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1.
本文研究结果表明：（１）神农架垂直带土壤矿物的风化脱硅作用较弱，粘土矿物以２：１型矿物为主，１：１型高岭含量很少。（２）随海拔升高，矿物的淋溶脱钾和层间羟基铝化作用增强，低海拔土壤的２：１型矿物以水云母为主，高海拔土壤以１．４ｎｍ矿物为主，其中１．４ｎｍ过渡矿物相对增多。（３）土壤的络合态铁、铝和非晶形铁，铝含量随海拔升高明显增大。（４）土壤的可变电荷量，阴离子交换量，交换性酸和铝饱和度等均随海拔  相似文献   

2.
P. Ildefonse 《Geoderma》1980,24(3):257-273
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3.
The presence of so-valled chlorite-like minerals has been reported in many soils of not only acid but also of alkaline reaction (1). The minerals have been designated by, many terms, for example, dioctahedral vermiculite (2), dioctahedral analogue of vermiculite (3), 14A mineral (4), chlorite-like mineral (5), interstratified chlorite-vermiculite (6), intergradient chlorite-expansible 2:1 layer silicate, intergradient chlorite-vermiculite, intergradient chlorite-vermiculite-montmorillonite, intergrade, or interlayered vermiculite (7), and 2: 1-2: 2 intergrade (1). The minerals designated by these terms are evidently of the same category, and some of them are synonymous. Although they are of intermediate properties, between true chlorite and true vermiculite or montomorillonite, they could be regarded as an independent group of minerals in the course of pedochemical weathering. Jackson (1), for instance, has given the minerals the position of “weathering index 9”, placing them between vermiculite and kaolin as equivalent to montmorillonite, or secondary chlorite and kaolin in his weathering sequence. An explanation of the diagenesis of the minerals has been recently attempted by synthesis of the chlorite-like structures from montmorillonite (8), (9) and vermiculite (10) and mineralogical analyses of soil clay fractions (7).  相似文献   

4.
Genesis of Secondary Al-(Fe-)Chlorites Comparing the results of soil investigations with those obtained from laboratory syntheses it was concluded that secondary Al-Fe-chlorites in soils of moderate cool-warm-humid climates mainly develop through protonisation of Al and Fe in the mineral structure of expanded dioctahedral vermiculites with subsequent hydrolysis in the interlayer space. In this process characteristics of the mineral itself (e.g. layer charge) as well as carbonic acid and soil organic acids (as proton suppliers) are the most important factors. From this, the further conclusion was drawn that in the pH-range 6, 5–6 secondary chlorites begin to develop increasingly until pH5 (development conditions) and in the pH-range 5–4,5“conservation conditions” exist. - At pH<4,5 secondary chlorites are unstable (dissolution conditions) through protonisation of Al-Fe-hydroxy polymers (reverse of hydrolysis) with subsequent solubilization and leaching especially through complexation by soil organic acids. - As remaining minerals in this weathering sequence smectites occur, resulting from the decrease of layer charge in vermiculites through the chloritization process, thus indicating that chloritization may be an important process for the genesis of smectites under acid weathering conditions.  相似文献   

5.
This paper is a review of some advances in the studies on 1.4-nm intergrade mineral of soils in subtropical China. 1)1.4-nm intergrade mineral occurs ubiquitously in soils of subtropical China. The 1.4-nm mineral in red soil and yellow soil is mainly 1.4-nm intergrade mineral, and in acidic yellow-brown soil (pH < 5.5) is vermiculite alone or 1.4-nm intergrade mineral together with vermiculite. The distribution and the content of 1.4-nm intergrade mineral in the mountain soils are more widespread and higher than those of the corresponding soils in horizontal zone. 2) The interlayer material of 1.4-nm intergrade mineral in these soils appears to be hydroxy-A1 polymers instead of hydroxy-Fe, proto-imogolite or kaolin-like material. There is a significant positive correlation between A1 amount extracted from the soil with sodium citrate after DCB extraction and pH value of the citrate solution after the extraction. The citrate can also extract a certain amount of silicon from the soil, but the silicon may not come from interlayer of 1.4-nm intergrade mineral. 3) It was seldom studied that either vermiculite or smectite did the natural 1.4-nm intergrade mineral come from in soil, or it was commonly thought to come from vermiculite. A recent report has revealed that it can come from smectite. There are some different behaviors between the 1.4-nm intergrade mineral derived from vermiculite and that from smectite. For example, they exert different influences on the formation of gibbsite. The 1.4-nm intergrade mineral derived from smectite may promote the formation of gibbsite in the yellow soil. 4) The type of 1.4-nm minerals in soils. i.e., vermiculite or 1.4-nm intergrade mineral, may be significant to soil properties, such as soil acidity, exchangeable Al, electric charge amount and specific surface area. Therefore, the management for the soil in which 1.4-nm mineral is mainly 1.4-nm intergrade mineral or vermiculite should be dealt with differently.  相似文献   

6.
Clay mineralogy and K-Ca-exchange properties of surface soils from the nutrient potential trial Hallertau (Bavaria) In soils of four locations of the Hallertau nutrient potential trial, with a soil texture consisting of sand, silty sand, silty loam and sandy clayey loam, clay mineral properties were measured with the standardized glycerol expansion method and with n-alkylammonium (Rnc-NH3+-clay). The expandable minerals of the sandy soils consist exclusively of smectites s.s., (s.s. = sensu stricto) with 0.42 to 0.28 charge equivalents per formula unit (p.f.u.). The expandable minerals of the loams are an assemblage of smectites s.s. and vermiculites. The total layer charge of the smectites s.s. extend from 0.54 to 0.28 charge eq. p.f.u. The fine clay fractions (< 0.1 μm) do not contain vermiculites. The layer charge density of vermiculites with homogeneous charge in the coarse fractions varies between 0.60 and 0.95 charge eq. p.f.u. The immediate K-Ca-exchange was extended with the values of the continued K exchange versus Ca at low K intensity. The Q/I isotherms of sandy soils have a more pronounced curvature than the isotherms of the loams; in all cases, however, the exchange curves have a continuous form. This phenomen is discussed in terms of the clay mineralogy of the soils. After 8 years without K fertilizing, samples gave values between 168 and 497 kg smectite-K/ha for the surface soils. The constant rates of K-desorption vary between 12.8 and 28.7 kg K/ha (surface soil). The rates are better differentiated between unfertilized and fertilized soils for the loams than for the sandy soils. The constant rates of K release were found to be controlled at an AR-level between 1.6 · 10?4 M1/2 (unfertilized sandy soil) and 5.2 · 10?4 M1/2 (fertilized sandy clayey loam soil).  相似文献   

7.
Chemical weathering can be approached from three interpretive points of view: distribution of the secondary minerals in landscapes, weathering of primary minerals and geochemistry of ions in solution. On granitic rocks it is posible to define both climatic and topographic sequences of distribution of clays in association with weathering products: gibbsite - kaolinite - hydrous iron oxides - hydrous manganese oxides - iron-rich montmorillonite - calcium carbonate - calcium sulfate - sodium carbonates and silicates. These stages appear as an absolute accumulation formed by filling of intergranular pores. Another sequence can be found not in intergranular pores but in the cracks and along the cleavages of primary minerals from which they are derived by relative accumulation. The order of appearance of these secondary minerals remains the same regardless of the nature of climates and the topographic position. The conditions of equilibrium are not identical in the interior of grains of different primary minerals nor in the pores outside of them and the secondary minerals found in the different situations are also not identical. This is well demonstrated by the chemistry of waters draining slopes. The equilibrium diagrams and balances between cations and silica sometimes result in disagreement, proving that equilibrium conditions are not satisfied between solutions circulating in the pores and clay minerals found inside the primary minerals.  相似文献   

8.
Acidic weathering of the sulfidic Upper Cretaceous Carlile and Pierre Shales in Nebraska has led to the precipitation of the Al sulfate–hydroxide minerals aluminite, alunite, “basaluminite”/felsöbányaite (e.g.,), the aluminum hydroxides gibbsite and bayerite, and the rare Al phosphate hydroxide vashegyite. Kaolinite has also been produced as a result of this acidic weathering. These minerals do not appear as neoformed constituents in any extant soils in the region, and their existence underscores the ability of pyrite oxidation to produce major changes in mineralogy on a Holocene to Recent time scale. Jarosite, hydronium jarosite, gypsum, halotrichite, and melanterite also appear as secondary minerals in the weathered shales. Acidic weathering and the formation of new minerals is extrapedogenic because it occurs well below the limit of modern soil sola. These processes also occur at the edges of major landscape elements and can be considered to have a strong lateral component processes, making them “per latus” processes in our usage.  相似文献   

9.
Weathering of soil minerals under forest seems to depend on the species present. To study the influence of tree species we placed unweathered vermiculites in the soil and assessed the impact in terms of saturation index of earth‐alkaline cations and cation exchange capacity in 64 forest stands, dominated by different species and growing side by side at 20 sites on acidic soils. The vermiculites were of two types, one with a large charge and the other with a small charge. Minerals were maintained in the soil for 1 and 3 years. The minerals placed in the topsoil and in soils with low buffering capacity were more acidified and weathered than those deeper in the soil and in less acid conditions. The vermiculites were transformed into hydroxylated interlayered vermiculites, and the formation of hydroxides in the interlayer space decreased the vermiculites' cation exchange capacities. The high‐charge vermiculite had a greater affinity for aluminium than the low‐charge variety. The effect of tree species was significant but small compared with factors such as soil type, depth and duration of incubation. Nevertheless, we can rank the acidifying and weathering caused by the trees in the following order: Picea abies, Abies alba > Pinus sylvestris, Pseudotsuga menziesii > Quercus spp., Fagus sylvatica. This in situ experimental approach enabled us to study potential trends in pedogenesis in few years.  相似文献   

10.
Chemical and mineral studies were carried out on weathered materials from six profiles developed on granites located in different areas of Brazil. Quartz and K-feldspar are the most abundant minerals overall. Kaolinite is the most common secondary mineral and is principally a feldspar weathering product. Mica breakdown is associated with smectite formation in semi-arid regions. In more humid regions mica weathering products include interlayered mica-vermiculite, vermiculite and kaolinite. Changes in the concentrations of Si, Al and K reflect the weathering behaviour of quartz, kaolinite, K-feldspar respectively, although K mobilities sometimes appear to be governed by processes related to the formation of secondary minerals. Ca and Mg are the first elements to exhibit depletion and their removal rates are very fast relative to K. P is also among the most mobile elements. Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba and Pb concentrations were measured. The first row transition metals are the most depleted. Rb and Sr are retained relative to Na, Mg, and Ca, and Ba accumulates as weathering proceeds. Y, Zr, Nb and Pb concentrations show little variation. The conclusion is that the factors controlling deep leaching are complex and the common notion that weathering rates are higher at lower latitudes should be reassessed.  相似文献   

11.
We have selected seven profiles located in a diapiric formation in the North of Spain. The profiles have been analyzed for the mineralogy and the chemical composition of original materials, soils developed above them and clay fractions. Three soils formed on basic rock of volcanic origin (ophite) and rich in alterable minerals, three others formed on clay marl and one soil formed on gypsiferous marl. Plagioclases, pyroxenes, vermiculites, and biotites are the main minerals found in the soil samples and ophitic rocks. Biotite, smectite, chlorite and interstratified chlorite–vermiculite make up the predominant mineralogical association in the clay fraction of the soils. Calcite, biotite and on top of all chlorite are the main minerals in the marls and the soils developed on them, with gypsum predominant in the gypsiferous marl. The mineralogy of its clay fraction is comprised mainly of chlorite and biotite. The variations in content of Al2O3, TiO2 and Na2O in the ophites are considered to be associated with the differences in the evolution of the pyroxenes. The variability of the chemical composition of the Keuper sediments and the soils is attributed more to the chaotic disposition of the Triassic materials in the formation of the diapir than to intense chemical weathering. The low concentrations of silica, iron, and aluminum extractable with ammonium oxalate indicate the low proportion of non-crystalline products. Fundamentally, it is the semiarid conditions in the study zone, together with the processes of extrusion and hydrothermal activity affecting the formation of the diapir, that are responsible for the genesis of the minerals.  相似文献   

12.
本文研究了中南地区不同纬度带花岗岩母质发育的黄棕壤、红壤、砖红壤的胶体表面性质与粘土矿物组合、14×10-10m矿物、氧化物的关系。结果表明:(1)黄棕壤、红壤、砖红壤粘粒的阳离子交换量、比表面和内表面占总表面的比例依次减小,这与其高岭石、粘粒氧化物含量依次增加,14×10-10m矿物含量依次减少有关,且也与14×10-10m矿物在黄棕壤中主要是蛭石,在红壤中主要是14×10-10m过渡矿物,砖红壤不含14×10-10m矿物的结论相符合。(2)在其他矿物类型和含量相近下,14×l0-10m矿物是蛭石的土壤与14×10-10m矿物是14×10-10m过渡矿物的土壤相比,前者的阳离子交换量、比表面、内表面占总表面的比例比后者高些,但土壤的活性酸度弱些,交换性铝含量比后者低些。  相似文献   

13.
Rock weathering has long been a subject of study for geologists, mineralogists, chemists and soil scientists since the dawn of this century. In methods for investigating rock weathering, three aspects seem to be present. The one is a chemical aspect in which weathering process is considered by comparing chemical composition of fresh parent rock with that of the weathered rock, the difference being attributed to gains or losses of chemica,l elements with respect to a supposed immobile element, usually aluminum. This aspect can elucidate the chemical behaviour of rock, that is, of material as an assemblage of constituent minerals in the environment of weathering. Among many such studies mentioned. PoLYNov's “Cycle of Weathering” (6) is one of the most comprehensive and fruitful acheivements. The second aspect is a mineralogical one, in which interests are directed toward skeletal minerals surviving against severe attacks of weathering. It is commonly observed that some of the original constituent minerals still remain in weathered material after others have been extinguished. The former minerals are more stable than the latter. On the basis of these observations, the sequence of resistantiability or stability to weathering can be determined for many rock forming minerals. GOLDICH's study of rock-weathering (3) is a representative one in this aspect. The third aspect is concerned with clay mineralogy. Primary rock-forming minerals are weathered into very finegrained materials most of which had been believed amorphous until techniques now used in clay mineralogical reserch proved their crystalline state. Besides primary skeletal minerals, weathered materials are now known to consist mainly of both amorphous and crystalline secondary minerals, mostly appearing in minus two micron fraction and being objects of interest in clay mineralogy. Any study of rock weathering hitherto performed stood more or less on the three aspects above mentioned but, all the abovementioned seem to fall into the common tendency of dealing with materials as bulk mass. That is, they were concerned much more with fresh rock versus its weathered end products as a whole rather than with the process or mechanism by which fresh rock changed into weathered material. Thus, in the temperate to subtropical humid region, it is known that, for example, kaolinite minerals, gibbsite, and some of 2: 1 type clay minerals are found in weathered materials of rocks and further that Na, K. Mg. Ca, and Si are leached away, while H, Al, and Fe are concentrated in the weathered products, but it is scarcely understood from what constituent minerals of the parent fresh rock any of the clay minerals now present in the weathered material were derived. Though, a mineralogical or chemical tracing of the courses of decomposing minerals from their initial phases to subsequent modified phases was already pioneered by STEPHEN (8). such a trend is believed, by the author, to be a fourth aspect necessary for further thorough understanding of rock weathering. This way of study may also serve in bridging between experimental data on chemical reactions of specific minerals with reagent solutions on the one hand and observations of mineralogical interrelation of parent minerals to resultant weathering products on the other hand. Granitic rock offers a suitable situation for this fourth aspect because of the ease in picking up mineral grains at various weathering stages due to the coarseness of its constituent minerals and also to its unique mode of physical disintegration.  相似文献   

14.
We performed a comparative experiment to investigate: (1) how the ubiquitous soil bacterium Bacillus subtilis weathers granite; and (2) which granite-forming minerals weather more rapidly via biological processes. Batch system experiments (granite specimen in a 500 ml solution including NaCl, glucose, yeast extract and bacteria B. subtilis at 27 °C) were carried out for 30 days. Granite surfaces were observed by SEM before and after the experiment. B. subtilis had a strong influence on granite weathering by forming pits. There were 2.4 times as many pits and micropores were 2.3 times wider in granite exposed to B. subtilis when compared with bacteria-free samples. B. subtilis appear to preferentially select an optimum place to adhere to the mineral and dissolve essential elements from the mineral to live. Plagioclase was more vulnerable to bacterial weathering than biotite among the granite composing minerals.  相似文献   

15.
J. Torrent  J. Benayas 《Geoderma》1977,19(1):37-49
Gibbsite appears as the main secondary mineral in a weathering profile from granite situated in west-central Spain. Distribution of the mineral throughout the profile suggests that it is the result of alteration under past climates not very different from that of today. The presence of halloysite and amorphous materials indicates that these products are probably the intermediate stages in the transformation of the primary minerals, such as plagioclase, to gibbsite. Kaolinite is only found in the modern soil overlying the deep weathered material and therefore is not a product of ancient weathering.  相似文献   

16.
A mica was inserted into the soil at four sites to try to identify, in situ , the physico-chemical changes in the soil caused by the introduction of different tree species, and especially conifers. Changes in the chemistry and mineralogy of the mixed-layered mica, mica-chlorite, vermiculite, after 1 1/2 and 31/2 years in the soil, showed good differentiation between soil horizons and between soil types. Differences due to tree species were present, but small. The mechanisms of mineral evolution can be defined with reference to experimental data obtained in the laboratory. In litter layers, the mica-chlorite sheet was transformed into a mica-vermiculite, and exchangeable cations predominated on the exchange sites. In the organo-mineral horizons, changes varied depending on the soil type: in the podzol, transformation was similar to that in the litter layers, but in the sol brun acide , changes were dominated by the Al fixation on the exchange sites and its rapid hydroxylation which blocks these sites, leading to the formation of Al intergrade minerals.
Different tree species produced deviations linked to their ability to cycle cations, and also to the different organic materials produced which can attack the mineral.
The method has the potential to define the present soil environment and weathering processes, but it needs a more complete experimental design and the use of statistics to clarify the effects of the parameters and their interactions.  相似文献   

17.
The effect of complex natural organic ligands on the weathering kinetics of aluminum oxide was investigated in laboratory experiments. A peat-derived humic substance and root exudates obtained from ectomycorrhizal (Picea abies — Hebeloma crustuliniforme) and non-mycorrhizal Norway Spruce trees; and γ-Al2O3 were used as a model system. The experimental weathering rates are in accordance with a surface-controlled dissolution mechanism. The effect of the humic material on dissolution rates appears to depend on the degree of protonation of the humic (macro)molecules: we observed dissolution-enhancement or -inhibition at pH 3 and 4, respectively. Ectomycorrhizal exudates proved to be effective weathering agents at pH 4, as opposed to humic material and non-mycorrhizal exudates. Our results suggest that (i) the role of humic materials in mineral weathering and podzolization is different from what is commonly thought, and (ii) mineral weathering rates in the rhizosphere may be higher than in the bulk soil.  相似文献   

18.
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19.
The clay mineralogy of thirty-two profiles located mainly in the Vale of Strathmore and developed on glacial till derived from Lower Red Sandstone sediments and lavas has been investigated by X-ray diffraction. The soils were selected so that the parent material was related predominantly to one of the rock types common in the Lower Old Red Sandstone succession—namely, marl, sandstone, lava, or conglomerate. Comparison of the < 1.4μm fractions separated from fresh rock samples with those separated from the C horizons of the soils clearly established the dominant influence of parent rock on the soil-clay mineralogy. The clay minerals inherited by the soil often include unusual trioctahedral expansible minerals such as saponite, interstratified vermiculite-chlorite, and smectite-vermiculite, as well as more common types like mica, montmorillonite, and chlorite. Kaolinite is also found but it is not certain that it is only of inherited origin. Weathering of the clays during soil formation brings about complete degradation of the expansible trioctahedral minerals, a process usually well advanced in the B or even at the top of the C horizon, and vermiculitization of mica. The latter process occurs mainly in the A horizon, with concomitant precipitation of interlayer aquohydroxy-aluminium ions thereby forming a vermiculite-chlorite intergrade. Chlorite and kaolinite appear to be little affected by weathering. The weathering transformations are most pronounced in freely drained acid soils (pH < s) and are at a minimum in poorly drained soils and where the pH remains above 6. The susceptibility to weathering of the trioctahedral expansible minerals results in relatively high values for exchangeable magnesium at the base of the profile.  相似文献   

20.
Formation of poorly crystallized weathering products in strongly to extremely acid forest soils Poorly crystallized weathering products, formed as a consequence of wide-spread extrem acidification and silicate weathering in forest soils, were examined using X-ray diffraction (XRD) and fluorescence (XRF), scanning electron microscopy (SEM, EDXRA) and chemical analyses. The investigations were carried out on five extremely acid forest soils (different Luvisols, a Gleyic Luvisol and a Luvic Podzol) derived from different parent materials (loess, sand loess, glacial sands/loam) in Northrhine Westfalia and Schleswig-Holstein. The results reveal an intense destruction of clay minerals and other silicates in the extremely acid topsoils leading to an accumulation of poorly crystallized to amorphous compounds. These weathering products occur predominantly as silicic coatings on the surface of soil aggregates or as small spherical precipitates on mineral surfaces. Besides Si they contain small amounts of Al and Fe.  相似文献   

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