Origin and nature of halloysite in Ando soils from Towada tephra,Japan

The origin and nature of halloysite in Ando soils from Towada tephra were investigated. These soils were formed from five tephras: Towada-a (1,000 years old), Towada-b (2,000 years old), Chuseri (4,000 years old), Nanbu (8,600 years old) and Ninokura (10,000 years old).Formation of halloysite took place only in the buried soils from Nanbu and Ninokura tephras occurring in an “accumulating zone”, where thicknesses of overburden tephra deposits were mostly 2.5 m or greater and silica enrichment of the clay fractions could occur.The amounts of halloysite were greater in (1) the soils from Ninokura tephra than in those from Nanbu tephra, and greater in (2) the humus horizons as compared to the nonhumus horizons of these same soils. The mean sizes of spheroidal halloysite particles and the ratios of numbers of tubular to spheroidal forms differed with differences in soil horizons and age.High-resolution electron micrographs of glycerol-solvated spheroidal halloysite particles had lattice images of 11 Å due to (001) from the exterior to the interior and had no indications of layer separation. Moreover, the central core of spheroidal halloysite with a diameter of 150 Å showed neither layer structure nor allophane spherules.Results obtained in this study thus indicate that spheroidal and tubular forms of halloysite were formed concurrently in these Ando soils.     

Implications of clay mineralogy to the weathering and chemistry of AP horizons of ando soils in Japan

The clay mineralogy of 22 samples of the Ap horizons of Ando soils was determined by a combination of methods. Of these samples, 15 did and 7 did not contain allophane and imogolite. Opaline silica was found in 4 samples, whereas aluminum—humus complexes, iron oxides and layer silicates were found in all samples. The presence of allophane and imogolite and the absence of opaline silica in a few Ap horizons was related to mixing of A₁ horizons and subsoils by cultivation and to lower supplies of organic matter relative to the amounts of aluminum released from volcanic ash by weathering. The contents of 2:1 and 2:1:1 layer silicates and their intergrades were larger in soils in which quartz predominated in fine fractions. It was inferred that aluminum bound with humus and in allophane-like constituents, rather than aluminum in allophane and imogolite, is important in reactions with phosphate and fluoride.     

ABSTRACT of the Articles Printed in Journal of the Science of Soil and Manure,Japan

A contrasting occurrence of clay minerals was found within a soil profile which was derived from volcanic materials in the suburbs of Fukuoka-city, Northern Kyushu. The soil profile is located on an isolated terrace, and the morphological characteristics of the soil correspond exactly to Andosols, so-called Kuroboku soils or Humic Allophane soils.

The clay fraction of upper horizons of the soil consists largely of alumina-rich gel-like materials, gibbsite, and layer silicates such as chlorite and chloritevermiculite intergrades, while that of lower horizons is composed of allophane and gibbsite or halloysite. There was no positive indication of allophane in the upper horizons. Corresponding with the clay mineralogical composition, quartz is abundant in the fine sand fraction of the upper horizons, while the mineral is very scarce or none in the lower horizons, suggesting a close relation between the petrological nature of parent volcanic materials and the mineralogical composition of weathering products. The dominant clay mineral in the volcanic 1.10il might be dependent on the petrological nature of parent materials, and allophane is mostly formed from andesitic materials, and alumina-rich gel-like materials and layer silicates have come from quartz andesitic materials. Allophane would transform to gibbsite or halloysite according to weathering conditions, and aluminarich gel-like materials change to gibbsite under a well-drained condition.

The soil materials have been so greatly weathered that some horizons contain gibbsite of even more than 40 per cent or halloysite over 70 per cent. The morphology and mineralogy are quite similar to so-cailed “non-volcanic Kuroboku soils.”     

ELECTRIC CHARGE CHARACTERISTICS OF ANDO A, AND BURIED A, HORIZON SOILS

The electric charge characteristics of four Ando soils (A₁ and μA₁) and a Chernozemic soil (Ap) were studied by measuring retention of NH₄⁺ and Cl^– at different pH values and NH₄Cl concentrations. No positive charge appeared in the Ando soils at pH values 5 to 8.5 except for one containing allophane and imogolite. The magnitude of their negative charge (CEC; meq/l00g soil) was dependent on pH and NH₄Cl concentration (C; N) as represented by a regression equation: log CEC =a pH +b log C +c, where the values of a and b were 0.113–0.342 and 0.101–0.315, respectively. Unlike the Chernozemic soil, Ando soils containing allophane, imogolite, and/or 2:1–2:1:1 layer silicate intergrades and humus showed a marked reduction of cation retention as pH decreased from 7 to 5. This was attributed to the charge characteristics of the clay minerals and to the carboxyl groups in humus being blocked by Al and Fe.     

Clay mineralogy of the B horizons of two hydrandepts,a Torrox and a Humitropept in Hawaii

The mineralogy of the clay fractions separated from the B horizons of two Hydrandepts (Hilo and Akaka soils), a Torrox (Molokai soil) and a Humitropept (Kolekole soil) was determined by a combination of methods.The Hydrandept B horizons were characterized by predominance of hydrous non-crystalline alumina and iron oxides associated with considerable amounts of humus and with very small amounts of silica. Allophane, allophane-like constituents and imogolite were present but in minor amounts. Gibbsite, goethite, chlorite and illite were also present as accessory minerals.The Torrox and Humitropept B horizons were characterized by predominance of kaolinite, hematite and goethite. The iron oxide minerals were present as fine particles (40–80 A diameter) often clustered to form larger aggregates. Neither imogolite nor allophane and allophane-like constituents were detected. Considerable amounts of dithionite-citrate soluble Al and humus were, however, present in the Humitropept B horizon, which may reflect the effect of an admixture of volcanic ash to the parent material.     

Phosphate fixation by ando soils different in their clay mineral composition

The phosphate fixation capacity at pH 4.5 and an equilibrium concentration of 250 mM phosphate was measured. The soil samples were divided into five groups according to their clay mineralogical composition. The first group soils contain opaline silica and allophanelike constituents, and some unidentified minerals, the second opaline silica and crystalline layer .i1icates, the third opaline silica and crystalline layer silicates with additional allophanelike constituents or aluminarich gel-like materials, the fourth allophanelike constituents, allophane and imogolite and the fifth crystalline layer silicates, allophanelike constituents and alumina-rich gel-like materials, plus some halloysite-like minerals, respectively. The first group soils had phosphate fixation capacities of 3,000 to 8,000, the second group soils 1,000 to 3,000, the third group loib 2,000 to 13,000, the fourth group soils 8,000 to 15,000 and the fifth group soil. 5,000 to 12,000 mg P₂O₅/100 g oven-dry soil, respectively. The fourth group soils in which allophane and imogolite predominated showed the highest phosphate fixation capacity.

The fractions which dissolved from almost all soil samples by treatments with 6% H₂O₂ Na₂S₂O₄-NaHCO₂-Na citrate and 2% Na₂CO₃ were estimated to have very high phosphate fixation capacities (8,000 to 19,000 mg P₂O₅/100 g dry-matter), and there was not much difference among the soil samples examined. Iron and aluminum combined with humus, allophanelike constituents, alumina-rich gel-like materials and halloysite-like minerals in addition to allophane and imogolite contribute to the phosphate fixation of Ando soils.     

Andosol to Luvisol evolution in Central Mexico: timing, mechanisms and environmental setting

Surface and buried Andosols and buried Luvisols of the Nevado de Toluca Late Quaternary tephra-paleosol sequence (Central Mexico) were studied to show whether these soils present an evolutionary sequence and to determine the pedogenic mechanisms and environmental factors involved in the evolutionary process. Micromorphological observations and mineralogical composition of fine sand and clay fractions were used to detect type and succession of soil-forming process. Some of the buried Andosols, defined as “intergrade” Andosols, have a predominantly blocky structure, humus-depleted areas, redoximorphic features and thin clay coatings in Ah horizons. Clay fractions of buried Andosols contain halloysite besides amorphous components, whereas in modern Andosols, allophane is dominant. Luvisols have micro-areas with granular structure and abundant phytoliths in the groundmass of Bt horizons assumed to be the relict Andosol features. Luvisol clay fractions are dominated by halloysite and kaolinite. Primary minerals show micromorphological weathering features in all studied soils being stronger in Luvisols; however, even in Luvisols, sand fractions consist mostly of unstable volcanic silicates. We hypothesise that the studied profiles form an evolutionary sequence: Andosols–“intergrade” Andosols–Luvisols; the soil transformation is supposed to be linked to progressive crystallisation of 1:1 clay minerals. Comparing the Nevado de Toluca paleosol properties with the existing data on volcanic soil climo- and chronesequences and assessing the regional paleopedological and lacustrine records of Quaternary paleoclimates, we concluded that wet/dry climatic oscillations took place during the formation of the studied paleosols. Rapid crystallisation of 1:1 minerals occurred during dry phases, which speeded up the Andosol to Luvisol transformation and made it independent from the primary mineral weathering status. The Andosol to Luvisol transformation accelerated by climatic fluctuations is thought to be a common soil evolutionary pathway in the subtropical and tropical regions of recent volcanism, which suffered contrasting precipitation oscillations in the Quaternary.     

THE CATEGORIES OF ALUMINIUM- AND IRON-HUMUS COMPLEXES IN ANDO SOILS DETERMINED BY SELECTIVE DISSOLUTION

Thirty-three samples of Ando soils were extracted by sodium pyrophosphate (O.IM; pH 10) and by dithionite-citrate. The Al, Fe, and C contents of these two extracts offer a means of differentiating the status of humus in relation to Al and Fe in the different horizons. The humus that forms at first in the Al horizon has a very low complexing ability for Al and Fe and little is dissolved by pyrophosphate. The humus evolves with time or pedogenesis into forms that complex Al and Fe released from volcanic ash by weathering, and which are dissolved by pyrophosphate. In the old horizons, the humus further reacts with additional Al and Fe, some of which may be present as hydrous oxides or allophane-like constituents, allophane and imogolite. This reaction probably makes the humus less soluble in pyrophosphate.     

The behavior of the clay fraction in model ecosystems of soil lysimeters

Changes in the mineralogical composition of the clay fraction (<0.001 mm) sampled from soils of the model lysimetric experiment of Moscow State University have been studied. The mineralogical composition of clay is represented by the paragenetic association of minerals typical of noncalcareous mantle loams in the center of the Russian Plain. The predominant smectitic phase consists of complex mixed-layered minerals (mica-smectite with high and low contents of the smectitic layers, chlorite-smectite with different ratios between the chloritic and smectitic layers) and individual smectites. Tri-and dioctahedral hydromica, kaolinite, chlorite, and clay-sized quartz are present in lower amounts. At the early stages of the experiment, the distribution of the smectitic phase in the soil profile is more contrasting than the distribution of the clay fraction. Under the impact of artificially planted meadows, forests, and agrocenoses, soil profiles with different distribution patterns of the clay fraction are formed. The weakly pronounced eluvial distribution pattern of the clay fraction has been registered. Under spruce and mixed stands, the loss of the clay fraction from the upper horizons is due to the hydrolysis of smectitic minerals in the acidified medium. Under broad-leaved stands, perennial herbs, agroecenoses, and fallow, the depletion of smectites from the upper horizons is due to lessivage. The relative accumulation of hydromica and kaolinite is observed in the uppermost soil layer.     

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.     

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.     

Clay mineralogy and some chemical properties of Ap horizons of Ando soils used for paddy rice in Japan

The clay mineralogy of the Ap horizons of Ando soils in Japanese paddies was determined by a combination of methods and compared with that of Ando soils of uplands. Six of 13 paddy soil samples contained allophane and imogolite and none contained gibbsite, whereas parallel figures were 15 and 7 for 22 upland soil samples. Substantial numbers of diatoms were found in 5 paddy and 1 paddy-converted upland soil samples. The lack of gibbsite was related to the stage of soil formation rather than the paddy condition, whereas the presence of diatoms was related to both. Regarding layer silicates, there was no particular difference between the paddy and upland soil samples but one unidentified mineral with unique morphology and infrared spectrum was found in two paddy soil samples. There was no particular difference in phosphate adsorption between the paddy and upland soil samples.     

Lability of soil organic carbon in tropical soils with different clay minerals

Soil organic carbon (SOC) storage and turnover is influenced by interactions between organic matter and the mineral soil fraction. However, the influence of clay content and type on SOC turnover rates remains unclear, particularly in tropical soils under natural vegetation. We examined the lability of SOC in tropical soils with contrasting clay mineralogy (kaolinite, smectite, allophane and Al-rich chlorite). Soil was sampled from A horizons at six sites in humid tropical areas of Ghana, Malaysian Borneo and the Solomon Islands and separated into fractions above and below 250 μm by wet sieving. Basal soil respiration rates were determined from bulk soils and soil fractions. Substrate induced respiration rates were determined from soil fractions. SOC lability was significantly influenced by clay mineralogy, but not by clay content when compared across contrasting clay minerals. The lability of SOC was lowest in the allophanic and chloritic soil, higher in the kaolinitic soils and highest in the smectitic soil. Our results contrast with conventional concepts of the greater capacity of smectite than of kaolinite to stabilize SOC. Contents of dithionite-citrate-bicarbonate extractable Fe and Al were inversely related to SOC lability when compared across soil types. A stronger inverse correlation between content of ammonium-oxalate extractable Fe and SOC lability was found when considering the kaolinitic soils only and we conclude that the content of active Fe (hydr-) oxides controls SOC stabilization in the kaolinitic soils. Our results suggest that the validity of predictive models of SOC turnover in tropical soils would be improved by the inclusion of soil types and contents of Fe and Al (hydr-) oxides.     

Postpyrogenic Polycyclic Soils in the Forests of Yakutia and Transbaikal region

Periodical forest fires are typical natural events under the environmental and climatic conditions of central and southern Yakutia and Transbaikal region of Russia. Strong surface fires activate exogenous geomorphological processes. As a result, soils with polycyclic profiles are developed in the trans-accumulative landscape positions. These soils are specified by the presence of two–three buried humus horizons with abundant charcoal under the modern humus horizon. This indicates that these soils have been subjected to two–three cycles of zonal pedogenesis during their development. The buried pyrogenic humus horizons accumulate are enriched in humus; nitrogen; total and oxalate-extractable iron; exchangeable bases (Са⁺² and Mg⁺²); and the fractions of coarse silt, physical clay (<0.01 mm), and clay (<0.001 mm) particles in comparison with the neighboring mineral horizons of the soil profile. The humus of buried pyrogenic horizons is characterized by the increased content of humic acids, particularly, those bound with mobile sesquioxides (HA-1) and calcium (HA-2) and by certain changes in the type of humus.     

Semiquantitative determination of imogolite and Al-rich allophane (Si / Al ≃ 1 : 2) in some volcanic ash soils in San'in region by a combination of thermogravimetry-differential thermal analysis and trimethylsilylation analysis of soil clays

Abstract

A method to determine the contents of imogolite and Al-rich allophane (Sil Al ? 1 : 2) in volcanic ash soils was presented. The method is based on the (1) assessment of the presence of Al-rich allophane in clays by successsive extraction with dithionite-citrate and oxalate-oxalic acid, (2) trimethylsilylation of soil clay with a mixture of hexamethyldisiloxane, HCl, and isopropyl alcohol, and determination of the content of monomeric Si based on the trimethylsilyl derivative of monomeric orthosilicate anion by gas / liquid chromatography, (3) determination of the total content of imogolite and Al-rich allophane based on the content of monomeric Si from imogolite, (4) determination of the imogolite content by Thermogravimetry (TG )-Differential Thermal Analysis (DTA) based on the weight loss due to endothermic dehydroxylation with maximum values at ca. 386°C, (5) calculation of the Al-rich allophane content by subtracting the imogolite content from the total content of these minerals, and (6) evaluation of the imogolite and Al-rich allophane content of soil by multiplying clay content of soil and the two mineral content of clay. The trimethylsilylation analysis was found to be reproducible, and the estimated total amounts of two minerals in clays by this method were adequately approximated to those evaluated from the amount of Si (= Si_o) extracted with oxalate-oxalic acid after extraction with dithionite-citrate. The variation in the abmldance of two minerals in the soil horizons of volcanic ash soils from the San'in region indicated that this method is suitable for the profile-study of volcanic ash soils.     

Dispersion of humic allophane soils with supersonic vibration

The difficulties in dispersing volcanic ash soils of Japan and New Zealand have been considered to be due to the association or aggregation of allophane (3, 5, 7–10). In particular, MIYAZAWA (9) has obtained evidence that stable microaggregates of Humic Allophane soils derived from volcanic ash have been formed by dehydration of allophane. Recently, several investigators (2, 4, 6, 8, 9, 12) have pointed out that ultrasonic vibration is effective in dispersing the fine particles of soils. With respect to the applicability of supersonic vibration to the particle-size distribution analysis of Humic Allophane soils, MIYAZAWA (9) stated that the maximum dispersion, as measured by the clay content, was obtained only with supersonic vibration using an acidic medium. KOBO and OBA (8) reported that calgon (sodium hexametaphosphate) as a dispersing agent was successfully applicable to most Humic Allophane soils, but the use of HCI was necessary for some highly allophanic subsoils, and that the effect of supersonic vibration on dispersion of the soils is attributed to the breakdown of aggregates larger than 20 microns in diameter. They also recommended a mixture of 10g of soil and 50 ml of water and 20 min. exposure for a supersonic vibrator (10 Kc, 300 W). With respect to the applicability of vibration treatment in the particle-size distribution analysis of Humic Allophane soils containing volcanic glasses in abundance, some apprehension may be entertained about the breakdown of primary minerals, especially of volcanic glasses (9, 10).     

Aluminum solubility of strongly acidified allophanic Andosols from Kagoshima Prefecture,southern Japan

Abstract

The aluminum solubility of acidified soils both from furrows and under tree canopies of a tea garden was studied using equilibrium experiments in 0.01 mol L^?1 CaCl₂ solution systems. The soils were originally classified as allophanic Andosols. The furrow soils were more severely acidified because of the heavy application of nitrogen fertilizer, especially in the upper soil horizons (pH[H₂O] of 3.6–3.8 in the A1 and 2A2 horizons). These acidified soils were characterized by the dissolution of allophanic materials (allophane, imogolite and allophane-like materials) and by an increase in Al–humus complexes. Ion activity product (IAP) values of the strongly acidified soil horizons were largely undersaturated with respect to imogolite (allophanic clay) or gibbsite. Plots of p(Al³⁺) as a function of pH strongly indicated that Al solubility of the soils was largely controlled by Al–humus complexes, especially in the A1 horizon. In the canopy soils, which were more weakly acidified (pH[H₂O] 4.9–5.0), Al solubility was close to that of gibbsite and allophanic materials, indicating that the solubility is partly controlled by these minerals.     

Allophane in Some Ando Soils

Allophane has been known to occur widely in volcanic ash soils in Japan and New Zealand. However, exact knowledge of its nature has not been well established, mainly because of extreme difficulty to separate it in pure state and of its x-amorphous nature. In the course of the studies on soil allophane, it was noticed that certain Ando soils contained two different mineral colloids together, in addition to crystalline clay minerals and free sesquioxides. X-ray examination revealed that one was x-amorphous colloid which would be called allophane, and the other an unknown colloid of low crystallinity. Imogolite*** Imogolite will be described in a subsequent paper by the present authors. was proposed as the name of the latter colloid by the present authors after imogo in which imogolite was first found. Imogo is a brownish yellow, volcanic ash soil. in the Kuma basin in the Kumamoto Prefecture³⁾. When deferration treatment is applied to the soils, allophane disperses both in an acid and alkaline media, whereas imogolite disperses in an acid medium and flocculates in an alkaline one.     

A climosequence of soils on late quaternary volcanic ash in highland Papua New Guinea

Some chemical, physical and mineralogical properties of three soils developed in volcanic ash at altitudes of 1040 m, 1720 m, and 2350 m in Papua New Guinea's Enga Province are presented. Silt-fraction mineralogy and total chemical analyses show that fresh ash occurs in the upper approximately 30 cm of profile at each site. This fresh ash is probably only a few thousand years old and overlies an older weathered ash (Tomba Tephra;more than 50000 years old). At the lowest site the majority of the primary minerals (predominantly amphiboles, volcanic glass and felspar, and some pyroxenes) have been decomposed by weathering to produce a high clay content. With increasing altitude, greater proportions of silt-sized, unweathered and partially altered primary minerals are recognised and molar ratios of calcium, magnesium, sodium and potassium to aluminum increase accordingly. In the clay fractions, allophane with Al/Si ratios of approximately 2.0 is dominant at the highest site, whereas with decreasing altitude lower proportions of allophane occur, Al/Si ratios decline and halloysite becomes dominant. Gibbsite is found in all three profiles     

Effect of Contrasting Trophic Conditions on the Priming Effect in Gray Forest Soils

Priming effects initiated by the addition of ¹⁴С glucose have been compared for humus horizons of soils existing under continuous input of fresh organic substrates and for buried soil horizons, in which entering of organic matter has been essentially limited. The effect of microrelief on the manifestation of priming effect in the humus horizons of gray forest soil on microhigh and in microlow has been estimated. Humus horizon in soils on microhigh, not activated by glucose, produced two times more СО₂ in comparison with soils of microlow. However, the introduction of glucose canceled the effect of microrelief on СО₂ emission. The intensity of absolute priming effect correlated with the С_org pool, initial microbial biomass, and enzyme activity, decreasing from humus horizons to the buried ones, and did not depend on microrelief. The effect of microrelief was observed, when assessing the priming effect relative to control (soil not activated by glucose): the value of relative priming effect was 1.5 times greater in А horizon of gray forest soil in microlow in comparison with that on microhigh being the result of increasing activity of enzymes.