Minor Ions Research Articles

Reduced-Order Models Blend Chemistry, Machine Learning for Water-Property Analysis

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213869, “Water Digital Avatar—Where Chemistry Is Mixed With Machine Learning,” by Jesse Farrell, SPE, and Sergey Makarychev-Mikhailov, SPE, SLB. The paper has not been peer reviewed. _ Water affects almost every operation in the exploration and production industry. Until now, time-intensive laboratory tests or cumbersome third-party simulators were required to extract physicochemical properties. In the complete paper, a family of machine-learning-based reduced-order models (ROMs) trained on rigorous first-principle thermodynamic simulation results is presented. The developed ROMs that predict water properties enable automated decision-making and improve water-management work flows. The presented approach can be extended to other oilfield, chemical, and chemical-engineering applications. Introduction The properties of the water phase and all produced fluids directly influence flow assurance, three-phase flow pressure/volume/temperature modeling, and fluid-compatibility aspects across the full life cycle of the well, including during well construction, stimulation, and production operations. Modeling these systems enables one to predict, mitigate, and, in some cases, completely prevent deleterious effects in tubing, the reservoir, and near-wellbore regions. First-principle thermodynamic simulations are often considered to be ground truth in the oilfield industry and are widely used in place of time-consuming laboratory experiments. The use of rigorous thermodynamic software, however, is not always practical. In certain cases, commercial and open-source simulators are overloaded with functionality unnecessary for a task, require training of personnel, and are often difficult to incorporate into digital work flows in the cloud or to deploy at the edge on surface equipment or the downhole tools available to model changing conditions in real time. This is where ROMs find their application because they are fast, reasonably accurate, and highly customizable solutions. The authors’ scientific hypothesis was that machine-learning-based ROMs can be used to quantify the physicochemical properties and scaling tendencies of oilfield waters in place of rigorous, first-principle thermodynamic models. Methods The United States Geological Survey (USGS) Produced Waters Geochemical Database was used as the initial data source for this study. The original database contains approximately 115,000 produced-water and other deep-formation water samples collected and characterized in the United States in the past 120 years. Although the USGS database is an excellent source, the data still required cleaning and enrichment. For the first step, inconsistent, poorly populated, and outlier samples were removed, which led to noticeable data attrition and resulted in approximately 85,000 “clean” records. The enrichment phase included several manipulations and alterations of the original data. The resulting data set is not always accurate regarding individual samples but is much better populated than the original one in terms of minor ion concentrations, and is believed to be representative on a large scale.

Hydrogeological conditions and hydrogeochemistry of the Kamenskoye hydro-radon occurrence, Novosibirsk, Russia

Hydrogeological and hydrogeochemical conditions, the concentrations of major and some minor ions and 222Rn were determined in the Kamenskoye hydro-radon occurrence in the Southern part of West Siberia. Two different aquifer systems were revealed in the hydrogeological section: the Quaternary sediments with pore waters and the Upper Paleozoic granites including the waters of regional fracturing zone and fracture-vein waters. They are located in a common mixing area and are affected by flooding and anthropogenic pollution. Mineral radon fracture-vein waters in granites, not affected by anthropogenic impact, have been revealed in two boreholes. These waters are cool, fresh (TDS 613.4 to 689.9 mg/L) and Si4+ content within a range from 10.3 to 13.6 mg/L. The pH of these waters is neutral to weakly alkaline (6.9–7.8), the gases dissolved in the waters are oxygen and nitrogen. The determined activity of 222Rn varies within the range from 1101 to 1570 Bq/L; 238U concentration varies between 5.6·10−3–6.5·10−3 mg/L, while 226Ra ranges from 2.7·10−9 to 1.8·10−8 mg/L. The relative fractions of cations (Mg2+, Ca2+, Na+, Sr2+, Ba2+) decrease with an increase in TDS value due to the formation of poorly soluble carbonate and sulphate compounds. The forms of Fe(II) are represented by Fe2+, FeHCO3+, FeCO30, and Fe(III) migrates in the forms of hydroxo complexes Fe(OH)2+ and neutral species Fe(OH)30. Manganese migrates mainly as a cation, while other forms (MnHCO3+, MnCO30) are less abundant, and MnSO40, MnCl+, MnOH+ are minor. The chemical forms of nickel and copper migration are free cations, as well as hydrocarbonate and carbonate complexes. Copper, as well as beryllium, also migrate as hydroxo complexes. The forms in which chemical elements migrate and their migration coefficients provide evidence that the equilibrium minerals become more complicated when passing from surface waters (greenalite, siderite, and ferrihydrite and greenalite) to the fracture-vein waters in the Upper Paleozoic granites saturated with dolomite, calcite, talc, magnesite and rhodochrosite.

Water Quality Indices for Evaluating the Groundwater for Drinking and Irrigation in the Wana District of Northwestern Iraq

The current study aims to assess the groundwater quality in the Wana area, Northwest of Mosul. Water samples were collected from 18 selected wells within the study area during the dry season of October 2020 and the wet season of April 2021. Field and laboratory measurements including electrical conductivity (EC), TDS, pH, Total hardness, and major and some minor ions analyses were performed following standard methods. The results revealed a wide variation of EC values ranging from 0.66 to 5.09 ds⋅m-1. All wells have hard water due to the presence of gypsum and carbonate rocks. The water quality index (WQI) values showed that wells drilled in the Fatha Formation and wells of mixed water from both the Fatha Formation and the Quaternary sediments provide low-quality drinking water. Wells that only penetrate the Quaternary sediments yield good-quality drinking water. According to the irrigation WQI, the Fatha Formation wells produce low-quality irrigation water, and the water quality of wells drilled in Quaternary sediments or that penetrate both the Fatha Formation and Quaternary sediments (mixed water) ranges from excellent to acceptable for irrigation purposes.

Geogenic and anthropogenic contamination in river water and groundwater of the lower Cauvery Basin, India

Degradation of water quality is a major challenge in both developed and developing countries since it poses a great risk to ecological health. The Cauvery river is one of the most important rivers of southern India, where the effect of seasonal variation on the quality of river water and its adjoining groundwater on the lower part of the basin has not yet been studied. Hence, the present study was carried out to evaluate the river water and adjacent groundwater for drinking and irrigational purposes, and also to identify the sources affecting the water quality. About 118 river water and 131 groundwater samples were collected over 4 months from May 2018 to August 2019. The water samples were analyzed for electrical conductivity (EC), pH, major and minor ions, and trace elements. The major, minor, and trace elements were then compared with the Bureau of Indian Standards and World Health Organization for drinking water quality assessment. The drinking water quality was assessed, indicating that both river water and groundwater were unsuitable in the coastal regions, especially during dry seasons. Irrigation water quality was also assessed, which indicates that most of the river water and groundwater samples were unsuitable near the coastal region. The quality of river water and groundwater in the lower Cauvery Basin was found to be better during wet periods compared to the dry season. It was observed that the rock–water interactions was the major factor controlling the water quality for groundwater and surface water, followed by anthropogenic activities such as disposal of domestic sewage and effluents into the river, as runoff from irrigated lands. The study emphasizes the development of a finer observational network for water quality, along with stringent monitoring of the disposal of contaminants in the rivers and groundwater.

Geoelectrical, Hydrogeological and Hydrochemical Investigations of the University of Calabar Campus (SE Nigeria): Implications for sustainable groundwater development

The rapid increase in population and infrastructural development has triggered unplanned groundwater development leading to severe stress on groundwater couple with several unsuccessful boreholes or failure of existing in the University of Calabar, Calabar (Nigeria). Hence, an integrated hydrogeological study was undertaken in the university using vertical electrical sounding (VES), to delineate and characterise aquifers and assess the groundwater quality for drinking and irrigation uses, in addition to evolution and human health risk assessment. The results reveal two water bearing units. The first is composed of medium-coarse-gravelly sand with thickness and resistivity in the range 3.6–118.8 m and 540–3500 Ω m, while the second underlying the first aquifer is composed of clayey, fine-medium sand with resistivity and thickness values in the range 44–2200 Ω m and 50 - α. Aquifer parameters from VES and pumping tests showed average hydraulic conductivity (K) and transmissivity (T) of 180 m/day and 25,740 m2/day for the first aquifer and 180 m/day and 21,384 m2/day for the second aquifer. Regionally, the groundwater flow in the university occurs toward the south. Hydrochemical data show that all the physical parameters, major and minor ions, trace and rare earth elements are within the maximum acceptable limits for drinking and agricultural uses. The dominant hydrochemical facies are Na+-Ca2+-Cl--SO42-, Mg2+-Ca2+-HCO3--Cl- and Ca2+-Mg2+-HCO3--Cl- with silicate weathering, ion exchange and reverse ion exchange as the major processess controlling the groundwater chemistry. Health risk of water through oral (drinking) and dermal (bathing) pathways showed that values of hazard quotients (HQs) and hazard index (HI) of all the trace elements (Al, As, Cd, Co, cr, Cu, Fe, Mn, Ni, Pb, Zn) were less than one. This suggests that these elements does not pose any adverse risks to the local people through drinking and bathing, but children are more sensitive than adults. This study will serve as a guide for future sustainable development and management of groundwater resource in the university and its environs.

Hydrogeochemical characterization of groundwater in a coastal area, central western Senegal

One of the most serious problems affecting coastal aquifers is seawater intrusion. Senegal is currently facing an increased demand for freshwater resources due to population growth and economic development in coastal areas. In areas affected by saltwater contamination, chloride concentrations as high as 8880 mg/L were measured in groundwater samples taken from wells near the coastal zone, indicating deterioration in water quality. Our study aims to identify the zones of degradation of the water quality by determining the chemical composition of groundwater and the geochemical processes controlling the chemical patterns. Hydrogeochemical (Piper and Chadha diagrams, chloroalkaline indices, normalized bivariate plots) and multivariate statistical (Hierarchical cluster analyses) techniques were used. Forty-two groundwater samples were collected and analyzed for concentrations of major and some minor ions, electrical conductivity (EC), total dissolved solids (TDS), temperature, and pH. From samples we were able to establish a diagnosis of the very heterogeneous quality of the groundwater in this area. The average pH of the groundwater is 7.6 and about 80% of the groundwater samples have a TDS below 1000 mg/L. On the other hand, the EC values are very heterogeneous with very high conductivities in coastal areas. Approximately, 80% of the groundwater samples have a TDS less than 1000 mg/L and EC values are very heterogeneous. The dominant water types in the study area are Na-Cl water type (less than 10% of the samples) characteristic of the spatial evolution of groundwater salinization from west to east, mixed Ca-Mg-Cl due to fresh water/salt water contact and Ca-Mg-HCO3 water-type (nearly 56% of the samples) to the east. A hydrogeochemical zonation of the aquifer, based on the presence of different water families allows us to visualize the highly degraded (west), mixed (center) and healthy (east) zones. Chloroalkaline indices and normalized bivariate plots show that the chemistry of groundwater is controlled mainly by water-rock interaction and evaporation processes. As water-rock interaction processes, dissolution of carbonate and evaporite, weathering of silicate, ions exchange regulates major ion chemistry.

Characterization of leachates from drainage asphalt pavement under multi-factor environmental treatments.

Pavement leachates could cause considerable environmental contamination. However, the influence of multiple environmental factors on the compositions of pavement leachates is still ill-understood. Therefore, it is necessary to analyse the variation of bitumen leachates with environmental factors and accordingly clarify the leaching mechanism. For this reason, a multi-environment device was invented to perform single-factor, two-factor and full-climate environmental treatments on open-graded friction courses (OGFC) asphalt mixtures. Subsequently, the acidity and alkalinity (pH) value, metal element composition and conductivity of the bitumen leachates with varying environmental treatments were characterized and analysed. Based on this, the leaching mechanism of bitumen leachates dissolved in water was proposed. The results indicated that the bitumen compositions were influenced by different environmental treatments, inducing the variation of pavement leachates. The primary substances of pavements leachates were composed of the organic acid substances and minor metal element ions. Accordingly, the experiment results demonstrated the increase of conductivity, and partial metal element concentration with the extension of treatment time. In terms of the pH value, an initial increase followed by a progressive decrease was observed.

The Rural Fires of 2017 and Their Influences on Water Quality: An Assessment of Causes and Effects.

As water is facing increasing pressures from population and economic growth and climate change, it becomes imperative to promote the protection, restoration and management of this resource and its watersheds. Since water quality depends on multiple factors both natural and anthropic, it is not easy to establish their influences. After the October 2017 fires that affected almost 30% of the Mondego hydrographic basin in Central Portugal, 10 catchments were selected for periodic physical-chemical monitoring. These monitoring campaigns started one month after the fires and lasted for two hydrological years, measuring the electric conductivity (EC), pH, dissolved oxygen (DO), turbidity (Turb), alkalinity (Alk), major and minor ions, and trace elements. The obtained data were then statistically analysed alongside the geomorphological characteristics of each catchment coupled with features of land-use and occupation. From the results, it was possible to establish that fire-affected artificial areas, through the atmospheric deposition and surface runoff of combustion products, had the most impact on surface water quality, increasing As, K-, Ca2+, Mg2+, NO3-, SO42- and Sr, and consequently increasing electrical conductivity. Agricultural land-use seems to play a major influence in raising the water's EC, Cl, K- and Na2+. Regarding natural factors such as catchment geology, it was found that the extent of igneous exposures influences As, and the carbonate sedimentary units are a source of Ca2+ and HCO32- concentrations and impose an increase in alkalinity. Rainfall seems, in the short term, to increase the water concentration in Al and NO3-, while also raising turbidity due to sediments dragged by surface runoff. While, in the long-term, rainfall reduces the concentrations of elements in surface water and approximates the water's pH to rainfall features.

Multi‐Ion Oscillitons—Origin of Coherent Magnetospheric EMIC Waves

AbstractThe recent spacecraft observations by MMS and Van Allen Probes associated with electromagnetic ion cyclotron (EMIC) waves in the Earth magnetosphere emphasize the important role of multi‐ion plasma composition for generation and characteristics of these emissions. We show that main properties of the coherent EMIC waves can be explained with the concept of “multi‐ion oscillitons” (Sauer et al., 2001, https://doi.org/10.1029/2001GL013047). In a plasma with two types of ions of different masses (e.g., protons and oxygen ions), oscillitons arise from the exchange of momentum and energy between the two ion components, with the electromagnetic field acting as a mediator. At frequencies near cross‐over frequencies of different wave modes in the multi‐ion plasma the nonlinear resonance which strongly amplifies the seed unstable mode can be excited. A small phase difference in oscillations of different ion species leads to a nonlinear wave beating and generation of wave packets. The “resonance” frequency is characterized by a local maximum of the phase velocity and the coincidence of phase and group velocity. It is suggested that the oscillitons are triggered by the instability due to the proton temperature anisotropy and may survive outside the source region for long distances. The generation of coherent waves by oscillitons is of a general nature and may contribute to understand the manifold of phenomena in other space plasma environments in which the dynamics of minor ion admixtures cannot be neglected. The concept of oscillitons can also be applied to the momentum exchange between particle groups of the same mass, but different temperature.

Perspectives for Quality Evaluation of Some Mineral Waters from Slanic Moldova

In the present study, using a combination of several analytical techniques such as conductometry/total dissolved solids (TDS), pH-metry, ICP-MS and UV-Vis spectrometry, 38 parameters (Na, K, Mg, Ca, Al, Fe, B, Li, Cr, Mn, Ni, Cu, Zn, Se, Sr, Ag, Cd, Ba, Pb, Be, V, Co, Ga, As, Rb, Cs, Hg, Tl, U, F−, Cl−, SO42−, NO3−, NO2−, HCO3−, CO2, electric conductivity (EC)/TDS and pH) for seven natural mineral waters (springs 1 bis, 5, 10, 14, 15, Sonda 2 and Sfantul Spiridon) from the Slanic Moldova area (Romania) were evaluated. Our data were compared with the historical chemical analyses records and also with the limits established by international and Romanian regulations for qualitative evaluation of natural mineral waters. In the case of the Evolution of the mineralization degree over time, it was observed that, in the interval 1933–2021, for all the studied sources, there were variations of mineralization that could be attributed to climatic and geological changes, mode of exploitation, as well as to analysis techniques used. Although decreases in mineralization were observed between 1981 and 2006 for water sources 1 bis, 10, 15 and S2, with a slight recovery and stability period between 2006 and 2021, they have retained their characteristics over time. Moreover, spring 14 retains its status as the most mineralized spring of the seven, although it also recorded a decrease in the mineralization degree between 2013 and 2018. Even if the concentration of major and minor ions showed some variation, highlighting the diversity of the water intakes and its changes over time for some of the springs, it is noticeable that these springs have kept their characteristics over time. It was identified that Sodium (Na+) was present in all natural mineral waters but predominated in sodium chloride, sodium bicarbonate and sodium sulfate. The concentration of potassium ion has shown a fairly significant fluctuation, in 2006 being registered the lowest values for most sources: 1 bis (88.00 mg/L), 5 (6.00 mg/L), 10 (81.00 mg/L), 14 (115.00 mg/L), 15 (45.20 mg/L), S2 (11.00 mg/L). By means of ICP-MS, trace elements that have never before been tested or reported were identified, thus completing the chemical fingerprint of these natural mineral waters to increase their value for routine or therapeutic uses or further sustainable exploitation.

Adapting classical water quality diagrams for ecohydrological and policy applications

Ecological values of water have gained increasing attention over the past decades in both (eco)hydrological research and water resources management. Water quality is an important ecological steering variable, and graphical water quality diagrams may aid in rapid interpretation of the hydrochemical status of a site. Traditionally used water quality diagrams for showing multiple variables (e.g. Stiff, Maucha) were developed primarily for hydrogeological purposes, with limited information on ecologically relevant nutrient parameters.This paper presents adapted classical water quality diagrams that retain the traditional information on ions for hydrogeological characterization, and additionally provide information on nutrients for ecological water quality characterization.A scaling factor is used for the minor ions to visually get them across more equally compared to the macro-ion ions in the water quality diagram. Scaling of minor ions is presented based on average concentrations, as well as on water quality policy norms. Four different water quality diagrams are presented, all with the same ions included, but with different appearances to suit different preferences of individual users. Regional, national and continental scale data are used to illustrate how the different diagrams show spatial and temporal water quality characteristics.The adapted diagrams are innovative with respect to adding comprehensive visual information on the four ecohydrologically relevant nutrient species levels (NO3, NH4, PO4, K), advanced insight in redox status from the combination of four redox sensitive parameters (Fe, NO3, SO4, NH4) and the option to scale minor ions relative to average measured concentrations or to water quality policy norms. Using policy norms for scaling has the advantage of providing an ‘alarm function’ of exceedance of norms when concentrations surpass the ring used in the diagram. We discuss possible standardisation of scaling factors to enable comparability between sites.

Hydro and Geochemical Characteristics of Ground Water Assessment in Puducherry Coastal Stretch, Puducherry Region

Abstract: In the recent years, settlement along the coastal stretch of Puducherry region are quiet in an alarming state which has degraded the entire coastal and the marine environment due to enormous anthropogenic activities carried out by the settlements for their livelihood beneficiaries .One of the major problem identified along the coastal areas of the Puducherry region at macro level are seawater intrusion at major settlement zones were erroneous pumping of ground water were done to meet out the demands of the settlements, which in turn has led to serious contamination by dissolved salts mixing into the available fresh water resources such as coastal aquifers which further demands sophisticated treatment processes. The aim of the present study is to analyze the collected water samples with respect to the seasonal variations from various identified aquifers of different geological formation and for its geo-hydro-chemistry and physico-chemical parameters by acceptable procedures. From the results obtained, it was found that, dominant major and minor ions were present in the majority of aquifers in and around the Puducherry region. The presences of ions in the aquifers of Pondicherry coastal region are been represented in an ascending order such as: Na>Ca>Mg>K and HCO3>CL>SO4. Moreover, the characteristic Fluoride (F), Nitrate .

Appraisal of groundwater quality and health risk in the Yalamlam basin, Saudi Arabia.

Groundwater quality in Yalamlam basin, Saudi Arabia, was appraised for drinking, irrigation, livestock and poultry applications by international standards, drinking water quality index (DWQI), irrigation water quality (IWQ) parameters, and irrigation water quality index (IWQI) calculations. Potential non-carcinogenic health risks due to high NO3- and F- water were assessed for various age groups using the United States Environmental Protection Agency (USEPA) models. Groundwater samples (n = 40) were analyzed for pH, electrical conductivity (EC), and major and minor constituents. The average total dissolved solids (TDS), EC, and total hardness (TH) in the groundwater are 3478 µS/cm, 1739mg/l, and 1240mg/l, respectively. High salinity, TH, NO3-, and F- in this aquifer restrict the usage of groundwater for drinking. DWQI values suggest that only 47.5% of samples are potable. According to USEPA recommendation, 72.5%, 80%, and 100% of samples for NO3- and 22.5%, 32.5%, and 40% of samples for F- surpassed the limit (HQoral > 1) for adults, children, and infants, respectively, which creates non-carcinogenic health hazards to the respective age groups. The total hazard index is greater than one in 75%, 87.5%, and 100% of samples computed for adults, children, and infants, respectively. Due to high salinity, 53% of samples are not pertinent for irrigation. USSL classification reveals that groundwater samples in the study site are recommended only for salt-tolerant crops and coarse-textured high permeability soil. In this study, IWQI is reclassified using salinity, which suggests that 68% of samples are moderately suitable for irrigation. Based on EC alone, 83% are desirable for livestock and poultry uses whereas integration of multiple parameters with EC indicates that only 53% are acceptable for all kinds of livestock and poultry uses in the study site. Spatial distribution of major and minor ions, DWQI, HQoral, and IWQI imply that groundwater quality is degraded from upstream to downstream. High salinity groundwater in the downstream wells is unsuitable for any application, which needs a proper treatment before use. Spatial maps created for various parameters are useful for identifying the good quality groundwater zone for groundwater development potential for various stakeholders.

Chemo-isotopic tracing of the groundwater salinity in arid regions: An example of Shahrood aquifer (Iran)

Understanding the origin of groundwater salinity is critical to efficiently manage the scarce water resources in arid regions. In the current research, the source and mechanism of groundwater salinity in the Shahrood aquifer, central Iran, have been assessed using combination of hydrochemical techniques and environmental isotopes. A total of 115 groundwater samples were collected and analyzed for the major and minor ions (HCO3, Cl, SO4, Ca, Mg, Na, K, Br and I) and isotopes (δ18O and δ2H). Based on the results of the chemical approach, halite and gypsum dissolution, Na-silicate weathering and calcite precipitation induced by common-ion effect are the main source of salinity (>7500 mg/L) in the saline water zone (SWZ) of the Shahrood aquifer. The SWZ groundwaters are more depleted in δ2H as compared with fresh water zone (FWZ) samples which plotted on the Shahrood local meteoric water line (SMWL). Development of a groundwater divide line at the central parts of the aquifer causes low velocity and then enhancing the residence time of the SWZ groundwaters mainly originated from isotopic-depleted sub-modern precipitations in surrounding high-elevated mountains. Mixing water zone (MWZ) is identified between FWZ and SWZ, where the relative fractions of the saline groundwaters vary in the range of 23–99%. Managing groundwater withdrawals is highly recommended; as the groundwater over-exploitations enhance invasion of the saline groundwaters from SWZ and then overall degradation of the water quality in the aquifer. This is the first model explaining the groundwater salinity source and mechanism of the Shahrood aquifer as a case of mountain-front recharged plain aquifer, providing guidelines for salinity assessments in other arid-land aquifers around the world.

Application of water quality indices and health risk models in the arid coastal aquifer, Southern Saudi Arabia.

A systematic study was performed in the arid coastal aquifer to evaluate groundwater quality using drinking water quality indices (DWQI) and health risk assessment models in southern Saudi Arabia. Groundwater samples were collected (n = 80) and analysed for major and minor ions. Results suggest that 85% of wells are unsuitable for drinking due to high salinity and hardness. Likewise, high NO3- and F- are encountered in 51% and 46% of wells, respectively. High salinity, Cl- and SO42- are noticed in the coastal wells, which are derived from saline sources, evaporation and anthropogenic activities. High NO3- is originated from anthropogenic sources and the nitrification process. Recharge of wastewater with high NO3- is mixed with high salinity groundwater in this shallow aquifer. DWQI indicates that 66% of samples are poor to unsuitable classes. Wells with poor quality groundwater existed in the coastal belt and water quality is degraded while moving from upstream to downstream. The average values of hazard quotient (HQoral, NO3-, F-) and total hazard index (THI) ensured that highly vulnerable groups are in the order of infants > children > adults. In the study region, the THI are > 1 in 75% (adults), 89% (children) and 94% (infants) of samples, respectively. The spatial distribution of HQoral reveals that groundwater in the coastal and southern regions is not advisable for direct oral ingestion, which causes serious non-carcinogenic health risk to inhabitants. Groundwater in these regions needs proper treatment to remove the contaminants before use.

Sudden depletion of Alfvénic turbulence in the rarefaction region of corotating solar wind high-speed streams at 1 AU: Possible solar origin?

A canonical description of a corotating solar wind high-speed stream in terms of velocity profile would indicate three main regions: a stream interface or corotating interaction region characterized by a rapid increase in flow speed and by compressive phenomena that are due to dynamical interaction between the fast wind flow and the slower ambient plasma; a fast wind plateau characterized by weak compressive phenomena and large-amplitude fluctuations with a dominant Alfvénic character; and a rarefaction region characterized by a decreasing trend of the flow speed and wind fluctuations that are gradually reduced in amplitude and Alfvénic character, followed by the slow ambient wind. Interesting enough, in some cases, fluctuations are dramatically reduced, and the time window in which the severe reduction of these fluctuations takes place is remarkably short, about some minutes. The region in which the fluctuations are rapidly reduced is located at the flow velocity knee that separates the fast wind plateau from the rarefaction region. The aim of this work is to investigate the physical mechanisms that might be at the origin of this phenomenon. To do this, we searched for any tangential discontinuity that might have inhibited the diffusion of these large-amplitude fluctuations in the rarefaction region as well. We also searched for differences in the composition analysis because minor ions are good tracers of physical conditions in the source regions of the wind under the hypothesis that large differences in the source regions might be linked to the phenomenon observed in situ. We found no positive feedback from these analyses, and finally invoked a mechanism based on interchange reconnection experienced by the field lines at the base of the corona, within the region that separates the open field lines of the coronal hole, which is the source of the fast wind, from the surrounding regions that are mainly characterized by closed field lines. Another possibility clearly is that the observed phenomenon might be due to the turbulent evolution of the fluctuations during the expansion of the wind. However, it is hard to believe that this mechanism would generate a short transition region such as is observed in the phenomenon we discuss. This type of study will greatly benefit from Solar Orbiter observations during the future nominal phase of the mission, when it will be possible to link remote and in-situ data, and from radial alignments between Parker Solar Probe and Solar Orbiter.

Role of cathepsins B and D in proteolysis of yolk in the catfish Clarias gariepinus.

Yolk processing pathways vary in the oocytes of benthophil and pelagophil teleosts. The present study investigated the yolk processing pattern in the oocytes of the fresh water catfish Clarias gariepinus at vitellogenic, maturation, and ovulated stages. This study concludes that during maturation stage, an electrophoretic shift in the major peptide band on Polyacrylamide gel electrophoresis (PAGE) occurs due to a decrease in the size of the yolk protein. The PMF spectrum of corresponding peptides from vitellogenic and ovulated oocytes revealed a difference in the minor ions. A minor difference in the molecular weight of the corresponding peptides occurs due to a difference in their amino acid composition. Maximal activity of the proteases cathepsin D and cathepsin B was observed in the vitellogenic oocytes, thus confirming their role in the processing of yolk. A significant transient increase in the activity of cathepsin B in the mature oocytes also suggests its role in oocyte maturation.

Investigation of Inclusion States of Silicate and Carbonate Ions in Hydroxyapatite Particles Prepared under the Presence of Sodium Silicate.

Biological hydroxyapatite (HA) contains the different minor ions which favour its bio-reactivity in vivo. In this study, the preparation of HA particles containing both silicate and carbonate ions under the presence of sodium silicate was investigated, and the physicochemical properties were evaluated according to the contents and states of silicate and carbonate ions. The increment in the silicate ion reduced the crystallinity and expanded the crystalline size along with a-axis. Solid-state 29Si–NMR spectra indicated the increase in the adsorption of oligomeric silicate species on the HA particle surfaces in addition to the substitution state of silicate ions, suggesting the occurrence of the surface coating of silicates on the surfaces. The possible states of carbonate and silicate ions at the HA surfaces will provide the bioactivity.

Deconvolution of Light-Induced Ion Migration Phenomena by Statistical Analysis of Cathodoluminescence in Lead Halide-Based Perovskites.

Studying the compositional instability of mixed ion perovskites under light illumination is important to understand the mechanisms underlying their efficiency and stability. However, current techniques are limited in resolution and are unable to deconvolute minor ion migration phenomena. Here, a method that enables ion migration to be studied allowing different segregation mechanisms to be elucidated is described. Statistical analysis is applied to cathodoluminescence data to generate compositional distribution histograms. Using these histograms, two different ion migration phenomena, horizontal ion migration (HIM) and vertical ion migration (VIM), are identified in different perovskite films. It is found that most passivating agents inhibit HIM, but not VIM. However, VIM can be reduced by deposition of imidazolium iodide on the perovskite surface. This method can be used to study perovskite‐based devices efficiency and stability by providing molecular level mechanistic understanding of passivation approaches leading to performance improvement of perovskite solar cells via rational design.

Hydrogeochemical evolution and assessment of groundwater quality in the Togo and Dahomeyan aquifers, Greater Accra Region, Ghana

Groundwater quality is generally better than surface water quality but this is not sacrosanct because during recharge and abstraction, groundwater may be subjected to variations due to influence from natural and anthropogenic processes. The Togo and Dahomeyan aquifers are threatened by several anthropogenic activities like dumping of domestic and industrial wastes in open landfill sites. These activities can be sources of groundwater constituents and can pose adverse health effects on humans and the ecosystem but little is known about the hydrogeochemical characteristics of groundwater and its quality in the area. Therefore, the present study is aimed at unravelling the hydrogeochemical characteristics and quality of groundwater in the Togo and Dahomeyan aquifers in the Greater Accra Region of Ghana. A total of 37 groundwater samples were collected and analysed for the concentrations of major ions, minor ions, and trace elements. The results were used to compute water quality parameters like electrical conductivity, sodium adsorption ratio, sodium percent, and magnesium ratio to assess the quality of the water for irrigation purposes. Groundwater shows acidic to slightly alkaline pH and evolved from Mg–Na–HCO3, Ca–Na–Mg–HCO3, Na–Ca–Mg–HCO3–Cl to Na–Mg–Ca–HCO3 with other mixed water types, which reflect the local geology. Geochemical modelling indicates that groundwater is supersaturated with respect to goethite and hematite and saturated with respect to calcite, aragonite, and dolomite in some samples. Hydrochemical graphing and multivariate statistical analysis indicate that the chemistry of groundwater in the area is primarily controlled by an interplay of chemical weathering, mineral dissolution, ion exchange reactions, agricultural activities, and sewage disposal. The groundwater is not entirely suitable for drinking purposes because of high concentrations of EC, TDS, Na+, Cl−, F−, Fe, Mn, Pb, Cr, and Ni, which exceed their maximum permissible limits provided by the World Health Organization. The computed parameters for assessing the quality of the water for irrigation reveal that 64.9% of the samples are suitable for irrigation purposes. However, 35.1% of the samples show very high salinity and sodium hazard and thus, are unsuitable for irrigation purposes. Therefore, it is recommended that mixing of the high salinity and sodium water with low salinity and sodium water can improve crop yields.