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1.
C.W. Childs  R.L. Parfitt  R. Lee 《Geoderma》1983,29(2):139-155
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.  相似文献   

2.
Abstract

The profile distribution of total, DTPA‐ and 0.1N HCl‐extractable Cu was determined in 11 Nigerian soil profiles formed from various parent materials including the coastal plain sands, shales, basalt, granite and banded gneiss.

Total Cu ranged from 7 to 72 ppm with a mean of 35 ppm0 The soils formed from basalt had the highest values while those on coastal plains had the least content. Generally, there was a higher content in the subsoils than in the surface horizons. The total Cu significantly correlated with percent clay and the free oxide contents of Fe and Mn.

DTPA ‐ and 0.1N HCl‐extractable Cu ranged from 0.08 to 2.81 ppm and 0.10 to 7.78 ppm, respectively. Soils on metamorphic rocks gave the highest values of DTPA‐extractable Cu. The DTPA‐extractable Cu ‐was only related to pH but the acid extractable Cu was associated with total Cu, clay, free Fe2O3 and MnO2 contents.  相似文献   

3.
The macromorphology, micromorphology and chemical nature of illuvial material in podzol B horizons and subsoils can be explained by contributions from two different migrating species: (a) a positively-charged mixed Al2O3-Fe2O3-SiO2-H2O sol incorporating minor amounts of adsorbed organic matter and silicate clay, and (b) negatively charged organic sols and solutions, carrying minor amounts of Al, Fe and clay. These species can also be generated within B horizons of high root activity. An alternative theory, that requires allophane to be formed in situ in the B horizon by microbial decomposition of precipitated organic complexes, fails to predict the observed distribution of allophane.  相似文献   

4.
M.M. Mortland 《Geoderma》1980,23(3):225-226
Weathering products of Vitrandept profiles on the Kaingaroa plateau, central North Island, New Zealand, were investigated by analysis of oxalate extracts and by chemical and mineralogical analysis of clays of selected soil horizons. Comparisons were made between profiles under a Pinus radiata (D. Don) stand and profiles under an adjacent area of manuka native scrub, Leptospermum scoparium (Myrtaceae).Clay fractions (< 2 μm) of A11 horizon under pine had significantly higher SiO2/Al2O3 mole-ratios (mean SiO2/Al2O3 = 12.2) than A11 horizon under manuka (mean SiO2/Al2O3 = 7.1). No effect of vegetation on clay fractions of B horizon was evident, these clays having much lower SiO2/Al2O3 mole-ratio (1.5). Oxalate-extractable Al, Fe and Si values of < 8-mm fractions of A, B and C horizons showed no differences attributable to present vegetative cover.SiO2/Al2O3 mole-ratios of oxalate extracts increased with increasing depth, and paleosols at > 2 m depth under pine had significantly higher SiO2/Al2O3 mole-ratios in oxalate extracts (mean SiO2/Al2O3 = 2.0) than paleosols under manuka (mean SiO2/Al2O3 = 1.6). That soil horizons at > 2 m depth are in the zone of resilication is indicated by: (1) the greater SiO2/Al2O3 mole-ratios of oxalate extracts of paleosols than surface horizons; (2) lysimeter leachate composition; and (3) the presence of authigenic halloysite at > 2 m depth in soil profiles.  相似文献   

5.
Abstract

The Ae, Bhf and Bf horizons of two podzolic soils from the Appalachian and Laurentian Highlands were treated with various reagents to remove the amorphous material prior to X‐ray diffraction analysis. Treatments were Na citrate, NaOH, Tiron, DCB and modified DCB, with a lower solid:liquid ratio. Samples treated with NaOH, Tiron and DCB were subsequently extracted with citrate. The latter extraction was necessary to remove Fe2O3 and SiO2 that was not solubilized in the first treatment. The effectiveness of the reagents to extract SiO2, Al203 and Fe2O3 decreased in the following order:

DCB 1:1 > Tiron = DCB > citrate > NaOH

The total weight loss of the samples represented about 1.8 times the sum of the oxides and reached up to 70% of the Laurentian Bf sample. Organic matter accounted for a part of the weight loss and its removal was more complete in the less crystalline samples of the Laurentian profile. Tiron was the best reagent to improve the X‐ray diffraction patterns, closely followed by DCB 1:1 treatment.

Removal of amorphous material and organic matter resulted in a decrease of the cation exchange capacity of the clay fraction, from a maximum of 73.5 meq / 100 g in the Laurentian profile to a minimum of 3.2 meq / 100 g in the Appalachian profile.

The results suggested that in the Laurentian profile, very poorly crystallized minerals possibly contributed to a part of the extracted material.  相似文献   

6.
根据泾阳泾河高漫滩沉积剖面中128个样品的元素、化合物含量与粒度分析,研究了泾阳泾河高漫滩剖面沉积特征与洪水变化.结果表明,元素Ma,Ni,Cu,Zn,Ga,Pb,Ba,Rb,V和化合物Al2O3,Fe2O3,K2O含量在剖面各层中变化明显,分辨率高,能够清晰地指示洪水以及降水量的变化.JYa剖面分为18个沉积层,指示了18次大小不同的洪水和18个降水较多的年份.沉积物粒度细,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3Fe2O2,K2O含量高,元素Ba含量低,指示沉积时洪水强度小,洪水水位低,降雨量少.沉积物粒度粗,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3,Fe2O3,K2O含量低;元素Ba含量高,指示沉积时洪水强度大,洪水水位高,降雨量多.在这18次洪水事件中,在同一次洪水沉积层内形成了两个以上薄层的元素和化合物含量、粒度成分的微小变化,指示多数期次的洪水发生时期常有两个以上洪峰出现.泾阳泾河高漫滩第14,12,13,8,5,1层洪水沉积反映了泾河泾阳段全流域性的年降水量增加,且年降水量至少达到约800 mm.  相似文献   

7.
Material balance in an aquic Hapludalf from loess by means of IR-phase analysis Grain size fractions of an aquic Hapludalf from loess near Göttingen were examined mineralogically and chemically. On the base of actual mineral composition (mode) by means of infrared spectroscopy weathering balances were made up. The results reveal a strong illite/mica loss of about 80 kg/m2, which is due to decomposition in the A-horizon, and which is not compensated by a slight gain in the B-horizon. The mineral balance of the total profile yields a clay degradation of 44 kg/m2. Furthermore, in the A-horizon the chemical balance gives evidence of considerable mobilizations and substantial losses mainly of SiO2, Al2O3, MgO and K2O combined in silicates. Depending on soil horizons and grain sizes the illites have K-contents varying from 4 to 8% K2O. Al2O3 and MgO also show distinct variations. Both components are correlated negatively and decrease (Al2O3) respectively increase (MgO) from the top to the bottom.  相似文献   

8.
A statistical approach was adopted to study the association between particle-size fractions and trace elements in soil, because conventional studies on the subject usually involve chemical methods of fractionation, which may lead to loss and upsets in natural distribution patterns. The results showed that both total and extractable contents of Zn, Al, Cu, Mn, Pb, and Fe are bound up either in clay or silt fractions, although variations as to the particular particle-size diameter range did occur among the different elements. An attempt to resolve these relationships fitting a linear mathematical function, y=a+bx, based on the statistical association of individual particle-size fractions with particular trace elements, gave satisfactory results. There was no evidence to indicate that certain size fractions could mobilize trace elements by virtue of their abundance in these soils. There was convincing statistical proof to show that amorphous Fe2O2, possibly by way of surface coating of finer particles, may retain a large proportion of the trace elements investigated.  相似文献   

9.
Minerals with large specific surface areas promote the stabilization of soil organic matter (SOM). We analysed three acidic soils (dystric, skeletic Leptic Cambisol; dystric, laxic Leptic Cambisol; skeletic Leptic Entic Podzol) under Norway spruce (Picea abies) forest with different mineral compositions to determine the effects of soil type on carbon (C) stabilization in soil. The relationship between the amount and chemical composition of soil organic matter (SOM), clay content, oxalate‐extractable Fe and Al (Feo; Alo), and dithionite‐extractable Fe (Fed) before and after treatment with 10% hydrofluoric acid (HF) in topsoil and subsoil horizons was analysed. Radiocarbon age, 13C CPMAS NMR spectra, lignin phenol content and neutral sugar content in the soils before and after HF‐treatment were determined and compared for bulk soil samples and particle size separates. Changes in the chemical composition of SOM after HF‐treatment were small for the A‐horizons. In contrast, for B‐horizons, HF‐soluble (mineral‐associated) and HF‐resistant (non‐mineral‐associated) SOM showed systematic differences in functional C groups. The non‐mineral associated SOM in the B‐horizons was significantly depleted in microbially‐derived sugars, and the contribution of O/N‐alkyl C to total organic C was less after HF‐treatment. The radiocarbon age of the mineral‐associated SOM was younger than that of the HF‐resistant SOM in subsoil horizons with small amounts of oxalate‐extractable Al and Fe. However, in horizons with large amounts of oxalate‐extractable Al and Fe the HF‐soluble SOM was considerably older than the HF‐resistant SOM. In acid subsoils a specific fraction of the organic C pool (O/N‐alkyl C; microbially‐derived sugars) is preferentially stabilized by association with Fe and Al minerals. Stabilization of SOM with the mineral matrix in soils with large amounts of oxalate‐extractable Alo and Feo results in a particularly stable and relatively old C pool, which is potentially stable for thousands of years.  相似文献   

10.
In order to investigate the paleoclimatic changes in S China during the late Quaternary and their influence on pedogenesis and soil classification, a yellow‐brown earth (YBE)–red clay (RC) profile in Langxi County, Anhui Province was studied. The grain‐size distribution and the major‐ and trace‐element compositions of the profile indicate that the YBE of the profile shares the same origin with the YBE in Jiujiang and Xuancheng and the Xiashu loess in Zhenjiang, and the underlying RC also has aeolian characteristics and shares the same origin with the Xiashu loess. Grain‐size characteristics, molecular ratios of SiO2/Al2O3, SiO2/(Al2O3+Fe2O3), and BA ([CaO+MgO+K2O+Na2O]/Al2O3) and other weathering indices (CaO/TiO2, MgO/TiO2, K2O/TiO2, Na2O/TiO2, and Rb/Sr) of the profile indicate that the RC is more strongly weathered than the YBE. Magnetic susceptibility (χlf) of the uniform red clay (URC) of the profile is significantly enhanced. However, that of the underlying reticulate red clay (RRC) is significantly decreased because of the paleogroundwater movement and cannot indicate its strong weathering properties. The YBE‐RC profile in Langxi County recorded a great climatic change during late Quaternary: At that time, the pedogenic development of the RC was terminated and widespread dust deposition occurred. The parent material of the RC may be aeolian deposits which were accumulated before the last interglacial and were strongly weathered and rubified under the subsequent interglacial climate. It is observed that red soils, derived from the RC, and yellow‐brown soils, derived from the YBE, coexist in the study area, which is contradictive to the theory of the zonal distribution of soils. Therefore, it is necessary to take into account the history of Quaternary climatic changes when studying pedogenesis.  相似文献   

11.
A thin layer of yellow-brown-colored earth was generally found on Quaternary red clay in Jiujiang, Jiangxi Province. A typical profile was established. Both particle size distribution and REE (rare earth elements) characteristics of the yellow-brown-colored earth of the profile fully suggested its aeolian origin and close similarity to Nanjing Xiashu loess. The study also implied aeolian origin of the underlying Quaternary red clay. Compared with the red clay, the yellow-brown-colored earth was less weathered because of its lower content of free iron and higher mole ratios of SiO2/Al2O3 and SiO2/(Fe2O3+Al2O3) as well as its less developed chemical microtextures of quartz grains. In order to study the ages of the two deposits comparatively, the thermoluminescent dating method was used. As a result, the bottom of the yellow-brown-colored earth was dated to 60±5 ka B. P. and the upper part of the red clay 388±54 ka B. P. It was suggested that the yellow-brown-colored earth was formed in the Late Pleistocene and was probably the aeolian deposit of the Last Glacial, which corresponded with the Malan loess in the Loess Plateau of the northwestern part of China; while the underlying red clay was formed in the Middle Pleistocene. A "yellow cap" on Quaternary red clay in Jiujiang implied a great climatic and environmental variation in the beginning of the Late Pleistocene in the southern part of China, especially in the middle and lower reaches of the Yangtze River. The event not only halted the rubification, once dominating the region, but also produced a widespread covering of aeolian deposit, as only occurred in the cold and dry environment.  相似文献   

12.
A large autochthonic soil of preoligocene age from lower devonian schist of the Eifel Paleosols of Mesozoic-Tertiary age and their sediments are very important for the reconstruction of the landscape history in the area of the Rhenish Massiv. But stratigraphically determined, as well as autochthonous soils with exact analytical datas scarcely exist. Therefore a thick, autochthonous profile of a red fossil soil rich in clay was investigated. It consists of a concretion zone, mottled clay zone and a pallid zone above a 30 m thick saprolithe zone from bleached Devonian clay and silt shales with sandstone layers. Stratigraphical investigations of the superficial layers improve a pre-Oligocene age of soil formation. Results of soil analysis show an absolute accumulation of red coloured Fe oxides in the upper horizons and an intensive formation of kaolinite from chlorites and micas. Quartz underwent solution only in the finest fractions. Desilication did not proceed so far, that gibbsite could be formed. Therefore the molar SiO2 : Al2O3 ratio of the clay fraction does not decrease below 2. Erosion of formerly existing, stronger weathered horizons can't be excluded. According to the FAO-UNESCO soil map of the world and the Soil Taxonomy the criteria for Oxisols and Ferralsols are closely fulfilled. By the systematic of the Federal Republic of Germany the palesol is to be classified as a red-plastosol.  相似文献   

13.
Original and published data on the contents of X-ray amorphous oxalate-soluble compounds of Al, Fe, and Si in mesomorphic eluvial soils of cold, moderately cold, and moderately warm continental humid and semihumid regions are generalized. The groups of soils developed from mafic igneous, metamorphic, and pyroclastic rocks are considered. It is shown that the content of oxalate-soluble oxides (OSOx) in the horizons of their maximal accumulation varies from less than 1% to 20–30%; the Alox/Feox ratio varies from 1 to 6.5. The leading factor dictating the amount and quality of the OSOx in the soils is the presence or absence of volcanic glass in the parent materials. The boundary between the soils with and without volcanic glass corresponds to the OSOx content of 5% and the Al2O3ox/Fe2O3ox ratio equal to 2. These criteria are more reliable than the Alox/Feox ratio used by foreign soil scientists to specify Andosols (Alox/Feox > 2). The contents of oxalate-soluble oxides of Al and Fe do not depend on the total contents of these oxides in the parent material and seem to be related to the presence of these elements in minerals with different resistance to weathering. Under the natural conditions described in this paper, the content of OSOx shows a very weak response to zonal (temperature-controlled) climatic changes and/or to changes in the degree of humidity and the continentality of the climate.  相似文献   

14.
Small fragments of intermeshed fibrous material of high electron density were observed by electron microscopy in the fine (< 0.5 μm) clay taken from an iron-rich cemented layer forming part of the B horizon of a Podzol (Typic Haplorthod). Each fibre was about 5 nm in width and about 100 nm in length. Similar material was also common in larger (0.5–2.0 μm) clay fractions but here it occurred as unbroken particles which resembled bacteria in shape and size. At high magnifications, individual fibres were seen to consist of very small (5 nm) particles aligned along the length of each fibre.Electron microanalysis of the fibrous material showed it to consist of iron, aluminium and silicon. The average composition (water-free basis) of seventeen bacteria-like particles was 66% Fe2O3, 22% Al2O3 and 11% SiO2. The particles were positively identified as aluminium-substituted goethite by selected-area electron diffraction.The fibrous material was completely dissolved by dithionite-citrate-bicarbonate treatment but was only slightly affected, if at all, by ammonium oxalate, pH3, in darkness. Other extraction data and X-ray diffraction results showed that the clay also contained considerable amounts of material of short range order, probably in the form of ferrihydrite and allophane.  相似文献   

15.
The profile distributions of oxalate- and pyrophosphate-soluble Al compounds and oxalate-soluble Si compounds in the main horizons of pale-podzolic soils of the Central Forest Reserve and the fractions <1. 1–5, and >5 μm have been considered. In the clay-eluvial part of soil profile, the content of these compounds is differentiated by the eluvial–illuvial type with a clear accumulation in the EL horizon compared to the AEL horizon. This distribution is largely ensured by their differentiation in the clay and fine silt fractions, while an accumulative distribution of mobile Al compounds is observed in fractions >5 μm. The high correlation between the Al and Si contents in the Tamm extracts from the clay and fine silt fractions with the (Alox–Alpy)/Siox molar ratios, which are in the range of 1–3 in the EL horizon, confirms that mobile compounds are accumulated in these fractions in the form of amorphous aluminosilicates. In the AEL and EL horizons, an additional amount of Al can pass into the oxalate solution from the fine fractions due to the dissolution of Al hydroxide interlayers of soil chlorites. The eluvial–illuvial distribution of mobile Al and Si compounds typical for Al–Fe–humus podzols within the clay-illuvial part of profiles of the soils under study can be considered as an example of superimposed evolution.  相似文献   

16.
The retention of dissolved organic matter in soils is mainly attributed to interactions with the clay fraction. Yet, it is unclear to which extent certain clay‐sized soil constituents contribute to the sorption of dissolved organic matter. In order to identify the mineral constituents controlling the sorption of dissolved organic matter, we carried out experiments on bulk samples and differently pretreated clay‐size separates (untreated, organic matter oxidation with H2O2, and organic matter oxidation with H2O2 + extraction of Al and Fe oxides) from subsoil horizons of four Inceptisols and one Alfisol. The untreated clay separates of the subsoils sorbed 85 to 95% of the dissolved organic matter the whole soil sorbed. The sorption of the clay fraction increased when indigenous organic matter was oxidized by H2O2. Subsequent extraction of Al and Fe oxides/hydroxides caused a sharp decrease of the sorption of dissolved organic matter. This indicated that these oxides/hydroxides in the clay fraction were the main sorbents of dissolved organic matter of the investigated soils. Moreover, the coverage of these sorbents with organic matter reduced the amount of binding sites available for further sorption. The non‐expandable layer silicates, which dominated the investigated clay fractions, exhibited a weak sorption of dissolved organic matter. Whole soils and untreated clay fractions favored the sorption of ”︁hydrophobic” dissolved organic matter. The removal of oxides/hydroxides reduced the sorption of the lignin‐derived ”︁hydrophobic” dissolved organic matter onto the remaining layer silicates stronger than that of ”︁hydrophilic” dissolved organic matter.  相似文献   

17.
Pedogenetic differentiation of soil properties in aggregates Besides the pedogenetic differentiation of soils in horizons a differentiation within horizons across aggregates seems possible. The objective of this study is to check if there is a differentiation of soil properties across aggregates. From a Braunerde, a Podzol-Braunerde, and 2 Podsols from Bavaria and Slovakia aggregates of 10–30 mm in diameter were selected manually from both topsoil and subsoil horizons and mechanically fractionated into a core and a surface fraction. In the aggregate fractions Corg, Alo, and Fed were determined. Corg is generally depleted in the surface fractions of the A-horizons compared to the core fractions. This may be due to favoured microbial degradation of organic matter compared to the aggregate core and preferential leaching of organic C. In the subsoil horizons of the Braunerde Corg is lower in the aggregate surface fraction, in the Podzol, however, it is higher. In Podzols preferential C-input and sorption to aggregate surfaces seems to dominate. Lower Alo? and Fed?concentrations in the aggregate surface fractions of all A-horizons may be explained by preferential acidification of aggregate surfaces as the aggregate surfaces mainly buffer the proton input into structured mineral soils. In the B-horizons only in Braunerde Alo and Fed are lower in the aggregate surface fractions than in the core fractions. The Podzol B-horizons show preferential illuvial enrichment of sesquioxides at aggregate surfaces. Thus, pedogenesis results in the differentiation of soil properties not only between horizons but also within horizons on the level of aggregates. The resulting different chemical properties of aggregate surface and core fractions may affect the sorption capacity of structured soils.  相似文献   

18.
《Geoderma》2007,137(3-4):455-465
Phosphorus (P) binding to minerals and ion exchange capacity in different clay fractions were examined for a non-calcareous soil in southwest Sweden. The soil had received pig slurry during three decades, 2 kg lower than the recent maximum load of 22 kg P ha− 1 year− 1 as regulated by livestock density legislation. The topsoil was found to contain 33% clay by weight. Illite was the predominant clay mineral and constituted 13% of total soil. Vermiculite (10%), K-feldspar (14%) and plagioclase (21%) also constituted significant proportions of the mineralogical matrix. Within the most fine-grained clay fraction, 50% of which was less than 0.1 μm in particle size, illite and vermiculite dominated totally, 50 and 23% respectively. In fine-grained (FG), most fine-grained (MFG) and colloidal fractions, there were strong relationships (Pearson correlation coefficient 0.98–1.00) between calcium (Ca) and P. There was a low molar ratio Ca:P in added manure and the presence of Ca–P complexes in the fine soil fractions was indicated. In contrast, in the coarse soil fraction (> 2 μm), there was a clear relationship (Pearson coefficient 0.97) between P and iron oxide (Fe2O3) and between P and aluminium oxide (Al2O3) throughout the soil profile. Thus even for non-calcareous soils, formation of Ca–P complexes should be taken into account with regards to losses of colloidal P to drainage water.  相似文献   

19.
In the previous study (1), it was shown that the size-fractions finer than 2 μ of the soil samples were abundant in siliceous amorphous materials. These materials are more siliceous in the specimens of the A horizons than in the C and tend to become more siliceous with increase of particle-size. Discrete amorphous silica is present in all the size-fractions finer than 2 μ and its amount is considerably greater in coarser clay fractions. Since the proportions of coarser clay fractions are greater in the whole clay fractions, it is considered that the amorphous silica of the coarser clay fractions play a significant role in determining the properties of all of the amorphous clay minerals contained. Amorphous silica exists not only in the fractions finer than 2 μ, but also in the fractions coarser than 2 μ, even in the fine sand fractions of the A horizons.  相似文献   

20.
Concentrations of dialysable silica in equilibrium with Al2O3-SiO2-H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non-dialysable proto-imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto-imogolite and aluminium hydroxide species. These findings indicate that imogolite-like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = -2929.7 kJ/mol. In Fe2O3-SiO2-H2O sols, the Fe : Si ratio of the non-dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron-free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols.  相似文献   

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