The hydrochemical genesis of groundwater brines of the Eastern arm of the Makgadikgadi basin.

<p>Hydrochemistry of groundwater brines of the eastern part of the large playa deposit in the Makgadikgadi basin in northern Botswana has been analyzed. Brine samples were collected from 37 production and monitoring wells in this area. Brine samples for analysis were filtered to 0.45 and analyzed for major and minor anions and cations as well as trace species. The results of the hydrochemical analysis revealed that the major element chemistry of these samples from the area is dominated by Na and Cl with minor components of K, CO3, HCO3, and SO4, and depleted in Ca and Mg, which is typical of seawater or coastal water. The brine type is Na-Cl type. However, the exact mechanism of the genesis of the brines is still ambiguous, hence comparison curves of Na/C1 against seawater concentration factor (SCF) and Ca/Mg against (SCF) in order to ascertain the brine genesis geochemically were employed. The relationship between the current results to previous seawater freezing and evaporation experiments by other researchers indicated that the brines were formed by seawater evaporation. Observed variations in hydrogeochemistry and salinity with depth support the results of previous studies indicating downward infiltration of brackish waters and evaporative and/or mixing processes. With respect to minor and trace element analysis, A comparison of measured concentrations of trace elements to their concentration in seawater when normalized against the concentration of chloride, it can be seen that the saline groundwater brines in the area are enriched in a number of trace elements including W, Th, Se, Pb while depleted in Sr. Enrichments in all of these elements which would be expected to exhibit conservative behavior in the brines suggest that the origin of the brine is not restricted to the simple evaporation of seawater or but to a combination of end members enriched in these elements such as riverine and groundwater inputs.</p>

Impact of test conditions on the bacterial bioassay in the presence of TiO2 nanoparticles

To assess the fate and behavior of engineered nanoparticles in the aquatic environment, it is crucial to conduct appropriate bacterial bioassay procedure. However, test conditions of bacterial bioassay are limitedly investigated; especially in the field of environmental media chemistry or aging of nanoparticles which interfere the procedure. For this purpose, TiO2 nanoparticles were treated with different test conditions by keeping them in 1% and 100% seawater for one day and 20 days. The bacterial bioassay of treated nanoparticles towards gram-negative (Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria were examined, as well as the mechanism by biochemical responses of bacteria and physicochemical properties of TiO2 nanoparticles. The viability response of tested bacteria reduced remarkably in seawater concentration, while treatment (aging) duration of tested nanoparticles slightly affected the viability response of tested bacteria. Moreover, key events which affected the bioassay response were changed with the treatment duration and media concentration. The results also showed that aging duration and concentration of the media influenced the main physicochemical properties due to the alterations in surface from aging media compared to unaged ones.

Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

During the Albian, the hyperextension of the Pyrenean passive margin led to a hyperthinning of the continental crust and the subsequent subcontinental mantle exhumation. The giant Trimouns talc-chlorite deposit represents the most prominent occurrence of Albian metasomatism in the Pyrenees, with the occurrence of the largest talc deposit worldwide. Consequently, this deposit, which is located on a fault zone and a lithological contact, represents one of the major drains at the scale of the Pyrenees and one of the best geological targets in order to determine the origin(s) of the fluid(s) that circulated during this period. Talc-chlorite ore is characterized by the presence of brines trapped in dolomite, quartz, and calcite fluid inclusions in the vicinity of the talc-rich zone. Considered as being responsible for the formation of talc, these fluids may be interpreted in several ways: (i) primary brines expelled from Triassic evaporites, (ii) secondary brines produced through halite leaching by diagenetic/metamorphic fluids, and (iii) brines derived from seawater serpentinization of mantle rocks. Stable isotope analyses (δ13C, δ18O, δD, and δ37Cl) and Cl/Br ratio measurements in fluid inclusions and their host minerals were carried out in order to determine the origin of the fluid(s) involved in the formation of the ore deposit. The data are consistent with a primary brine origin for the mineralizing fluid, which could have been expelled from the Triassic levels. Other hypotheses have been tested, for example, the production of brines via the seawater concentration during serpentinization. The geochemical proxies used in this study provide equivocal results. The first hypothesis is by far the most realistic one considering the numerous occurrences of Trias formations nearby, their deformation during the extension, and the drainage of the expulsed brines as evidenced by the high-salinity fluid inclusions found all around the deposit. Alternatively, the exhumation of the mantle is considered as a major source of heat and stress that favored brine migration along the major shear zones. Our results fit well with brine circulation in a hyperextensional geodynamic context, which is related to the formation of the talc-chlorite ore, the thinning of the continental crust, and the exhumation of the subcontinental mantle, in accordance with recent works.

Effect of initial seawater concentration on forming ice slurry for thermal energy storage in fishing vessel

Ice slurry technology has great potential in maximizing the chilling process of fish. Seawater is widely used as base solution of ice slurry due to Natrium Chloride content as freezing point depressant. In this study, effect of initial seawater concentration was investigated experimentally. The initial concentration of seawater was varied at 1, 1.5, 2, 2.5 and 3 wt%, respectively. Performance of systems and microscopic of ice particles were also observed. Ice slurry generated from 1 wt% seawater solution gives good agreement toward formation time of ice slurry. The diameter of particle ice increases with decrease in concentration. For application in thermal energy storage of fishing vessel, it is recommended to use low concentration of seawater.

Reconsidering the role of carbonate ion concentration in calcification by marine organisms

Marine organisms precipitate 0.5–2.0 Gt of carbon as calcium carbonate (CaCO3) every year with a profound impact on global biogeochemical element cycles. Biotic calcification relies on calcium ions (Ca2+) and usually on bicarbonate ions (HCO3−) as CaCO3 substrates and can be inhibited by high proton (H+) concentrations. The seawater concentration of carbonate ions (CO32−) and the CO32−-dependent CaCO3 saturation state (ΩCaCO3) seem to be irrelevant in this production process. Nevertheless, calcification rates and the success of calcifying organisms in the oceans often correlate surprisingly well with these two carbonate system parameters. This study addresses this dilemma through the rearrangement of carbonate system equations which revealed an important proportionality between [CO32−] or ΩCaCO3and the ratio of [HCO3−] to [H+]. Due to this proportionality, calcification rates will always correlate as well with [HCO3−] / [H+] as they do with [CO32−] or ΩCaCO3 when temperature, salinity, and pressure are constant. Hence, [CO32−] and ΩCaCO3 may simply be very good proxies for the control by [HCO3−] / [H+], where [HCO3−] serves as the inorganic carbon substrate and [H+] functions as a calcification inhibitor. If the "substrate–inhibitor ratio" (i.e., [HCO3−] / [H+]) rather than [CO32−] or ΩCaCO3 controls biotic CaCO3 formation, then some of the most common paradigms in ocean acidification research need to be reviewed. For example, the absence of a latitudinal gradient in [HCO3−] / [H+] in contrast to [CO32−] and ΩCaCO3 could modify the common assumption that high latitudes are affected most severely by ocean acidification.

Wettability Alteration in Limestone and Dolomite With Brines and CO2

Wettability test is one of the most used tools for evaluating rock/fluid interaction in oils reservoir. In the present paper two carbonate outcrop rocks are evaluated for wettability alterations when subjected to brine injections of varying salinities and content of dissolved CO2. The evaluation included a qualitative appraisal via spontaneous imbibition tests and a quantitative assessment by the Amott-Harvey procedure. Rocks refer to limestone and dolomite samples with petro-physical properties similar to the Brazilian pre-salt reservoirs. Testing fluids are a medium gravity crude oil, seawater concentration brine, formation equivalent brine and the carbonated version of these brines. Results show additional oil recovery directly associated with wettability alteration provoked by brine concentration changes. Increments in recovery were observed independently if the brine concentration decreased or increased in the replacement process. For dolomites and limestone wettability changed in the direction of turning the rock from oil-wet to neutral wet. Tests carried out with equivalent carbonated brines show that similar alteration in the wetting properties also occur. Alterations were as well independent of the increase or decrease of the salt concentration in the brine changed. However, CO2 or its derived ions dissolved in the brines seem to inhibit the mechanism of wettability change when rocks are subject to changes in brine salt concentrations.

Reconsidering the role of carbonate ion concentration in calcification by marine organisms

Marine organisms precipitate 0.5–2.0 Gt of carbon as calcium carbonate (CaCO3) every year with a profound impact on global biogeochemical element cycles. Biotic calcification relies on calcium ions (Ca2+) and generally on bicarbonate ions (HCO3−) as CaCO3 substrates and can be inhibited by high proton (H+) concentrations. The seawater concentration of carbonate ions (CO32−) and the CO32−-dependent CaCO3 saturation state (ΩCaCO3) seem to be irrelevant in this production process. Nevertheless, calcification rates and the success of calcifying organisms in the oceans often correlate surprisingly well with these two carbonate system parameters. This study addresses this dilemma through rearrangement of carbonate system equations which revealed an important proportionality between [CO32−] or ΩCaCO3 and the ratio of [HCO3−] to [H+]. Due to this proportionality, calcification rates will always correlate equally well with [HCO3−]/[H+] as with [CO32−] or ΩCaCO3 when temperature, salinity, and pressure are constant. Hence, [CO32−] and ΩCaCO3 may simply be very good proxies for the control by [HCO3−]/[H+] where [HCO3−] would be the inorganic carbon substrate and [H+] would function as calcification inhibitor. If the "substrate-inhibitor ratio" (i.e. [HCO3−]/[H+]) rather than [CO32−] or ΩCaCO3 controls CaCO3 formation then some of the most common paradigms in ocean acidification research need to be reviewed. For example, the absence of a latitudinal gradient in [HCO3−]/[H+] in contrast to [CO32−] and ΩCaCO3 could modify the common assumption that high latitudes are affected most severely by ocean acidification.

Determine the Consumption of Fluorescent Scale Inhibitor SC260 Using Dibenzofuran-2-Sulfonic Acid Hydrate

Fluorescence spectra and signal stability of the fluorescent scale inhibitor SC260 and dibenzofuran-2-sulfonic acid hydrate in deionized water and in seawater concentration experiment were described. There was no impact on respective excitation and emission peaks of each other and the change of fluorescence intensity was no more than 5%. The relationship between fluorescence intensity and concentration of SC260 and BFN were linear. Because the fluorescence signals of SC260 and BFN were stable in seawater concentration experiment, the consumption of fluorescent inhibitor SC260 in seawater was studied.