Concentration Of Dissolved Salts Research Articles

Temperature Dependence of Adsorption and Effectiveness for a Pyrimidinium-Type Corrosion Inhibitor on Mild Steel

In the oil and gas industry, produced water with a high dissolved salt content is a common byproduct of hydrocarbon extraction from conventional and unconventional wells. Other than salts, corrosive gases such as CO2 are abundant in the production stream, which dissolve and acidify the solution, posing a risk of internal pipeline corrosion. To mitigate this issue, injection of corrosion inhibitors has emerged as a cost-effective approach. In various aggressive conditions, heterocyclic molecules that contain nitrogen atoms have proven to be highly effective corrosion inhibitors for many alloys. In this study, tetrahydropyrimidinium (THP-C14) inhibition efficiencies were investigated at temperatures of 25°C, 55°C, and 80°C using electrochemical methods, including linear polarization resistance and potentiodynamic sweeps. Corrosion inhibition data were then correlated with THP-C14 concentration, using the five adsorption isotherms: Langmuir, Temkin, Frumkin, Flory-Huggins, and Dhar-Flory-Huggins models. These isotherms utilize different assumptions to establish the correlation between coverage and inhibitor concentration. The suitability of these five isotherm models for describing the corrosion inhibition behavior of THP-C14 was examined. In addition, the thermodynamic parameters (Kad, ΔadGo) of adsorption for THP-C14 at 25°C, 55°C, and 80°C were calculated and compared using the aforementioned adsorption isotherm models. Finally, a mechanism was proposed for the adsorption behavior of the THP-C14 corrosion inhibitor model compound. Chloride ions were important for inhibitor adsorption.

Development of Low-Cost IoT System for Monitoring Piezometric Level and Temperature of Groundwater

Rural communities in Mexico and other countries with limited economic resources require a low-cost measurement system for the piezometric level and temperature of groundwater for their sustainable management, since anthropogenic action (pumping extractions), natural recharge and climate change phenomena affect the behavior of piezometric levels in the aquifer and its sustainability is at risk. Decrease in the piezometric level under a balanced level promotes salt intrusion from ocean water to the aquifer, salinizing and deteriorating the water quality for agriculture and other activities; and a decrease in water level under the pumps or well drilling depth could deprive communities of water. Water temperature monitoring is essential to determine electric conductivity and dissolved salt content in groundwater. Using IoT technology, a device was developed that monitors both variables inside the well, and the ambient temperature and atmospheric pressure outside the well. The measurements are made in real time, with sampling every second and sending data to a dedicated server every 15 min so that the visualization can be accessed through a device with Internet access. The time series of the variables measured inside and outside the well were obtained over a period of three months in the rural community of Agua Blanca, Guasave, Sinaloa, Mexico. Through these records, a progressive temporary drawdown of the piezometric level is observed, as well as the frequency of pumping. This low-cost IoT system shows potential use in hydrological processes of interest such as the separation of regional and local flow, drawdown rates and recognition of geohydrological parameters.

ECOLOGICAL WATER QUALITY

Water quality – is a description of water’s chemical and biological composition and physical properties, which characterize it as an abiotic component of aquatic ecosystem and determine its suitability for specific consumption purposes.
 Ecological water quality (environmental water quality) – refers to the ecological well-being of an aquatic ecosystem, with the main focus on protection of the aquatic environment and human life and health. It comprises a complex of physical, chemical, biological and other parameters reflecting specific features of abiotic and biotic components of aquatic ecosystems.
 The requirements for physical, chemical and biological properties of water are set in the water quality standards, which may be developed by particular countries or introduced by international organizations.
 Ecological water quality depends upon natural and human factors. Natural factors are in their turn divided into abiotic (for example, geological, meteorological, hydrological) and biotic (for example, the ratio of primary production and organic matter destruction). The main human factors affecting water quality include artificial modification of aquatic ecosystems’ hydrological conditions and their pollution with diverse chemical compounds.
 There are a lot of approaches to ecological water quality assessment according to both abiotic (physical and chemical) and biological parameters. Physical and chemical methods take into account such parameters as water transparency, suspended particulate matter concentration (turbidity), ion composition, water hardness, total dissolved salts content, nutrients and organic matter content, dissolved gases concentration, pH. Biological methods are based upon assessing the living organisms’ (biological indicators’) response to mineral and organic substances, present in water. Various living organisms can be used as biological indicators: algae, in particular – diatoms, higher aquatic plants, different species of aquatic invertebrates and fishes. While physical and chemical methods characterize water quality at the moment of sampling, biological methods provide an integral picture of water quality for a certain time period. Besides, biological methods are more informative, because they reflect the aquatic ecosystem’s response to pollution.
 On the whole, the most reliable data on ecological water quality can be obtained by combining physical, chemical and biological methods.

The Effect of Variance Discharge on the Dissolved Salts Concentration in the Euphrates River upper reach, Iraq

The Euphrates River Basin in Iraq suffers from climate changes represented by the scarcity of precipitation and the increase in temperatures, which is directly reflected in the discharge rates and the increase in total dissolved solids, and consequently, the increase in the dissolved loads in the river. Four measurement stations (Haditha, Ramadi, Fallujah, and Al-Hindiya) in the upper reach of the Euphrates River were investigated. Available data were analyzed from 1970 to 2020 related to precipitation (mm) and temperatures (°C). The results showed a clear decrease in precipitation rates over the years, while a clear increase in air temperature rates was observed. The discharge rates decreased temporally and spatially downstream as follows: 502, 383.7, 382.1, and 211.8 m³/s in Haditha, Ramadi, Fallujah, and Al-Hindiya, respectively. The average total dissolved solids (ppm) from 2005 to 2020 shows a gradual increase downstream, 698.8, 764.8, 833, and 922.3 ppm. The dissolution load classification curves for 2005 to 2020 show an increase in the downstream dissolved loads of 0.781, 0.786, 0.927, and 0.944 million tons/month in Haditha, Ramadi, Fallujah, and Al-Hindiya, respectively. It reflects the increase in the dissolution process of basin materials cumulatively downstream. It is recommended that careful management of the transmission of pollutants of agricultural and anthropogenic activities outputs into the river without any treatments for the downstream reaches will be required.

PHYSICOCHEMICAL PROPERTIES OF WILDLIFE GEOPHAGIC SOIL: A PRELIMINARYASSESSMENT FOR POSSIBLE UTILIZATION IN PHARMACEUTICAL INDUSTRIES

The act of consuming soil (geophagy) has been reported both in man and wildlife. Most previous studies have concentrated more on various type of geophagic soilswith less attention on termite mounds (TMs), thus limiting our understanding the cause(s) of geophagy. This study investigated the physico-chemical constituents of wildlife geophagic TMsincomparison with non-geophagic forest soil (FS). Composite soil samples were collected each from four different TMs and a FS. Samples were analyzed for pH, texture, electrical conductivity (EC), water retention capacity (WRC), moisture content (MC) and colour.Soils were analyzed in triplicates following standard methods. Datagenerated were analyzed statisticallywith SPSS version 17.Theresult indicated acidic pH for both TMs(strongly to slightly acidic) and FS (slightly acidic). Clay content, EC, WRC and MC were significantly higher in TMs than FS.The colour of TMs ranged from reddish brown(4R 4/5) to dark brown (2.5R 5/7 or 5R 6/8) as against that of FS which was black (2R 2/4). Wildlife may be consuming TMs in preference to FS for; detoxification (high clay content), ant-diarrhea (high WRC and MC), Fe-supplement (brown colour of TMs) and dissolved salt content (high EC). Detailed studies intomineralogical and microbiological compositions of TMs may be needed to further justify the rolesof geophagy in wildlife.

Enhanced transport in a porous medium due to dissolved salt

An experiment is presented showing enhanced water transport across a porous layer compared to pure water vapor diffusion. The enhanced transport is explained by the presence of brine in the layer and the dependence of the equilibrium vapor pressure with the dissolved salt concentration. The impact of the salt presence is further demonstrated by a comparison with the case of pure water. A significantly longer period of sustained evaporation is obtained in the presence of salt. The transport enhancement effect can last over long periods of time when the conditions are such that the porous layer reaches a dynamic equilibrium between condensation and evaporation. Also, the porous layer can adapt to changes in the boundary conditions via changes in the brine saturation and associated modifications in the salt concentration and the equilibrium vapor pressure. The transport enhancement effect is also illustrated in relation with the dynamics of salt crusts.8 MoreReceived 18 February 2022Accepted 24 May 2022DOI:https://doi.org/10.1103/PhysRevFluids.7.064304©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDisplacement of immiscible fluidsEvaporationFlows in porous mediaSurface tension effectsFluid Dynamics

Electrodialysis Can Lower the Environmental Impact of Hemodialysis.

The hemodialysis technique, used worldwide for patients with chronic kidney disease, is considered as a treatment with a high economic and ecological impact, especially for water consumption. Getting ultrapure water for the preparation of the dialysate to clean patient’s blood from toxins leads to high volumes of salt-enriched water that directly goes to sewage. The aim of this work is to propose operating conditions for electrodialysis to allow the reuse of reverse osmosis (RO) rejects. We first performed a parametric study to evaluate the influence of different parameters, such as flow rates, initial concentration, and applied voltage on the demineralization rate (DR) and specific energy consumption (SPC) with a NaCl model solution. The optimal conditions for desalination (i.e., a potential of 12 V, and flow rate of 20 L·h−1) were then successfully applied to real samples collected from a dialysis center with total dissolved salts concentration of about 1.4 g/L (conductivity of 2.0 mS·cm−1). We demonstrated that the choice of adequate conductivity targets allowed meeting the physico-chemical requirements to obtain water re-usable for either rehabilitation swimming pool, manual or machine washing of instruments before sterilization or irrigation. Saving this water could contribute in the reduction of the environmental impact of hemodialysis.

Characterization of halophyte biochar and its effects on water and salt contents in saline soil.

Biochar is a beneficial soil amendment; however, biochar-based properties are mainly determined by the feedstocks and the pyrolysis temperature. Nevertheless, considering the vast biomass of halophyte, little is known about how the halophyte-derived biochar improves saline soils. In this study, we firstly produced biochars by using three different halophytes, including Tamarix chinensis (recretohalophyte), Suaeda salsa (euhalophyte), and Phragmites australis (pseudo-halophyte) at 300, 500, and 700 °C, and compared their chemical and physical properties. We applied halophyte (Tamarix chinensis and Phragmites australis) biochars (pyrolysis at 500 °C) into 0-20 cm saline soil at 2% and 4% (w/w) rates to investigate the saline soil water, salt, and pH dynamics in a 12-month column experiment. The results showed that as the pyrolytic temperature increase, biochar yield and pore diameter decreased by 37.5-44.0% and 34.6-89.7%, respectively; in contrast, biochar pH, specific surface area, and total volume increased by 24.8-47.8%, 3-37 times and 1-9 times, respectively. The halophyte types significantly controlled biochar carbon and dissolved salt content and electrical conductivity. Halophyte biochar application can increase soil water and salt content, and application of 4% of Tamarix chinensis-derived biochar can increase more soil moisture than the soil salinity, and it can maintain soil pH at a stable level, which would be a potential way to improve saline soil properties. The results are valuable for choosing halophyte types and optimizing pyrolytic temperatures for halophyte biochar production through specific environmental usage.

Limnological Conditions and Photosynthetic Pigments in Clearwater Lakes of the Volga-Vyatka Karst Province

The features of summer stratification and vertical distribution of photosynthetic pigments (chlorophylls and bacteriochlorophylls) in five karst lakes in the Middle Volga region (Republics of Tatarstan and Mari-El) are studied. The water of the investigated lakes has low color and sulfate concentration and low-to-medium total dissolved salts content. Anoxic conditions develop in the hypolimnion in all lakes after the establishment of summer thermal stratification. Reduced iron and sulfur compounds are found in the anaerobic zones of most lakes. In these lakes, deep maxima of chlorophyll and bacteriochlorophylls are formed, indicating the presence of biomass maxima of microbial plankton, consisting of both oxygenic and anoxygenic phototrophs. The presented data demonstrate also a wide variety of features of both chemical stratification and vertical distribution of phototrophic organisms in the studied lakes, which are probably associated with differences in the limnological characteristics of lakes, their water composition, and the history of their existence.

Photocatalytic Porous Silica-Based Granular Media for Organic Pollutant Degradation in Industrial Waste-Streams

Photocatalytic treatment of organic contaminants in industrial wastewaters has gained interest due to their potential for effective degradation. However, photocatalytic slurry reactors are hindered by solution turbidity, dissolved salt content, and absorbance of light. Research presented here introduces the development and application of a novel, photocatalytic, porous silica-based granular media (SGM). SGM retains the cross-linked structure developed during synthesis through a combination of foaming agent addition and activation temperature. The resultant media has a high porosity of 88%, with a specific surface area of ~150 m2/gram. Photocatalytic capabilities are further enhanced as the resultant structure fixes the photocatalyst within the translucent matrix. SGM is capable of photocatalysis combined with diffusion of nucleophiles, electrophiles, and salts from pore space. The photocatalytic efficiencies of SGM at various silica contents were quantified in batch reactors using methylene blue destruction over time and cycles. Methylene blue concentrations of 10 mg/L were effectively degraded (>90%) within 40 min. This effectiveness was retained over multiple cycles and various methylene blue concentrations. SGM is a passive and cost-effective granular treatment system technology which can translate to other organic contaminants and industrial processes.

Low-salinity carbonated water injection in sandstone reservoirs: interplay between oil recovery improvement, salinity and fines migration

Carbonated water injection (CWI) is described as a chemical-enhanced oil recovery method in which CO2-enriched water is injected into oil reservoirs as a displacing fluid. Although confirmed by many that a considerable amount of recovery improvement is attainable through CWI in both lab and field scales, the interaction of salinity on the performance of CWI and its potential fines migration is not very well understood. This study examines the efficiency of oil recovery improvement during low-salinity carbonated water injection (LSCWI) in a sandstone reservoir, while total dissolved salt concentration varies. To this end, a series of coreflooding experiments were performed on homogeneous sandstone cores at 80°C and 2000psi, and the amount of oil recovery was measured. From the experiments, it was observed that CWI could extract more crude oil than conventional water flooding in all salinities. In particular, the highest oil recovery was observed in the lowest salinity (61.2% in CWI and 42% during water flooding), indicating that by carbonating low-salinity water, oil recovery is enhanced by 20%. Moreover, the influence of salinity reduction on recovery enhancement was such that 9% of recovery improvement observed during conventional water flooding when salinity decreased from 40000 to 1000ppm. At the same time, this improvement was around 15% for CWI, suggesting that salinity reduction can be more effective in CWI rather than water flooding in recovery improvement. It was also found out that while recovery improvement and fines migration are both highly affected by water salinity, there is a synergy between the efficiency of CWI and onset of fines migration, which is one of the underlying mechanisms in oil recovery improvement during LSCWI into clay-containing sandstone reservoirs.

Impact of salinity on seed germination and seedling performance of tomato (<em>Solanum lycopersicum L.</em>) cv KC-1

An experiment was conducted to evaluate the effect of salt stress on seed germination and seedling performance of<em> Solanum lycopersicum L. </em>(tomato) cv KC-1 under controlled environment and also to select salt tolerant seedlings for plant regeneration. This experiment was laid out in a completely randomized design with three replications. Uniform seeds of tomato cv KC-1 were surface sterilized and placed on sterilized filter paper in the petridishes. Subsequently they were wetted with 5 ml of distilled water as a control or one of the NaCl (sodium chlorite) salt solutions (0, 20, 40, 60 and 80 mM NaCl. Seed germination percentage were calculated and seedling growth attributes were recoreded after seeding. Results showed that germination percentage decreased with increasing salinity levels (0 mM, 20 mM, 40 mM, 60 mM, 80 mM). Germination percentage was less than 50% for seed treated with NaCl above the level of 40 mM. Minimum value (18.3%) was recorded in 80 mM of salinity. Shoot and root lengths, dry and fresh weights of shoots and roots, relative water content and total dissolved salt content of first leaves (cotyledons) were significantly affected (P&lt;0.001) by salt stress after 12 days of seeding. Salinity levels had a considerable effect on all parameters tested in this study. Salt content of first leaves increased with increasing NaCl concentrations. Germination and early seedling growth of Tomato cv. KC-1 was greatly affected in salt concentrations above 40 mM NaCl levels under controlled environmental conditions.

Non-potable Water Quality Assessment Methodology for Water Conservation in Arid Climates

This paper documents a non-potable water (NPW) quality assessment methodology for a decentralized non-potable water system in Abu Dhabi (AD), capital city of the United Arab Emirates (UAE), which is dominated by sandy and salty soil, high temperature, and humidity. The context is a medical facility case study (MFCS) in AD, which includes a landscape 50% as large as its building footprint. The project identified the need to investigate the impact of air handling unit (AHU) air conditioning (A/C) condensate water (CW) quality on soil health and building hydraulic systems. The aim of the research was to measure the impact of using recycled on-site NPW sources in a MFCS in AD, to alleviate the use of desalinated potable water and reduce associated energy consumption, operation cost, and greenhouse gas emissions for landscape irrigation (LI) and water feature (WF) use. CW has been tested in 2016 and in 2017 and analysed against local authority’s parameter limits to establish suitability for LI and WF use. The findings are that in AD CW classification and characterization is a gap in knowledge whereby salinity and toxicity concentration limits should be addressed by the local authority because CW has an impact on soil infiltration rate due its low dissolved salt content as evidenced by the water test results. The recommendations for this paper are to develop a sustainable water conservation and reuse (SWC) strategy forming the basis for a water protocol by the competent authority for regional medical facility including a methodology for assessing on-site NPW quality for outdoor reuse to reduce soil infiltration problems and consequently conserve water and associated energy. The next steps are to confirm if the MFCS soil infiltration rate is affected by the CW or other factors, and to test additional NPW types.

Dynamics and ecological distributions of the Archaea microbiome from inland saline lakes (Monegros Desert, Spain).

We characterized the rich Archaea microbiome of shallow inland lakes (Monegros Desert, NE Spain) by 16S rRNA gene tag sequencing covering a wide salinity range (0.1%-40% w/v) along 3 years. Up to 990 operational taxonomic units (OTUs; >97% identity) were detected allocated in 14 major archaeal phyla and heterogeneously distributed along the salt gradient. Dynamics and idiosyncratic ecological distributions were uncovered for the different phyla. A high genetic richness was observed for Woesearchaeota and Pacearchaeota (>370 OTUs each), followed by Halobacteria (105), Nanohaloarchaeota (62) and Thermoplasmata (19). Overall, the distribution of genetic richness was strongly correlated with environmental niche amplitude, but not with occurrence. We unveiled high occurrence for a very rich Woesearchaeota assemblage, and an unexpected positive correlation of Pacearchaeota abundance with salinity at >15%dissolved salt content. The estimated dynamic behaviour (temporal 'turnover' rates of presence/absence data) unveiled Thaumarchaeota and Halobacteria as the most dynamic groups, and Aenigmarchaeota and Thermoplasmata as the most stable. The DPANN Pacearchaeota, Woesearchaeota, and Nanohaloarchaeota showed intermediate rates, suggesting higher resilience to environmental perturbations. A rich and dynamic Archaea microbiome was unveiled, including unseen ecological traits for relevant members of the still largely unknown DPANN group, supporting a strong ecological differentiation between Pacearchaeota and Woesearchaeota.

Cyanobacterial Growth in Minimally Amended Anaerobic Digestion Effluent and Flue-Gas.

Anaerobic digestion (AD) is an important industrial process, particularly in a biorefinery approach. The liquid effluent and carbon dioxide in the off-gas, can be used to produce high-value products through the cultivation of cyanobacteria. Growth on AD effluent is often limited due to substrate limitation or inhibitory compounds. This study demonstrates the successful cultivation of Synechococcus on minimally amended AD effluent, supplemented with MgSO4 and diluted with seawater. An 8 L airlift reactor illustrated growth in a pilot scale setup. Higher biomass yields were observed for cyanobacteria grown in diluted AD effluent compared to minimal medium, with 60% total nitrogen removal in the effluent. It was demonstrated that controlling the pH, increasing dissolved salt concentrations and adding MgSO4 to the effluent allowed for the successful cultivation of the cyanobacterium, circumventing the addition of clean water for effluent dilution. This could ultimately increase the feasibility of anaerobic digestion-microalgae integrated biorefineries.

Preliminary Monitoring of Physico-Chemical Parameters of Water Wells from the Village of Bivolari (The Moldavian Plain)

Abstract The main objective of the paper is focused on water quality research in the village of Bivolari, Iasi County. The Bivolari settlement is situated in the Prut meadow and develops along the road connecting Iasi and Stefanesti. The research done in this paper starts from the collection of data on water pH, water LDO (oxygen concentration), CDC (dissolved salt content) and water temperature. The parameters were measured for 7 months using the HACH-LANGE multiparameter of the Geoarchaeology Laboratory at Alexandru Ioan Cuza University of Iasi (Inter-disciplinary Platform ArheoInvest). The study is structured in two sections: scientific substantiation and applicative research. The scientific substantiation part analyzes the water features in the context of the integrated management approach as well as an analysis of the quality aspects of the water supply. The applied research part required monthly field measurements in 50 fountains (without the winter season). The approached subject is is complex and up-to-date because the citizen is a priority for EU Member States (EUPAN, 2009): the aspect of “customer satisfaction” represents a capital priority. Finally, the database is structured into two categories: spatial information such as maps; tabular information attached to spatial data. The paper also follows the transition from the field of research into the field of application by presenting models of data representation, which are at the same time tools adapted to the practical needs. In order to achieve this goal, the concept of quality (both in terms of product - drinking water and local consumer) is defined and addressed in an integrated manner. Of the 50 wells monitored, only one had a water shortage in the last 10 years, and in two other cases there were problems with household waste and dead animals that damaged the water supply. Some fountains can dry at intervals of 3-4 years.

Hydrochemistry of shallow groundwater and springs used for potable supply in Southern Brazil

Landscape characteristics and access type may exert a strong influence on groundwater quality, thereby adversely affecting human health. The aim of this study was to evaluate groundwater quality in springs and shallow wells of rural areas in terms of hydrochemical properties and different water quality indexes by comparing distinct microregions, groundwater sources (springs and shallow wells), and surrounding properties (e.g., presence of livestock, presence of fences, other protection structures, and restrictions on human access). Physical–chemical, chemical, and microbiological parameters were analyzed over 12 months between 2013 and 2014 in the Marombas River basin located in Santa Catarina State, Southern Brazil. Land use and landforms played an important role in controlling groundwater hydrochemistry in rural areas. The type of groundwater source (springs or shallow wells) did not influence water quality, although springs tended to be more susceptible to bacterial contamination, especially in areas with livestock in the surroundings. Chemical relationships allowed classifying these waters as predominantly calcium–magnesium bicarbonate or calcium–magnesium chloride, the latter being the most common in the study region. Groundwater was acidic, with low dissolved salt content, large range in dissolved oxygen concentrations, low turbidity, and presence of fecal coliforms in most studied months. Results indicate that water might be affected by septic tank leakage associated with wastewater and output from agricultural fields, given precarious installation and conservation conditions of springs and shallow wells in this region. When comparing the results with drinking water standards established by Brazilian Health Ministry, 70% of springs and shallow wells were found not suitable for consumption, especially due to organoleptic properties, high aluminum concentrations, and presence of fecal coliforms. Water quality indexes demonstrated that groundwater is suitable for agricultural uses (irrigation, livestock, and fish farming) and drinking, if treated via disinfection, filtering, or boiling before consumption. Nevertheless, use of this water resource, especially without any treatment—as is currently common among users—raises concerns related to its susceptibility to spread waterborne diseases, and lack of information among water users regarding procedures to improve water quality.

Application of Classical Thermodynamics to Conductivity in Nonpolar Media: Experimental Confirmation.

We previously proposed ( Gourdin-Bertin , S. and Chassagne , C. J. Chem. Phys. 2016 , 144 ( 24) ) a simple theoretical model to account for the evolution of conductivity with dielectric permittivity in nonpolar media. In this article, we validate the theory experimentally for the case of an ionogenic species kept at a constant chemical potential (i.e., in equilibrium with a nondissolved salt, in contrast to previously published conductivity measurements carried out as a function of various fully dissolved salt concentrations). To our knowledge, it is the first time that this type of experiment has been performed explicitly.

Naturally occurring radium (Ra) in home drinking-water wells in the Sandhills region of South Carolina, USA: Can high concentrations be predicted?

A strong relationship exists between concentrations of several principal constituents of water chemistry and naturally occurring radium in water from home wells in the large Sandhills region of the inner coastal plain of South Carolina, United States, an area of common radium problems (75% (21 of 28 of randomly selected wells in the main study area were above the U.S. Environmental Protection Agency (USEPA) maximum contaminant level (MCL): 5 picocuries per liter for 226Ra plus 228Ra). Ingested radioactive radium is potentially carcinogenic, and water far above the MCL occurs in places. One focus here was to determine if elevated radium concentrations can reliably be predicted using more easily measured characteristics of water chemistry. The initial phase investigated (1) concentrations of radium in well water within a smaller (~10 km radius) test area of known common problems plus (2) the associated water chemistry. This revealed a correlation between elevated radium and raised electrical conductance, total dissolved solids, calcium, nitrate, magnesium, hardness, and lowered pH. All are potentially useful screening tools for the many other rural home wells of this region. Natural groundwater in these highly leached sands is of very low dissolved salt content of all types, and local human influence on geochemistry is thus indicated. Predictive utility was examined by two additional series of wells (1) of higher radium contamination or (2) of elevated calcium concentration, both identified from file data. Higher radium wells were retested for water chemistry and higher calcium wells for radium content. Overall, a similar association between radium and water chemistry was observed.

Solute transport in porous media during drying: The chlorine isotopes point of view

Drying-out phenomena during injection of dry gas (CO2, CH4, H2, …) in geological reservoirs can be damaging for industrial processes as it can alter the transport properties and the injectivity of a reservoir due to salt precipitation. The distribution of salt precipitate, which may result in clogging of the formation, depends on two competing transport processes. Brine capillary-driven flows, which provide a continuous supply of dissolved salt towards the drying zone, and molecular diffusion, which tends to rehomogenize dissolved salt concentrations. In this study, we experimentally investigated the possibility that chlorine isotopes could be used as a geochemical tool to constrain the interplay of salt precipitation and solute transports process in drying saline porous media. Drying experiments were carried out on Lavoux carbonate plugs initially saturated with a 100gL−1 NaCl brine and dried in an oven at controlled temperature (60°C) with vapor evacuation. Cl-content and δ37Cl profiles along the length of the plugs were obtained for different evaporation stages (Sw=1; Sw=0.82; Sw=0.68). The results show a clear Cl-ion redistribution during drying, with Cl-accumulation near the plug evaporative surface together with the growth of salt efflorescence on the surface. A “u”-shaped profile of δ37Cl values is observed in the drying porous media. After 30h of drying, salt crystals as well as the upper and lower parts of the plug present higher isotope ratios than the initial brine, while the center of the plug presents lower ratios. These experimental results suggest, as predicted by previous experimental and theoretical studies, that 35Cl and 37Cl are transported without fractionation by upward capillary flow to the evaporative surface, where salt precipitation occurs with a small preference for the heavier isotope. The resulting concentration gradient drives backward diffusion. Because 35Cl moves faster than 37Cl by diffusion this leads to more negative δ37Cl towards the center of the plug. Cl-isotopes transport modeling results suggest that backward advection may also have occurred, as indicated by a relatively high effective diffusion coefficient and a low Cl-isotope fractionation factor. This study provides new insights regarding the use of Cl-isotopes to characterize drying of porous media.