三峡库区坡地表层风化特征研究

Extractability and mobility of Cu and Zn and their relationships with 1） accumulation of Cu and Zn and 2） soil pH were studied in three sandy soils （Wabasso, Ankona, and Winder） from commercial citrus groves in Florida, USA. The soils, with a broad range of Cu and Zn concentrations, were fractionated by a modified procedure of Amacher, while Cu and Zn mobility were evaluated using column leaching. The extractability of Cu and Zn increased with decreasing soil pH. Also with increasing total soil Cu and Zn for extractable Cu in the Wabasso sand a threshold level, where the metal extraction rate increased, was noted at 100 mg kg^-1, whereas for extractable Zn in the Wabasso sand the threshold level was found at 60 mg kg^-1 and in the Ankona sand at 120 mg kg^-1. These results suggested that the release potential of Cu and Zn was greater in the Wabasso sand than in the Ankona sand. The column leaching experiment showed that at total soil Cu or Zn concentrations 〈 100 mg kg^-1 all leachates had low Cu and Zn concentrations. However at total concentrations 〉 200 mg kg^-1 for Cu and 〉 150 mg kg^-1 for Zn with decreasing soil pH, the concentrations of both Cu and Zn in the leachates increased exponentially. Also in these sandy soils soluble Cu and Zn mainly originated from the exchangeable fractions, and pH was a key factor controlling Cu and Zn extractability and mobility.     

Characteristics of Regolith developed on basalt in Pahang,Malaysia

Abstract

The characteristics and degree of weathering in a deep regolith developed on basalt were investigated. A representative 15m deep regolith of soil‐saprolite‐rock sequence, located in Pahang state, Malaysia, was selected. The intensity of weathering in this deep regolith was assessed by various weathering indices as well as changes in the physicochemical properties and clay mineralogy of the regolith. The values of all weathering indices and other assessments gave strong evidences of intense weathering during saprolite formation. The low CËC and base cation values even in the saprolite layers were accounted By the extreme depletion of major elements such as potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg), and significant enrichment of aluminum (Al), iron (Fe), titanium (Ti), copper (Cu), and niobium (Nb) occurred during saprolitization. The extreme weathering pattern of basalt differed from those described in granite and metamorphic rocks found in Peninsular Malaysia.     

Iron oxides in four Red Mediterranean soils on metarhyolite and metadolerite in Kilkis,Greece

The various iron fractions were quantified by selective dissolution (Fe_d, Fe_o, Fe_t) in four Red Mediterranean soils, developed on metarhyolite and metadolerite. They were similar in all profiles. A strong trend of iron removal from the surface horizon and of its subsequent illuvial translocation to the argillic horizons was observed. In all profiles, Fe_o was not related to the organic matter content indicating the Mediterranean xeric soil environment. The Fe_o/Fe_d ratio and the percentage of crystalline iron oxides (Fe_d-Fe_o) suggested that the pedoenvironment in which the profiles P1, P2 were formed, allowed the high crystallization of iron oxides. As indicated by the Fe_d/Fe_t values, the weathering process was more intense in the metarhyolite-developed soils. In contrast, the metadolerite-developed soils present conditions of poorly crystallized iron oxides and a lower degree of development.     

青藏高原爬坡沙丘地表沉积物特征分析——以柴达木盆地托拉海河为例

为了阐明青藏高原爬坡沙丘的物源及沉积学意义并揭示其形成机理,对托拉海河爬坡沙丘进行断面采样,分析爬坡沙丘不同地形部位的粒度与地球化学元素特征。结果表明,托拉海河爬坡沙丘地表沉积物的粒度组成总体以极细砂、细砂、中砂为主,粒度特征表现出明显的风成特点;不同地形部位,粒度特征呈现不同的递变规律,自河床到迎风坡顶粒径变粗,分选变好,迎风坡顶到背风坡,粒径粗细混杂,分选变差。沉积物地球化学元素组成以Si、Al、Ca为主,和上陆壳(UCC)相比,除Co、As、CaO、SiO2以外,其余元素都有一定的亏损,不同部位化学元素分布具有一定相似性,且常量氧化物之间有较好的相关性,表明其具有相似的沉积环境。A-CN-K图解及CIA值揭示了托拉海河爬坡沙丘地表沉积物化学风化处于较低程度,大部分化学元素没有显著的风化或迁移,整体属于早期去Na、Ca的阶段;A-CNK-FM图则表明整个断面Fe、Mg元素在空间分布上存在一定的差异,Fe、Mg流失主要是差异风力风选的结果。从化学风化指标来看,不同地形部位风化程度不同,河床风化程度最弱,山地迎风坡的风化程度最强;河床与河流阶地的物源呈现多样性,而迎风坡和背风坡物源较为单一,可能是古沙翻新和就地起沙。因此,初步认为托拉海河爬坡沙丘的形成经历了两个阶段:一是古沙丘形成阶段;二是现代爬坡沙丘形成阶段。在不同空间尺度上,托拉海河爬坡沙丘地表沉积物的理化特征差异与风动力和水动力的差异有关,反映出沉积物对风、水交互作用的响应。     

Evaluating the degree of weathering in landslide-prone soils in the humid tropics: The case of Limbe,SW Cameroon

This study analyses the behaviour and mobility of major and some trace elements during the physical and chemical development of landslide-prone soil profiles in Limbe, SW Cameroon. The soils result from in situ weathering of Tertiary basaltic and picrobasaltic rocks. Textural and chemical characterisations, together with two mass balance models are applied to understand the mobility and redistribution of elements during the weathering of pyroclastic cones and lava flows. Weathering indices are used to estimate the extent of weathering. The chemical composition of the samples is evaluated by Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP–OES) and their mineralogical composition by X-Ray Diffraction (XRD) analyses. It is observed that intensive weathering results in thick meta-stable soils in which significant loss of Ca, K, Mg, Na and Sr has taken place. There is a noticeable relative enrichment in all analysed trace elements (Ba, Zr, Y, Sc, V, Ni, and Co). Ti, Fe, Al, Mn, P and Ce tend to be leached in some horizons and concentrated in others. Zr, Ti, and Ce concentrations are greater in the soils than in the bedrock but show slight fluctuations in the soil and saprolites hence cannot be used as immobile elements for mass balance evaluations. Y increases progressively with advanced weathering. Major secondary mineral phases developed through weathering are a mixture of expanding (smectites) and non-expanding clays (kaolinite, halloysite and mica). The profiles show the presence of textural heterogeneities that can be exploited as slip surfaces. Data plotted in Si–Al–Fe diagram point out that the most advanced stage of weathering noted in these profiles is the kaolinisation stage.     

侵蚀性花岗岩坡地不同地貌部位土壤剖面风化特征研究

为揭示发育于侵蚀性风化花岗岩坡地上不同地貌部位土壤剖面的风化发育特征,在浙江省选择了典型的风化花岗岩坡地:浙江省嵊州市水土保持监测站为研究区,在监测站同一坡面不同侵蚀强度的坡顶、坡中、坡底选取3个典型的土壤剖面(140 cm),从下至上等距离(20 cm)采集土壤样品,共采集21个土样。进行了各层土壤基本理化特性和化学全量的分析,并分别计算了3个剖面不同层次的主要化学风化系数及总的风化强度,结果表明:(1)在强烈侵蚀的花岗岩风化残积坡地发育的土壤,总体发育成熟过程较弱,其进一步的发育与典型的地带性土壤的发育有很大的差异,侵蚀过程严重地影响了土壤的进一步成熟,侵蚀强度越大,则土壤发育越差。(2)土壤剖面总的风化强度不大,上下层的递变差异很小,脱硅富铝化过程随着剖面深度的增加风化程度越来越弱。(3)土壤剖面的化学分层不明显,各种风化指标均在60 cm左右形成了一个分界层,其上受水力侵蚀影响明显,其下呈现出的特性以继承残积母质为主。(4)不同地貌部位的风化发育程度排序为:坡底坡中坡顶,其与采样坡面的侵蚀强度排序正好相反。(5)风化程度与有机质和黏粒含量具有较为明显的正比关系,在侵蚀环境下,土壤的物理特性对风化的影响明显,在沉积环境下土壤有机质的影响大于黏粒含量的影响。总之,由于受侵蚀的影响,坡地土壤剖面的淀积层不发育,剖面呈现出的假淀积层不是由淋溶作用形成的,而是具有一定风化程度的风化残积层,结果导致发育于山地丘陵侵蚀性坡地的土壤层次划分不同于常规的土壤层次划分。     

Weathering of chlorite in a soil derived from a chloritoschist under humid tropical conditions

Eight samples from a soil derived from greenschist were chosen to represent the weathering transformation of chlorite and were subjected to chemical and mineralogical analyses by X-ray, D.T.A., selective and acid dissolution techniques. Regularly interstratified chlorite-vermiculite is the major weathering product in the sand and silt fractions, whereas nontronite predominates in the clay fraction. Kaolinite and a “chlorite-like” mineral progressively appear in the clay fraction as the soil surface is approached. The results show that the genetic link suspected between the clay chloritic component and the kaolinite does not withstand a detailed examination. The clay chloritic mineral is a disordered remnant of the regularly interstratified chlorite-vermiculite and it appears in the clay fraction of the solum concommitantly with the argillitization of the silt fraction. Kaolinite occurs in close association with nontronite and would perhaps form with this mineral a true mixed-layer phase. The unequal distribution of aluminium, iron and magnesium amongst the available sites in the parent chlorite appears to be a factor that strengthens the divergent behaviour of these elements during the weathering.     

Weathering of gneiss in Calabria,Southern Italy

The effects of weathering in a Mediterranean climate on the mineralogy and microfabric of Paleozoic gneiss of the Sila Massif, Calabria, southern Italy, have been studied. Field observations show highly weathered rock forms a residual soil. Micromorphological and mineralogical properties of bedrock and saprolite show that the weathering process is characterized by at least two major stages, having two distinct rock microfabrics. In the first stage, the morphological features of the original rock are preserved and weathering is manifested mainly by microfracturing, and large portions of the rock remain unaltered. The second stage of weathering involves further development of microcracks and progressive chemical attack on the minerals. This latter stage occurs along both compositional and microstructural discontinuities, with etch pitting of feldspar, and neoformation of clay minerals and ferruginous products replacing feldspar, biotite, and iron-bearing garnet. The determination of quantitative petrographic indices provides a measure of the various stages of weathering.     

The influence of slope aspect on soil weathering processes in the Springerville volcanic field,Arizona

A comparison was made between soils on north- and south-facing slopes of six cinder cones in the Springerville volcanic field (SVF), Arizona, in order to determine the influence of slope aspect on soil weathering processes. Twenty-four soil pedons were sampled on different aspects of six cinder cones. To control for the influence of slope on pedogenesis, all sample sites possessed slopes of 17±2°. Soil weathering processes were characterized by solum depth, texture, and Ca:Zr chemical weathering indices. Quartz and mica were used to identify eolian additions to the volcanic soils. Accelerated rates of weathering and soil development were found to occur in soils on south-facing slopes while no trend with aspect was found for eolian additions. Accelerated rates of weathering and soil development may influence cinder cone degradation and cone morphology.     

Rare earth and other trace and major elemental distribution in a pedogenic calcrete profile (Slimene,NE Tunisia)

A calcrete profile developed on the top of a calcareous consolidated dune located in a coastal area of NE Tunisia (semi-arid climate) was studied with the aim to investigate the behavior of the chemical elements (rare earth elements—REE—and other trace and major elements) during the processes associated with calcrete formation, particularly dissolution and precipitation of carbonates in the vadose zone. The profile shows a vertical sequence, with clear zonations from the surface downwards: a reddish soil at the land surface, a nodular horizon, a laminar-structured level, and the consolidated old dune. Chemical and mineralogical analyses of samples from all levels were performed by neutron activation analysis and X-ray diffraction (bulk samples and < 2 μm fraction). Detailed studies of iron speciation and iron minerals were done by Mössbauer spectroscopy. Microfauna, mineralogical and chemical variations in the Slimene weathering profile point to a long term aerial exposure of the old dune in a semi-arid carbonated environment leading to the development of a pedogenic calcrete profile. The mineralogical variations with depth indicate carbonate dissolution at the surface and downward leaching of calcium. Secondary carbonates overgrow primary ones and precipitate as coating or concretions below. Minerals found in the upper levels correspond to original materials of the old dune and also weathering phases and atmospheric inputs. Phyllosilicates decrease while calcite and K-feldspars increase with depth. Kaolinite was the only clay mineral found in the old dune. Illite and chlorite were also found in all samples with calcrete. Authigenic smectite formation occurs above the laminar-structured calcrete due to restricted drainage conditions. The most significant chemical variations associated with the calcrete formation are (i) enrichment of Co, U, Br, and REE in calcrete; (ii) depletion of middle REE in the upper levels, particularly Eu, and enrichment of middle REE and heavy REE in calcrete; and (iii) Hf, Zr, Cr, Th, Cs, Ta, Ga, Rb, and K appear to be retained in the upper levels, where calcite has been dissolved. Here iron is more reduced. Fe³⁺ occurs in iron oxides (goethite and hematite), and clay minerals. The ratio goethite/hematite appears to increase down the profile; and Fe²⁺ is mainly present in clay minerals.     

巫山黄土成因及其发育土壤特征研究

  目的  为探明巫山黄土成因,了解该类母质发育土壤的发生学特征。  方法  以典型巫山黄土及其发育土壤剖面为研究对象,通过野外调查采样和室内分析,详细考察剖面形态、颗粒组成、常量元素地球化学特征及其他相关理化性质,计算探讨硅铝率（ Sa ）、化学蚀变指数（ CIA ）、钠钾比（ Na/K ）、铁游离度等风化指标。  结果  （1）巫山黄土的颗粒组成以粉粒为主,平均含量为53.29%,与典型风尘沉积物相似,同时,巫山黄土与其他区域风成黄土的主要元素硅、铝、铁含量非常接近,上陆壳（UCC）标准化曲线也较为相似;（2）该剖面100 ~ 140 cm深度与其他深度相比,有机碳和硒含量较高,CaCO₃相当物含量和δ13C值较低,推测在此深度堆积过程中的气候较为温湿,并可能出现过植物的生长;（3）巫山黄土剖面的 Sa 为8.73 ~ 9.17、 CIA 为65.96 ~ 69.10、 Na/K 为0.74 ~ 0.89、铁游离度为22.88% ~ 29.74%,与其他地区风成黄土相比,巫山黄土风化程度强于洛川黄土而弱于下蜀黄土和成都黏土,与汉江黄土和甘孜黄土十分接近。  结论  巫山黄土应为风积成因,处于中等化学风化程度,以脱盐基为主,脱硅富铁铝化程度弱,可能与汉江黄土或甘孜黄土同源。     

Parent material and chemical weathering in alpine soils on Mt. Mansfield,Vermont, USA

We compared the elemental composition of soil and bedrock samples to determine the extent of chemical weathering and the nature of the soil parent material in alpine soils on Vermont's highest summit. Previously it was unclear whether these soils formed through weathering of bedrock, glacial till, or eolian sediment, or solely through the accumulation of organic matter. In eighteen profiles, no evidence was found to indicate that soils have developed in glacial till, despite evidence that the mountain was completely inundated by the Laurentide Ice Sheet. In contrast, results strongly support the theory that pedogenesis in this environment involves in situ bedrock weathering under a thickening blanket of acidic organic litter. Weathering indices reveal an increase in weathering intensity upwards from the bedrock, and trends of normalized rare earth elements demonstrate a strong similarity between bedrock and soil samples. Leaching has concentrated less mobile elements such as Al, Cr, La, P, Pb, and Ti in soil horizons and removed mobile elements such as Co, Fe, K, Mg, Mn, Si, and Zn. X-ray diffraction reveals that chlorite, which is present in all bedrock samples and some saprolites, has weathered completely from upper soil horizons, and that hydrobiotite, vermiculite, kaolinite, gibbsite, and goethite have formed in the soil. Ratios of immobile elements (Ce, Cr, Nb, Ta, Ti, Y, and Zr) in soil and bedrock samples are, however, notably different. Furthermore, the moderately mobile trace elements Cu, Mo, and Sr are actually more abundant in soil than in bedrock, and soil concentrations of Zr are up to an order-of-magnitude greater than in bedrock samples. Together these data argue for at least a modest eolian influx, which may have arrived during the regression of Lake Vermont during the latest Pleistocene or from an outwash source in the immediate post-glacial period. Similarly, increased Ca and Na concentrations in soil samples may signify modern deposition of dust bearing Ca (from agricultural fields) and Na (from roads).     

Equatorial weathering,landform development and the formation of white sands in north western Kalimantan,Indonesia

The morphology and geochemistry of weathering profiles in Miocene granodiorites from the coastal lowlands of NW Kalimantan, Indonesia (1°N lat.), indicate long-term weathering rates, landform development and mechanisms for the formation of `white sands' found widely in valleys and depressions. Samples are analysed from convex hill, piedmont glacis, and valley slope profiles. All profiles above the saturated zone are strongly gibbsitic, but kaolinite minerals are dominant below the water table. The profiles are interpreted as expressions of the perhumid Equatorial climate (rainfall 3000 mm y<sup>−1</sup>) acting within a dynamic regime of landscape lowering during the Neogene, the current profiles being largely Quaternary (0.4–0.6 ka). Possible effects of Quaternary tectonic and environmental changes are considered, including those caused by a Late Pleistocene drier climate when there was greater water table fluctuation and surface erosion. Landform evolution is a form of dynamic etchplanation with a long-term rate of landscape and weathering profile lowering of ca. 50 mm ka<sup>−1</sup>. Within this regime some of the `white sands' may be residual weathering products locally redistributed by colluvial or alluvial processes. They originated in the podzolising environment of the weathering profile, and later experienced post depositional (diagenetic) changes within the hydromorphic regime of the valley floor.     

Weathering of a gypsum-calcareous mudstone under semi-arid environment at Tabernas,SE Spain: laboratory and field-based experimental approaches

The weathering of a Late Miocene gypsum-calcareous mudstone outcropping in large badland areas of SE Spain, under a semi-arid Mediterranean climate, was studied by means of two experimental approaches. Field and laboratory experiments were carried out to reproduce, though in accelerated form, some of the weathering conditions of the consolidated mudstone. In the laboratory, three sequences of 5, 10 and 20 wetting–drying cycles were produced on undisturbed blocks of fresh mudstone samples. At the end of the three sequences, samples were analysed for their micromorphology, elemental and soluble salt chemistry, and total mineralogy. Unweathered dry samples, as blanks, and permanently wet samples were also analysed. In the field, two small plots of freshly exposed mudstone were monitored over 3 years for their response to natural weathering in terms of morphological changes and sediment output. The porosity was increased by a few wetting–drying cycles, as assessed by significant increases in water absorption capacity of the mudstone. A combination of three factors is responsible for mudstone weathering: repeated cycles of wetting–drying, the presence of geologically-induced cracks and fissures, and dissolution–crystallisation of relatively soluble minerals, gypsum being the most abundant within this category. A few wetting–drying cycles were sufficient to reveal ion migration (specially Na⁺, Ca⁺⁺, Mg⁺⁺, SO₄⁻, HCO⁻ and Cl⁻) within the mudstone, explaining mineral dissolution. In the field, surface weathering rates from 0.7 to 8 mm year⁻¹ were measured. Weathering rates were found to be proportional to the number of rainfall events during the sampling periods, confirming what was found in laboratory conditions, namely, that the number of wetting–drying cycles has the greatest influence on weathering. These weathering rates might be considered as the probable range of incision rates under present semi-arid conditions.     

THE ORIGIN OF THE RED MEDITERRANEAN SOILS IN EPIRUS, GREECE

To determine the contribution of limestone weathering to soil formation the insoluble residues of six samples of the Pantokraton limestone were separated by treatment with 2M acetic acid at pH 3. The mean insoluble residue content is only 0.15% and to produce a soil depth of 40 cm it has been calculated that about 130 m of limestone would have to be weathered. No correspondence was found between the particle size distribution of the residues and of the overlying red soils, and the high siltrclay ratios of the soils do not indicate prolonged subtropical weathering. The particle size distribution of the soils is akin to that of aerosolic dusts. The dust loading of the atmosphere in the eastern Mediterranean is among the highest recorded, and it is proposed that the soils have developed on dust blown by sirocco winds from the deserts of N. Africa.     

Efficient mineral weathering is a distinctive functional trait of the bacterial genus Collimonas

The mineral weathering ability of 45 bacterial strains belonging to the genus Collimonas and coming from various terrestrial environments was compared to that of 5 representatives from the closely related genera Herbaspirillum and Janthinobacterium. Using glucose as the sole carbon source in a microplate assay for quantifying the release of iron and protons from biotite, all Collimonas strains proved to be very efficient weathering agents, in contrast to the Herbaspirillum and Janthinobacterium strains. The weathering phenotype was also evident during growth of collimonads on mannitol and trehalose, but not on gluconic acid. All Collimonas strains were able to solubilize inorganic phosphorus and produce gluconic acid from glucose, suggesting that acidification is one of the main mechanisms used by these bacteria for mineral weathering. The production of siderophores may also be involved, but this trait, measured as the ability of collimonads to mobilize iron, was shared with Herbaspirillum and Janthinobacterium strains. These findings are discussed in an ecological context that recognizes collimonads as mycophagous (fungal-eating) and efficient mineral weathering bacteria and suggests that this ability has evolved as an adaptation to nutrient-poor conditions, possibly as part of a mutualistic relationship with mycorrhizal fungi.     

秦岭北坡土壤发生特性与系统分类

根据野外调查资料和典型土壤剖面理化性质 ,包括室内化验数据综合分析表明 :秦岭北坡土壤的主要发生特性随海拔高度呈有规律的变化 ,依照《中国土壤系统分类 (修订方案 )》检索 ,土壤垂直带谱结构为 :土垫旱耕人为土—简育干润淋溶土—简育湿润淋溶土—酸性湿润雏形土—暗沃寒冻雏形土—暗瘠寒冻雏形土     

Fire and aspect induced differences on the erodibility and hydrology of soils at La Costera, Valencia, southeast Spain

This paper presents measurements of soil aggregation parameters and rainfall simulation experiments from areas of Mediterranean scrubland vegetation in La Costera district, in the southern part of Valencia Province, Spain. Data were obtained using a portable rainfall simulator and from laboratory studies of aggregate stability, using the water-drop test and ultrasonic dispersion methods. Three locations were chosen to enable the influences of aspect and the post-fire recovery time of the vegetation on soil erosion and hydrology to be investigated. The slopes studied were (a) a north-facing slope burnt ten years before the experiment, (b) a south-facing slope burnt at the same time, and (c) a north facing slope, burnt two years before the experiment, similar to slope “a” in terms of its basic characteristics. The experiments demonstrate the importance of both wildfires and aspect on hydrological and erosional soil surface processes.The north facing slope at La Costera (slope a) has a higher aggregate stability than the corresponding south facing slope (slope b). The recently burnt north facing slope (c) is intermediate in terms of aggregation, but has the most erodible soils because of the lower infiltration rates and the low vegetation and litter cover. Nevertheless, for the slopes burnt ten years previously, the south-facing slope is more erodible than the north-facing one.The results suggest that the forest fire ten years ago did not produce a persistent degradation of the ecosystem, only higher soil and water losses during the first years following the fire. A southern aspect, where vegetation recovery rates are slower and the hydraulic stress is higher, favours the development of soils with a relatively low aggregate stability.     

Cenozoic paleosols San Diego area,California

Ancient weathering profiles provide mute evidence of the major climatic regimes that operated in the southern California area during the Cenozoic Era. A tropical climate during part of the Paleocene and Early Eocene caused severe weathering of Jurassic andesitic rocks, Cretaceous granitic rocks and Late Cretaceous and Early Eocene terrigenous rocks. Erosional remnants of this paleosol exist as buried soils up to 30 meters thick and as exhumed soils on some modern hills. The main weathering horizon is overwhelmingly composed of kaolinite with residual quartz grains and minor amounts of iron oxides. This tropical climate was in effect at 35° to 40° north latitude.Late Eocene sedimentary rocks were deposited under a semi-arid climate with 50 to 60 cm of annual rainfall that was concentrated during one season. This interpretation is based on: 1) the dominance of conglomerate and immature sandstone in the Upper Eocene section compared to the relative scarcity of claystone, 2) the immaturity of the clay mineral suite which is dominated by smectite and vermiculite, 3) the presence of fractured clasts presumably split by growth and differential expansion of salts, 4) the multiple caliche beds that individually are up to one meter thick, and 5) the paleohydrology of the fluvial deposits which transported rhyolite gravels over 300 km distance from an eastern bedrock source about 4,000 m high in a river of 1.3 sinuosity with 100 year flood discharges up to 30,000 m³/sec.The extensive marine terraces in San Diego are mantled by relict soils that record composite weathering characteristics from glacial and interglacial climates from Late Pliocene to present. Maximal development of the paleosol includes an ironstone concretion layer (B_ir horizon) above an illuvial clay layer (B_t horizon) which rests on an iron- and silicacemented hardpan (C_m horizon).     

贵州喀斯特山区典型土壤氧化铁特征及其与土壤类型分异关系

以贵州省喀斯特山区30个典型土壤剖面为研究对象,采集土样,测定不同形态的氧化铁含量、计算相应的风化度指标,通过分析不同形态氧化铁含量、风化度指标与土壤类型分异的关系,探讨了氧化铁特征对喀斯特山区典型土壤类型分异的指示作用.结果 表明:游离氧化铁是区内土壤氧化铁的主要存在形态(26.62～75.99 g kg-1);绝大...