride type water. Spring II and III are less saline and represent a different fluid circulation and/or shorter residence time. The two latter springs are characterized by peripheral (shallow) dilute chloride-bicarbonate type waters. Decreasing key parameters especially in Spring III during the winter suggest that superficial mixing with rain and meteoric water results in high temporal variations. Cation and stable carbon isotope geothermometry applied to the studied springs reveals an average reservoir temperature of ~210, 110 and 90 °C for Spring I and II and III, respectively. The geochemical and isotopic data allowed to depict a conceptual model where the hydrothermal reservoir for Spring I is residing in carbonate and evaporitic rocks (most likely the Qom Formation) situated at a depth of 3–4 km whereas those of Spring II and III are likely sourced from a shallower depth (1–2 km) in correspondence with carbonate and porous and permeable volcanic rocks.Integration of hydrofacies with conceptual hydrological and geological models forms the base towards a proper understanding of water circulation patterns, increasingly important for sustainable water management and geothermal applications.

Genesis of Glauberite Sedimentation in Lop Nur Salt Lake - Constraints from Thermodynamic Simulation of the Shallow Groundwater in the Tarim River Basin, China

This study was carried out in Lop Nur Salt Lake, which is one of the largest closed playa in the world and is located in the lowest part of the Tarim Basin at its east end. The objective of this study was to further reveal the genesis of the giant glauberite sedimentation in Lop Nur Salt Lake by thermodynamic simulation of the shallow groundwater in the Tarim River basin with the Equilibrium and Evaporation (EQL/EVP) program, as the shallow groundwater of the Tarim River basin may represent the recharging water body into Lop Nur. The shallow groundwater of the Tarim River basin is of the sodium sulfate subtype and the magnesium sulfate subtype and is dominated by the sodium sulfate subtype. The shallow groundwater is poor in Ca2+ but is rich in SO42−. We use the EQL/EVP program, an equilibrium model that simulates the evaporation of dilute waters as well as of concentrated brines, to simulate the evaporation of the shallow groundwater, and got the results showing good agreement between predicted and observed mineral sequences and assemblages. The simulation results clearly showed that a small amount of glauberite can be formed under an open system, a large amount of glauberite can be precipitated under a closed system, and that the amount of glauberite precipitated under the closed system is approximately 100 times higher than that under open system, indicating that a closed system is more conducive to the formation of glauberite. However, even in the closed system, the amount of glauberite precipitated by simulated evaporation is much less than the observed amount that is deposited in Lop Nur. Therefore, it is inferred that Lop Nur must also be recharged by deep calcium-rich waters. With the Tarim River basin and deep calcium-rich waters as the recharge sources and under arid climate conditions, the water of Lop Nur was concentrated by evaporation, minerals began to accumulate over a long period of time, and a large amount of glauberite was formed, which provides storage space for potassium-rich brine in Lop Nur.

Geographical origin determines responses to salinity of Mediterranean caddisflies.

Many freshwater ecosystems worldwide, and particularly Mediterranean ones, show increasing levels of salinity. These changes in water conditions could affect abundance and distribution of inhabiting species as well as the provision of ecosystem services. In this study we conduct laboratory experiments using the macroinvertebrate Smicridea annulicornis as a model organism. Our factorial experiments were designed to evaluate the effects of geographical origin of organisms and salinity levels on survival and behavioral responses of caddisflies. The experimental organisms were captured from rivers belonging to three hydrological basins along a 450 Km latitudinal gradient in the Mediterranean region of Chile. Animals were exposed to three conductivity levels, from 180 to 1400 μS/cm, close to the historical averages of the source rivers. We measured the behavioral responses to experimental stimuli and the survival time. Our results showed that geographical origin shaped the behavioral and survival responses to salinity. In particular, survival and activity decreased more strongly with increasing salinity in organisms coming from more dilute waters. This suggests local adaptation to be determinant for salinity responses in this benthic invertebrate species. In the current scenario of fast temporal and spatial changes in water levels and salt concentration, the conservation of geographic intra-specific variation of aquatic species is crucial for lowering the risk of salinity-driven biodiversity loss.

An overview of the Muara Laboh geothermal system, Sumatra

The Muara Laboh geothermal system is a liquid-dominated, fracture-controlled reservoir showing some characteristics of both intrusion-related and fault circulation systems. The developed reservoir has moderate to high-temperature (230–310 °C) with a long NNW outflow (160–230 °C) extending to the Sapan Malulong boiling chloride springs. Reservoir fluids generally have low salinity (∼400-1600 ppm Cl) with benign chemistry and low non-condensable gas (NCG) content (∼0.5 to 2 wt% in steam). The proven reservoir is divided into distinct SW and NE sectors. The principal deep upflow zone (270 to 310 °C) is located in the SW and is associated with Patah Sembilan volcano and satellite vents (Anak Patah Sembilan). The SW upflow is characterized by relatively low salinity (∼400-600 ppm Cl), whereas fluids in the NE emerge from a second upflow along faults and fractures at 240–250 °C (1200–1600 ppm Cl) and ascend to an initial-state steam cap near the Idung Mancung fumarole. The shallow NE part of the geothermal system is hosted mainly by Quaternary to Miocene Age andesitic to rhyolitic rocks, whereas the deeper SW part of the system occurs in a Mesozoic to Cenozoic Age plutonic complex and its host rocks that are cut by younger dikes. Rock porosity and permeability trends can be related to reservoir age, volcanic deposit type, and alteration history. Fracture permeability is high, whereas matrix porosity (<1-7%) and permeability are moderate to low and decrease with depth. The volcanic sequence is capped by tuffs dated at ∼34,000 to 41,000 years BP, incapsulated in debris flows. This sequence may have formed during and shortly after likely sector collapse episodes of the Patah Sembilan volcano. The shallow clay cap of the system wraps around the crater, suggesting that it was excavated during crater formation.Permeable fracture patterns and their origins differ somewhat between the deep SW and the shallow NE reservoir. In the deep SW reservoir, fluids ascend along fractured margins of stock and dike intrusions. Steeply dipping intrusions and open fractures strike from WNW to NNW, subparallel to the main Great Sumatra Fault trend, with a secondary set of N to NE fractures and intrusions parallel with the inferred maximum horizontal stress direction (SHMax). In the shallower NE steam cap and outflow, N to NE steeply dipping fractures dominate, with bounding N to NNW faults. Bulk rock alteration includes shallow argillic and transitional clay zones overlying phyllic and propylitic zones. High-T propylitic alteration (secondary amphibole) and rare potassic alteration (secondary biotite) are associated with intrusion. Vein paragenesis in the SW reservoir indicates that portions of the initially permeable propylitic zone have been sealed by calcite and quartz ± prehnite. Late calcite veins suggest ingress of steam-heated bicarbonate waters contributed to resealing of the system. These relationships suggest that the SW system underwent extensive boiling, fluid loss, and inflow of dilute bicarbonate waters, possibly related to sector collapse and partial excavation of the topseal of the system (now Patah Sembilan crater).

Measuring Perchlorate and Sulfate in Planetary Brines Using Raman Spectroscopy

Liquid water likely exists on the surface of Mars and below the icy crusts of Europa, Enceladus, and Titan. Pluto, Ceres, and Ganymede also show evidence of liquid water at or near the surface. Quantitative solute analyses would provide critical data needed to understand geochemical conditions throughout our solar system, including potential habitability of planetary bodies. We have developed and tested a Raman spectroscopic method for measuring perchlorate and sulfate in brines and dilute waters that utilizes simple Raman peak height ratios rather than peak area ratios. Ratios of the target anion and OH- bending water peaks yield linear fits with positive slopes and r2 values >0.99. Calibration fits for each solute–brine combination and ultrapure water yield similar linear equations, suggesting this method can detect and quantitatively measure solutes in complex aqueous solutions. No sample preparation or physical contact with the sample is required. Therefore, this method can be employed without contami...

A field-based characterization of conductivity in areas of minimal alteration: A case example in the Cascades of northwestern United States

The concentration of salts in streams is increasing world-wide making freshwater a declining resource. Developing thresholds for freshwater with low specific conductivity (SC), a measure of dissolved ions in water, may protect high quality resources that are refugia for aquatic life and that dilute downstream waters. In this case example, methods are illustrated for estimating protective levels for streams with low SC. The Cascades in the Pacific Northwest of the United States of America was selected for the case study because a geophysical model indicated that the SC of freshwater streams was likely to be very low. Also, there was an insufficient range in the SC data to accurately derive a criterion using the 2011, US Environmental Protection Agency field-based extirpation concentration distribution method. Instead, background and a regression model was used to estimate chronic and acute SC levels that could extirpate 5% of benthic invertebrate genera. Background SC was estimated at the 25th centile (33μS/cm) of the measured data and used as the independent variable in a least squares empirical background-to-criteria (B-C) model. Because no comparison could be made with effect levels estimated from a paired SC and biological data set from the Cascades, the lower 50% prediction limit (PL) was identified as an example chronic water quality criterion (97μS/cm). The maximum exposure threshold was estimated at the 90th centile SC of streams meeting the chronic SC level. The example acute SC level was 190μS/cm. Because paired aquatic life and SC data are often sparse, the B-C method is useful for developing SC criteria for other systems with limited data.

Estimation of ion adsorption using iterative analytical model in capacitive deionization process

Capacitive deionization (CDI) is an upcoming technique that can replace existing processes for removing and recuperating metal ions from dilute industrial waste waters. CDI removes ions via electro ...

Evaluation of the Potential for Dissolved Oxygen Ingress into Deep Sedimentary Basins during a Glaciation Event

Geochemical conditions in intracratonic sedimentary basins are currently reducing, even at relatively shallow depths. However, during glaciation-deglaciation events, glacial meltwater production may result in enhanced recharge (Bea et al., 2011; and Bea et al., 2016) potentially having high concentrations of dissolved oxygen (O2). In this study, the reactive transport code Par-MIN3P-THCm was used to perform an informed, illustrative set of simulations assessing the depth of penetration of low salinity, O2-rich, subglacial recharge. Simulation results indicate that the large-scale basin hydrostratigraphy, in combination with the presence of dense brines at depth, results in low groundwater velocities during glacial meltwater infiltration, restricting the vertical ingress of dilute recharge waters. Furthermore, several geochemical attenuation mechanisms exist for O2, which is consumed by reactions with reduced mineral phases and solid organic matter (SOM). The modeling showed that effective oxidative mineral dissolution rates and SOM oxidation rates between 5 × 10−15 and 6 × 10−13 mol dm−3 bulk s−1 were sufficient to restrict the depth of O2 ingress to less than 200 m. These effective rates are low and thus conservative, in comparison to rates reported in the literature. Additional simulations with more realistic, yet still conservative, parameters reaffirm the limited ability for O2 to penetrate into sedimentary basin rocks during a glaciation-deglaciation event.

High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry.

RationaleLi and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single‐step cation‐exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices.MethodsThe column method utilises the macro‐porous AGMP‐50 resin and a high‐aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High‐precision isotope determination was conducted by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICPMS) on the Thermo Scientific™ NEPTUNE Plus™ fitted with 1013 Ω amplifiers which allow accurate and precise measurements at ion beams ≤0.51 V.ResultsSub‐nanogram Li samples (0.3–0.5 ng) were regularly separated (yielding Mg masses of 1–70 μg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long‐term external 2σ precisions of ±0.39‰ for δ7Li and ±0.07‰ for δ26Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption.ConclusionsThe possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.

Biological Phosphorus Recovery: Review of Current Progress and Future Needs.

This review summarizes the main species of polyphosphate accumulating organisms (PAOs) and algae, illustrates their pathways and key enzymes, discusses biological phosphorous (P) recovery from dilute waters, and identifies research avenues to encourage adoption and implementation. Phylogenic analysis indicates that the Proteobacteria phylum plays an important role in enhanced biological phosphorus removal (EBPR). The use of meta-transcriptome analysis and single cell-based techniques to help overcome the challenges associated with non-PAO competition was discussed. For algae capable of luxury phosphorus uptake, fundamental research is needed to illustrate the phosphorus regulation process and key proteins involved. Emerging technologies and processes have great potential to further advance phosphorus recovery, including combined PAO/algae reactors, bioelectrochemical systems, and biosorption by phosphorus binding proteins. As the paradigm shifts toward holistic resource recovery, research is needed to explore P+ recovery with other resources (e.g., metals from sludge), using a combination of biological and chemical approaches.

Jarosite dissolution rates in perchlorate brine

Perchlorate salts and the ferric sulfate mineral jarosite have been detected at multiple locations on Mars by both landed instruments and orbiting spectrometers. Many perchlorate brines have eutectic temperatures <250 K, and may exist as metastable or stable liquids for extended time periods, even under current Mars surface conditions. Therefore, jarosite-bearing rocks and sediments may have been altered by perchlorate brines. Here we measured jarosite dissolution rates in 2 M sodium perchlorate brine as well as dilute water at 298 K to determine the effects of perchlorate anions on jarosite dissolution rates and potential reaction products. We developed a simple method for determining aqueous iron concentrations in high salinity perchlorate solutions using ultraviolet-visible spectrophotometry that eliminates the risk of rapid oxidation reactions during analyses. Jarosite dissolution rates in 2 M perchlorate brine determined by iron release rate (2.87 × 10−12 ± 0.85 × 10−12 mol m−2 s−1) were slightly slower than the jarosite dissolution rate measured in ultrapure (18.2 MΩ cm−1) water (5.06 × 10−12 mol m−2 s−1) using identical methods. No additional secondary phases were observed in XRD analyses of the reaction products. The observed decrease in dissolution rate may be due to lower activity of water (ɑH2O = 0.9) in the 2 M NaClO4 brine compared with ultrapure water (ɑH2O = 1). This suggests that the perchlorate anion does not facilitate iron release, unlike chloride anions which accelerated Fe release rates in previously reported jarosite and hematite dissolution experiments. Since dissolution rates are slower in perchlorate-rich solutions, jarosite is expected to persist longer in perchlorate brines than in dilute waters or chloride-rich brines. Therefore, if perchlorate brines dominate aqueous fluids on the surface of Mars, jarosite may remain preserved over extended periods of time, despite active aqueous processes.