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1.
For the past ten years much work has been carried out on clay minerals of volcanic ash soils. Most investigators have reported that allophane is dominant among clay minerals of volcanic ash soils and crystallizes to halloysite or meta-halloysite with the advance of weathering (1–8). On the other hand, UCHIYAMA, MASUI and ONIKURA (1960) found that montmorillonite predominates in the clay fraction of volcanic ash soil in Kawatabi (9). Furthermore, MASUI, SHOJI and UCHIYAMA (1966) showed that the major crystalline clay minerals of volcanic ash soils in the Tohoku district are montmorillonite, vermiculite, intergradient montmorillonite-vermiculite and chlorite (10). They also showed that these minerals increase with the advance of weathering and that kaolin minerals are minor constituents.  相似文献   

2.
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.”  相似文献   

3.
Soil samples were investigated from three different climatic regions of Japan. The soil profiles were well drained and consisted of a number of buried soils. Organic matter and free iron oxides were removed from the samples which were then fractionated. Laminar opaline silica particles occurring in the 0.2 to 5 μm fractions were examined electron-optically following ultrasonic and cold 5 per cent sodium carbonate treatment. Four types of opaline silica particles were distinguished: circular, elliptical, rectangular, and rhombic. The opaline silica particles are extremely thin. They show fine-grained uneven surfaces and weathered and alkali-treated opaline silica particles appear to be very porous suggesting that the particles are actually composed of extremely fine silica spheres. Opaline silica panicles occur only in the 0.2 to 5 μm fractions and are most abundant in the 0.4 to 2 μm fractions. Of the four types the circular and elliptical types predominate. The elliptical type is the most common in the fine fraction and the circular type in the coarse fraction. Compared with B- or C-horizons, the A-horizon of a profile tends to be relatively rich in opaline silica. Opaline silica particles are abundant in recent volcanic ash soils, particularly in Hokkaido soils < 500 years old. Soils of this area more than 7000 years old contain opaline silica particles whereas they are rare in Kanto soils > 6000 years old and in Kyushu soils > 4000 years old. Hokkaido has much lower mean annual temperatures and rainfall than Kanto or Kyushu. This may have caused slower weathering of opaline silica in the Hokkaido soils. Conditions for formation of opaline silica may be less favourable in subsoils because supersaturation of silica and concentration of bases is less likely to occur in subsoils than in surface soils.  相似文献   

4.
A weathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100–115,000 years in the Etna region served as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements. Although the soils were influenced by ash depositions during their development and the soil on the oldest lava flow developed to a great extent under a different climate, leaching of elements and mineral formation and transformation could still be measured. Leaching of major base cations coupled with a corresponding passive enrichment of Al or Fe was a main weathering mechanism and was especially pronounced in the early stages of soil formation due to mineral or glass weathering. With time, the weathering indexes (such as the (K + Ca)/Ti ratio) tend to an asymptotic value: chemical and mineralogical changes between 15,000 and 115,000 years in the A and B horizons were small. In contrast to this, the accumulation of newly formed ITM (imogolite type materials) and ferrihydrite showed a rather linear behaviour with time. Weathering consisted of the dissolution of primary minerals such as plagioclase, pyroxenes or olivine, the breakdown of volcanic glass and the formation of secondary minerals such as ITM and ferrihydrite. The main mineral transformations were volcanic glass ? imogolite ? kaolinite (clay fraction). In the most weathered horizons a very small amount of 2:1 clay minerals could be found that were probably liberated from the inner part of volcanic glass debris. The rate of formation and transformation of 2:1 clay minerals in the investigated soils was very low; no major changes could be observed even after 115,000 years of soil evolution. This can be explained by the addition of ash and the too low precipitation rates. In general, soil erosion played a subordinate role, except possibly for the oldest soils (115,000 years). The youngest soils with an age < 2000 years had the highest accumulation rate of organic C (about 3.0 g C/m2/year). After about 15,000 years, the accumulation rate of organic C in the soils tended to zero. Soil organic carbon reached an asymptotic value with abundances close to 20 kg/m2 after about 20,000 years. In general, the preservation and stabilisation of SOM were due to poorly crystalline Al- and Fe-phases (pyrophosphate-extractable), kaolinite and the clay content. These parameters correlated well with the organic C. Imogolite-type material did not contribute significantly to the stabilisation of soil organic matter.  相似文献   

5.
C.J. Chartres  C.F. Pain 《Geoderma》1984,32(2):131-155
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  相似文献   

6.
Abstract

The advanced classification of brown forest soils (BFS) is based on the specific properties of these soils, including the acid ammonium oxalate extractable aluminum (Alox) and lithic fragment contents, as well as their vertical distributions in the soil profile. In the present study, these properties were used to classify BFS, resulting in four types: (1) H-Alox-NGv BFS, (2) H-Alox-Gv BFS, (3) M-Alox BFS, (4) L-Alox BFS. H-Alox-NGv BFS is derived from volcanic ash characterized by a high Alox content and no lithic fragment, whereas L-Alox BFS is derived from weathered bedrock and has a low Alox content. H-Alox-Gv BFS and M-Alox BFS are derived from mixtures of volcanic ash and weathered bedrock. H-Alox-Gv BFS is characterized by high Alox content and many lithic fragments, whereas M-Alox BFS has moderate Alox content. H-Alox-NGv BFS and black soils (BLS) develop from accumulated volcanic ash, as indicated by declining Alox and clay content with decreasing depth in the surface horizons, as a result of successive additions of less-weathered volcanic ash to the soil surface.  相似文献   

7.
Soils found on fan surfaces in the Kokoda Valley are derived from both volcanic ash and river alluvium. The alluvium is variable, some of it being mixed with volcanic ash. The main differences in the micromorphology of the soils appear to be related to the relative amounts of volcanic ash present in the soil profile. The plasma of soils formed on volcanic ash is isotropic in thin section. The plasma of alluvial soils exhibits increasing birefringence with decreasing amounts of volcanic ash. It is suggested that random structures in the clay fraction of the volcanic ash may account for its isotropic nature.  相似文献   

8.
The determination of the specific gravity of allophane is an interesting and important problem, but it is no exaggeration to say that we have no satisfactory answer to this question in spite of numerous studies. In this note, the specific gravities of allophane, weathered pumices and volcanic ash soil were determined with a pycnometer, and the values compared with those of the other clay minerals and non-volcanic ash soils.  相似文献   

9.
The surface morphology of quartz grains can indicate the degree of weathering of soil material. We have compared two methods of assessing the relative weathering of soils on the basis of differences in the surface morphology of quartz sand grains in a catena of soils in Rwanda. One method is based on the presence or absence of surface features indicative of weathering or freshness, while the other uses the frequency and size of dissolution etch pits. A ranking of relative weathering could be obtained using the first technique for the slightly and somewhat weathered soils but not for the weathered soils. On the other hand, weathering trends and differences between the horizons studied were detected in weathered soils using the second method. The introduction of more specific definitions of the weathering classes used in the latter method leads to clear improvement of the inter-observer reproducibility of the weathering classification. The surface features on the quartz grains suggest that the soil at the summit is less weathered than the other soils of the sequence. Quartz grains from the well-drained soils on the slopes, which are subjected to more intense leaching and thus to stronger chemical weathering, have more triangular etch pits and chatter marks. In the imperfectly drained soils in the valley bottom quartz grains are less etched because dissolution is inhibited by the oversaturation in silica of the drainage waters.  相似文献   

10.
In advanced stages of volcanic ash soil formation, when more clay is formed, soil porosity values and soil water retention capacities are large and the soils show pronounced shrinkage on drying. Soil shrinkage is a key issue in volcanic soil environments because it often occurs irreversibly when topsoils dry out after changes from permanent grassland or forest to agriculture. European Andosols have developed in a wide range of climatic conditions, leading to a wide range in intensity of both weathering and organo‐mineral interactions. The question arises as to whether these differences affect their shrinkage properties. We aimed to identify common physically based shrinkage laws which could be derived from soil structure, the analysis of soil constituents, the selected sampling size and the drying procedure. We found that the final volumetric shrinkage of the initially field‐wet (56–86% of total porosity) or capillary‐wet (87–100% of total porosity) undisturbed soil samples was negatively related to initial bulk density and positively related to initial capillary porosity (volumetric soil water content of soil cores after capillary rise). These relationships were linear for the soil clods of 3–8 cm3, with final shrinkage ranging from 21.2 to 52.2%. For soil blocks of 240 cm3 and soil cores of 28.6 cm3 we found polynomial and exponential relationships, respectively, with thresholds separating shrinkage and nearly non‐shrinkage domains, and larger shrinkage values for the soil cores than for the soil blocks. For a given sample size, shrinkage was more pronounced in the most weathered and most porous Andosol horizons, rich in Al‐humus, than in the less weathered and less porous Andosol horizons, poor in Al‐humus. The Bw horizons, being more weathered and more porous, shrank more than the Ah horizons. We showed that the structural approach combining drying kinetics under vacuum, soil water analysis and mercury porosimetry is useful for relating water loss and shrinkage to soil structure and its dynamics. We also found that the more shrinkage that occurred in the Andosol horizon, the more pronounced was its irreversible mechanical change.  相似文献   

11.
Low availability of phosphorus (P) in Turkish soils is a significant problem of agricultural production depending on carbonates in slightly weathered and iron/aluminum oxides in highly weathered soils. Thus, crop-based P fertilization along with inherited nature of P partition can lead to changes in the amounts and geochemical fractions of phosphorus. For this reason, horizon-based surface samples were taken from 16 soil series that belong to four orders with different pedotransfer functions. The geochemical phosphorus fractions were sequentially extracted by sodium bicarbonate (NaHCO3), sodium hydroxide (NaOH), citrate-dithionite-bicarbonate buffer system (CBD), hydrochloric acid (HCl), and aqua-regia. Results indicated that weathering sequence was inversely related to plant available P fractions. The fertilizer P was possibly converted to HCl-extractable (Ca-Pi) fraction in calcareous soils through NaOH-Po and NaHCO3-Po fractions whereas it accumulated in the CBD-P fraction in relatively weathered soils. The carbonates and Al/Fe oxides were most significant constituents in P partitioning as consequences of parent material and weathering chronosequence.  相似文献   

12.
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13.
A chrono-toposequence of five soils formed in strongly weathered granite in the South Island of New Zealand was described on the basis of soil profile morphology, landscape position, and the degree of weathering of the underlying granite. The sequence contains five progressively younger soils on increasing slopes from crest to backslope formed in a Parent Material of originally uniform mineralogical and chemical composition as Parent Rock under a uniform climate and vegetation. All profiles of the sequence are strongly weathered and leached with the final member of the sequence being considered to represent a terminal steady-state system.Changes in a number of chemical and physical soil properties were described with the increasing soil development (i.e. increasing weathering and leaching) represented in the sequence profiles. Profile soil weights (< 2mm) remained approximately constant, once weathering of stone material (> 2 mm) to fines was completed. An initial increase in profile silt and clay content was followed by a decline in both fractions with a corresponding increase in the sand fraction. Proportions of kaolin/metahalloysite initially increased and 2:1–2:2 Al intergrades decreased, but the final three sequence profiles had similar clay mineralogies with kaolin/metahalloysite being the main component. Profile weights of oxidisable carbon and total nitrogen followed an exponential decline after an initial increase between the first two sequence profiles. Profile cation-exchange capacity, total exchangeable bases, percent base saturation, and exchangeable cations showed no trends with increasing soil development. Depth-gradients of these parameters together with oxidisable carbon and total nitrogen became less pronounced, with the apparent tendency towards a steady-state system in the final sequence profile. Multiple regression analysis indicated that oxidisable carbon was the main contributing factor to cation-exchange capacity followed by clay content.Profile weights of total calcium and potassium were closely correlated and showed an approximately exponential decline with increasing soil development, whereas total magnesium showed a relatively linear decline. Total aluminium and iron both showed an initial increase and then declined. The relative rates of loss of the five total elements studied were in the order: Ca > Mg > K, Fe > Al.  相似文献   

14.
The physical, chemical, and mineralogical properties as well as the micromorphology of five indurated volcanic ash soils in Kyushu, Japan were investigated. The indurated soils were divided into two types based on the physical and chemical properties. Type 1 was not indurated in its moist state, but shrank and became very hard by air-drying. Type 1 included the buried volcanic ash soils whose physical and chemical properties were similar to those of other buried volcanic ash soils except for the property of induration by air-drying. The mechanism of the induration is still unknown, although it is considered to have occurred during the long period after the deposition of tephra under the influence of soil formation processes. Type 2 included the tephra layers that were indurated in both moist and air-dried states. The carbon and clay contents of type 2 were remarkably lower than those of type 1. Type 2 had not been affected by the soil formation process but had undergone induration soon after the deposition of the tephra. Neither type 1 nor type 2 could be classified into any indurated horizons that are defined in the present soil classification system. For the improvement of soil productivity, type 1 should be harrowed thoroughly soon after its exposure to the surface, and type 2 should be harrowed or removed using farm machinery.  相似文献   

15.
Some allophanic soils in Japan, developed from deposits of volcanic ashes have aggregates, the sizes of which are mostly those of silt and sand, and which are very stable against the ordinary soil dispersion treatment such as decomposition of organic matter with hydrogen peroxide and addition of deflocculants to the suspension, but can be broken to smaller particles by mechanical forces. Oba and Kono (1, 2) reported that there were aggregates stable even against deferration treatment in the soils, especially plenty in ones developed from basic volcanic ashes, and these aggregates could be broken up into clay of allophane mainly by a sonic-wave vibration technique. Miyazawa (3) recognized that the aggregates were only found in Andosols developed under warm-temperate climates, being concentrated in B horizon, but not so much in A horizon and few in gleyey subhorizon, and assumed that they were formed under a specific weathering like seasonal wetting and drying. Yasuo et al. recognized a high correlation between the degree of aggregation and free iron oxide content of the soils in Kanto Plain and suggested that sesquioxide and structure of allophane might associate with the aggregate fonnation. On the other hand, airdrying of volcanic ash soils sometimes reduces their dispersibilities through irreversible formation of aggregates. Kishita (5) found that this effect of drying was remarkable at subsoiLs, and similar results were obtained by TAPA et al. (6). The poor dispersibility and the irreversible change by drying are known also about volcanic ash soils of New Zealand (7, 8), and Latin America (10, 11), Hawaii (9).  相似文献   

16.
The size fraction of soils is one of the important factors that influence the retention of heavy metals. The sorptive properties of soils for heavy metals are principally associated with clay and silt-size fractions. Phosphate fertilizers that are applied to highly weathered tropical soils contain a wide concentration range of cadmium (Cd) as an impurity. Tropical soils contain kaolinite and oxides of Al, Fe, and Mn, which have the ability to sorb Cd. However, the distribution of Cd in different size fractions and the chemical speciation of particulate-bound Cd in the clay size fractions when introduced to soil and allowed to incubate at field moisture capacity merits attention. Cadmium was, therefore, applied to selected surface Kenyan soils varying widely in physicochemical properties to investigate its distribution in different soil particle size fractions and the speciation of particulate-bound species in clay size fractions after incubation. The Cd content in different particle fractions was analyzed by graphite furnace atomic absorption technique after HF-HClO4 digestion. The particulate-bound Cd species were investigated using chemical sequential extraction method. The study showed that clay size fraction of the natural and the Idaho monoammonium phosphate (MAP)-fertilizer or the Cd perchlorate-added MAP chemical reagent-treated soils contained the highest amount of the total Cd. However, silt and sand fractions of the treated soils also retained appreciable amounts of Cd. Speciation studies revealed that metal-organic complex-bound Cd was the most predominant compared to other particulate-bound Cd species in the clay size fractions of the soils treated with Idaho MAP fertilizer or the Cd perchlorate-added MAP chemical reagent. The distribution of total Cd in the different soil particle size fractions and the speciation of particulate-bound Cd in the clay size fractions varied with the soil type. The results indicate that clay size fractions can retain Cd making it less available; however, the influence of farming practices, which affect Cd mobility, should not be overlooked.  相似文献   

17.
Abstract

Properties and classification of four selected volcanic ash soils from Abashiri, Hokkaido were studied and the transition of Andisols to Mollisols was discussed. Two of the four pedons (Brown Andosol and Cumulic Andosol)1 showed morphological, clay mineralogical, physical, and chemical properties common to most Andisols in Japan. However, the properties of the other two pedons (Acid Brown Forest soil and Brown Forest soil)1 were considerably different from those of common Andisols in Japan. It was found that the changes in the andic soil properties or transition of Andisols to Mollisols was closely related to the progression of clay weathering, mainly the transformation of noncrystalline clay materials to halloysite. One of the four pedons (Brown Forest soil)1had the clay fraction dominated by halloysite from the uppermost horizon down to the bottom of the profile and satisfied both andic and mollic requirements. Thus we concluded that the pedon is a transitional soil between Andisols and Mollisols and that the transition is closely related to the duration of surface weathering under relatively weak leaching conditions. The four pedons were classified according to the Andisol Proposal (Leamy et al. 1988, New Zealand Soil Bureau) as follows:

Pedon 1: Medial, amorphic (allophane/imogolite), frigid Typic Hapludand (Brown Andosol).1 Pedon 2: Medial, amorphic (allophane/imogolite), frigid Typic Melanudand (Cumulic Andosol).1 Pedon 3: Medial, amorphic (allophane/ imogolite), over kandic, frigid Typic Melanudand (Acid Brown Forest soil).1 Pedon 4: Medial, kandic, frigid Typic Hapludand (Brown Forest soil).1  相似文献   

18.
The influence of mean annual rainfall and soil texture on the 137Cs vertical distribution in soils from southern Chile The influence of mean annual rainfall and soil texture on the vertical distribution of 137Cs from global fallout was studied in undisturbed volcanic ash soils from southern Chile. The areal concentration and translocation depth increase with the mean annual precipitation. In spite of the high rainfall at the sampled area (970 - 2500 mm a?1), the highest 137Cs contamination was found in the upper 10 cm layer. The vertical migration is reduced by the high adsorption capacity of these volcanic ash soils, but on the other side increased in soils with high large-pore volumen. The translocation depth reaches only up to 26 cm in the clay soils, 35 cm in the silty soils and 70 cm in the sandy soil.  相似文献   

19.
The early stage of weathering / soil formation processes from new volcanic mudflow (new lahar materials) brought from Mt. Pinatubo was examined. For this purpose, comparative studies on the physical / chemical characteristics of the new lahar materials and soils formed by the deposition of old lahar materials were conducted. Original soils contained less coarse sand, more silt, and clay than the new lahar materials. Increase in the clay content of the original soils reflected the progression of weathering. The occurrence of a higher leaching process of Fe, Ca, and Mg and of a moderate accumulation of organic matter in the original soils was suggested, based on the differences in the soil elemental composition and chemical properties. Values of base saturation and phosphate absorption coefficient (PAC) of the new lahar materials were 388% and 44, while those of all the original soils ranged 15–160% and 55–894, respectively. With the progression of weathering, the PAC value tended to increase gradually while the base saturation value decreased abruptly under the environmental conditions prevailing in the Philippines.  相似文献   

20.
It has been reported by many workers that various soil properties influence the retention of boron added to soils, but there is little infomration on the relative importance of these properties to boron retention and there is something controversial in the published results regarding the effects of different soil properties such as organic matter content, soil reaction, available calcium content and texture on boron retention (15). The present study was undertaken to obtain more detailed informations on the relationships between boron adsorption and different properties of soils, and on comparative contribution of soil constituents such as organic matter, sesquioxides and inorganic colloids to boron adsorption of soils. In Japan, boron deficiency symptoms of crops often appear in the fields of volcanic ash soils, and many experiments on boron application have been conducted to amend the boron deficiencies of the soils. It is considered that volcanic ash soils may have special characteristics concerning boron retention in comparison with nonvolcanic ash soils. In the present study, therefore, some volcanic ash soils were also taken as samples in addition to non-volcanic ash soils to confirm their speciality to boron retention.  相似文献   

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