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1.
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
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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
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《Soil Science and Plant Nutrition》2013,59(2):300-308
Abstract To evaluate the relationship between the amount of available Silicon (Si) in paddy soils and their mineral properties on the Shounai Plain in Japan, which is formed from several parent materials, we evaluated the amount of available Si, the particle size distribution, the oxide composition of crystalline minerals and the amount of oxalate-extractable Si (Sio), iron (Feo) and aluminum (Alo) in the soil. The amount of available Si in the soil and the oxide content of the crystalline minerals differed among four soil groups that were distinguished by their clay mineral composition. There was no difference in the particle size distribution among the soil groups. The amount of available Si was positively related to the SiO2/Al2O3 ratio of clay, the CaO concentration of silt and fine sand, and the amounts of Sio, Feo and Alo in the soil. The amount of available Si in the soils was negative correlated with the Na2O and K2O concentrations of silt, the K2O concentration of fine sand, and the coarse sand content. These results suggest that the amount of available Si in soils is affected by the weathering resistivity of their minerals and that the particle size distribution and mineral composition are related to the available Si of the soils. Mineralogical properties, including the particle size distribution and mineral composition such as the SiO2/Al2O3 ratio × clay fraction content and the amounts of CaO and MgO in silt-sized particles, were positively correlated with the amount of available Si in the soil, but these correlations were not found for fine sand-sized particles. The Sio, Feo and SiO2/Al2O3 ratio × clay fraction contents contributed approximately 50% to the amount of available Si in the soils. The amount of available Si in the soil was divided into two groups according to the location of the paddy field. The amount of soil-available Si in the alluvial plain was affected by the geology upstream through the mineral composition. 相似文献
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Clay minerals in a soil chronosequence derived from basalt on Hainan Island, China and its implication for pedogenesis 总被引：1，自引：0，他引：1
A soil chronosequence consisting of six profiles formed on quartz tholeiite basalt ranging in age from 10,000 years to 1. 8 Million years (My) was studied here. Soil clays were identified using XRD diffractogram decomposition methods for samples obtained from the A and C horizons of profiles. The results showed that kaolinite minerals dominated in all the clay fractions. Gibbsite was prominent in the C horizons in the soils from older rocks. Clays in the A horizon of relatively young soils showed an initial stage of illite formation, followed by smectite mixed layer minerals (illite-smectites and then vermiculite-illite) and finally by vermiculite. The initial presence of illite is interesting as there is no magmatic micaceous or phyllosilicate phase in these basalts and the formation of illite we attribute to a secondary process, probably created by alkali transport by plant materials. The change in 2:1 clay mineralogy reflects the overall change in Si/Al ratios in the soils over longer periods of weathering. In all cases gibbsite is more abundant in the C horizons than the A horizons. The difference in gibbsite content between the A and C horizons we attribute to plant transport of siliceous phytolite material to the surface. Continued high rainfall over long periods of time removed the alkali faster than the plants could bring it to the surface, which led to continuous lowering of 2:1 minerals from younger to older in the soil chronosequence. Nevertheless a 2:1, silica-rich mineral persists in the clay assemblages although in very minor amounts. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(15-16):1815-1826
Abstract Five representative soil profiles were excavated along a toposequence selected in the Itagunmodi area of South‐Western Nigeria. The soils were subjected to physical, chemical, and mineralogical analyses. The results indicated soils with high fine sand and clay contents, but low silt content. The soils were found to vary from slightly acid to strongly acid (pHH2O = 4.0 to 6.2). Organic C, available P, and Kjeldahl N contents decreased with increasing depth. Cation exchange capacity (CEC) ranged from 3.11 to 28.75 cmol(+)/kg soil. Base saturation was low (<51%). From a total elemental analysis, Si was found to be the dominant element, followed by Al, and then Fe. Extractable P, and exchangeable K, Mg, and Ca were quite low. The dominant minerals in the fine sand fraction were quartz, feldspar, zircon, hornblende, tourmaline, and opaque ores. The variation in the zircon/tourmaline (two resistant minerals) ratios with depth suggests a stratification of the parent material. The change in the quartz/feldspar ratios was an indication that the degree of weathering in the soil profile is not uniform. 相似文献
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《Soil Science and Plant Nutrition》2013,59(3):362-368
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. 相似文献
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Neither the specific surface area values (from N2 sorption) nor the ethylene glycol monoethyl ether (EGME) retention values of 21 soil samples from New Zealand and Fiji could all be accounted for by the sum of the contributions from their component minerals. Much EGME is probably retained by internal surfaces of inter layered and interstratified clay minerals. EGME retention correlated well with cation exchange capacity (CEC) and a number of measures of water content of these soils. The water contents of air-dried soils (measured as ‘moisture factors’ or the ratios of air-dry and oven-dry weights) showed almost as close a relationship to CEC as EGME retention for this set of 21 subsoils. Moisture factors and CEC were closely related, within groups defined by dominant clay mineralogies, for a much wider selection of 1318 New Zealand soil horizons with low carbon contents. The relationships between surface area and a number of other soil properties including dispersibility of soils were also examined. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(5):397-405
Abstract A second order equation best described the relationship between exchangeable Mg and both total and acid‐soluble Mg in select temperate and tropical soils. The relationship between acid‐soluble and total Mg was linear. Soil types differ in their Mg contents. On a per unit weight of material bases the finer soil particles contained more than 95 percent of the total soil inorganic magnesium. In tropical soils, as in temperate soils, the total Mg content of surface horizons tends to decrease with severe weathering, soil erosion and movement of soil colloidal particles down the profile. 相似文献
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R. M. Khalitov E. N. Perova E. V. Abakumov R. R. Suleimanov 《Eurasian Soil Science》2017,50(8):961-970
The mineralogy of soils and parent rocks of the Iremel Ridge has been studied by the methods of micromorphology, laser diffraction, computed X-ray microtomography, and X-ray fluorescence analysis. In hard rock and soil, the major minerals have been identified: quartz, illite, and a chlorite-group mineral (Fe analogue of sudoite), as well as accessory minerals: monazite, xenotime, rutile, zircon, and florencite. It has been found that chlorite, illite, and quartz are present in all horizons of the studied peaty-podzolic soil. Insignificant amounts of mixed-layered mineral and kaolinite could be suggested in the T and EL horizons of peaty-podzolic soil. The mixed-layered mineral is most probably of soil origin, which is related to the transformation of illites inherited from the parent rock under acidic conditions. 相似文献
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Osamu Sato 《Soil Science and Plant Nutrition》2013,59(2):159-167
Abstract Pg contents of soils chosen from the major soil groups occurring in the mountain area of Central Japan were measured by the method presented by the author in a previous paper. The Pg contents of the soils ranged from 0 to 0.58 per cent of the dry soils. In podzolic soils, Pg contents were high in A horizons and gradually decreased with depth and in some cases of brown forest soils, Pg contents were highest in B horizons. The percentage of Pg in humic acid ranged from 0 to 8.6 per cent, and the highest value was observed in the C horizon of Dando Bo soil, Pg contents were high in humid and acidic soils containing much humic acid. Humidity, soil pH and humus content may affect the Pg accumulation by controlling the activity of Pg-producing fungi. ? log K values of Pb were calculated to estimate the degree of humification of P type humic acids and indicated that Pb's were relatively immature. 相似文献
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Soils of the nearly level “Landes du Médoc” in southwestern France have a pattern of alternating bodies of hydromorphic podzols (Haplaquods) and low humic hydromorphic soils (Psammaquents). The soils are formed in a sedimentary mantle of coarse, quartzose sands with a slight microrelief consisting of low, elongated ridges and shallow, intervening troughs. The water table is at shallow depths throughout the plain, even at the surface in places. The podzols on the crests of the low ridges have distinct A2 and cemented B2 h horizons. Podzols persist down the sides of ridges but going downslope first lose the A2 horizon and then the cementation of the Bh horizon. Soils in the shallow troughs have A1 and Cg horizons without B horizons.The fine silt (2–20 μm) and clay (0–2 μm) fractions of the parent sand contain primary trioctahedral chlorite, mica, feldspars, and quartz, with the last mineral predominant. During soil development, the first three minerals undergo weathering at different rates and to different extents. Chlorite is most strongly weathered, followed in order by plagioclases and K-minerals. In the fine silt fraction, weathering seems to occur mostly by fragmentation of particles. In the clay fraction, the phyllosilicates successively form irregularly interstratified minerals with contractible but not expandable vermiculitic layers, interstratified minerals with contractible and expandable smectitic layers, and finally smectites.The extent to which the silicate minerals are weathered becomes progressively greater from the low humic hydromorphic soils to the podzols with friable Bh horizons to the podzols with cemented Bh horizons. Smectite is present only in the A2 horizons of these last podzols.The aluminum release by weathering of silicate minerals is translocated in part in the form of organo-metal complexes into the Bh horizons of the podzols. Greatest concentrations of Al are associated with coatings of monomorphic organic matter on mineral grains in the cemented Bh horizons, in which some Al has also crystallized into gibbsite. That mineral was not detected in friable B horizons of podzols nor in the low humic hydromorphic soil. Contrary to expectations, the mobile Al did not enter interlayer spaces of expanding 2:1 clay minerals. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(5-6):726-740
Abstract Soil color is a soil property that may be used as an interpreting index in estimating processes and properties. Quantifying color allows one to obtain information for rapidly estimating the related processes in soils. CIELAB color parameters L*, a*, and b* of ground (air‐dried and sieved) soil samples and aggregate surfaces of four soil profiles formed in calcareous colluviums in northern Turkey were analyzed. Values of color parameters measured in ground and intact soils were compared and related to soil properties by the regression technique. Results revealed that the L* value obtained with a ground soil sample was a significant predictor of organic matter in A horizons (p < 0.001). Although calcic horizons yielded the highest L* values, no significant relationship was obtained between calcium carbonate contents and lightness of soils in any of horizons studied. The parameters of b* could adequately be used to quantify dithionite‐extractable iron oxide contents in soils studied. The results further showed that the CIELAB color parameters obtained with ground samples were more informative than that of aggrevated samples in relating color parameters to soil properties. 相似文献
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Mineralogical, physical and chemical analyses of the soils derived from Xiashu loess were carried out. The primary minerals of these soils were found to be mainly composed of light minerals, such as quartz, feldspar and mica, with traces of heavy minerals. Clay minerals, more complicate in composition, were dominated by hydromica, accompanied by smectite, vermiculite, chlorite, kaolinite, 2:1/1:1 randomly interstratified minerals and small amounts of quartz, goethite, lepidocrocite and hematite, Clay minerals were characterized by low crystallinity and fine particle size. In light of the quartz/feldspars ratio of the 0.01-0.05mm silt fraction, and the clay mineral composition, the freeness of iron oxide, and the silica/sesquioxide and silica/alumina ratios in < 0.002mm clay fraction, it is concluded that the weathering intensity of these soils was lower than those of red soil and yellow earth, but higher than that of brown earth, and that the soil allitization, depotassication and hydroxylation of cl 相似文献
16.
The organic matter in soils may be stabilized by its interactions with minerals. We have studied such interactions in a Haplic Alisol under forest in which clay and organic matter have migrated from an eluvial A horizon to accumulate in an illuvial B horizon. We have tried to trace the fate of organic matter in these horizons (Ah and Bvt) by determining clay mineralogy, carbon and nitrogen content, hydrolysable amino acids, lignin signature by alkaline CuO oxidation and carbon species by 13C CPMAS NMR of bulk soils and particle‐size fractions. In both horizons, most of the organic matter was present in O–alkyl and methylene structures, each contributing one‐third to the bulk organic matter. In the Ah horizon the ratios of carbon‐to‐nitrogen, and yields for lignin and hydrolysable amino acids decreased as the particle‐size class decreased, but side‐chain oxidation of lignin compounds increased with decreasing particle size. In contrast to previous observations, the proportions of O–alkyl carbon increased as particle size decreased, constituting a major proportion of the organic carbon in the clay‐size fractions from both the Ah and Bvt horizons (≥ 38%), while proportions of methylene carbon decreased. Illite was the dominant mineral in the fraction ≤ 6 μm, whereas the mobile fine clay fraction (<0.2 μm) was rich in smectites – minerals with large surface areas. Our results support the hypothesis that potentially labile organic matter, such as O–alkyl carbon typically present in polysaccharides, may be stabilized against further degradation in organomineral complexes. 相似文献
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I. Basile-Doelsch † R. Amundson W. E. E. Stone C. A. Masiello J. Y. Bottero F. Colin F. Masin D. Borschneck & J. D. Meunier 《European Journal of Soil Science》2005,56(6):689-703
In soil carbon dynamics, the role of physicochemical interactions between organic matter and minerals is not well understood nor quantified. This paper examines the interactions between soil organic matter and poorly crystalline aluminosilicates in a volcanic ash soil on La Réunion in the southern tropics. The soil examined is a profile composed of a surface soil (L-Ao-E-Bh) overlying four buried horizons (horizons 2Bw, 3Bw, 4Bw, 5Bw) that have all developed from successive tephra deposits. Non-destructive spectroscopy (XRD, FTIR and NMR of Si and Al) showed that the mineralogical composition varies from one buried horizon to another. Further, we show that buried horizons characterized by large amounts of crystalline minerals (feldspars, gibbsite) have the least capacity to store organic matter and the fastest carbon turnover. In contrast, buried horizons containing much poorly crystalline material (proto-imogolite and proto-imogolite allophane, denoted LP-ITM) store large amounts of organic matter which turns over very slowly. To understand the mechanism of interactions between LP-ITM and organic matter better, we focused on a horizon formed exclusively of LP-ITM. We demonstrate, using Δ14C and δ13C values, that even though LP-ITM is extraordinarily effective at stabilizing organic matter, C linked to LP-ITM is still in dynamic equilibrium with its environment and cycles slowly. Based on Δ14C values, we estimated the residence time of organic C as ∼ 163 000 years for the most stabilized subhorizon, a value that is comparable to that for organic carbon stabilized in Hawaiian volcanic soils. However, this calculation is likely to be biased by the presence of microcharcoal. We characterized the organo-mineral binding between organic matter and LP-ITM by 27Al NMR, and found that the organic matter is not only chelated to LP-ITM, but it may also limit the polymerization of mineral phases to a stage between proto-imogolite and proto-imogolite allophane. Our results demonstrate the important role of poorly crystalline minerals in the storage of organic C, and show that mineral and organic compounds have to be studied simultaneously to understand the dynamics of organic C in the soil. 相似文献
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The 14C age of soil organic matter is known to increase with soil depth. Therefore, the aim of this study was to examine the stabilization of carbon compounds in the entire soil profile using particle size fractionation to distinguish SOM pools with different turnover rates. Samples were taken from a Dystric Cambisol and a Haplic Podzol under forest, which are representative soil types under humid climate conditions. The conceptual approach included the analyses of particle size fractions of all mineral soil horizons for elemental composition and chemical structure of the organic matter by 13C cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. The contribution of phenols and hydroxyalkanoic acids, which represent recalcitrant plant litter compounds, was analyzed after CuO oxidation.In the Dystric Cambisol, the highest carbon concentration as well as the highest percentage of total organic carbon are found in the <6.3 μm fractions of the B and C horizons. In the Haplic Podzol, carbon distribution among the particle size fractions of the Bh and Bvs horizons is influenced by the adsorption of dissolved organic matter. A relationship between the carbon enrichment in fractions <6.3 μm and the 14C activity of the bulk soil indicates that stabilization of SOM occurs in fine particle size fractions of both soils. 13C CPMAS NMR spectroscopy shows that a high concentration of alkyl carbon is present in the fine particle size fractions of the B horizons of the Dystric Cambisol. Decreasing contribution of O-alkyl and aromatic carbon with particle size as well as soil depth indicates that these compounds are not stabilized in the Dystric Cambisol. These results are in accordance with data obtained by wet chemical analyses showing that cutin/suberin-derived hydroxyalkanoic acids are preserved in the fine particle size fractions of the B horizons. The organic matter composition in particle size fractions of the top- and subsoil horizons of the Haplic Podzol shows that this soil is acting like a chromatographic system preserving insoluble alkyl carbon in the fine particle size fractions of the A horizon. Small molecules, most probably organic acids, dominate in the fine particle size fractions of the C horizons, where they are stabilized in clay-sized fractions most likely due to the interaction with the mineral phase. The characterization of lignin-derived phenols indicated, in accordance with the NMR measurements, that these compounds are not stabilized in the mineral soil horizons. 相似文献
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Abul Kashem Bal Ram Singh 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(2):134-139
Abstract The distribution of DTPA-extractable Cd, Ni and Zn in four profile samples collected from areas contaminated with wastes from tannery, city sewage, pharmaceutical and paper mills located at different places in Bangladesh was investigated. Soil samples were analysed for the total and their DTPA-extractable metal contents. The total concentration of metals in the soil horizons ranged from 0.07 to 0.62 mg kg?1 for Cd, 31 to 54 mg kg?1 for Ni and 59 to 838 mg kg?1 for Zn, respectively. These metal concentrations were highest in the surface and lowest in the subsurface horizons. This trend was also observed for the DTPA-extractable amounts of these metals. The relative extractability, expressed as the ratio of DTPA to total contents (aqua regia-extractable) was 33 to 46% for Cd, 2 to 10% for Ni and 3 to 28% for Zn, respectively, in the A1 horizon, while in the B and C horizons the ratios decreased gradually as did total concentration, indicating that metal contamination was primarily limited to the surface horizon. For all three metals, the above mentioned ratio was highest in the city sewage soil and the lowest in the paper mill soil. In general, the extent of contamination among the profiles investigated was in the following order: city sewage>tannery>pharmaceutical>paper mill soil. Higher ratios of DTPA-extractable Cd, Ni and Zn in the city sewage soil than the other soils may create a risk for the contamination of agricultural products and ground water. 相似文献