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1.
The pH of various saline solutions — waters from the Dead Sea, Red Sea, the Mediterranean and salt springs from the Tiberias area — and of their artificial equivalents was found to increase on dilution with distilled water. The effect is confined to waters containing more than 1.2–1.5% dissolved solids, and is roughly proportional to the original salinity of the solution. The effect is not found in solutions devoid of HCO3− salts. It is concluded that in strong brines, dissociation of bicarbonate salts is depressed; on dilution dissociation increases, hydroxide ions are formed and the pH increases. It follows that in evaporate sediments carbonate minerals might be stable at pH-values as low as 5.5. 相似文献
2.
WILLIAM M. LAST 《Sedimentology》1989,36(1):109-123
Ceylon Lake, a small salt playa located in southern Saskatchewan, is typical of many shallow ephemeral lacustrine basins found in the northern Great Plains of western Canada. The present-day brine, dominated by magnesium, sodium, and sulphate ions, shows wide variation in composition and concentration on both a temporal and a spatial basis. The modern sediments overall exhibit relatively simple facies relationships. An outer ring of coarse grained shoreline and colluvial clastics surrounds mixed fine grained clastics and salts and, in the centre of the basin, salt pan evaporites composed mainly of mirabilite, thenardite, and bloedite. Coring of the late Pleistocene and Holocene sedimentary fill shows that the lake has evolved from a relatively dilute, deep water, clastic dominated basin through a shallower, brackish water, carbonate-clastic phase, and finally into the present salt dominated playa. The thick sequence of evaporites preserved in the basin suggests evolution of the brine from a Na-rich solution to a mixed Mg-Na system. The most important post-depositional processes affecting Ceylon Lake sediments are mud diapirism and salt karsting. 相似文献
3.
柴达木盆地察汗斯拉图矿区蕴藏着极为丰富的钾盐类矿产资源。钾盐察ZK02孔设计1500 m,钻遇地层为新近系盐湖相沉积地层。在钻进过程中易产生缩径、造浆、掉块、坍塌等现象,钻遇盐岩层或含钙、镁离子盐水入侵时,钻井液性能易发生变化,给钻探施工带了困难。根据盐矿钻孔地质条件和技术要求,设计3级口径的钻孔结构。在施工中,针对巨厚层砂砾碎屑岩的特点,选择加重卤水钻井液护壁,起到了安全护壁效果,并采用研制的卤水钻井液混合搅拌器,提高了配浆速度,保证了钻井液性能和质量。卤水钻井液和卤水钻井液混合搅拌器的使用,为柴达木盆地深层卤水钾盐矿区的钻探施工探索出了快速配制钻井液提供了借鉴。 相似文献
4.
5.
The Okavango Delta of semi-arid northern Botswana is a large alluvial fan (22,000 km2) covered by permanent and seasonal swamps from which 96% of the annual discharge is lost by evapotranspiration. Many small islands (1ha) within the permanent swamps are the sites of accumulation of sodium carbonate salts and many contain saline pans. The associated alkaline soils are toxic to vegetation. An understanding of the processes involved in alkalinization could be of potential benefit to long-term conservation planning in this unique ecosystem. The relation between soil chemistry and mineralogy, and swamp and groundwater chemistry were investigated on an island in the swamps. The study revealed that the water table beneath the island is depressed and swamp water enters the groundwater regime of the island from the margins and below, and flows toward the centre. The water becomes progressively more saline, initially owing to transpiration by trees and ultimately by evaporation in the central parts of the island. As a result of increasing salinity, amorphous SiO2 and magnesium calcite precipitate in the soils beneath the marginal zone of the island, raising the land surface, while the more soluble alkali carbonates are concentrated in the centre of the island as surface crusts and brine ponds. Leaching of these salts into the soil during the rainy season and gravity-driven flow of saline brines in the dry season causes the downward movement of Al and Fe in the central zone of the island. K-feldspar and possibly amorphous allophane develop in the deeper soils under the central zone of the island. 相似文献
6.
Philippe Leroy Arnault Lassin Mohamed Azaroual Laurent André 《Geochimica et cosmochimica acta》2010,74(19):5427-776
The surface tension of the air/water interface is a phenomenon of particular interest in the water-unsaturated zone of porous media because it influences the contact angle and consequently the capillary water volume. A mechanistic model based on the modified Poisson-Boltzmann equation and the Pitzer theory is described and used to predict, under isothermal and isobaric conditions, the surface tension of 1:1 electrolytes at high salinity. These theories enable the determination of the electrical potential at the air/water interface and the activity coefficient of the ionic species in the bulk pore water, respectively. Hydration free energies of the structure-making and structure-breaking ions that influence the surface tension at high salinity are taken into account. Structure-making ions flee the air/water surface because they can better organize the water dipoles in bulk water than at the interface. Structure-breaking ions are positively adsorbed at the air/water interface because the bulk water can better organize their hydrogen-bonding network without these ions. The resulting surface tension increases and decreases, respectively, compared to the surface tension of pure water. The predictions are in good agreement with the surface tension data of 1:1 electrolytes (NaCl, KCl, HCl, NaNO3, KNO3, HNO3 aqueous solutions) and the optimized parameters depend on the effective electrostatic diameters of cations and on the hydration free energies of the ions at the interface. 相似文献
7.
The results presented in this paper shows that high concentrations of sodium hydroxide causes abnormal changes on the volume
change behaviour of illite–smectite (interstratified mineral) soil due to mineralogical changes. The higher swell that occurs
is shown in the form of a new second stage of swelling. Increase in negative charges on soil particles and mineralogical changes
after interaction with soil, respectively, are responsible for the swelling in these two stages. However, potassium hydroxide
does not induce such high swelling in soils. This is mainly due to the fixation of potassium ions. Hence an attempt has been
made to control the swelling induced by sodium hydroxide by making used of potassium chloride as an additive. Potassium fixation
which is not substantial at neutral pH is favoured at higher pH Addition of potassium chloride salt solution (as 2 and 5%
solution) can reduce only the first stage of swelling by linking the unit layers of mineral by reducing development diffuse
double layer near clay surface. Potassium chloride is unable to prevent the formation of mineralogical alteration due to soil
alkali interaction and hence the swelling associated with mineralogical changes. X-ray diffraction studies have revealed that
mineralogical changes leading to formation of zeolite by soil alkali interaction is not inhibited by potassium ions. Morphological
changes studied by scanning electron microscope corroborate these observations. Also the compressibility of soil which is
increased in alkali solution is reduced in the presence of potassium salts. This reduction is due to reduction in the first
stage of swelling. 相似文献
8.
The distribution of crystalline salt minerals in deposits in the McMurdo region of Antarctica has been examined to study the origin of these salts. Sulphate, chloride, sodium and calcium salts are most frequently encountered. Salts containing chloride and sodium ions become less common away from the coast. Sulphate salts are more regularly distributed but tend to be related isotopically to sea water sulphate. Salts containing magnesium ion tend to exist mainly on substrates composed of basic igneous rocks, whereas calcium and carbonate salts are present on all rock types in the region.These distributions show that salts of marine origin are regionally and quantitatively most important but that chemical weathering of mafic materials in rocks and soils is also significant. However, biological, volcanic and hydrothermal processes are or have been active contributing to salts in local areas, that include penguin rookeries and eastern Taylor Valley, the summit area of Erebus Volcano, and subsurface rocks, respectively. 相似文献
9.
Robert O Fournier 《Geochimica et cosmochimica acta》1976,40(12):1553-1561
In order to determine whether gas (steam) containing a small amount of dissolved alkali chloride is effective in promoting base exchange of Na+ and K+ among alkali feldspars and coexisting brine or brine plus solid salt, experiments were carried out at 400–700°C and steam densities ranging down to less than 0.05. For bulk compositions rich in potassium, the low pressure results are close to previous high-pressure results in composition of the fluid and coexisting solid phase. However, when the bulk composition is more sodic, alkali feldspars are relatively richer in potassium at low pressure than at high pressure. This behaviour corresponds to enrichment of potassium in the gas phase relative to coexisting brine and precipitation of solid NaCl when the brine plus gas composition becomes moderately sodic.
The gas phase is very effective in promoting base exchange between coexisting alkali feldspars at high temperature and low water pressure. This suggests that those igneous rocks which contain coexisting alkali feldspars out of chemical equilibrium either remained very dry during the high-temperature part of their cooling history or that the pore fluid was a gas containing very little potassium relative to sodium. 相似文献
10.
The maximum flotation response for three naturally occurring calcium minerals, apatite, calcite and fluorite with sodium oleate collector correlated directly with the minimum interfacial tension of the air/solution interface. For fluorite and apatite the minimum surface tension occurred about the mid-pH region and was attributed to the formation of pre-micellar associated species in solution. In the case of calcite the minimum was observed at high pH since the presence of high concentrations of calcium ions in solution appeared to reduce the concentration of amphililic species in the low and mid-pH regions.Microelectrophoresis data demonstrated that the three minerals acquired a negative charge in sodium oleate solution, resulting from adsorption of oleate species on the mineral surfaces.The flotation behaviour of the systems were shown to be related to the species distribution diagrams suggesting that the role of the acid soap dimer, soap dimer, molecular and lattice species could make a significant contribution to the character and composition of the interfacial films.High flotation response was explained by strong adhesion between the hydrophobic particle and bubble. It was suggested that the reduction in surface tension may not be the major factor contributing to the flotation efficiency but indicated the presence of associated surfactant species in solution which could also synergistically adsorb at the solid/liquid interface, increasing the hydrophobic character of the mineral surface. This would maximize the magnitude of the contact angle and hence the strength of the adhesion between particle and bubble. This adsorption behaviour is not in general agreement with conventionally non-hydrolyzable collector theory which is usually based on electrostatic models. 相似文献