Exchangeable Cation Composition Research Articles

Some chemical parameter relations in a population of German forest soils

Existing pools of soil chemical data may be used in the investigation of conceptual models about soil chemical processes. Data from more than 2000 soil samples from German forests were pooled and interpreted to establish parameter relations that are related to soil acidification. A saturated water extract and an extraction of exchangeable cations by ammonium chloride were used. Activities in the soil solution were calculated by a complexation model. The change in exchangeable cation composition with decreasing pH is shown, the main process being the displacement of Ca by Al. Cation exchange selectivity coefficients do vary less than 1 log unit between most cases. For some cation pairs and regions in Ca-saturation the coefficients are much more constant. Ion activity products for gibbsite, alunite, and jurbanite indicate that one or more of these precipitates may contribute to solution composition control between pH 3.5 and 5 at least.

Aggregate slaking and dispersion class, bulk properties of soil

Diffuse double-layer swelling of soils with aggregates in dispersion classes 1 and 2 can cause piping failures in earthen structures. For saturated aggregates in classes 3 or 4 from clay soils, the matric suction at which shrinkage starts depends on the size of the clay particles. As a result, cracks form sooner in highly swelling soils and aggregates around the cracks do not slake. This makes the soils easy to irrigate. Non-cracking clay subsoils may be difficult to drain because porosity created by ripping is lost by slaking. Very few Na-ions are needed on exchange sites to move class 3a aggregates into class 2. The number required is increased in neutral to acid soils because of cationic forms of aluminium on exchange sites. Aggregates from the tops of columns of a natrustalf were found to be in class 3, the bases in class 2. It is deduced that it is unlikely that the tops move seasonally. The results axe also used to illustrate the difficulty of defining natric horizons by exchangeable cation composition. The main challenge to improving soil structure and crop yield is where surface soils with aggregates in class 3a overlie clay subsoils with aggregates in classes 1 or 2.

スメクタイトを含む軟岩の劣化防止に関する研究

Soft rocks, especially smectite bearing tuffs and mud stones, sometimes cause the serious troubles such as ground pressure, landslide and crumbling of cut slope.To study preventive methods of the surface deterioration for smectite bearing soft rocks, experiments in laboratory were carried out. In these experiments, four kinds of preventive methods such as a soak method, a wet curing by covering with mat, an ion exchange method and a seal method have been attemped to six samples of soft rocks. In result, it has become clear to be closely related with exchangeable cation composition of smectite and effect of preventive method. All of the methods are effective to Ca-type smectite bearing soft rocks. On the other hand, only the seal method is applicable to Na-type one.Field test by the seal method was carried out in tunnel consisted of Na-type smectite bearing tuff. The preventive affect using polymer cement or high molecular resin has been ascertained to extend from three to six months. This result indicates that the prevention of deterioration by the seal method is applicable in the case of short term to foundation rock at dam and cut slope etc.

Phosphate sorption by soil in relation to exchangeable cationcComposition and pH

The influence of exchangeable cation composition on the sorption of phosphate (P) was studied using samples of an acid, clay loam subsoil which had been saturated with Ca2+ or Na+. The Na-soil always sorbed less P than the Ca-soil but the difference between the two systems was strongly pH-dependent. Sorption by the Na-soil declined rapidly as pH increased, to the extent that at pH 7.6 it was only 22% of that sorbed at pH 4.1. Although sorption by the Casoil also decreased with an initial pH increase, it increased again once pH exceeded approximately 5. The difference in sorption between the Ca, and Na-soils was only about 20% at low pH but it increased considerably above pH 5. At the highest comparable pH value (6.7), the Ca-soil sorbed almost 4 times as much P as the Na-soil. The observed cation-induced differences in P sorption by this soil cannot be explained simply by the formation of insoluble Ca-P compounds or surface Ca-P complexes in the Ca-saturated samples. A more plausible interpretation appears to derive from the effect of cation saturation on electrostatic potential. A model of P sorption which incorporates electrostatic potential effects indicated that the pH-dependence of the cation effect is likely to be due to a more rapid decrease in potential in the Na- than in the Casoil as pH is increased. However, in the absence of any measured values for potential, it is not possible to apply this model in a general way.

Changes in soil solution composition and pH in urine‐affected areas of pasture

SUMMARYChanges in soil solution composition and concentrations of exchangeable cations and mineral N in undisturbed cores of pasture soil were investigated in two experiments following applications of sheep urine to the cores. The major cations applied in the urine were K+ and Na+, and the major anions were HCO3− and Cl−. Addition of urine increased concentrations of exchangeable K+, Na+ and NH4+ and measured ionic strength of the soil solution throughout the surface 15 cm of soil, demonstrating that the urine moved through the core by macropore flow immediately following addition. Immediately following urine application the ionic strength in soil solution in the surface 2.5 cm of soil increased from 4–6 MM to 24–41 mM.Hydrolysis of urine‐urea was extremely rapid, and in less than 1 d high concentrations of NH4+‐N (i.e. 270–370 mg N kg−1) had accumulated in the surface 0–2.5 cm of the urine patch, and soil pH had risen by over one unit. Nitrification then proceeded and, after approximately 15 d, NO3− became the dominant form of mineral N present. During nitrification, soil pH declined and the ionic strength of the soil solution increased substantially with NO3− becoming the dominant anion present in solution. There were concomitant increases in the concentrations of Ca2+ and, to a lesser extent, Mg2+ in the soil solution as NO3− concentrations increased. After approximately 30 d, concentrations of exchangeable NO3− had risen to 250–330 mg N kg−1, soil solution NO3− concentrations had increased to about 80 mmol, dm−3, and ionic strength in the soil solution had increased to 130–140 mM. These results demonstrate the dominating effect of N transformations in causing large fluctuations in the pH, ionic composition and ionic strength of the soil solution in the urine patch. It was concluded that nutrient availability in the patch was affected directly by nutrient addition in urine, and also probably indirectly through the fluctuations in soil solution pH and ionic strength that occur.

Incubation Studies of the Fate of Organic Nitrogen in Soils Amended with Activated Sludge

AbstractMineralization of sludge organic N and the effect of transformations in nitrogen compounds on soil solution composition were studied in incubated soil‐sludge mixtures. Four soils were incubated with sludge at four mixing ratios (1–15% sludge) for 90 d at 35 °C under continuous flow of water saturated air. Soil‐water contents were maintained at 60% of the 0.033 MPa tension. The extent of ammonification was 41 to 61% of the amount of sludge organic N added. Both soil properties and sludge content affected the extent of ammonification. The soils' effect was relatively small. Only the clayey and sandy soils differed significantly (54.5 vs. 47.9%). The effect of sludge loading was more pronounced. At 1 and 5% sludge contents the ammonification was significantly greater (53 and 56% ammonified) than at 10% (48%) or 15% (43%) sludge contents. The reduced ammonification at the higher sludge and clay content might be related to the more intense nitrification‐induced salinization observed in these treatments. Sludge content and soil properties affected the initial rates of both ammonification and ammonia volatilization. Ammonification was linearly related to sludge and clay content, whereas the volatilization rate was similarly related to sludge content but inversely related to cation exchange capacity (CEC). Estimated half‐lifes for the added organic N is 2 to 8.5 d. Up to 87% of the ammonified sludge N, was lost as gaseous species, mostly as ammonia. Sludge application to soils and subsequent transformations could greatly influence soil solution chemistry and composition of exchangeable cations, depending mainly on its content.

Colloid-chemical and mineralogical differences of smectites taken from argillized layers, both from within and outside the slip surfaces in the Kamenose landslide

Colloid-chemical activity of three smectitic clays taken both from within and outside the slip surfaces in the Kamenose landslide was assessed in terms of the relative viscosity increment (RVI) and sediment volume (SV) of the clay sol saturated with sodium and calcium. The RVI and SV are fundamentally determined by the average thickness of smectite particles in the sol that swell osmotically after Na-saturation and form larger packets after Ca-saturation. Among the three smectites, the smectite taken from the argillized layer where no slip surface developed showed the lowest degree of osmotic swelling and packet formation. This smectite was found to be composed of montmorillonite and beidellite-nontronite in a roughly equal amount, whereas the smectites from the slip surfaces were mostly of montmorillonite-type. The residual strengths of the Kamenose soils are considerably varied at the effective normal stress below 100 kPa. This variation of the residual strengths was not well explained by the differences in the <2-μm clay fraction and smectite contents and in the exchangeable cation composition. However, the colloid-chemical differences are inversely correlated with the residual strengths of those smectite-dominated soils. The high colloid-chemical activity of smectite possibly leads to lowering of the residual strength, through promoting reorientation of particles on the shear surface.

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

AbstractYucca Mountain is being studied as a potential site in southern Nevada for an underground, high-level nuclear waste repository. A major consideration for selecting this site is the presence of abundant zeolites in Miocene ash-flow tuffs underlying the region. Beneath Yucca Mountain four diagenetic mineral zones have been recognized that become progressively less hydrous with depth.Zone I, the shallowest zone, is 375–584 m thick in the central part of Yucca Mountain, but 170 m thick to the north. Zone I contains vitric tuffs that consist of unaltered volcanic glass and minor smectite, opal, heulandite, and Ca-rich clinoptilolite. Zone II thins south to north from 700 to 480 m and is characterized by complete replacement of volcanic glass by clinoptilolite with and without mordenite, and by lesser amounts of opal, K-feldspar, quartz, and smectite. Zone III thins south to north from 400 to 98 m thick and consists of analcime, K-feldspar, quartz, and minor calcite and smectite. Heulandite occurs locally at the top of zone III in the eastern part of Yucca Mountain. Zone IV occurs in the deepest structural levels of the volcanic pile and is characterized by albite, K-feldspar, quartz, and minor calcite and smectite.Clinoptilolite and heulandites in zone I have uniform Ca-rich compositions (60–90 mole % Ca) and Si:Al ratios that are mainly between 4.0 and 4.6. In contrast, clinoptilolites deeper in the volcanic sequence have highly variable compositions that vary vertically and laterally. Deeper clinoptilolites in the eastern part of Yucca Mountain are calcic-potassic and tend to become more calcium-rich with depth. Clinoptilolites at equivalent stratigraphic levels on the western side of Yucca Mountain have sodic-potassic compositions and tend to become more sodium-rich with depth. Despite their differences in exchangeable cation compositions these two deeper compositional suites have similar Si:Al ratios, generally between 4.4 and 5.0. Analcimes have nearly pure end-member compositions, typical of these minerals formed by diagenetic alteration of siliceous volcanic glass; however, K-feldspars are Si-rich compared to the ideal feldspar formula.Bulk-rock contents of Si, Na, K, Ca, and Mg of zeolitic tuffs generally differ significantly from stratigraphically equivalent vitric tuffs, suggesting that zeolite diagenesis took place in an open chemical system. Both the whole rock and the clinoptilolite are relatively rich in Ca and Mg in the eastern part of Yucca Mountain and rich in Na in the western part. The Ca- and Mg-rich compositions of the zeolitized tuffs in the eastern part of Yucca Mountain may be due to cation exchange by the sorptive minerals with ground water partially derived from underlying Paleozoic carbonate aquifers.Diagenetic zones become thinner and occur at stratigraphically higher levels from south to north across Yucca Mountain, probably due to a higher geothermal gradient in the northern part of the area. The diagenetic zones were established when the geothermal gradient was greater than it is today, probably during the thermal event associated with the development of the Timber Mountain-Oasis Valley caldera complex north of Yucca Mountain.

Experimental Evaluation of Two Operational Standard States for Montmorillonite in Metastable Hydrolysis Reactions

AbstractTwo conventions have been used to represent smectite formulas in mineral hydrolysis reactions: exchangeable cations are either included in (monophase structure) or excluded from (charged structure) the Standard State phase designation. Replicate mixtures of K‐saturated Belle Fourche montmorillonite, kaolinite, goethite, and magnesite were taken through a series of consecutive equilibrations with 0.01, 0.1 or 1.0 M KCl solutions using low solution/solid ratios. Apparent chemical equilibrium with respect to magnesite was used as an indication of system‐wide meta‐equilibrium. Following equilibration, the aqueous phases were recovered by immiscible displacement. Total soluble K, Mg, Si, pH, and ambient CO2 were measured. The solutions were chemically speciated using an ionassociation computer model. Hydrolysis reactions were developed based on the two smectite standard state phase designations. Reaction equilibrium constants and Gibbs free energies of formation (ΔG°) for montmorillonite were calculated. In the case of the monophase structure model, these parameters were functions of exchangeable cation composition. The mean ΔG° (montmorillonite) values for the charged structure and monophase structure models differed in absolute value but were equally precise. These results suggested that a characteristic metastable equilibrium was obtained in the experimental system. Justification for the selection of one convention over the other must be based on criteria other than precision.

Effects of Exchangeable Cation Composition on the Thermal Expansion/Contraction of Clinoptilolite

AbstractTo understand and predict the effects of a thermal pulse induced by a radioactive waste repository on clinoptilolite-bearing rocks, the lattice parameters of 6 natural and 3 cation-exchanged (Ca, K, Na) clinoptilolites were studied as a function of temperature. The samples were examined at room temperature, under vacuum, and at 50°C increments to 300°C using a high-temperature X-ray powder diffractometer. The unit cell of all samples decreased in volume between 20° and 300°C Na-saturated clinoptilolite underwent the greatest volume decrease (8.4%) and K-saturated clinoptilolite the smallest (1.6%), of the clinoptilolites studied. The volume decrease for the Ca-saturated clinoptilolite was 3.6%. The highest percentage decrease for each sample was along the b axis, generally 80–90% of the total volume decrease. The change in the a axis was the smallest and was usually &lt;5%, although 26.5% of the contraction of the Na-exchanged clinoptilolite was along a. The bulk of the volume contraction of many samples occurred on evacuation at room temperature, demonstrating that the observed changes were due to water loss and not to temperature-induced structural changes. Low-angle scattering was significantly reduced upon evacuation for every sample, and the 110 reflection of clinoptilolite at 7.45°2θ became obvious, whereas it was not in the untreated samples.These data show that the effects of heating on the unit-cell volume of clinoptilolite depend strongly on the exchangeable cation content. Significant reductions in the unit-cell volumes of natural, mixed Na-K-Ca clinoptilolites could take place in rocks in a repository environment, particularly if the clinoptilolites occurred in unsaturated, dehydrated rock. The unit-cell volumes of clinoptilolites in partially saturated rocks at temperatures below 100°C, however, should not decrease significantly.

Aqueous Geochemistry and the Exchangeable Cation Composition of Glauconite in the Aquia Aquifer, Maryland

ABSTRACTThe cation composition of water in the Aquia aquifer of southern Maryland changes systematically in the direction of ground‐water flow. In the upgradient parts of the aquifer, calcium is the dominant cation in solution. Between 10 and 20 miles downgradient, calcium and magnesium are dominant. Between 20 and 35 miles downgradient, magnesium and potassium are dominant, and, beyond 40 miles downgradient, sodium is the most abundant cation in solution. The exchangeable cation composition of glauconite in the Aquia aquifer changes systematically in the direction of flow in a manner similar to the changes in water chemistry. These observations are interpreted as evidence that cation exchange reactions are processes that simultaneously alter water composition and glauconite composition along the flowpath.Exchange parameters K’and n for glauconite in the Aquia aquifer were determined for the reactions: image image image The exchange parameters for each reaction were tested by an indirect method. Molar ratios of exchangeable cations or glauconite were calculated from water chemistry data using the derived k’and n values. In each case, the trend of calculated molar ratios compared favorably with measured molar ratios. The calculated exchange parameters demonstrate that the exchange process is not linear for the Ca2+ ‐Na+ and Mg2+ ‐Na+ ion pairs.The sum of exchangeable cations on glauconite samples is significantly lower in the outcrop area than downgradient. Corresponding to this, the concentration of dissolved silica and dissolved oxygen in Aquia water is high near the outcrop area and decreases downgradient. This pattern suggests that incongruent dissolution of glauconite is an additional process that modifies glauconite composition near the outcrop area but is less important downgradient.

THE QUANTITY AND QUALITY OF NUTRIENT CATIONS IN SOME MICHIGAN SPODOSOLS

Using total and exchangeable cation composition and mineralogy, we evaluated the quantity and character of nutrient cations in some Michigan forest Spodosols. Quantities of bound calcium and magnesium in the A horizons of these soils were found to be about 7 to 20 times the exchangeable amounts, while bound potassium was present at levels about 300 times the exchangeable quantities. The total elemental analyses were consistent with mineralogical evaluations of the 0.1 to 1-mm fractions of the A horizons of these coarse-textured soils, which showed orthoclase feldspar as the most abundant nutrient-bearing mineral. Quantities of coarse fragments (>2 mm) were variable but generally small, and these fragments were largely composed of minerals that appeared resistant to weathering and nutrient release. These data and other available information indicate that although significant bound reserves are evident, the exchangeable nutrient pools probably provide most of the cations necessary for tree growth on these and similar soils.

Influence of Exchangeable Cation Composition on the Size and Shape of Montmorillonite Particles in Dilute Suspension

AbstractViscosity and light-transmission measurements of dilute suspensions of montmorillonites having different exchangeable cations were used to calculate relative particle sizes as a function of cation composition, where particle size is expressed as the number of clay plates per tactoid relative to the number of plates per tactoid for Li-montmorillonite, after exchange of Li, Na, K, Cs, and Mg by Ca. Tactoid sizes increased in the order Li &lt; Na &lt; K &lt; Mg &lt; Ca, with the number of plates per tactoid relative to Li-montmorillonite varying from 1.5 for Na- to 6.1 for Ca-montmorillonite. The results for tactoid sizes derived from light transmission and those derived from viscosity data are in reasonable agreement with each other and with literature data for similar systems. Upon exchange of Ca-counterions for Li-, Na-, or K-coun-terions, a sharp initial decrease in tactoid size was observed over approximately the first 30% of cation exchange. Upon further exchange, tactoid sizes changed only slightly, but when Ca was exchanged for Cs or Mg, a much more gradual decrease in particle size was observed.

The Correlation between Exchangeable Cation Compositions of Smectites and the Quality of Ambient Seepage Water from the Seikan Undersea Tunnel (2)

The Correlation between Exchangeable Cation Compositions of Smectites and the Quality of Ambient Seepage Water from the Seikan Undersea Tunnel (2)

Sodium/Calcium Exchange in Montmorillonite and Illite Suspensions

AbstractThe effect of salt concentration and exchanger composition on Na/Ca exchange in montmorillonite and illite suspensions (0.02 to 0.08 g clay/g water) was studied, where the equivalent fraction of exchangeable Ca, ECa, ranged from 0.6 to 1. A theoretical evaluation based on double‐layer theory for montmorillonite indicates that the formation of tactoids and internal surfaces at the Ca3+ end of the exchange isotherm can cause the Vanselow selectivity coefficient, KV, to depend on exchangeable cation composition and total electrolyte concentration. Whereas for montmorillonite, KV increased with ECa (0.6 &lt; ECa &lt; 1), as predicted for internal surfaces, the reverse was true for illite, where external surfaces predominate. Likewise, for a given Na adsorption ratio, dilution of the equilibrium solution for illite (0.6 &lt; ECa &lt; 1) and for montmorillonite (ECa ≃ 0.6) decreased KV as predicted for external surfaces.The average Gapon selectivity coefficient for the montmorillonite (0.011) and illite clays (0.023) with ECa ≤ 0.8, suggests that the value for soils, (0.0148) reflects their mixed mineralogy.

Cation-exchange characteristics of Amazon River suspended sediment and its reaction with seawater

The cation-exchange characteristics of Amazon River suspended sediment have been studied in order to determine the contribution of exchangeable cations to the geochemical fluxes from the river. Sediment samples were obtained throughout most of the Amazon Basin. The range of exchangeable cation compositions is very narrow in the river and in seawater as well. In river water, the exchangeable cation complement (equivalent basis, exclusive of H +) is 80% Ca 2+, 17% Mg 2+, 3% Na + plus K +. In seawater Na + and Mg 2+ are about equal (38%) while Ca 2+ ~ 15% and K + ~ 9%. On reaction with seawater, river suspended sediment took up an amount of Na + equal to nearly one-third of the dissolved river load, as well as amounts corresponding to 15–20% of the dissolved fluvial K + and Mg 2+. These estimates reflect an unusually high suspended-sediment:dissolved-solids ratio of 6.4 at the time of sampling. At a more representative world average ratio of four, the uptake of Na + would be 20% of the dissolved fluvial load, and that for K + and Mg 2+ about 10%. Over the annual cycle of the Amazon, it is estimated that ion exchange has a still smaller effect, as a consequence of the low average suspended-solids:dissolved-solids ratio of 1.7. Variations in the ratio X Ca X Mg , the equivalent fraction of exchangeable Ca 2+ and Mg 2+, throughout the river, can be described by a single isotherm. This same isotherm accurately describes the distribution of exchangeable Ca 2+ and Mg 2+ on sediment equilibrated with seawater, despite that a high proportion of exchange sites is occupied by Na + and K +.

On the question of the formation of engineering geological properties in saline clays

A number of properties of basal clays is shown to be retained by the weathering products that have developed on them in the Stavropol region. Tertiary eluvial and Quaternary deposits formed in the arid zone have thus inherited from the basal Maikop clays a high degree of dispersion, the composition of exchangeable cations and the mineral composition of the clay fraction.

Composition of Exchangeable Cations in Submerged Paddy Soil and Acidifying Process Associated with Exposure to Air

Composition of Exchangeable Cations in Submerged Paddy Soil and Acidifying Process Associated with Exposure to Air

Calcium‐Magnesium‐Potassium Equilibria in Some California Soils

AbstractIon exchange equilibria in several soils were studied to seek equilibrium equations that could be used in chromatographic models dealing with movement and distribution of fertilizer potassium in soil profiles. Soil samples were equilibrated with mixtures of CaCl2, MgCl2, and KCl solutions and then extracted with NH4OAc to determine exchangeable cation compositions at equilibrium. It was necessary to correct the exchangeable cation concentrations by subtracting the cations extracted from nonexchangeable sources by NH4OAc. Vanselow's, Davis', Gapon's, or Kerr's equations would not describe the equilibria. Empirical equations of the form: urn:x-wiley:03615995:saj2sssaj197303615995003700060019x:equation:saj2sssaj197303615995003700060019x-math-0001 and urn:x-wiley:03615995:saj2sssaj197303615995003700060019x:equation:saj2sssaj197303615995003700060019x-math-0002 did describe the equilibria with all three cations present, and over a wide range of composition, for all soils studied. In these equations Ai is the solution ion activity, k is the distribution coefficient, Ei is the equivalent fraction of the exchangeable cation, and Di and Pi are arbitrary constants that are characteristic for each soil and each cation.

Effect of Liming on the Exchangeable Cation Composition and Availability of Six Costa Rican Soils

Effect of Liming on the Exchangeable Cation Composition and Availability of Six Costa Rican Soils