Interlayer materials of partially interlayered vermiculites in Dystrochrepts derived from Tertiary sediments

Interlayer materials of partially interlayered vermiculites (PIV) in 15 Dystrochrepts derived from Tertiary sediments were analysed by dissolution with hot 1/3M sodium citrate or 0.15 M oxalate-oxalic acid in combination with XRD and IR spectroscopy. Both the citrate and oxalate treatments dissolved Al from all soil clays. The dissolution of Al by the citrate treatment paralleled the dissolution of Si and the interlayer collapse of PIV, whereas that by the oxalate treatment did not, indicating that the interlayer materials contain not only Al but Si. The materials dissolved by the citrate treatment had a molar Si/Al ratio ranging from 0.72 to 0.24 that decreased with the increasing interlayering of PIV. Differential IR spectroscopy indicated the dissolution of aluminosilicates possibly having Si-O, Al-OH and Si-O-Al bonds, but not Si-O-Si bonds. The extent of interlayering of PIV showed a good correlation with the amount of Al dissolved by the citrate treatment and increased with increasing soil pH (H₂O) from 4.5 to 5.2 and with decreasing exchangeable Al in soil.
Formation of a hydroxy-Al sheet partially bonded with Si-tetrahedra was suggested as a possible model of the interlayer structure of PIV. The differences between PIV in the studied Inceptisols and other soils are discussed.     

Participation of silicon in cation‐anion balance as a possible mechanism for aluminum and iron tolerance in some gramineae

Abstract

Silicon (Si) has been suggested as a factor in aluminum (Al) tolerance of some species of the gramineae when grown on acid soils. Silicon concentrations are generally much higher in monocot plants than in dicot plants, and the phenomenon is related to the fact that mineral cation:mineral anion uptake ratio is much higher in dicots than in monocots. When large amounts of anionic Si, supposedly as sulfate (SO₄ ^4‐), participate in cation‐anion balance to add to the excess of anion uptake, equivalent amounts of hydroxyl ions should be expelled from roots which can increase rhizosphere pH and decrease uptake of Al and iron (Fe). The magnitude of OH^? released by roots for a 5000 kg/ha crop with an excess uptake of 1% Si can be equivalent to 357 kg lime per hectare. This could be very significant in decreasing Al and Fe uptake from acid soils when localized in the rhizosphere. Success of agriculture on highly acid soils may be enhanced by use in a rotation of crops and cultivars that have the ability to accumulate Si.     

Release Kinetics of Si,Al, Fe,and Mn from Acid Soils in the Presence of EGCG

Plant polyphenols can affect soil processes. In the present study, batch experiments were conducted to study the effects of epigallocatechin gallate on the release kinetics of silicon (Si), aluminum (Al), iron (Fe), and manganese (Mn) from acid Anthrosol and Luvisol. The results indicated that the optimal model describing the release kinetics of these elements was a double constant, simple Elovich, or parabolic diffusion equation, and a first-order equation was not suitable. These elements went through an initial rapid-release phase, followed by a slower-release phase. The order of release amounts and rates for Anthrosol was Si > Al > Fe > Mn, but they were different at different phases. However, the order for Luvisol was always Al > Mn > Si > Fe. Meanwhile, the release amount and rate of every element was in the order Luvisol > Anthrosol. The results of this study could help to resolve Al and Mn toxicity in acid soils.     

Movement of aluminium as an inorganic complex in some podzolised soils,New Zealand

Chemical and mineralogical data are presented for three Spodosols (podzols) and a related Inceptisol (yellow-brown loam). Allophane with an Al/Si atomic ratio close to two is identified in the B horizons of all four soils, and minor amounts of imogolite are present in association with allophane in all but one soil where small-particle gibbsite occurs. Parent materials for these soils are essentially non-vitric. Allophane (Al/Si = 2) has been estimated quantitatively in all soils using oxalate-extractable Si (Si₀) and is selected clay fractions using both Si₀ and infrared spectroscopy. Maximum concentrations of allophane (Al/Si = 2) range from 5% to 18% of fine earth (< 2 mm) fractions and all occur in B horizons. Fe₀ values are low relative to Al₀ values except for the upper horizons of the Inceptisol. Al₀ values peak in B horizons and the ratio pyrophosphate-extractable Al to Al₀ decreases from about 1 in A and upper B horizons to 0.1–0.4 in lower B horizons.An interpretation of the data is consistent with recent proposals that the movement of Al in podzolisation is due primarily to the formation of inorganic complexes with Si. Chemical criteria for spodic horizons should be consistent with the total illuviation of Al and Fe (and perhaps Si), rather than just the organic-bound fraction of Al and Fe in these horizons as indicated by amounts in extractants such as pyrophosphate.     

FORMATION, COMPOSITION AND STRUCTURE OF HYDROXY-ALUMINOSILICATE IONS

Formation of hydroxy-Al (HA) and hydroxy-aluminosilicate (HAS) ions was studied in solutions of A1C1₃, orthosilicic acid and NaOH. Evidence for incorporation of Si into HA is that HA retarded the development of silicomolybdate colour and Si was retained by a cation-exchanger. The reaction is believed to be mainly a condensation reaction between the hydroxyl groups in Al–OH–Al and Si–OH groups. The HAS with Si/Al ratio 0.3–0.6 showed infrared spectra similar to allophane-like constituents in Ando soils.     

Optimum conditions for extraction of Al,Fe, and Si from soils with acid oxalate

Abstract

Acid oxalate reagent was used at various concentrations, pH values, shaking times, and soil to solution ratios to find the optimum conditions for the extraction of Al, Fe, and Si from short‐range‐order materials in soils and stream‐bed deposits. The optimum conditions vary with the nature of the soil sample and its components. For most soils maximum amounts of Al, Fe, and Si were extracted with 0.15M acid oxalate reagent at pH 3.0 with a soil to solution ratio of 1:100 and shaking for 4 h in the dark at 20°C. Soils with more than 5% oxalate‐extractable Al or Fe require a 0.20M oxalate solution at pH 3.0 with a soil to solution ratio of 1:200.

Allophane is extracted by acid oxalate reagent after shaking for 2 h and it may be estimated from the 4 h oxalate‐extractable Si values. Ferrihydrite is extracted after shaking for 4 h, and it may be estimated from the oxalate‐extractable Fe values. Either sodium oxalate or ammonium oxalate may be used     

低分子量有机酸对可变电荷土壤铝活化动力学的影响

从动力学角度研究了几种低分子量有机酸对2种酸性土壤中铝的活化和活化铝在土壤固/液相之间分配的影响。结果表明:对于络合能力弱的醋酸和乳酸,主要通过质子作用活化铝,且活化作用明显小于盐酸。而络合能力较强的苹果酸、草酸和柠檬酸,主要通过络合作用促进铝的释放,且这种作用随有机酸根阴离子络合能力的增强而增加。在氧化铁含量较高的砖红壤中,苹果酸、草酸和柠檬酸通过专性吸附增加土壤表面负电荷,从而增加土壤交换态铝;但在氧化铁含量较低的红壤中,草酸和柠檬酸主要通过形成可溶性铝络合物降低交换态铝。活化铝在土壤固/液相间的分配主要决定于溶液中有机阴离子与土壤固相表面对铝离子的竞争。醋酸和乳酸活化的铝主要以交换态铝存在;而草酸和柠檬酸活化的铝主要以有机酸-铝络合物存在于溶液中,特别是在氧化铁低的红壤中,这将促进铝在土壤-水体中的迁移。     

Laboratory Dissolution Studies of Rocks from the Borrowdale Volcanic Group (English Lake District)

Laboratory studies were conducted to investigate the rates ofrelease of Na, Mg, Al, Si, K, Ca and Fe from 10 samples of metamorphosed igneous rock of the Borrowdale Volcanic Group (BVG), consisting mainly of plagioclase feldspars, chlorite andquartz, with minor amounts of hornblende, epidote and carbonates.Experiments were performed using freshly-prepared rock pieces (ca. 12 mm cubes), in batch mode, but with frequent changes of the solution phase so that accumulation of dissolved solutes wasminimised. The initial element release rates were relatively high, but declined with time to reach approximate (pseudo-) steady state conditions. Element release rates declined withpH in the pH range 2–7, the dependence upon pH decreasing in the order Al ～ Fe > Si > Mg ～ Ca > K ～ Na. Thepseudo-steady state rates for Si were comparable to steady state values for single minerals. Calcium showed the greatestsample-to-sample variation (more than 100-fold). Rock dissolutionwas far from stoichiometric, with Ca and Mg being present in thesolution phase in proportions greater than in the rock, and Al and Si in lower proportions. In some samples the release rates ofMg and Ca were equal, while in others the Ca rate was up to 100times that of Mg. The rate of release of Ca is correlated with the carbonate content of the rocks. The results indicate that the main source of Ca in the faster-dissolving samples is calcite, while the highest release rates of Mg are consistent with dissolution of dolomite. Aluminium, Si and Fe are probablyreleased predominantly from chlorite. The results are discussed in terms of the supply of base cations to stream waters drainingcatchments underlain by rocks of the BVG.     

Ammonium-calcium exchange equilibria in soils and weathered pumices that differ in cationexchange materials

The retention of NH₄+ and Ca²+ on soil and weathered pumice samples containing constant and/or variable charge components was measured in different NH₄CI-CaCl₂ solutions. The NH₄+/Ca²+ selectivity of each sample was evaluated using a quotient of the partition of NH₄+ on the exchange sites and in the solution relative to that of Ca²+. It increased with decreasing pH and increasing NH₄Cl-CaCl₂ concentration for a given equivalent fraction of NH₄+ in the solution. These effects were quantitatively explained in terms of the changes of NH₄+ and Ca²+ concentrations in the solution and in the diffuse double-layer of the ion-exchange material as predicted by the law of mass action and the electric double layer theory. The NH₄+/Ca²+ selectivity of different exchange materials showed a similar variation among their exchange sites and increased in the order humus, allophane and imogolite (Si/Al ratio 0.5) < allophane (Si/Al ratio 1.0), montmorillonite < vermiculite, illite < halloysite. The origin of negative charge, the steric features around the exchange sites and clay-humus interaction are suggested as being important in determining the NH₄+/Ca²+ selectivity.     

Chemical significance of aluminium extracted from three horizons of an acid forest soil, using chloride salt solutions

Aluminium is usually important in exchange reactions in acid soil, but amounts extracted are strongly affected by procedure. We examined the impact of proton release, following salt addition, on Al removal from three horizons (Oe, Oa and A₁₂) of an acid, brown forest soil. The Al was first extracted with either 1 M KC1, 1 m NH₄C1 or 0.5 m CuCl₂ on the three horizons limed to pH 5.5. For any lime addition, both the pH drop following salt addition and the amounts of extracted Al were greater with CuCl₂ than with KC1 or NH₄C1. For the Oa and A₁₂ horizons there was a single inverse linear relation between amount of Al extracted and the pH of final extract, independent of the extracting cation. In the Oe horizon CuCl₂ extracted constant amounts of Al, whereas the quantity of Al removed by KC1 or NH₄C1 increased linearly as pH declined below pH 3.6. Extra Al was mobilized following unbuffered KC1 extraction, a side effect induced by the extracting procedure itself. Al mobilization increased with increasing H⁺ additions. In the Oe horizon, equilibrium was established rapidly (≤ 24 h), and decreasing the pH of the soil-KCl suspensions to 2.0 resulted in extracted Al amounts equal to or slightly greater than those obtained with CuCl₂ solutions. Al amounts extracted with acidified KC1 solutions from the A₁₂ were close to those obtained using CuCl₂ solutions at similar pH in the extract. In the samples from the A₁₂ layer, increasing the equilibration time resulted in increasing proton consumption and equivalent release of Al ions in the extract.     

Silicon effects on aluminum toxicity to mungbean seedling growth

The effects of silicon (Si) on the toxicity of aluminum (Al) to mungbean (Phaseolus aureus Roxb.) seedlings were studied in a growth chamber. Mungbean seedlings were grown in a nutrient solution with combinations of three concentrations of Si (0,1, and 10 mM) and three concentrations of Al (0, 2, and 5 mM) in randomized completely block design experiments for 16 days. Silicon at 1 mM in the solution decreased root length, fresh and dry weights, and chlorophyll content, and showed no significant effect on epicotyl length and seedling height, and protein contents of shoots or roots in mungbean seedling under no Al stress. But, Si at 10 mM showed marked toxic effects on mungbean seedling growth and increased protein contents of the shoots or roots. In contrast, under 2 mM Al stress, Si addition at 1 mM had significant increasing effect on root length, fresh and dry weights, and chlorophyll content. It also had decreasing effect on protein contents of the shoots or roots, and had no effect on epicotyl length and seedling height. Silicon addition at 10 mM showed no effect on morphological and physiological measurements of mungbean seedling. However, Si at 1 mM added to solution only increased seedling height, epicotyl length, fresh weight, and chlorophyll content, but decreased dry weight and protein content of the roots under 5 mM Al stress, significantly. Silicon addition at 10 mM showed similar toxic effects on mungbean seedling growth under 5 mM Al stress to that under no Al stress.     

Freisetzung von Aluminium in mitteldeutschen sauren Braunerden aus Löß-Sandstein-Fließerden

Release of aluminium in Northwest-German Acid Brown soils on loess-sandstone solifluction deposits In soil and clay from root zones (50 resp. 80cm) of acid brown soils, the Si and Al released during weathering was determined by fractionated extraction with 0.5 N NaOH in order to arrive at a quantitative approximation of the possible clay and silicate destruction. Extracted Al was 4-10 times higher than Si, and showed a steep gradient between Ah- and B-horizon. The Al(clay)/Al(soil) ratio varied between 0.5 to 1 depending on the admixture of sandstone material to the loess. Assuming that the clay-extracted Al was derived from the destruction of clay, we arrived at a minimum value for affected clay of 1-4,5% of the soil mass or 10 to 40% of the present clay substance. Clay destruction is discussed as Al-release leaving behind a non-crystalline Si-O-OH lattice.     

Crystallochemistry and surface properties of biogenic opal

The very low solubility of phytoliths or biogenic silicas (which are minor constituents of most soils) and their ability to stabilize nitrogenous fulvic acids in podzols are attributed to chemisorbed Al^VI on the surface making the silica less soluble and the surface OH groups very reactive towards organic anions in an acid medium. The surface Si/Al ratio of phytoliths is very low (1.5–8) in comparison with the Si/Al ratio (8–20) for the whole sample. The pK values of the reactions in which surface groups are involved are pK₁= 1.8 for deciduous phytoliths to 3.8 for more aluminous coniferous phytoliths; the pK₂ range is 8.2–9.0. The zero point of charge which is correlated with pK values varies from 5 to 6.     

Reaktionen von Ca-Montmorillonit und Ca-Vermiculit mit Kohlensäure

Reaction of Ca-Montmorillonite and Ca-Vermiculite with CO₂ The treatment of Ca-montmorillonite and Ca-vermiculite with carbonic acid (Pco₂ = 2 atm) has shown the following results: In the pH range of ± 3.9–6.0 Ca is exchanged by H directly only on pH dependent (variable) charge sites (Cav), whereas, Ca on permanent charge sites (Ca_p) is exchanged only by lattice cations mainly Al released by proton attack. Therefore, with regard to proton uptake from carbonic acid the two Ca-clays behave as extremely weak acids. The exchange of Ca_v proceeds rapidly that of Ca_p much more slowly, the first one is essentially reversible the latter at least not within a short period of time. The proportion of Ca_v is found from a graphical extrapolation of the Ca saturation-pH-function (fig. 3). Al released during the initial stage of the reaction is non exchangeable, prevents the expandable minerals partly from collapsing on K tratement (verm. much more than mont.) and has an OH/Al ratio of about 2. On treating the same clay sample several times or at low suspension concentrations exchangeable Al with OH/Al = O occurs. Exchangeable hydrogen was never detected. Vermiculite is less resistent against carbonic acid than montmorillonite. The results were discussed in respect to the mechanism of release of lattice constituents and in respect to Al release under the influence of CO₂-concentrations of soils.     

不同氮磷用量对红枣果实品质和产量的影响

水资源匮乏与土壤肥力不足一直是阻碍新疆红枣果业发展的重大问题。为探究不同氮磷用量对红枣产量和品质的影响,给红枣树合理施肥提供指导。在南疆阿里尔市枣园,以主干结果型灰枣树为研究对象,采用单因素随机区组试验设计,在滴灌条件下研究了不同施氮量和施磷量下灰枣果实可溶性糖、可滴定酸、糖酸比、Vc等品质指标与产量的变化。结果表明,各施氮处理吊干枣的可溶性糖含量、可滴定酸含量均明显高于鲜枣,但鲜枣的Vc含量和糖酸比却均明显高于吊干枣。随施氮量增加,吊干枣果实中可滴定酸含量、糖酸比均呈先降低后增加趋势。其中以施N 690.0 kg/hm2时吊干枣可溶性糖含量较高,糖酸比较低;施N 495.0 kg/hm2时吊干枣可滴定酸含量较低,糖酸比较低;施N 592.5 kg/hm2时鲜枣Vc含量较高,糖酸比较高,吊干枣产量最高,为8 061 kg/hm2。各施磷处理鲜枣的可溶性糖含量、可滴定酸含量明显低于吊干枣,但鲜枣的Vc含量明显高于吊干枣,糖酸比波动较大,变化无明显规律。随施磷量增加,鲜枣和吊干枣果实中可溶性糖含量和Vc含量均呈先增加后降低趋势;可滴定酸含量呈先降低后增加趋势;糖酸比鲜枣呈先增加后降低再增加趋势,吊干枣呈先降低后增加趋势。施P2O5 517.5 kg/hm2时吊干枣可溶性糖含量和鲜枣Vc含量较高,吊干枣产量最高,为6 983 kg/hm2。施P2O5 435.0 kg/hm2时吊干枣可滴定酸含量较低。综合可见,施N 495.0 kg/hm2、P2O5 517.5 kg/hm2 为南疆枣园最优施肥量。     

EFFECT OF pH ON THE REACTION OF SODIUM FLUORIDE WITH HYDROUS OXIDES OF SILICON, ALUMINIUM, AND IRON, AND WITH POORLY ORDERED ALUMINOSILICATES

The release of hydroxyl ions from silica and ferric oxide gels on treatment with sodium fluoride solution is very small above pH values of 7.6 and 9 respectively. Hydroxyl release from alumina gel and poorly ordered aluminosilicates is appreciable at pH 9 and varies little with pH, but that from crystalline forms of alumina decreases with decrease of pH. For poorly ordered aluminosilicates, the ratio (OH′ released at pH 8.0): (OH′ released at pH 6.8) is directly proportional to the mole fraction Al/(Al+Si). The measurement of hydroxyl release at differing pH values may enable determination of hydrous alumina separately from the total poorly ordered inorganic gel material; moreover, the amount of hydroxyl released at high pH values is related to phosphate sorption capacity.     

硅对减轻水稻的铝胁迫效应及其机理研究

通过分析溶液中Al离子形态变化和根内Al的分布 ,探讨Si对减轻水稻Al胁迫的效应及其机理。结果表明 ,pH4.5的溶液培养条件下Al在短时间内即可明显地抑制水稻根系的生长 ,加入不同形态的硅酸可有效地减轻Al对水稻的胁迫 ,根的伸长量接近或达到对照处理的水平。加Si降低了溶液中单质态Al离子的浓度 ,改变了溶液中Al的形态。分子筛柱层析分离和离子交换树脂吸附分析发现 ,溶液中产生了新的Al化合物 ,阳离子交换态Al的比率由 78%降低到 48% ,而交换态Si的比率由 0 %增加到 20%。Al主要聚集于根质外体特别是细胞壁中 ,加入低分子态硅酸增加了根全Al和质外体Al的含量 ,但是却降低了细胞壁Al的含量 ,而加入高分子态硅酸明显地降低了根全Al、质外体、共质体和细胞壁Al的含量     

An assessment of EDTA as an extractant of organic-complexed and amorphous forms of Fe and Al in soils

EDTA solutions proposed as selective extractants of amorphous and organic forms of Fe and Al in soils and synthetic materials were tested. Extraction of Fe and Al from some soil samples continued at a decreasing rate beyond 120 days. For some soil samples and synthetic materials the amounts of Fe and Al extractable by EDTA (90 days) were markedly lower than those extractable by acid ammonium oxalate (2 h). Extraction of samples for 1 h with EDTA was shown to release amounts of Fe and Al far below those considered to be complexed with organic matter. The EDTA extraction procedures tested should not replace either acid ammonium oxalate for estimating amorphous forms of Fe and Al or pyrophosphate for estimating organic forms of Fe and Al in soils.     

Squeezed soil-pore solutes — A comparison to lysimeter samples and percolation experiments

This paper presents data on the chemical composition of soil pore fluids that have been obtained by a high-pressure squeezing technique and lysimeter sampling. Cation-exchange capacity has been calculated from cations extracted by a simple percolation method. All pore water concentrations are greatly influenced by the pH in solution. Most pore water concentrations do not simply parallel the corresponding mineralogical and chemical composition of the solids. The depth of the acidification front, as determined by analysis of samples obtained by percolation, is much better reflected in the chemical composition of the squeezed soil pore fluids than in the lysimeter samples. Distinct gradients are seen in Al concentration. In the B-horizons, concentrations of Al are close to the solubility of gibbsite. The pore water concentration profiles of Si and K apparently indicate dissolution of K-silicates, in particular K-feldspar. Contrary to the squeezed pore solutions the sulphate maximum concentration in the soil profile is not recorded by lysimeter samples. Mineral saturation indices show that pore solutions by squeezing are close to the saturation concentrations for K-jarosite and K-alunite. Sulphur-rich phases from the soil are compatible with mixtures of alunite jarosite, zaherite, basaluminite, and hydrobasaluminite. In the upper soil horizons the liquid/solid ratios [calculated as: concentration in solution (µg/ml) * solution fraction in solids (ml/g)/concentration in solids (µg/g)] increase in the order Ph < OC ≈ Zn < Cd and range from 10^?6 to 10^?3, indicating that Ph is most strongly held and still accumulates in the organic top soil. In the underlying deeper mineral horizons the ratios for Pb, Zn, and Cd decrease by one order of magnitude.     

Soil Aluminum Effects on Growth and Nutrition of Cacao

In acid soils, Al toxicity and nutrient deficiencies are main constraints for low yield of cacao ( Theobroma cacao L.). A controlled growth chamber experiment was conducted to evaluate the effect of three Al saturations (0.2, 19, and 26%) adjusted by addition of dolomitic lime on growth and nutrient uptake parameters of cacao. Overall, increasing soil Al saturation decreased shoot and root dry weight, stem height, root length, relative growth rate, and net assimilation rate. However, increasing soil Al saturation increased leaf area, specific leaf area (total leaf area/total leaf dry wt), and leaf area ratio (total leaf area/shoot+root wt). Increasing soil Al saturation decreased uptake of elements. Nutrient influx (IN) and transport (TR) decreased significantly for K, Ca and Mg, and showed an increasing trend for S and P as soil Al saturation increased. However, increasing soil Al saturation significantly increased nutrient use efficiency ratio (ER, mg of shoot weight produced per mg of element in shoot) of Ca, Mg and K and decreased ER for other elements. Reduction of soil acidity constraints with addition of lime and fertilizers appear to be key factors in improving cacao yields in infertile, acidic, tropical soils.