Effects of drying on the ion exchange capacity and cation adsorption properties of some New Zealand soils

Abstract

The effect of drying on the cation (CEC) and anion (AEC) exchange capacity, and on potassium (K) and magnesium (Mg) adsorption by three New Zealand soils was investigated. Air‐drying resulted in no significant changes in these properties compared with the field‐moist samples. Oven‐drying at 105°C significantly decreased the CEC and increased the AEC of most soils compared with air‐dried samples. The decrease in CEC was related to increased solubility of organic matter and a decrease in surface area on which charge could be developed. The increase in AEC was attributed to a decrease in soil pH.

Potassium and Mg adsorption by two soils decreased following oven‐drying. This was consistent with the effect of drying on CEC. For the remaining soil, K adsorption increased following oven‐drying. This was attributed to K fixation.     

鄂、湘两省山地土壤粘粒矿物的研究──Ⅳ.幕阜山土壤的粘粒矿物与表面性质

本文对幕阜山五个海拔高度计２１个土层的土样，测定了粘粒矿物组成，阳离子交换量，电荷量和对磷酸根的吸附。结果表明，随着海拔升高、粘粒的层状矿物，氧化物组成和有机质含量出现规律性变化，从而导致了粘粒的表面电荷性质和离子吸附特性出现相应差异，表现为阳离子交换量和阴离子交换量升高，土壤可变电荷量增高，对磷酸根离子的吸附量增大，解吸率降低。     

Charge characteristics in relation to free iron and organic matter of soils from Bambouto Mountains, Western Cameroon

We have examined the charge characteristics, with special emphasis on the role of free Fe and organic matter, of humid tropical soils from Bambouto Mountains, Western Cameroon. The soils, which are formed from tuff, basalt and trachyte, are dominated by kaolinite and sesquioxides. The amounts of Fe oxides in them increase somewhat with depth. Open 2:1 phyllosilicates are present in trace amounts. The point of zero charge of the variable charge components, pH₀, is around 4 in the topsoil (0–20 cm) and around 6 at 100–150 cm depth. In the subsoils, pH₀ exceeds soil pH presumably because of large quantities of Fe oxides. Deferration increases both soil pH and pH₀, but diminishes the anion exchange capacity. Oxides and oxyhydrates of Fe have positive surface charge, so their removal from the soils would result in overall loss of positive charge. Increases in soil pH would bring about an increase in the cation exchange capacity of the soils. Hence, management practices that reduce soil acidity should reduce loss of essential basic cations via leaching.     

Cation exchange capacity and base saturation of imperfectly drained surface coastal plain soils

Abstract

Testing three imperfectly drained forest soils (Alfisols and Ultisol) by nine methods showed that cation exchange capacities were highly pH dependent. Adding lime increased CEC values obtained by buffered and unbuffered methods but decreased CEC values when total bases were added to total acidity or salt replaceable acidity. No method tested completely explained the change in CEC caused by liming. Fractionation of the whole soil CEC Indicated an appreciable masked charge caused by an apparent complexing of amorphous metal oxides with clay or organic matter. In both buffered and unbuffered solutions, calcium saturation usually gave higher CEC values than monovalent ion saturation.     

电位滴定法研究可变电荷土壤表面酸碱性质的进展

我国长江以南地区的土壤富含铁铝氧化物,其土壤胶体表面电荷具有可变性,显著不同于温带地区的恒电荷土壤,因而称之为可变电荷土壤。开展可变电荷土壤的表面特性研究对农业可持续发展、土壤资源保护等均具有重要的现实意义。电位滴定法是开展可变电荷土壤表面特性研究最直接有效的方法。本文首先总结了电位滴定法的实验条件设置对可变电荷土壤表观电荷零点的影响,在此基础上,归纳了应用电位滴定法结合表面络合模型开展可变电荷土壤酸碱特性的研究进展,分类讨论了黏土矿物组成、氧化物、有机质等相关影响因子对可变电荷土壤酸碱缓冲能力的影响,并展望可变电荷土壤表面酸碱缓冲能力的未来研究。本文将有助于初学者理解可变电荷土壤,呼吁更多学者关注可变电荷土壤的酸碱缓冲特性研究及其在土壤资源可持续利用中所起的重要作用。     

EFFECTS OF TEMPERATURE ON THE MEASURED CATION-EXCHANGE CAPACITIES OF ANDO SOILS

The CEC was measured by a method which eliminates washing for removal of excess saturating salt. The effect of temperature on the CEC of soils and clays varied and depended on their major cation-exchange materials; the ratio of the CEC measured at 10–20 °C to that measured at 50–60 °C was 0.36 to 0.59 for allophane, imogolite, and/or humus, 0.62 to 0.75 for kaolin minerals, and 0.90 to 0.99 for montmorillonites. The CEC, increased at higher temperature in a neutral n acetate solution, was only partly reduced by lowering the temperature again. There was no evidence for an acceleration of cation diffusion with increasing temperature. A structural alteration in which some ‘bound’ functional groups are set free for ionization is proposed as a major cause of the large CEC increase observed for Ando soils at higher temperature.     

土壤电化学性质的研究——Ⅹ.红壤胶体的表面性状和离子专性吸附对表面电荷性质的影响

根据可变电荷和永久电荷共存的土壤体系的模式,研究了一个砖红壤和一个红壤胶体的表面电荷特性。由于两种土壤胶体的矿物成分和铁铝氧化物的含量不同,砖红壤胶体的pH。值、ZPNC和IEP都高于红壤胶体者。红壤胶体的永久负电荷量多,其pH₀与ZPNC的差值也大。土壤加3%的有机质淹水培育4个月后,胶体的腐殖质含量增加不足0.5%,对胶体的pH₀的影响不明显。砖红壤胶体用磷酸盐或硅酸盐处理后,表面正电荷减少,负电荷增多,pH₀值和IEP都降低。磷酸盐的效应较硅酸盐为甚。不同浓度的KCl溶液中存在少量SO₄^2-时,砖红壤胶体的正电荷减少,负电荷增加,ZPNC和pH₀值降低;如存在少量Ca²⁺,则pH₀值升高。以单一的K₂SO₄、为支持电解质时,pH₀值较KCl者为高。     

INACTIVATION OF CLAY pH-DEPENDENT CHARGE IN ORGANO-MINERAL COMPLEXES

In 24 soils the CEC of untreated samples, of samples treated with hydrogen peroxide, and of samples treated with dimethyl sulphate, was determined at pH 3, S and 8. The CEC of clay and organic matter was calculated from multiple regression equations and compared with values after treatment with peroxide and after methylation. At pH 3 and pH 5 the CECs of clay by the three methods were similar, whereas at pH 8 they were significantly lower on untreated samples. The results are interpreted in relation to the formation of organo-mineral complexes and to the interaction of the acid functions of the clay and organic matter.     

Charge distribution of selected venezuelan soils with some pedogenic and agrotechnological implications

Abstract

A study of the electrical charge distribution of selected Venezuelan soils (two Oxisols, two Ultisols, and one Alfisol) by potentiometric titration (PT) and ion adsorption (IA) procedures, showed that all soils have a predominance of negative charge at their natural pH level and within the experimental pH range used (3.5–7.5). The only exception was the Amazonas 2 soil, which has a point of zero net charge (PZNC) at pH 3.5. Potentiometric titration (PT) results allowed us to find the point of zero salt effect (PZSE) of these soils, which is related to their pedogenetic development. The order found, from older to younger, was: Guanipa (Oxisol) > Amazonas (Oxisol) > Lomas de Cubiro (Ultisol) > Altos de Pipe (Ultisol) > Barinas (Alfisol). The Stoop's method, used to determine the PZSE of the soils, was found to be a more efficient and shorter way than PT for this purpose. Ion adsorption (IA) was a more realistic way than PT to determine charge distribution for the studied soils. The soils were classified according to their charge distribution, following Gillman and Sinclair (4), as type 1 (Barinas, Lomas de Cubiro, Altos de Pipe, Amazonas 1) and type 2 (Amazonas 2 and Guanipa). This classification has agrotechnological and management implications related to the effect of added amendments, fertilizer and pollutants that would interact as ions in these soils. The low anion exchange capacity (AEC) of all these soils means low absorption capacity for non‐specifically adsorbed anions, and therefore, their probable ease of leaching down through the soil profile.     

THE COVARIANCE OF PHOSPHATE SORPTION WITH OTHER SOIL PROPERTIES IN SOME BRITISH AND TROPICAL SOILS

Phosphate sorption capacity estimated by Piper's (1942) ‘anion exchange capacity’ and Bache and Williams's (1971) phosphate sorption index were correlated with soil pH, clay, organic matter, ‘free iron oxides’ and ‘extractable aluminium’ (McLean et al., 1958) for topsoil and subsoil samples from twenty tropical and twenty British acidic soil profiles. These two groups of soils did not differ significantly in phosphate sorption. Extractable aluminium and free iron oxide were well correlated with phosphate sorption, free iron oxide being superior to aluminium in freely drained British soils but not in poorly drained ones. Organic matter content correlated well with phosphate sorption for the poorly drained British soils, and for the tropical soils when sorption capacitywas measured using a high phosphate concentration.     

Effect of organic matter on changes in soil zinc fractions found in wetland soils

Abstract

Zinc fractions occurring in five wetland soils as a function of organic matter application and soil redox potential were studied under laboratory conditions. The results indicate that a large portion of native or added Zn is bound to the soil mineral component. Exchangeable and organic complexed Zn and Zn bound to amorphous and crystalline sesquioxides were found to be in dynamic equilibrium. Exchangeable and complexed Zn were positively correlated with both native and/or added organic matter, while Zn bound to the amorphous and crystalline sesquioxides were negatively correlated with added organic matter. As soil redox potential decreased, the amount of exchangeable and organic complexed Zn decreased, while Zn bound to the amorphous and crystalline sesquioxides increased. Zinc fractions examined varied, depending upon soil cation exchange capacity, clay and organic carbon content.     

The cation- and anion exchange characteristics of soils with a large sesquioxide surface area

The theory on colloids with a pH-dependent surface potential indicates that the anion exchange capacity of soils containing hematite or similar oxides depends on pH, electrolyte concentration and valency of counterions. These relationships were tested for the salinity- and pH-range of importance to agriculture, using a percolation technique. MgSO₄ was chosen as impregnating salt to minimize the overall error caused by salt exclusion. The assumptions on the anion exchange behaviour proved to be correct; moreover they applied also to a considerable fraction of the cation exchange. The results were formulated in terms of multiple linear regression equations relating the exchange capacities to pH and the square root of the electrolyte concentration. Consequently, the adsorption behaviour of ferruginous soils can not be characterized by the determination of CEC and AEC at one level of pH- and salt concentration in solution. Due to the inefficiency of the ethanol washing step, two standard methods overestimated CEC by a factor 2 to 4.     

Contribution of organic matter and clay minerals to the cation exchange capacity of soils

Abstract

The cation exchange capacity (CEC) at pH 7 was measured for samples of 347 A horizons and 696 B horizons of New Zealand soils. The mean CEC was 22.1 cmolc/kg for the A horizons and 15.2 cmolc/kg for the B horizons. Multiple regressions were carried out for CEC against organic carbon (C), clay content, and the content of seven groups of clay minerals. The results, significant at p <0.001, were consistent with most of the CEC arising from soil organic matter. For the samples of A horizon, the calculated CEC was 221 cmolc/kg per unit C and for the B horizons was 330 cmolc/kg C. There was also a contribution from sites on clay minerals. Multiple regression indicated that smectite had a higher CEC (70 cmolc/kg) than other minerals but it was not as high as that of type smectites; kaolin minerals had the lowest CEC. There was a significant effect of interaction between organic matter and some clay minerals on the CEC. Samples from B horizons containing allophane had lower CEC than those not containing allophane which is consistent with allophane reacting with carboxyl groups on organic matter. For the samples from the A horizons, however the CEC was higher when allophane was present.     

Pb adsorption by soils

Pb adsorption for 12 soils from Tuscany was studied. The data fitted the Langmuir and the Freundlich isotherms over a large range of concentrations. Results showed that organic matter and clay content were responsible for adsorption maxima. The effect of Mn oxides, explained independently of organic matter and clay, was negligible. The adsorption maxima were generally found to be greater than CEC; the possible mechanisms are discussed.     

Carbon storage in loess derived surface soils from Central Germany: Influence of mineral phase variables

The influence of the soil mineral phase on organic matter storage was studied in loess derived surface soils of Central Germany. The seven soils were developed to different genetic stages. The carbon content of the bulk soils ranged from 8.7 to 19.7 g kg^—1. Clay mineralogy was confirmed to be constant, with illite contents > 80 %. Both, specific surface area (SSA, BET‐N₂‐method) and cation exchange capacity (CEC) of bulk soils after carbon removal were better predictors of carbon content than clay content or dithionite‐extractable iron. SSA explained 55 % and CEC 54 % of the variation in carbon content. The carbon loadings of the soils were between 0.57 and 1.06 mg C m^—2, and therefore in the ”︁monolayer equivalent” (ME) level. The increase in SSA after carbon removal (ΔSSA) was significantly and positively related to carbon content (r² = 0.77). Together with CEC of carbon‐free samples, ΔSSA explained 90 % of the variation in carbon content. Clay (< 2 μm) and fine silt fractions (2—6.3 μm) contained 68—82 % of the bulk soil organic carbon. A significantly positive relationship between carbon content in the clay fraction and in the bulk soil was observed (r² = 0.95). The carbon pools of the clay and fine silt fractions were characterized by differences in C/N ratio, δ¹³C ratio, and enrichment factors for carbon and nitrogen. Organic matter in clay fractions seems to be more altered by microbes than organic matter in fine silt fractions. The results imply that organic matter accumulates in the fractions of smallest size and highest surface area, apparently intimately associated with the mineral phase. The amount of cations adhering to the mineral surface and the size of a certain and specific part of the surface area (ΔSSA) are the mineral phase properties which affect the content of the organic carbon in loess derived arable surface soils in Central Germany most. There is no monolayer of organic matter on the soil surfaces even if carbon loadings are in the ME level.     

Deoxyribonucleic Acid Homology Among Strains of Soybean-Nodulating Bacteria

Abstract

Characteristics of Brown Forest soils developed under different bio-climatic conditions from low to high eleyations in the Kinki District were studied with special reference to their pedogenetic processes. The Brown Forest soils at high elevations were characterized by a lower bulk density, higher capacities to adsorb organic matter, phosphate, and moisture, which were correlated with the ratio of the amorphous content to the clay content (the value of the ratio of (Feo + Alo)/clay), as compared to those at low elevations. Considering the fact that the value of the (Feo + Alo)/clay ratio was not correlated with the volcanic glass index, the formation of an amorphous fraction at high elevations was considered to proceed according to the following mechanism.

Low temperature at high elevations (above 700 m) may retard the crystallization of oxide minerals. The amorphous oxides with variable positive charge thus formed may adsorb organic matter, confering a darker color and high moisture and high phosphate retention capacities to the subsoil. Adsorbed organic matter stabilizes these amorphous oxides, thus enhancing the amorphous properties and inhibiting crystallization. A1 translocation due to the weak podzolization may contribute to the increase of the content of amorphous materials.

Characterization of the B horizons in forest soils in Japan, in terms of the values of the ratios of (Feo + Alo)/clay, (Fed-Feo)/Fet, and Alo/Ald, (CEC -ECEQ/CEC and STPT-ZPC, suggested that forest soils might be classified into four groups.     

Über die Sorptionseigenschaften von Waldböden bezüglich gelöster organischer Substanzen

About the sorption of dissolved organic matter to forest soils This investigation characterizes the major forest soils of the temperate climatic zones (leptosols, vertisols, cambisols, luvisols, podzols, stagnosols, gleysols) as sorbents for dissolved organic matter (DOM). Sorption isotherms were obtained for 135 soil horizons from 36 profiles. When solutions containing no DOC were added, the release of dissolved organic carbon (DOC) was highest for horizons rich in organic C (A and Bh horizons). In subsoil horizons DOC release was much lower. Most of the investigated top soils (A and E horizons) and Bh, Bg, and C horizons showed a weak DOC sorption. This was caused by low contents of sorbents (clay and sesquioxides) and/or high contents of organic C. Organic C seems to reduce the DOC sorption by occupying binding sites. Subsoils rich in clay and sesquioxides like Bs, Bt, and Bw horizons showed a strong retention of DOC. Under the aerobic conditions of the experiments, some of the subsoils of stagnosols and gleysols also showed a strong sorption of DOC. However, in sorption experiments conducted after an anaerobic incubation, the DOC sorption decreased significantly.     

水溶性有机碳在各种粘土底土中的吸附：土壤性质的影响

Clay-rich subsoils are added to sandy soils to improve crop yield and increase organic carbon (C) sequestration; however, little is known about the influence of clay subsoil properties on organic C sorption and desorption. Batch sorption experiments were conducted with nine clay subsoils with a range of properties. The clay subsoils were shaken for 16 h at 4 ^oC with water-extractable organic C (WEOC, 1 224 g C L^-1) from mature wheat residue at a soil to extract ratio of 1:10. After removal of the supernatant, the residual pellet was shaken with deionised water to determine organic C desorption. The WEOC sorption was positively correlated with smectite and illite contents, cation exchange capacity (CEC) and total organic C, but negatively correlated with kaolinite content. Desorption of WEOC expressed as a percentage of WEOC sorbed was negatively correlated with smectite and illite contents, CEC, total and exchangeable calcium (Ca) concentrations and clay content, but positively correlated with kaolinite content. The relative importance of these properties varied among soil types. The soils with a high WEOC sorption capacity had medium CEC and their dominant clay minerals were smectite and illite. In contrast, kaolinite was the dominant clay mineral in the soils with a low WEOC sorption capacity and low-to-medium CEC. However, most soils had properties which could increase WEOC sorption as well as those that could decrease WEOC sorption. The relative importance of properties increasing or decreasing WEOC sorption varied with soils. The soils with high desorption had a low total Ca concentration, low-to-medium CEC and low clay content, whereas the soils with low desorption were characterised by medium-to-high CEC and smectite and illite were the dominant clay minerals. We conclude that WEOC sorption and desorption depend not on a single property but rather a combination of several properties of the subsoils in this study.     

Surface Chemical Properties of Colloids in Main Soils of China

Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.     

Characteristics of the soils developed under broad-leaved evergreen forests in okinawa prefecture and the kinki district with special reference to their pedogenetic processes

Abstract

Properties of sesquioxides, clay mineralogical composition, and charge characteristics of the soils developed under broad-leaved evergreen forests in Okinawa Prefecture (subtropical climate) and the Kinki District (warm temperate climate) were studied with special reference to their pedogenetic processes in order to reexamine the corresponding parameters of Brown Forest soils and related soils in Japan.

The soils in Okinawa Prefecture were characterized by a higher degree of weathering as compared to the soils in the Kinki District. Major differences involved the values of the Fed/Fet ratio for the soil samples throughout the profile, and those of the ratios of (Fed-Feo)/Fet, CEC/clay, and (Feo + Alo)/ clay and the content of CaO plus Na₂O for the B horizon. The soils in the Kinki District did not show andic soil properties, nor Al translocation in the profile and, both of which were characteristic of Brown Forest soils developed under cool temperate climatic conditions at high altitudes in the same District.

The difference in the degree of weathering were reflected on the charge characteristics at the very surface of the soils, i.e., the surface of the particles of the soils in Okinawa Prefecture exhibited a lower reactivity as compared with those of the soils in the Kinki District.