Formation Of Carbonic Acid Research Articles

Understanding the Seasonal Dynamics of the Groundwater Hydrogeochemistry in National Capital Territory (NCT) of India Through Geochemical Modelling

A geochemical assessment of seasonal dynamics in the groundwater chemistry of the National Capital Territory (NCT), Delhi, was attempted through geochemical modelling, mineral precipitation sequences with rainfall and water evaporation cycle. Saturation indices calculated using PHREEQC indicated that the degree of water–rock equilibrium changes significantly from pre-monsoon to post-monsoon. The schematic model of SI change with water table fluctuation showed that during monsoon, as rainwater percolates through the soil, partial pressure of CO2 becomes higher than that of the atmospheric value and led to the formation of more carbonic acid that react with the carbonate minerals to produce $${{{\text{HCO}}_{3}^{-} }}$$ , Mg2+ and Ca2+. The thermodynamic stability relationships of water chemistry in the Na, K, Ca and Mg silicate systems showed that for the samples with higher EC equilibrium between clay and primary minerals is not likely to be the main processes controlling variation in the groundwater chemistry. Chloro-alkaline indices (CAI) are positive when the groundwater level is high and become negative with the lowering of water level, i.e. when water level is high, reverse ion exchange is dominant. In case of pre-monsoon season, lower and negative value of CAI-1 and CAI-2 indicates dominance of ion exchange process and increases dissolved solid concentration in groundwater. The conceptual geochemical model depicted that water table fluctuation resulting from heavy pumping/withdrawal and recharge in association with the variation in DO, $${{{\text{HCO}}_{3}^{-} }}$$ and Fe regulates the water–mineral equilibrium. The conceptual geochemical model explained the hydrogeochemical processes and their variations with water table fluctuation and, thus, highlighted the descriptive capabilities of PHREEQC. The study suggested that in the subsurface environment, complex interactions are simultaneously functioning, and hence, significant seasonal variations are likely to be very influential due to monsoonal recharge and subsequent changes in the saturation states of the water.

Crystal Growth of Cyclodextrin-based Metal-organic Framework for Carbon Dioxide Capture and Separation

Crystalline cyclodextrin-based metal-organic framework (CD-MOF) was synthesized by vapor diffusion of methanol into a KOH solution of ▪-cyclodextrin (▪-CD). Its CO2 adsorption behaviors were evaluated both qualitatively and quantitatively. The adsorption behaviors of CD-MOF to separate and capture CO2 have been tested by using thermogravimetric analysis in the multiple adsorption-desorption process. The chemical sorption of CO2 was found to be caused by the formation of reversible carbonic acid. The adsorption amount of CO2 was tested in pure CO2 gas and 25vol% CO2 in Ar gas. As a result, there is no difference of the adsorption amount against the CO2 concentration and the saturated adsorption amount was 24 mg-CO2/g-CD-MOF at 30oC.

Long-Term Effects of CO2 Sequestration on Rock Mechanical Properties

The long-term geological sequestration of carbon dioxide (CO2) in underground formations (deep saline aquifers) is the most economically viable option to decrease the emissions of this greenhouse gas in the atmosphere. The injection of CO2 in carbonate aquifers dissolves some of the calcite rock due to the formation of carbonic acid as a result of the interaction between CO2 and brine. This rock dissolution may affect the rock integrity and in turn will affect the rock mechanical properties. The effect of CO2 on the rock mechanical properties is a key parameter to be studied to assess the aquifer performance in the process of geological sequestration and to get a safe and effective long-term storage. The main objective of this study is to address the impact of geological sequestration of CO2 on the mechanical properties of carbonate aquifer and caprocks. In addition, the effect of the storage time on these properties is investigated. In this study, CO2 was injected into the brine-soaked core samples under simulated downhole conditions of high pressure and high temperature (2000 psi and 100 °C). The mechanical properties of these core samples were analyzed using indirect tensile strength (ITS), unconfined compression, and acoustics testing machines. The effect of CO2 sequestration on the engineering operations such as well instability and aquifer compaction will be investigated based on the experimental results. Results showed that CO2 sequestration affected the mechanical properties of the carbonate rocks as well as the caprocks. Long time soaking of CO2 in brine allowed for the formation of enough carbonic acid to react with the cores and this greatly impacted the rock mechanical and acoustic properties. The significant impact of CO2 storage was noted on Khuff limestone (KL), and the good candidate among the carbonate rocks studied here for geological sequestration of CO2 is found to be Indiana limestone (IL). The stress calculations based on the experimental results showed that CO2 may affect the wellbore stability and care should be taken during drilling new wells in the sequestration area. Aquifer compaction based on KL measurements showed that the aquifer will compact 1.25 ft for a 500 ft thick carbonate formation due the CO2 sequestration for 90 days.

Acetazolamide reduces postoperative pain following laparoscopic inguinal herniorrhaphy.

Carbonic acid accumulation, which results from CO2 insufflation, can produce visceral and referred pain in the postoperative setting. Acetazolamide inhibits carbonic anhydrase, an enzyme that accelerates carbonic acid formation. We hypothesized that preoperative administration of acetazolamide would decrease postoperative pain in patients undergoing laparoscopic inguinal herniorrhaphy. A retrospective review was conducted of patients who underwent laparoscopic preperitoneal inguinal herniorrhaphy at the Medical College of Wisconsin between October 2012 and September 2014. Beginning in January 2014, patients began receiving 250mg of acetazolamide preoperatively; patients prior to that time did not. The visual analog scale (range 0-10) was used to assess both preoperative pain and postoperative pain. A total of 66 patients underwent laparoscopic inguinal herniorrhaphy during the study interval. Of these, 22 (33%) patients received acetazolamide preoperatively, and 44 (67%) were included as controls. Overall mean pain scores were lower in the acetazolamide group (1.9±1.45 vs 2.9±1.5, p=0.04). Specifically, patients who received acetazolamide reported lower pain scores immediately after surgery (0.6±1.2 vs 1.9±2.3, p=0.01) and on post-op day one (2.3±0.9 vs 4.0±2.1, p=0.04). Total morphine equivalents administered to manage postoperative pain were significantly less for the acetazolamide group (4.3±4.8mg) when compared to the control group (8.9±8.4mg), p=0.04. Perioperative complications did not differ between the groups (p=0.16). Acetazolamide appears to reduce pain in the immediate postoperative setting. Patients who received acetazolamide had lower pain scores postoperatively and required fewer narcotics for pain management prior to discharge.

Structure, dynamics and stability of water/scCO2/mineral interfaces from ab initio molecular dynamics simulations.

The boundary layer at solid-liquid interfaces is a unique reaction environment that poses significant scientific challenges to characterize and understand by experimentation alone. Using ab initio molecular dynamics (AIMD) methods, we report on the structure and dynamics of boundary layer formation, cation mobilization and carbonation under geologic carbon sequestration scenarios (T = 323 K and P = 90 bar) on a prototypical anorthite (001) surface. At low coverage, water film formation is enthalpically favored, but entropically hindered. Simulated adsorption isotherms show that a water monolayer will form even at the low water concentrations of water-saturated scCO2. Carbonation reactions readily occur at electron-rich terminal Oxygen sites adjacent to cation vacancies that readily form in the presence of a water monolayer. These results point to a carbonation mechanism that does not require prior carbonic acid formation in the bulk liquid. This work also highlights the modern capabilities of theoretical methods to address structure and reactivity at interfaces of high chemical complexity.

PHYSIOLOGY. Regulation of breathing by CO₂ requires the proton-activated receptor GPR4 in retrotrapezoid nucleus neurons.

Blood gas and tissue pH regulation depend on the ability of the brain to sense CO2 and/or H(+) and alter breathing appropriately, a homeostatic process called central respiratory chemosensitivity. We show that selective expression of the proton-activated receptor GPR4 in chemosensory neurons of the mouse retrotrapezoid nucleus (RTN) is required for CO2-stimulated breathing. Genetic deletion of GPR4 disrupted acidosis-dependent activation of RTN neurons, increased apnea frequency, and blunted ventilatory responses to CO2. Reintroduction of GPR4 into RTN neurons restored CO2-dependent RTN neuronal activation and rescued the ventilatory phenotype. Additional elimination of TASK-2 (K(2P)5), a pH-sensitive K(+) channel expressed in RTN neurons, essentially abolished the ventilatory response to CO2. The data identify GPR4 and TASK-2 as distinct, parallel, and essential central mediators of respiratory chemosensitivity.

Receptor in the brain controls breathing

Physiology Control of breathing in mammals depends primarily not on sensing oxygen, but rather on detecting concentrations of carbon dioxide in the blood. Failure of this system can cause potentially deadly sleep apnias. Taking a hint from insects, which use a heterotrimeric guanine nucleotide–binding protein-coupled receptor (GPCR) to sense carbon dioxide, Kumar et al. demonstrate that the GPCR GPR4 is essential to control breathing in mice. GPR4 senses protons generated by the formation of carbonic acid in the blood and works with a pH-sensitive potassium channel called TASK-2 in a set of brain cells that control breathing. Science , this issue p. [1255][1] [1]: /lookup/doi/10.1126/science.aaa0922

Analysis of asphaltene deposition, carbonate precipitation, and their cementation in depleted reservoirs during CO2injection

AbstractCarbon dioxide (CO2) injection in depleted oil reservoirs is a potential means of reducing CO2emissions. In this regard, CO2‐related formation damages are considered key technical and economical issues. When CO2is injected after water flooding, it can be stored by hydrodynamic trapping, dissolution, and mineral trapping. This process leads to the formation of carbonic acid, which may react and dissolve the carbonates. The precipitation of these carbonates can reduce oil productivity and CO2injectivity. In this study, we develop an analytical model to predict the amount of asphaltene deposition, rock dissolution, and their cementation. Primarily, we develop an analytical model that treats the asphaltene deposition and carbonate dissolution in radial geometry. Then, this model predicts cementation, which is evaluated to determine the effect of cementation on reservoir permeability. Finally the developed model is compared with experimental data and determined the factors affecting the cementation. From analyses of different cases, cementation is a few percent but its percentage increases with time. The results presented in this study indicate that the amount of cementation depends on asphaltene percentage, flow rate, flow period, and reservoir depth. The model assumes constant reservoir temperature and no capillary and gravity forces. However, these forces might increase asphaltene‐carbonate cementation in the reservoir.© 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Hydroxyl radical initiated oxidation of formic acid on mineral aerosols surface: a mechanistic, kinetic and spectroscopic study

Environmental context The presence of air-borne mineral dust containing silicates in atmospheric aerosols should be considered in any exploration of volatile organic compound chemistry. This work reports the mechanisms, relative energies and kinetics of free-radical reactions with formic acid adsorbed on silicate surface models. We find that silicate surfaces are more likely to act as a trap for organic radicals than to have a catalytic effect on their reactions. Abstract Heterogeneous reactions of atmospheric volatile organic compounds on aerosol particles may play an important role in atmospheric chemistry. Silicate particles are present in air-borne mineral dust in atmospheric aerosols, and radical reactions can be different in the presence of these mineral particles. In this work, we use quantum-mechanical calculations and computational kinetics to explore the reaction of a hydroxyl free radical with a formic acid molecule previously adsorbed on several models of silicate surfaces. We find that the reaction is slower and takes place according to a mechanism that is different than the one in the gas phase. It is especially interesting to note that the reaction final products, which are the formyl radical attached to the cluster surface, and a water molecule, are much more stable than those formed in the gas phase, the overall reaction being highly exothermic in the presence of the surface model. This suggests that the silicate surface is a good trap for the formed formyl radical. In addition, we have noted that, if a second hydroxyl radical approaches the adsorbed formyl radical, the formation of carbonic acid on the silicate surface is a highly exothermic and exergonic process. The carbonic acid molecule remains strongly attached to the surface, thus blocking CO2 formation in the formic acid oxidation reaction. The spectroscopic properties of the systems involved in the reaction have been calculated, and interesting frequency shifts have been identified in the main vibration modes.

A biphase H2O/CO2system as a versatile reaction medium for organic synthesis

We review activity on the usage of a biphase H2O/CO2 system in organic synthesis as a reaction medium of green chemistry. The formation of self-neutralizing carbonic acid in such a system eliminates the problem of salt disposal, typical for acid-catalyzed reactions with the usual mineral and organic acids. A large variety of different reactions to be performed in the biphase H2O/CO2 system are discussed in detail, including cyclization/cycloaddition, hydroformylation, hydrogenation, reduction, coupling, rearrangement, substitution, addition, halogenation, hydrolysis, oxidation and others. These reactions cover a significant part of modern organic synthesis. The main physical properties of carbonic acid being formed in the biphase H2O/CO2 system and their dependence on the temperature and pressure of saturating CO2 are analyzed. The problem with the search for the most optimal reaction conditions from the viewpoint of selection of appropriate pressure and temperature regions for the best yields and selectivity achievable is addressed in general. Comparison with formation and utilization of peroxycarbonic acids, alkylcarbonic acids and carbamic acids by means of saturation with pressurized CO2 of some other biphase systems is discussed in relationship to organic synthesis as well. The influence of a CO2 admixture on the unique properties of high temperature water, another promising green solvent, is also considered.

PH, geoelectrical and membrane flux parameters for the monitoring of water-saturated silicate and carbonate porous media contaminated by CO2

Characteristics of potable water aquifer contaminated by CO2 are investigated using well-defined laboratory experiments. The porous media domain was prepared with silica sand and limestone in separate experiments. The investigations used combinations of techniques to measure various parameters in the water-saturated porous media domain on which pressure of CO2 was imposed, under various conditions, which correspond to different geological depths. Measured parameters included the pH, geoelectrical parameters, and the diffusion of the CO2 gas through the water-saturated porous media domain using non-porous silicone rubber sheet. Experimental results revealed the existence of three stages in the profile of pH change with time as CO2 dissolved and diffused in the water-saturated porous media domain, which was composed of silica sand. The first stage was characterised by rapid decline in the pH. This is associated with quick dissolution of CO2 and the formation of carbonic acid together with bicarbonate. The second stage showed short rise in pH value, which was attributed to the reverse reaction, i.e., the formation of aqueous and gaseous CO2 and water from the carbonic acid. The third stage was that of the equilibrium in the forward and the reverse reactions, marked by steady state in pH value, which remained unchanged till the end of the experiment. The bulk electrical conductivity (σb) of the water-saturated porous domain increased in the presence of CO2. This is attributed to the formation of ionic species, especially bicarbonate, as CO2 dissolved in the domain. The rise in σb coincided with the first stage of the change in the pH of the system. In addition, the σb was higher in limestone than silica sand, and it increased with pressure of the domain. But, the bulk dielectric constant (εb) showed no change with the dissolution of the CO2 under different conditions. Furthermore, permeation of CO2 through the silicone rubber indicated the diffusion of the CO2 gas through the water-saturated domain. CO2 flux through the membrane was shown to increase with depth or pressure of the domain. A mathematical expression derived in this work shows the dependence of σb on the pH and the initial value of σb. Predictions of the changes in the σb for different porous domains show the reliability of the mathematical expression developed in this work.

A review of the protection strategies against internal corrosion for the safe transport of supercritical CO2 via steel pipelines for CCS purposes

The transport of carbon dioxide (CO2) from its source to a storage site is a key component of the carbon capture and storage (CCS) process. CO2 transportation by steel pipelines presents a durability risk in the form of internal corrosion damage from supercritical or liquid CO2 transmission. This risk is due to the formation of carbonic acid as a result of any H2O presence, and in situ speciation of acids such as sulphurous (H2SO3), sulfuric (H2SO4), hydrochloric (HCl), and nitric acids (HNO3) due to the presence of impurities. This review paper aims to present three key potential protection strategies to mitigate or reduce the threat of corrosion damage for reliable and potentially cost-effective transport of CO2. This includes review of (a) relevant corrosion inhibitors, (b) corrosion resistant alloys (CRAs) for CO2 transport pipeline, and (c) the role and physical properties of a protective iron carbonate layer (FeCO3).

The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates

The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb2+) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb2+ concentrations within the plume. Dissimilarities between ensemble Pb2+ concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb2+ concentrations are the same for all three geochemical conditions. Correlation between reactive surface area and hydraulic conductivity, either positive or negative, results in variation in τeq and Leq.

Palladium/Carbon dioxide cooperative catalysis for the production of diketone derivatives from carbohydrates.

The one-pot production of industrially valuable diketone derivatives from carbohydrates is achieved through a bifunctional catalytic process. In particular, Pd/C-catalyzed hydrogenation of HMF in water and under CO2 affords 1-hydroxypentane-2,5-dione with up to 77% yield. The process is also eligible starting from fructose and inulin, affording 1-hydroxyhexane-2,5-dione with 36% and 15% yield, respectively. The key of the process is reversible in situ formation of carbonic acid, which is capable of assisting Pd/C during the hydrogenation reaction by promoting the dehydration of carbohydrates and the ring-opening of furanic intermediates. Interestingly, by changing the reaction medium from H2 O to a H2 O/THF mixture (1:9), it is possible to switch the selectivity of the reaction and to produce 2,5-hexanadione with 83% yield. Within the framework of sustainable chemistry, reactions presented in this report show 100% carbon economy, involve CO2 to generate acidity, require water as a solvent, and are conducted under rather low hydrogen pressures (10 bar).

Experimental and Modeling Study of Salt Precipitation During Injection of CO2 Contaminated With H2S Into Depleted Gas Fields in the Northeast of the Netherlands

Summary Depleted gas fields are among the most probable candidates for subsurface storage of carbon dioxide (CO2). With proven reservoir and qualified seal, these fields have retained gas over geological time scales. However, unlike methane, injection of CO2 changes the pH of the brine because of the formation of carbonic acid. Subsequent dissolution/precipitation of minerals changes the porosity/permeability of reservoir and caprock. Thus, for adequate, safe, and effective CO2 storage, the subsurface system needs to be fully understood. An important aspect for subsurface storage of CO2 is purity of this gas, which influences risk and cost of the process. To investigate the effects of CO2 plus impurities in a real case example, we have carried out medium-term (30-day) laboratory experiments (300 bar, 100°C) on reservoir and caprock core samples from gas fields in the northeast of the Netherlands. In addition, we attempted to determine the maximum allowable concentration of one of the possible impurities in the CO2 stream [hydrogen sulfide (H2S)] in these fields. The injected gases—CO2, CO2+100 ppm H2S, and CO2+5,000 ppm H2S—were reacting with core samples and brine (81 g/L Na+, 173 g/L Cl−, 22 g/L Ca2+, 23 g/L Mg2+, 1.5 g/L K+, and 0.2 g/L SO42−). Before and after the experiments, the core samples were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) for mineralogical variations. The permeability of the samples was also measured. After the experiments, dissolution of feldspars, carbonates, and kaolinite was observed as expected. In addition, we observed fresh precipitation of kaolinite. However, two significant results were obtained when adding H2S to the CO2 stream. First, we observed precipitation of sulfate minerals (anhydrite and pyrite). This differs from results after pure CO2 injection, where dissolution of anhydrite was dominant in the samples. Second, severe salt precipitation took place in the presence of H2S. This is mainly caused by the nucleation of anhydrite and pyrite, which enabled halite precipitation, and to a lesser degree by the higher solubility of H2S in water and higher water content of the gas phase in the presence of H2S. This was confirmed by the use of CMG-GEM (CMG 2011) modeling software. The precipitation of halite, anhydrite, and pyrite affects the permeability of the samples in different ways. After pure CO2 and CO2+100 ppm H2S injection, permeability of the reservoir samples increased by 10–30% and ≤3%, respectively. In caprock samples, permeability increased by a factor of 3–10 and 1.3, respectively. However, after addition of 5,000 ppm H2S, the permeability of all samples decreased significantly. In the case of CO2+100 ppm H2S, halite, anhydrite, and pyrite precipitation did balance mineral dissolution, causing minimal variation in the permeability of samples.

Utilizing Rare Earth Elements as Tracers in High TDS Reservoir Brines in CCS Applications

Abstract In this paper we report the result of research associated with the testing of a procedures necessary for utilizing natural occurring trace elements, specifically the Rare Earth Elements (REE) as geochemical tracers in Carbon Capture and Storage (CCS) applications. Trace elements, particularly REE may be well suited to serve as in situ tracers for monitoring geochemical conditions and the migration of CO 2 -charged waters within CCS storage systems. We have been conducting studies to determine the efficacy of using REE as a tracer and characterization tool in the laboratory, at a CCS analogue site in Soda Springs, Idaho, and at a proposed CCS reservoir at the Rock Springs Uplift, Wyoming. Results from field and laboratory studies have been encouraging and show that REE may be an effective tracer in CCS systems and overlying aquifers. In recent years, a series of studies using REE as a natural groundwater tracer have been conducted successfully at various locations around the globe. Additionally, REE and other trace elements have been successfully used as in situ tracers to describe the evolution of deep sedimentary Basins. Our goal has been to establish naturally occurring REE as a useful monitoring measuring and verification (MMV) tool in CCS research because formation brine chemistry will be particularly sensitive to changes in local equilibrium caused by the addition of large volumes of CO 2 . Because brine within CCS target formations will have been in chemical equilibrium with the host rocks for millions of years, the addition of large volumes of CO 2 will cause reactions in the formation that will drive changes to the brine chemistry due to the pH change caused by the formation of carbonic acid. This CO 2 driven change in formation fluid chemistry will have a major impact on water rock reaction equilibrium in the formation, which will impart a change in the REE fingerprint of the brine that can measured and be used to monitor in situ reservoir conditions. Our research has shown that the REE signature imparted to the formation fluid by the introduction of CO 2 to the formation, can be measured and tracked as part of an MMV program. Additionally, this REE fingerprint may serve as an ideal tracer for fluid migration, both within the CCS target formation, and should formation fluids migrate into overlying aquifers. However application of REE and other trace elements to CCS system is complicated by the high salt content of the brines contained within the target formations. In the United States by regulation, in order for a geologic reservoir to be considered suitable for carbon storage, it must contain formation brine with total dissolved solids (TDS) > 10,000 ppm, and in most cases formation brines have TDS well in excess of that threshold. The high salinity of these brines creates analytical problems for elemental analysis, including element interference with trace metals in Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) (i.e. element mass overlap due to oxide or plasma phenomenon). Additionally, instruments like the ICP-MS that are sensitive enough to measure trace elements down to the parts per trillion level are quickly oversaturated when water TDS exceeds much more than 1,000 ppm. Normally this problem is dealt with through dilution of the sample, bringing the water chemistry into the instruments working range. However, dilution is not an option when analyzing these formation brines for trace metals, because trace elements, specifically the REE, which occur in aqueous solutions at the parts per trillion levels. Any dilution of the sample would make REE detection impossible. Therefore, the ability to use trace metals as in situ natural tracers in high TDS brines environments requires the development of methods for pre-concentrating trace elements, while reducing the salinity and associated elemental interference such that the brines can be routinely analyzed by standard ICP-MS methods. As part of the Big Sky Carbon Sequestration Project the INL-CAES has developed a rapid, easy to use process that pre-concentrates trace metals, including REE, up to 100x while eliminating interfering ions (e.g. Ba, Cl). The process is straightforward, inexpensive, and requires little infrastructure, using only a single chromatography column with inexpensive, reusable, commercially available resins and wash chemicals. The procedure has been tested with synthetic brines (215,000 ppm or less TDS) and field water samples (up to 5,000 ppm TDS). Testing has produced data of high quality with REE capture efficiency exceeding 95%, while reducing interfering elements by > 99%.

Sulfur implantation in CO and CO2 ices

We present new experimental results concerning the implantation of multiply charged sulfur ions (90 and 176 keV) in frozen CO and CO2. CO2 layers have been capped with a water ice layer to study chemical reactions induced at the interface between the two species. The results indicate that SO2 is formed after implantation in both CO and CO2 and the respective formation yields are 0.20 +/- 0.05 and 0.38 +/- 0.20 molecules ion(-1) for 176-keV S11+ in CO and 90-keV S9+ in CO2, respectively. Possibly, CS2 has been produced in CO2 and OCS in CO. Ion implantation produces also all of the chemical modifications observed with other ion beam. In particular a large number of carbon chains are formed after implantation in CO. Chemical reactions and mixing are induced at the water/carbon dioxide interface and lead to the formation of carbonic acid (H2CO3). The results are discussed in the light of their relevance in some astrophysical environments both in the star-forming regions and in the Solar system.

Hydrogeological processes controlling the release of arsenic in parts of 24 Parganas district, West Bengal

A study was conducted to understand the hydrogeological processes dominating in the North 24 Parganas and South 24 Parganas based on representative 39 groundwater samples collected from selected area. The abundance of major ions was in the order of Ca2+ > Na+ > Mg2+ > K+ > Fe2+ for cations and HCO3 − > PO4 3− > Cl− > SO4 2− > NO3 − for anions. Piper trilinear diagram was plotted to understand the hydrochemical facies. Most of the samples are of Ca-HCO3 type. Based on conventional graphical plots for (Ca + Mg) vs. (SO4 + HCO3) and (Na + K) vs. Cl, it is interpreted that silicate weathering and ion exchange are the dominant processes within the study area. Previous studies have reported quartz, feldspar, illite, and chlorite clay minerals as the major mineral components obtained by the XRD analysis of sediments. Mineralogical investigations by SEM and EDX of aquifer materials have shown the occurrence of arsenic as coating on mineral grains in the silty clay as well as in the sandy layers. Excessive withdrawal of groundwater for irrigation and drinking purposes is responsible for fluctuation of the water table in the West Bengal. Aeration beneath the ground surface caused by fluctuation of the water table may lead to the formation of carbonic acid. Carbonic acid is responsible for the weathering of silicate minerals, and due to the formation of clay as a product of weathering, ion exchange also dominates in the area. These hydrogeological processes may be responsible for the release of arsenic into the groundwater of the study area, which is a part of North 24 Parganas and South 24 Parganas.

Osteocytes: Regulating the Mineral Reserves?

Osteocytes are increasingly recognized as multifunctional cells that help orchestrate bone and mineral metabolism— and are currently one of the hottest topics in the field. In addition to their putative role as detectors/transducers of mechanical strain in bone, osteocytes are a major source of sclerostin, a key inhibitor of Wnt signaling and bone formation, and appear to be important regulators of osteoclast function via their production of NF‐kB ligand (RANKL) and osteoprotegerin. It has also long been believed that osteocytes could remove or even replace mineralized bone around their lacunae and canaliculi. Thanks to a number of studies and reviews in recent years, this once‐ controversial concept of “osteocytic osteolysis” is now verymuch back on the agenda. In this issue of the Journal of Bone and Mineral Research, Kogawa and colleagues present evidence that sclerostin could act to stimulate the dissolution of bone mineral by osteocytes by increasing their expression of some of the same resorptive machinery used by osteoclasts. The authors show that treatment of cultured MLO‐Y4 and primary human osteocyte‐like cells with recombinant human sclerostin increased the expression of mRNA for a number of resorptionmarkers, most notably carbonic anhydrase 2 (CA2). The authors found that sclerostin caused both intracellular and extracellular acidification in cultures of the osteocyte‐like cells, albeit in a non–dose‐dependentmanner. The classic CA inhibitor, acetazolamide decreased the sclerostin‐ stimulated extracellular acidification in MLO‐Y4 cells, whereas antisense knockdown of CA2 led to an extracellular alkalinization, with elimination of the effect of acetazolamide. Sclerostin additionally caused a slight stimulation of calcium release from mineralized layers of primary osteocyte‐like cells, an effect that was also blocked by acetazolamide. Stimulation of mRNA for CA2, tartrate‐resistant acid phosphatase (TRAP), chloride channel 7 (CLCN7), and cathepsin K by sclerostin in the MLO‐Y4 cell line was inhibited by small interfering RNA (siRNA) constructs for Lrp4, Lrp5, or Lrp6, suggesting the possible involvement of Wnt signaling. Last, sclerostin treatment increased the plan area of osteocyte lacunae by about 25% in cultured samples of trabecular bone taken from patients undergoing hip surgery, an effect that was again abrogated by acetazolamide. The concept of osteocytic osteolysis was first mooted in 19th century, although is perhaps now most closely associated with Belanger. He suggested that either parathyroid hormone (PTH) or a low‐calciumdiet can induce osteocytes to enlarge their lacunae. In its broadest sense, the term osteocytic osteolysis implies dissolution of not only the mineral component of bone adjacent to lacunae and canaliculi but of the collagenous matrix, too. These ideas provoked vigorous rebuttals but began to gain traction again following reports that osteocyte lacunar area wasmarkedly increased in rats continuously infused with PTH for 4 weeks and in mice infused with prednisolone for 3 weeks. Moremodest increases in lacunar sizewere also observed inmice subjected to ovariectomy. More recently, some of the coauthors of the paper by Kogawa and colleagues have presented a comprehensive study of the effects of lactation on osteocyte lacunae in mice. Lactation was shown to be associated with increases in lacunar area of about 20–40% in tibias and lumbar vertebrae; these increases were reversed with 7 days of cessation of lactation. The effects were mimicked by PTH‐related protein (PTHrP) and abrogated by targeted deletion of PTH receptor 1. Increased expression of mRNAs for osteoclast‐specific markers (including cathepsin K, which cleaves collagen) was also noted in “osteocyte‐enriched” bones of lactating animals. These reversible changes in osteocyte lacunar size have been referred to as “remodeling,” although this process clearly differs from bone remodeling by osteoclasts and osteoblasts, which involves obvious turnover of substantial quantities of both mineral and organic matrix. Despite suggestions that removal and replacement of collagenous matrix around osteocytes might occur in extreme pathophysiological situations, such as in the ultra‐high turnover bone of egg‐ laying hens, there seems to be little wider evidence for such a process. Removal of mineral alone might be sufficient to account for the enlargement of osteocyte lacunae observed by light or scanning electron microscopy if the resulting thin layer of demineralized collagenous matrix shrinks back against the lacunar walls during dehydration for specimen preparation. In vivo, such a layer of demineralized (hydrated) matrix adjacent to the osteocyte could presumably serve as a scaffold to facilitate

The Influence of Bubbles on the Perception Carbonation Bite

Although many people naively assume that the bite of carbonation is due to tactile stimulation of the oral cavity by bubbles, it has become increasingly clear that carbonation bite comes mainly from formation of carbonic acid in the oral mucosa. In Experiment 1, we asked whether bubbles were in fact required to perceive carbonation bite. Subjects rated oral pungency from several concentrations of carbonated water both at normal atmospheric pressure (at which bubbles could form) and at 2.0 atmospheres pressure (at which bubbles did not form). Ratings of carbonation bite under the two pressure conditions were essentially identical, indicating that bubbles are not required for pungency. In Experiment 2, we created controlled streams of air bubbles around the tongue in mildly pungent CO2 solutions to determine how tactile stimulation from bubbles affects carbonation bite. Since innocuous sensations like light touch and cooling often suppress pain, we predicted that bubbles might reduce rated bite. Contrary to prediction, air bubbles flowing around the tongue significantly enhanced rated bite, without inducing perceived bite in blank (un-carbonated) solutions. Accordingly, though bubbles are clearly not required for carbonation bite, they may well modulate perceived bite. More generally, the results show that innocuous tactile stimulation can enhance chemogenic pain. Possible physiological mechanisms are discussed.