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1.
To explain why soils rich in variable charge materials often lack 1 M KCI-extractable Al ions, I proposed a mechanism, an “induced hydrolysis” of exchangeable Al ions in the presence of variable charge materials at high salt concentrations. I extracted exchangeable Al from mixtures of a montmorillonite saturated with Al and a synthetic goethite using a 1 M KCI solution. The amount of the extractable Al (per unit weight of the montmorillonite) decreased with increasing proportion of the goethite in the mixtures. I interpreted this experimental result as supporting the proposed mechanism, i.e., H+ released in the hydrolysis of Al is adsorbed on the goethite in a concentrated KCI solution and this removal of H+ induces further hydrolysis, resulting in the polymerization or precipitation of Al as hydroxides. I calculated the amount of monomeric, therefore extractable, Al as a function of the goethite content in the 1 M KCI-montmorillonite-goethite mixtures. The calculated amounts agreed well with the experimentally determined ones in the whole range of goethite content examined. 相似文献
2.
THE SPECIFIC ADSORPTION OF DIVALENT Cd, Co, Cu, Pb, AND Zn ON GOETHITE 总被引：17，自引：0，他引：17
The specific adsorption of divalent Cd, Co, Cu, Pb, and Zn on goethite is measured as a function of pH. For each mole of heavy metal adsorbed approximately two moles of H+ ions are displaced from the interface. Using these results the heavy metal adsorption data are expressed as functions of the solution concentrations of both H+ and metal ions, and the interfacial reaction is described by the equation, 2SH+M2+= S2M+2H+. The adsorption data are consistent with an electrochemical model of the simultaneous adsorption of H+ ions and divalent metal ions on to the oxide. The intrinsic affinities of the metal ions for the oxide surface increase in the order, Cd < Co < Zn < Pb < Cu. However, besides the affinity of the metal ion for the surface, the adsorption curves are considered to be influenced by surface charge, the adsorption density of the metal ions and their size. The analysis of the data in terms of H+ and M2+ ion adsorption is considered to be complementary to the hydrolysis model for heavy metal adsorption. 相似文献
3.
The fraction of nonexchangeable ammonium (NH4+) can play an important role in N cycling of soils as a sink (fixation) or a source (release) of NH4+. Recently fixed nonexchangeable NH4+ especially seems to be a significant source for N release. The aim of our study was to determine the effect of residence time on the kinetics of nonexchangeable NH4+ release from illite and vermiculite. Calcium-saturated illite and vermiculite, containing NH4+ that was “fixed” for one and 60 d, were extracted with a H-resin for 0.25 to 384 h. Both clay minerals “fixed” significantly more NH4+ in 60 d than in 1 d, but vermiculite “fixed” more NH4+ than illite. The kinetics of nonexchangeable NH4+ release from illite and vermiculite were well described by the Elovich equation and by a heterogeneous diffusion model. In vermiculite the percentage of nonexchangeable NH4+ release decreased from 84% to 78% when the time of fixation increased from 1 to 60 d. In illite time of residence has not influenced the complete release of newly fixed NH4+. 相似文献
4.
Nutrient solutions can be considered as aqueous solutions of inorganic ions. The pH of a nutrient solution is a property that is inherent to its composition. If another pH is aimed at, this can only be reached by changing the elemental composition. The pH of an aqueous solution is determined by the initial concentration of acids and bases. In the case of nutrient solutions, this is dihydrogen phosphate (H2PO4 ‐), bicarbonate (HCO3 ‐) and/or ammonium (NH4 +). In this study, formulas are derived to calculate the pH of a nutrient solution as a function of the concentration of H2PO4 ‐, NH4 +, and/or HCO3 ‐. The pH of a nutrient solution affects the dissociation, complexation, and precipitation reactions occurring in nutrient solutions. These chemical reactions significantly impact elemental speciation and bioavailability, and therefore, have to be taken into account in hydroponic plant nutritional research. The term “speciation”; indicates the distribution of elements among their various chemical and physical forms like: free ions, soluble complexes, chelates, ion pairs, solid and gaseous phases, and different oxidation states, all of which influences their reactivity, mobility and bioavailability. A good knowledge of the chemical reactions occurring in nutrient solutions is the first prerequisite in hydroponic plant nutritional research. The pH of a nutrient solution is determined by its initial concentration of H2PO4 ‐, NH4 +, and HCO3 ‐. 相似文献
5.
The pH of a soil was altered by incubating it with either lime or acid at 60°C for 1 day. Subsamples were then mixed with fluoride solutions in order to measure the effects of pH on fluoride retention. The results were compared with those previously obtained with phosphate on the same soil. At equal concentration of total fluorine in solution, fluoride retention was greatest at about pH 5.5 and decreased at both lower and higher pH. The decrease at low pH appeared to be caused by the formation of complexes between fluoride and aluminium in solution. As a result, only a small proportion of the total fluorine in solution was present as fluoride ions. At equal concentrations of fluoride ions, fluoride retention decreased with increasing pH. It was shown that this decrease could be explained by decreases in the electrostatic potential of the variable charge materials. The decrease in potential was steeper than that required to describe phosphate retention. This is consistent with the plane of adsorption of fluoride ions being closer to the plane of adsorption of H+ and OH? ions. 相似文献
6.
《Communications in Soil Science and Plant Analysis》2012,43(11-12):2201-2214
Abstract Solubility and kinetic data indicated that concentrations of aluminum (Al) extracted with 1 M KCl are determined by the solubility of a precipitated A1(OH)3 phase in soils dominated by variable charge minerals. Kinetic studies examining the release of Al on non‐treated and KCl treated residues indicated the precipitation of an acid‐labile Al phase during the extraction procedure. The log ion activity products estimated for the KCl extracts ranged between 8.1–8.6 for the reaction Al(OH)3 + 3H+ < = > Al3++ 3H2O, which was similar to the solubility product of several Al(OH)3phases. The mechanism proposed for Al precipitation indicated that Al released by exchange with added K+ hydrolyzed and released H+ that was readily adsorbed on surfaces of variable charge minerals. The increased ionic strength of the extracting solution further increased the amount of H+adsorbed to the variable charge surface and reduced the H+ concentration in the aqueous phase. Consumption of H+ induced further hydrolysis of Al, resulting in supersaturation of the extracting solution and formation of polynuclear hydroxy Al species. It was concluded that the 1 M KCl extraction does not quantitatively extract salt exchangeable Al from variable‐charge soils. 相似文献
7.
几种氧化铁的离子吸附特性研究 总被引：3，自引：1，他引：3
氧化铁是土壤中常见的氧化物,其中较为普遍的是针铁矿和赤铁矿,在某些土壤中也含有纤铁矿和无定形氧化铁.它们通常以极小的颗粒单独存在,或以胶膜状包裹在其它矿物颗粒的外面,有较大的比表面积,易受环境的影响,因此具有较高的活性,并对许多土壤的物理化学性质产生重要的影响.某些重金属离子和某些污染物进入土壤后的动向和行为也深受土壤中氧化铁的影响. 相似文献
8.
胡敏酸对铵钾在粘土矿物上交互作用的影响 总被引：1，自引：0，他引：1
ZHANG Wen-Zhao CHEN Xiao-Qin ZHOU Jian-Min LIU Dai-Huan WANG Huo-Yan DU Chang-Wen 《土壤圈》2013,23(4):493-502
Interaction of ammonium (NH+4) and potassium (K+) is typical in field soils. However, the effects of organic matter on interaction of NH+4 and K+have not been thoroughly investigated. In this study, we examined the changes in major physicochemical properties of three clay minerals (kaolinite, illite, and montmorillonite) after humic acid (HA) coating and evaluated the influences of these changes on the interaction of NH+4 and K+on clay minerals using batch experiments. After HA coating, the cation exchange capacity (CEC) and specific surface area (SSA) of montmorillonite decreased significantly, while little decrease in CEC and SSA occurred in illite and only a slight increase in CEC was found in kaolinite. Humic acid coating significantly increased cation adsorption and preference for NH+4, and this effect was more obvious on clay minerals with a lower CEC. Results of Fourier transform infrared spectrometry analysis showed that HA coating promoted the formation of H-bonds between the adsorbed NH+4 and the organo-mineral complexes. HA coating increased cation fixation capacity on montmorillonite and kaolinite, but the opposite occurred on illite. In addition, HA coating increased the competitiveness of NH+4 on fixation sites. These results showed that HA coating affected both the nature of clay mineral surfaces and the reactions of NH+4 and K+with clay minerals, which might influence the availability of nutrient cations to plants in field soils amended with organic matter. 相似文献
9.
John O. Reuss 《Water, air, and soil pollution》1977,7(4):461-478
This paper deals with problems concerning measurements of rainfall acidity and interpretation in terms of possible effects on the soil-plant system. The theory of acidity relationships of the carbon dioxide-bicarbonate equilibria and its effect on rainfall acidity measurements is given. The relationship of a cation-anion balance model of acidity in rainfall to plant nutrient uptake processes is discussed, along with the relationship of this model to a rainfall acidity model previously proposed in the literature. These considerations lead to the conclusion that average H+ concentration calculated from pH measurements is not a satisfactory method of determining H+ loading from rainfall if the rain is not consistently acid. Calculating loading from H+ minus HCO3 ? , strong acid anions minus basic cations, or net titratable acidity is suggested. The flux of H+ ions in soil systems due to plant uptake processes and sulfur and nitrogen cycling is considered. H+ is produced by oxidation of reduced sulfur and nitrogen compounds mineralized during decomposition of organic matter. Plant uptake processes may result in production of either H+ or OH? ions. Fluxes of H+ from these processes are much greater than rainfall H+ inputs, complicating measurement and interpretation of rainfall effects. The soil acidifying potential due to the oxidation of the NH4 + rainfall is examined, with the conclusion that acidity from this source is of a similar magnitude to direct H+ inputs common in rainfall. 相似文献
10.
11.
To clarify the mechanisms of pH buffering in forest ecosystems, field observations of pH and ionic concentrations in precipitation (R), throughfall (Tf), stemflow (Sf), and leachates from organ c horizons (Lo) were conducted for three years at three stands in Tomakomai (TK) and Teshio (TS) in Hokkaido, northern Japan. Weighted mean rates of H+ input as wet deposition at TK and TS were estimated in the range from 0.3 to 1.0 and 0.4–0.6 kmolc ha?1 y?, respectively. While the net H+ flux was reduced significantly by the forest canopy, net fluxes of other ions by throughfall, especially for Na+, Cl?, and SO4 2?, were apparently greater than those by precipitation. The canopy modification of the H+ flux was more remarkable under deciduous stands than under coniferous stands, suggesting that the efficiency of conifers as the collectors of dry deposition is greater than that of deciduous ones. More than 50% of H+ flux due to throughfall was absorbed by the organic horizons and the weighted mean pH of Lo at TK and TS was in the range from 4.9 to 5.5 and 5.0–5.5, respectively. Results from field observation and field leaching experiments, showed that the major H+ sinks of the organic horizons are exchange reaction of Ca2+, Mg2+ and K+. Organic acids or organo-metallic complexes of lower pK(=5.0–5.5) played a significant role as counter anions in O horizons leachate in coniferous forests. Our results indicate the importance of biogeochemical modifications in the canopy and organic horizon in acid buffering mechanisms of forest ecosystems. 相似文献
12.
The use of bentonites as soil amendment has met with little success in reducing plant uptake of radiocaesium. However, bentonites exchanged with K+ have pronounced Cs+ binding capacity when subjected to wetting–drying cycles. Fifty‐four different bentonites were collected and characterized for cation exchange capacity and chemical composition. The radiocaesium interception potential (RIP) increased up to 160‐fold (mean 25) when the bentonites were converted to the K‐form and subjected to wetting–drying cycles. This increase in radiocaesium sorption was ascribed to a collapse of the clay sheets into an illite‐like structure, and was most pronounced in bentonites with a high layer charge. The RIP values of K‐bentonites subjected to 25 wetting–drying cycles ranged from 0.22 to 44.3 mol kg?1. The RIP yields, i.e. the RIP in soil–bentonite mixtures expressed per unit bentonite added, were even higher and ranged up to 99 mol kg?1. This upper limit is about 10‐fold higher than the RIP value of illite (～ 10 mol kg?1), the principal 137Cs sorbent in soils of temperate climates. Wetting–drying also promoted fixation of radiocaesium in soils amended with K‐bentonites. About 30% of added 137Cs could be desorbed with 1 m ammonium acetate (NH4Ac) from an unamended soil after 25 wetting–drying cycles, while only between 8 and 21% of 137Cs could be desorbed from a soil amended with bentonite and a K‐salt. These findings support the proposition that addition of K‐bentonite may be effective in reducing availability of 137Cs in soils. 相似文献
13.
Interaction between dilute (mg L?1) NaF solutions and clay suspensions (0.08 % w/v) has been examined as a function of pH (range 3 to 8), clay type (Na+- or Ca2+-kaolinite, illite, montmorillonite) and NaF concentration. No F loss from solution was detected at pH > 6.5, while enhanced uptake was found on decreasing the pH, especially in the 4 to 3 region. Removal of F from 1 to 6 × 10?4 M NaF was only slightly dependent on weight of solid, but did increase with [F?]. It is proposed that F losses are due to the formation of sparingly soluble Al species (e.g. cryolite, Na fluoro silicate), occasionally augmented with CaF2 formation (Ca2+-clays). The Al is released by proton attack on the lattice, following conversion of the suspended solids into the unstable H+-form, either through acid addition (pH < 5) or through hydrolysis of the Na+-form material. The latter process was most pronounced with the illite and montmorillonite samples. The amount of F fixed by montmorillonite was roughly double that held by the other two clays, and had a maximum value (pH 3) of ～ 4 mg g?1, using 11 mg L?1 NaF solutions. Soluble fluoro-complexes, similar in quantity to the retained F, were detected, in many of the studies. It was concluded that contact of the clay components of soils or sediments with mg L?1 levels of F in adjacent aqueous phases would result in only a minor proportion being retained. 相似文献
14.
The difference in effect on acidification and species of aluminum speciation between HNO3 and H2SO4for two contrasting types of soils in surface charge was investigated. The results show that the effect of H2SO4 on acidification of variable charge soils (Ferric Acrisol and Haplic Acrisol) of subtropical regions wasweaker than that of HNO3, due to the specific adsorption of SO4 2- and the accompanied release of OH-. For two constant charge soils, Haplic Luvisol andEutric Cambisol, the difference in effect between the two acids is small. The concentrations of total inorganic monomeric aluminum, Al3+, Al-F complexes and Al-SO4complexes in the extract from variable charge soils are alsolower in H2SO4 systems than those in HNO3 systems, whereas the reverse is true for constant charge soils, except the concentration of Al3+. For variable charge soils, Al-F complexes are the major species of inorganic monomeric aluminum at high pH butAl3+ might contribute to a largepart at low pH, while for constant charge soils Al-F complexes contribute almost exclusively to the inorganic monomeric aluminum. The presence of a large amount of SO4 2- in the extract from the constant charge soilsleads to a higher proportion of Al-SO4 complexes in totalinorganic monomeric aluminum than that from variable charge soil, although the numerical value of proportion is small. 相似文献
15.
Cesium-137 (137Cs) is strongly adsorbed on clay minerals, especially on illite. The adsorption of Cs+ on reference clay minerals, however, has not been fully investigated in relation to the presence of illite. The objective of this study was to clarify the effect of impurities (i.e., illite and vermiculite), present in reference smectite group minerals and kaolin minerals, on the retention of Cs+. The clay mineralogy of the reference minerals was characterized by X-ray diffraction (XRD). The radiocesium interception potential (RIP) was measured as an index of the Cs+ retention ability of clays. The content of illite in clay was represented by the total potassium (K) content given that illite is a major source of K in the clay fraction. The content of vermiculite in clay was represented by the Cs fixation capacity induced by Cs saturation followed by heating of samples at 110°C. Metabentonite and beidellite gave extremely high RIP values compared with other smectite group minerals, although a peak for illite (at 1.0 nm) was not observed in XRD analysis. The reference smectite and kaolin minerals showed a range of RIP values, even though their RIP values are theoretically zero. The RIP values had a significant positive correlation with the total K content of all the reference clay minerals (rs = 0.621*). This indicated that the retention ability for 137Cs depended more on the content of illite, as impurity, rather than the type of bulk mineral. Hence, the contribution of illite to the magnitude of the RIP was elucidated by the combination of measurement of total K content and XRD analysis. 相似文献
16.
Remigio Paradelo Daniel Vázquez-Nion Benita Silva Ángela González María Teresa Barral 《Compost science & utilization》2016,24(1):1-10
We evaluated the utilization of granite powder—a residue of stone cutting and polishing resulting from its preparation for construction and ornamental use—in the preparation of nursery potting mixtures, within a general objective of waste recycling and reuse. Granite powder was blended with two composts of different origins and properties: one elaborated from the organic fraction of municipal solid waste (MSW), and another from pine bark. Since all materials presented pH values over 8, which are excessive for growing most vegetal species, the use of iron sulphate to acidify them has been assessed. Three doses of iron sulphate (14, 69, and 97 g kg?1, equivalent to 0.1, 0.5, and 0.7 meq H+ g?1) were added to the granitic powder and mixtures with 25 or 75% (v/v) of each compost, which were incubated in the laboratory during 30 days. Doses of iron sulphate above 0.1 meq H+ g?1 resulted in excessive electrical conductivity (>2 dS m?1) in all the samples, and too low pH values (<5) in most of them. The productivity of granite powder/compost mixtures acidified with 0.1 meq H+ g?1 was tested in a greenhouse experiment with ryegrass, where it was observed that plant productivity increased with respect to a control commercial substrate based on peat, in particular when the MSW compost was employed. On the basis of the physicochemical properties of the mixtures and the results of the greenhouse experiment, the use of granite powder mixed with 75% of MSW compost (v/v), acidified with 14 g kg?1 of iron sulphate (0.1 meq H+ g?1) is recommended. 相似文献
17.
Christoph Schimansky 《植物养料与土壤学杂志》1991,154(3):195-198
Influence of Aluminium and Protons on Uptake and Transport of Magnesium (28Mg) by Barley Plants (Hordeum vulgare L.) Studies concerning the influence of Al and H+ ions on the Mg2+ uptake by barley plants have shown that low Al concentrations in the uptake solution (0.1 mM) are sufficient to seriously disturb 28Mg uptake and transport into the shoot. Extended Al treatment additionally led to significant growth depressions which contributed secondarily to mineral imbalance. High H+ concentration in the uptake solution (pH 4.0) affected 28Mg uptake in a similar way as Al (ion competition), but it hardly produced any negative effect on plant growth. A modification of the ionic environment by adding Ca2+ did not improve 28Mg uptake. On the contrary, free Ca2+ ions had an additional competitive effect on 28Mg uptake in addition to Al and H+ ions. 相似文献
18.
C. BÜHMANN 《European Journal of Soil Science》1993,44(2):347-360
K-fixing potential of 29 illite/smectite mixed-layer minerals, covering a broad range in layer ratios and stacking arrangements, has been investigated utilizing X-ray diffraction as the principal investigative tool. Samples were derived from a borehole core transecting Permian sedimentary rocks. In 93% of all samples, K+ was retained against replacement with Mg2+ from a 1 M MgCI2 solution in an average of 33% of the smectitic interlayers, defined via expansion to 1.7 nm upon ethylene glycol solvation after Mg-saturation. This non-ideal smectite behaviour points to a vermiculite-type layer charge. Ordered structures fixed on average 20% more K than did random ones, but results were widely scattered. The Greene-Kelly test revealed predominantly tetrahedral substitution, intercalation with dodecylammonium chloride molecules a high interlayer charge density in samples with a high K-fixing capacity. The findings have implications in two fields: in pedology, soils developed from thermally altered sedimentary rocks may inherit a considerable potential for K–fixation; in mineral identification, interlayers in illite/smectite interstratifications fully expanded to 1.7 nm upon ethylene glycol solvation despite their vermiculite–type layer charge. Glycerol solvation provided equally inconsistent results, while dodecylammonium spacings seemed to correlate reasonably well with interlayer charge density characteristics. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(1-2):125-136
Abstract A simple and precise method for determination of surface charge density of soils is described. It involves saturating the negative and positive exchange sites with NH+ 4 and NO‐ 3 ions, respectively, removing the excess solution by centrifugation, and determining the ions on the exchange sites by a steam distillation method. Results showed that the concentration and type of saturating ions and the extractant used significantly affected the surface negative charge densities. The average value of surface negative charge densities of 10 surface soils from Iowa, Chile, and Costa Rica by the proposed method agreed closely with that obtained by the original method proposed by Schofield in 1949 (14.6 vs. 13.7 cmol(‐) kg‐1 soil). The advantages of the proposed method are no need for the laborious extraction steps and simplicity of the steam distillation method for determination of NH+ 4 and NO‐ 3 in soil samples. 相似文献
20.
B. S. COULTER 《European Journal of Soil Science》1969,20(1):72-83
Conventional K: Al exchange isotherms for montmorillonite showed that Al3+ was strongly preferred to K+ in o-oin solutions. The exchange coefficient, K', calculated using the isotopically exchangeable K, was greater than unity and did not vary with the Al-saturation or with the initial pH of the AlCl3 solutions. Isotherms for vermiculite, illite, and soils in o·oin solutions also showed Al3+-preference but unlike those for montmorillonite were not asymptotic to qAl/qo= 1, qAl being the amount of adsorbed Al and qo the total adsorbed (Al + K), indicating that some of the isotopically exchangeable K could not easily be exchanged by Al3+ ions; this difficultly exchangeable K (DEK) was estimated for each exchanger. K' values for vermiculite, illite, and soils were less than unity and did not vary with Al-saturation or initial pH if the isotopically exchangeable K was corrected for DEK. This showed that K+ was adsorbed more strongly than Al3+. Strengths of K+ adsorption referred to Al3+ as the counter-cation were in order: soils > vermiculite, illite > montmorillonite. 相似文献