福建周宁黄红壤的磁学特征及其磁性矿物转化

对我国亚热带地区发育于花岗岩之上的一个黄红壤剖面进行了系统的环境磁学测量,对土壤样品的磁化率、等温剩磁、磁滞回线等常温磁学参数进行测量,对代表性样品进行热磁分析,并结合色度、常量地球化学元素和漫反射光谱参数,探讨亚热带黄红壤的磁性特征,以及在相对湿冷的气候条件下,黄红壤中的磁性矿物具有怎样的转化规律。结果表明：亚热带黄红壤中强磁性矿物为亚铁磁性的磁铁矿、磁赤铁矿,弱磁性矿物为反铁磁性的赤铁矿、针铁矿。随着成土作用/风化作用增强,磁性矿物颗粒变细。母质和气候条件是影响区域磁性差异的重要因素,次生磁性矿物（特别是赤铁矿与针铁矿）的含量主要受气候条件控制。在相对湿冷的气候条件下,磁性矿物的转化以强磁性的磁铁矿与磁赤铁矿转化为弱磁性的赤铁矿与针铁矿为主。气温（而非降水）是湿润亚热带地区花岗岩风化壳上发育土壤中针铁矿和赤铁矿含量以及相对比例的主导影响因素。     

福建周宁黄红壤的磁学特征及其磁性矿物转化

对我国亚热带地区发育于花岗岩之上的一个黄红壤剖面进行了系统的环境磁学测量,对土壤样品的磁化率、等温剩磁、磁滞回线等常温磁学参数进行测量,对代表性样品进行热磁分析,并结合色度、常量地球化学元素和漫反射光谱参数,探讨亚热带黄红壤的磁性特征,以及在相对湿冷的气候条件下,黄红壤中的磁性矿物具有怎样的转化规律。结果表明：亚热带黄红壤中强磁性矿物为亚铁磁性的磁铁矿、磁赤铁矿,弱磁性矿物为反铁磁性的赤铁矿、针铁矿。随着成土作用/风化作用增强,磁性矿物颗粒变细。母质和气候条件是影响区域磁性差异的重要因素,次生磁性矿物（特别是赤铁矿与针铁矿）的含量主要受气候条件控制。在相对湿冷的气候条件下,磁性矿物的转化以强磁性的磁铁矿与磁赤铁矿转化为弱磁性的赤铁矿与针铁矿为主。气温（而非降水）是湿润亚热带地区花岗岩风化壳上发育土壤中针铁矿和赤铁矿含量以及相对比例的主导影响因素。     

安徽凤阳石英岩发育土壤的磁学性质及环境磁学意义

通过对安徽凤阳石英岩发育土壤典型剖面的磁学参数测量,结果表明,A层和B层中的磁性矿物含量明显高于C层,且A层和B层中磁性矿物的粒度明显比C层细.C层的磁学性质由磁铁矿主导,A层和B层的磁学性质由磁赤铁矿主导.磁赤铁矿是石英岩在成土过程中形成的次生矿物.土壤中磁赤铁矿的出现及含量的变化指示成土作用的强弱.石英岩的磁性对土壤的磁性影响甚小,而成土作用和生物作用对土壤磁性增强起到了主要作用.     

发育于石英岩之上的表土磁学性质及其环境磁学意义

通过对石英岩及发育于石英岩之上表土的磁化率(X)、频率磁化率(Xfd)、等温剩磁(IRM)、非磁滞剩磁(ARM)、κ-T曲线等磁学参数测定和石英岩显微镜下观察,结果表明,石英岩中磁性矿物含量极少;表土中含磁铁矿、磁赤铁矿、铁的氢氧化物等磁性矿物,磁性矿物主要以稳定单畴(SSD)和超顺磁性颗粒(SP)形式存在,磁赤铁矿是石英岩在成土过程中形成的次生矿物.表土磁性增强,说明石英岩的磁性对表土磁性影响甚小,而成土作用对表土磁性增强起到了重要作用.表土的磁化率值和磁赤铁矿含量都反映了成土作用的强弱.     

应用穆斯堡尔谱(Mössbauer Spectroscopy)研究土壤磁性的发生机理

通过穆斯堡尔谱(MS)和磁测的综合分析,结果表明,我国磁性最强的昆明玄武岩红壤的磁性矿物,主要为磁赤铁矿、磁铁矿和钛赤铁矿。这些磁性矿物可解释为原生钛磁铁矿、钛铁晶石、钛铁矿的“离钛氧化作用”的产物,钛的游离使矿物向纯的磁铁矿、磁赤铁矿和赤铁矿转化,从而形成了土壤的强磁性和一定的磁化率剖面特征。     

低丘侵蚀红壤垦种熟化过程中土壤磁性特征演变规律

应用磁测方法并结合土壤理化指标 ,对相同母质发育但利用方式和熟化程度不同的浙西红壤磁性特征进行研究。结果表明 ,6种利用方式的红壤中 ,耕植年限长、熟化程度高的红壤由于土壤结构、p H值和有机质含量的改善 ,磁性特征有明显变化 ,磁性矿物由亚铁磁性矿物向不完整反铁磁性矿物方向发展 ,且超顺磁性矿物和单畴磁性矿物含量减少。此外 ,耕植年限相同的红壤磁性相近 ,裸地红壤的磁性低值反映了裸地表土强烈侵蚀状况。     

新疆天山天池景区表土磁性特征的时空变化

以天山天池5A级景区表土为研究对象,分别于2015年和2017年两次采集表土样品,采用磁测、统计和GIS方法对其磁学特征、时空变异性进行研究。结果表明:表土样品载磁矿物以低矫顽力亚铁磁性矿物(磁铁矿和磁赤铁矿)为主,同时含有一定不完全反铁磁性矿物(赤铁矿和针铁矿),磁性矿物含量适中,磁性矿物粒度主要由假单畴粗颗粒和含量相对较低的超顺磁性细颗粒混合而成;表土样品中磁性矿物特征随时间变化显著,2017年磁性矿物含量、粗颗粒比例高于2015年;从景区表土样品磁性参数空间分布看,两期分布图变化趋势相似,2015年的高值区位于旅游核心景点区域及湖泊南部区域,2017年的高值区由2015年的高值区扩大到环湖区域且在核心景点区域含量增高;除自然因素外,由于研究区远离工业区、城市等污染源,两期磁性矿物含量和粒度产生的时空差异主要是两年的旅游交通活动输入的磁性污染物不断累积引起的。研究发现,监测景区表土磁性参数的时空变化有助于圈定可能污染范围的变化和判别污染物来源。     

磁性参数在红壤退化评价指标中的应用

选择浙西金华地区兰溪实验观测站六种不同退化程度的红壤为研究对象 ,分析了反映红壤退化程度的物理、化学和生物指标及红壤磁测参数与它们之间的内在联系。结果表明 ,磁性参数与反映红壤退化程度的理化及生物指标均有显著或较显著的相关性。退化程度较轻的香樟林和混交林表现了较低的细晶粒磁性矿物含量和较高的反铁磁性矿物含量 ,退化程度较高的杉木林、桔园、草地则相反 ,细晶粒磁性矿物含量较高且亚铁磁性矿物的相对含量上升。磁性参数和土壤理化生物指标之间良好的相关性表明 ,磁性参数可以作为指示红壤退化程度的重要指标。     

太湖流域水稻土的磁化率剖面

土壤磁学是一门新兴的土壤学分支学科。它以研究土壤磁性为中心内容,把现代磁学理论以及磁测、磁查和磁诊断等研究手段和方法应用到土壤学中来^[2]。土壤磁性的强弱,可用磁化率作为指标。土壤磁化率的大小,主要决定于含铁矿物的种类和数量,特别是强磁性矿物(亚铁磁性的磁铁矿Fe₂O₃·FeO和磁赤铁矿γ-Fe₂O₃)的数量。     

土壤磁化率-温度(κ-T)曲线测定中的影响因素研究

土壤磁化率-温度曲线(κ-T)可用于鉴定土壤中磁性矿物类型。以水稻土、红壤、黄壤和砖红壤为对象,采用BaringtonMS2κ-T磁化率/温度系统,测定了不同土壤类型中磁性矿物种类。结果表明:水稻土κ-T曲线在300℃出现矿物相变点,黄壤、红壤和砖红壤在350℃出现相变点;水稻土和黄壤κ-T曲线呈现出磁铁矿的居里点(580℃),表明土壤磁性载体以磁铁矿为主;红壤和砖红壤的κ-T曲线呈现赤铁矿的居里点(680℃)。将水稻土和红壤分别制成2 mm、1 mm、0.30mm和0.15 mm的颗粒大小,称取相同质量土样(1 g)研究不同颗粒大小对土壤κ-T曲线测定的影响;称取过2 mm筛土样0.5 g、1 g、1.5 g和2 g,研究不同称样量对κ-T曲线测定的影响。结果表明:不同土壤类型,颗粒大小和称样量对κ-T曲线的测定有一定影响,但不会改变土壤中磁性矿物的相变点。它们对红壤和砖红壤的κ-T曲线测定影响甚少,对水稻土和黄壤的影响较大。实验证明在颗粒大小上选择过0.30 mm筛的土样,称样量上选择大于1 g的土样可以得到较明显的κ-T曲线,不会掩盖矿物的相变点。     

台湾红壤及森林土壤中之氧化铁

本文综合汇整近年来在台湾，应用高梯度磁场分离技术，配合一般化学分析，Ｘ－射线衍射法，磁测分析，电子显微镜观察与电子衍射鉴定，以及铁－５７穆期堡尔谱学分析等方法，研究红壤与森林土壤中，氧化铁的分布及其结构性质之成果回顾；关于氧化铁之分布情形，其研究结果显示：台湾红壤中普遍存在有赤铁矿与针铁矿等氧化铁矿物，而在化育自大屯山更新世纪安山岩母质与澎湖列岛更新世纪玄武岩母质的红壤中，以及兰屿绿岛海边之银白色     

华中南部某些土壤针铁矿的形态

The morphologies of goethites in latosol, red soils, yellow-brown soil and the paddy soils developed from red soils were studied in comparison with the morphology of synthetic goethite by means of the X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis. The synthetic goethite displayed acicular particles elongated in the c-direction. The goethites in the latosol, red soils and yellow-brown soil were platy particles stretched in two directions or isodimensional particles, and those in the paddy soils from red soils were acicular, short columnar, platy or isodimensional particles. Various morphologies of the goethites probably suggested their different dominant crystal faces, surface charge distribution and surface adsorption characteristics.     

Diagnostics of manganese-iron nodules in soddy-podzolic soils at different degrees of gleyzation from their magnetic properties

The composition and magnetic properties of manganese-iron nodules in soddy-podzolic soils at different degrees of hydromorphism were studied. The data of chemical analysis, magnetic measurements, and X-ray diffraction analysis indicate that the nanoparticles of magnetite act as a strongly magnetic phase in these nodules. The distribution of strongly magnetic nodules in soils and the absence of correlation between the content of magnetite and the magnetic parameters of the enclosing soil material indicate that the nodule magnetite is of soil origin.     

贵州碳酸盐岩发育土壤磁学性质及其发生机理

本文对贵州碳酸盐岩发育土壤的磁化率、磁化率频率系数和等温剩磁等磁学参数的系统测定以及磁性矿物研究表明，碳酸盐岩发育土壤磁学性质及其变化特征主要受成土地球化学作用和环境影响，具有十分重要的环境指示意义。本文在采用高梯度磁性分离土壤中氧化铁矿物基础上，综合运用Ｘ射线衍射分析、电子探针分析、透射电镜和穆斯堡尔谱等方法，讨论了碳酸盐岩发育土壤中磁性矿物的形成机理。     

Red soils with white net-like veins and their climate significance in south China

The microstructure, particle size distribution, mineral and chemical compositions of both the white net-like veins and the red matrix of the Xuancheng laterite soil section in Anhui, south China, in the middle to lower reaches of the Yangtze River, were investigated using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), polarized light microscopy observation, and particle size distribution analysis. There was more quartz while less clay minerals in the white veins relative to the red matrix. In particle size distribution patterns the more abundant 5-20 μm particle size component of the white veins resulted from their higher quartz content. Discrepancy in degree of weathering between the white veins and the red matrix was derived from the depletion of Fe₂O₃ (total) and MnO₂ and the relative accumulation of SiO₂ in the white veins. White veins across the lithological layers and inclusions of relict red matrix material in the white veins indicated that the net-like soils originated from an initial uniform red soil. The white spots or veins were derived from the long-term modification of the pre-existing soil or concurrent weathering soils. Hydrodynamic conditions of the groundwater exerted influence on the formation of white veins. The formation process of the white net-like veins was different from that of the red matrix, suggesting that the white vein materials reflected a hydrological imprint upon the result of these conditions. The net-like soils in south China were compatible to the mottled soils in Africa, Australia, India, and Brazil. However, much more intense depletion of Fe oxide and much better developed white veins in the net-like soils of south China suggest probably even warmer and more humid palaeoclimatic conditions relative to those in Africa, Australia, India, and Brazil during the period.     

Iron oxide and clay minerals and their relation to colours of red and yellow podzolic soils near Sydney,Australia

The iron oxide and clay minerals in some typical red and yellow podzolic soils from New South Wales have been investigated by X-ray diffraction and infra-red spectroscopy. The dominant iron oxide mineral is goethite containing about 13–14 mol % AlOOH, this being the mineral which gives the yellow soils their characteristic colour. The red soils also contain finely divided hematite which masks the colour of the goethite. Lepidocrocite was not detected in any of the soils examined. The dominant clay minerals are kaolinite and dioctahedral interstratified illite-smectite, the latter being more concentrated in the finer clay fractions, especially in soils developed on calcareous greywacke. In the red podzolic soil developed on Ashfield shale, illite-smectite is strongly interlayered with well-ordered aluminous material. Dickite occurs in this soil.     

红壤及其同源红壤性水稻土各粒级磁化率分布规律的研究

红壤经水耕熟化作用后各粒级磁化率大幅度下降，粒级间磁化率差异变小，分布曲线趋于平缓。母质对各粒级磁化率的分布曲线的形状影响颇大。铁子、假砂和铁质岩屑之含量决定着粗砂粒级（０．２５～１ｍｍ）的磁化率大小     

应用穆斯堡尔谱和X射线法研究红壤性水稻土的氧化铁矿物

应用穆斯堡尔谱和X射线法分析研究红壤性水稻土的氧化铁矿物,研究结果表明,红壤性水稻土的氧化铁矿物组成、特性及其形成转化与起源土壤具有明显的差异。水稻土的成土条件不利于赤铁矿的形成。红壤的粘粒氧化铁矿物以赤铁矿和高铝替代(>20摩尔%)的针铁矿为主。经淹水种稻后,赤铁矿逐渐被转化为低铝替代的针铁矿或其它形态氧化铁。渗育型水稻土P层的赤铁矿含量比相应的母土低,其针铁矿铝替代量较其它水型的水稻土高。而潴育型水稻土W层和潜育型水稻土G层粘粒氧化铁矿物均以针铁矿为主,其铝同晶替代量低(<15摩尔%),且颗粒细小,结晶度较低。这些结果反映了水稻土的成土条件和发生特点,同时对水稻土发生分类具有重要的意义。     

Red soil chemistry and mineralogy reflect uniform weathering environments in fluvial sediments, Taiwan

Purpose

Information on the physicochemical properties, mineral species and micromorphology of lateritic soils and gravel soil layers in paleo-environmental soil profile is severely lacking. Red soil profile of the Taoyuan terrace was employed to demonstrate its different extents of lateritic weathering. The objectives of this study were to compare the physicochemical properties of lateritic soils and gravel soil layers and identify using conventional and synchrotron X-ray diffraction (XRD) analyses mineral species in nanoparticles separated by automated ultrafiltration device (AUD) apparatus.

Materials and methods

Soil samples were collected from paleo-environmental lateritic soils. Soil samples were examined using elemental analysis, conventional and synchrotron XRD analyses, high gradient magnetic separation, separation and collection of nanoparticles by AUD apparatus, and transmission electron microscopy (TEM).

Results and discussion

The soil pH, redness index, quantities of free Al- and Fe-oxides (Al_d and Fe_d), and clay content of lateritic soils are higher than those of gravel soil layers. Illite, kaolinite, gibbsite, quartz, goethite, and hematite were identified in clay fractions and nanoparticles by conventional and synchrotron XRD analyses. TEM images show presence of hematite nanoparticles on the surface coating of kaolinite nanoparticles and aggregated hematite nanoparticles overlapping the edge of a kaolinite flake in a size range of 4?C7?nm. Synchrotron XRD techniques are more straightforward and powerful than conventional XRD with random powder methods for identifying nanoparticles in red soils, particularly for illite, kaolinite, goethite, and hematite nanoparticles. According to chemical compositions of clay fractions and red soil features in the Taoyuan terrace, these red soils can be taken as lateritic red earths or red earths.

Conclusions

This work suggests that physicochemical properties, mineral species, and micromorphology of red soil at all depths can shed light on the extent of paleo-environmental lateritic weathering.     

福建主要土壤的粘粒云母含量和供钾潜力

利用X射线衍射法估算了福建省221个土壤样品中粘粒云母含量并讨论了与粘粒云母含量变化有关的因素。结果表明母质是影响粘粒云母含量的主要因素。海积物、河积物及页岩上发育的土壤粘粒云母含量一般较高;基性岩上发育的土壤粘粒云母含量一般较低。风化度较高的赤红壤、红壤、黄红壤和黄壤等土类的粘粒云母含量一般较低。风化度较低的C层的粘粒云母含量一般较B层和A层高,但异源母质的堆积可以使A层粘粒云母含量高于B层和C层。