城市道路区土壤的磁学性质及其发生学意义

土壤磁学性质测定简便快捷,且具有特定的土壤发生学意义。本研究以南京市主城区11个道路土壤剖面共63个样品为研究对象,通过对低频磁化率和频率磁化率2个常用磁学性质以及土壤游离铁、活性铁、颗粒组成、有机碳、pH、碳酸钙相当物等土壤发生学特性的测定和相关性统计分析,结果表明:城市道路土壤磁性矿物来源和成土过程具有多样性;磁性矿物主要来源于燃煤飞灰、汽车尾气中的粗粒磁性矿物,其中可能伴生污染物质的输入;较高的pH和碳酸盐不利于细粒磁性矿物的形成。城市土壤磁学性质与其他发生学特性的系统研究,有利于阐明城市土壤的形成过程。     

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。     

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。     

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.     

安徽凤阳水泥工业区内污染土壤剖面的磁学研究

通过对安徽省凤阳县水泥工业区典型污染土壤剖面和水泥厂降尘的磁学参数测量,结果显示,两类样品中主要磁性矿物都是磁铁矿,土壤剖面20 cm以下样品的磁学性质由成土母质控制,磁性矿物含量较低,磁性矿物以稳定单畴和超顺磁性颗粒为主,土壤剖面0~20 cm样品由于受到水泥厂降尘影响,其磁学性质发生了变化,土壤中磁性矿物含量升高,磁性增强,磁性矿物粒度相对变粗。土壤剖面的磁学参数随深度的变化关系反映了水泥厂降尘对土壤剖面的污染过程和现状。     

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.     

水泥厂周边稻田土壤剖面磁学性质及其环境意义

为了研究工业粉尘对农田土壤磁学性质的影响,在水泥厂周边挖掘了2个稻田土壤剖面(L01、L02)和1个山林土壤剖面(L04),同时设置对照剖面(L03),采用环境磁学方法,分别对4个土壤剖面磁学参数、矿物成分和化学成分进行了分析。结果表明:水泥厂周边3个土壤剖面中主要矿物成分是石英、伊利石、针铁矿、蒙脱石、方解石等。稻田土壤剖面中存在亚铁磁性矿物和反铁磁性矿物,但亚铁磁性矿物含量较低,剖面L01和L02的χ(质量磁化率)、χ_(ARM)(非磁滞剩磁磁化率)、SIRM(饱和等温剩磁)平均值分别为12.05×10~(–8) m~3/kg、52.71×10~(–8) m~3/kg、9.74×10~(–4) Am~2/kg和9.40×10~(–8) m~3/kg、43.82×10~(–8) m~3/kg、7.67×10~(–4) Am~2/kg,这2个剖面中磁性矿物粒径较粗,超顺磁性颗粒含量较低,χ_(fd)(频率磁化率)平均值分别为3.41%和3.08%。剖面L04中亚铁磁性矿物含量较高,其χ、χ_(ARM)、SIRM平均值分别为53.85×10~(–8) m~3/kg、393.73×10~(–8) m~3/kg、26.90×10~(–4) Am~2/kg,该剖面中磁性矿物粒径细,超顺磁性颗粒含量高,χ_(fd)平均值高达14.20%。由于受到水泥粉尘的影响,水泥厂周边3个土壤剖面(L01、L02、L04)0～20 cm土壤磁学性质和ω_(CaO)(CaO质量分数)都发生了明显变化,磁性增强,磁性矿物粒径变粗,ω_(CaO)升高,3个土壤剖面中ω_(CaO)与磁学参数χ、χ_(ARM)、SIRM均存在正相关关系。因此,稻田土壤剖面的磁学参数χ、χ_(ARM)、SIRM和ω_(CaO)对水泥粉尘的影响具有较好的指示作用,两类参数的值越高,指示稻田土壤被水泥粉尘影响越严重。     

川西地区表土磁学性质及其环境意义

通过对川西地区表土样品进行系统的岩石磁学分析,并且结合气候要素探讨表土磁学性质与环境要素之间的关系。结果表明:(1)川西表土在成土过程中生成的细粒超顺磁(SP)和单畴(SD)的亚铁磁性矿物是磁化率增强的主导因素。该地区表土磁性增强机制与黄土高原类似。(2)在空间上,川西高原西部和南部地区的磁性矿物含量要高于东部和北部地区,而成都平原西部地区成土作用最强,磁颗粒细且含有较多高矫顽力磁性矿物。(3)川西表土的磁学参数和气候要素的研究发现年平均降水量(MAP)在600～1000 mm之间磁化率、频率磁化率与MAP呈正相关关系,而磁学参数组合χ_(fd)%/HIRM、ARM/HIRM、χ_(ARM)/SIRM与MAP在这一降雨区间也呈正相关关系,然而这些磁学参数与MAP的相关系数不如黄土高原,可能与研究区复杂的地形、相对湿润的成土条件有关。     

水耕人为土磁性矿物的生成转化机制研究回顾与展望

随着环境问题的日益突出,人为活动对土壤的影响越来越深刻,需加强对"人为作用"的研究以便解释现代土壤磁性的过程和变化。水耕人为土在发育过程中人为作用的方式多种多样,明确其磁性矿物的生成和转化机制及其影响因素有利于理解人为活动对现代土壤磁性的作用。但目前水耕人为土磁学研究还比较零散,缺乏系统性,已有研究结果有待深入梳理。本文对已有的相关研究报道,包括水耕人为土磁性参数的演变特征、磁性矿物的生成转化机制以及对成土因素的响应等进行综合评述。最后,对当前研究的不足和存在问题进行总结,并对研究方向进行了展望,以期有助于环境磁学的发展。     

MAGNETIC SUSCEPTIBILITY OF THE SOIL AND ITS SIGNIFICANCE IN SOIL SCIENCE – A REVIEW

The magnetic susceptibility of soil minerals is discussed, and in particular that of the ferrimagnetic minerals, maghemite, magnetite, and the titanomagnetites since one or more of these usually dominates soil magnetic properties. The magnetic susceptibility of soil depends on the shape, size, and concentration of these minerals as well as on the method of measurement. Measurements performed in a weak alternating magnetic field are the most reliable. The identification, formation, and occurrence of soil maghemite is considered in detail since it is usually of pedogenic origin and occurs in (magnetically) detectable amounts in most soils. Moderate concentrations (>1 per cent) of magnetite or titanomagnetite in soils may be accurately measured if some of the material is first magnetically separated and its susceptibility determined. An example is given of the use of susceptibility measurements. Pedogenic maghemite may be determined in soils developed from parent materials of low susceptibility. A very rough value of 8.8 × 10^?4 m³ kg^?1 is suggested for the mass susceptibility of such maghemite (excluding magnetic concretions). Although susceptibility has been suggested as an indicator of soil forming processes, this is only possible within an area containing fairly uniform parent material.     

Mapping contemporary magnetic mineral concentrations in peat soils using fine-resolution digital terrain data

Small-scale spatial variability in the concentration of magnetic minerals in peat soils has been explained by differences in the deposition and interception of magnetic minerals at the soil surface and the retention of magnetic minerals within the soil. Each of these processes is controlled by topographic conditions. Recent advances in the field of digital terrain analysis and the availability of fine-resolution digital elevation models means that the relationship between the concentration of magnetic minerals in peat soils and topography can be explored using quantitative methods. Alport Moor is an ombrotrophic peat moorland in the Peak District National Park, UK. 24 peat cores were collected from Alport Moor covering an area of 0.1 km². Each core was analysed for mass specific magnetic susceptibility. Three topographic attributes (topographic wetness index, difference from mean elevation and elevation as a percentage of elevation range) were extracted from a high resolution LiDAR digital elevation model of Alport Moor. Stepwise multiple regression analyses show that topographic wetness index and difference from mean elevation are excellent predictors of variation in peak magnetic susceptibility and total magnetic susceptibility inventories for peat soils of this upland area. The results demonstrate that the contemporary concentration of magnetic minerals in the peat soils of Alport Moor is controlled by micro- and local-scale variations in water table position. The results also suggest that the contemporary level of magnetic minerals in the peat soils of Alport Moor is controlled by the retention of such particles in the soil environment. Differences in the deposition and interception of magnetic minerals play a secondary role in controlling magnetic mineral concentrations. Spatial maps of magnetic susceptibility reveal that peat soils adjacent to gully edges at Alport Moor have the highest concentration of magnetic minerals. The mapping approach used in this study could be applied to other peatland environments.     

Soil influence on landmine detection—insights from a field study in Mozambique

Purpose

Electromagnetic induction based metal detectors are commonly used in landmine clearance operations. Their performance can be seriously deteriorated by magnetic properties of the soil in which the landmines are buried.

Materials and methods

Soil magnetic parameters were studied at three locations in Southern Mozambique where soils had caused severe problems during former landmine clearance campaigns. Field work comprised a geological and pedological survey of soils and the parent rock materials. Soil and rock samples were analyzed to determine pedological standard parameters and magnetic susceptibility. Geochemical analysis, scanning electron microscopy, and thermomagnetic analysis helped to clarify the mineral composition and to specify the origin and properties of the magnetic minerals. The spatial distribution of the topsoil magnetic susceptibility was investigated in the field and characterized using geostatistical analyses.

Results and discussion

Despite different degrees of weathering of the investigated soils, their magnetic mineral composition is dominated by lithogenic (Ti-) magnetites. Moreover, there are clues for the pedogenic neoformation of ultrafine-grained ferrimagnetic minerals in two of the three topsoils. The deterioration of metal detector performance at the sites results from the high frequency dependence of magnetic susceptibility at two locations and from the distinct spatial variability of topsoil magnetic susceptibility at all locations.

Conclusions

To assess soil effects on the performance of modern metal detectors the investigations of frequency-dependent susceptibility and of spatial susceptibility distribution are the most meaningful tools. Summarizing, the topsoil magnetic properties of the investigated sites are predominantly influenced by their parent material and to a minor degree by pedogenic neoformation.     

土壤溶质迁移的柱滞留方程

The relationship between magnetic properties and particle size of soils derived from metamorphic rock,basalt,granite,Quaternary red clay,limestone and mudstone from Zhejiang Province,East China was studied,Based on the variations of the mass magnetic susceptibility (χ),anhysteretic remanent magnetization (ARM),and saturation isothermal remanent magnetization (SIRM) with soil particle size,the relationship could be classfied into three groups.For the soils derived from metamorphic rock and basalt,magnetic values were the highest in the gravel and coarse sand fractions and decreased with decreasing soil particle size.The soils derived from sedimentary rock had a bimodal distribution of magnetic values.with peaks in 1-0.5 and 0.005-0.0005mm fractions.The soil developed on granite was characterized by a peak of magnetic value in 0.001-0.0005mm fractions.The soil developed on granite was characterized by a peak of magnetic value in 0.001-0.0005 mm fractions.Frequency-dependent susceptibility(χfd)and ratios of magnetic parameters (ARM/χ,SIRM/χand SIRM/ARM) of soil particle fractions showed that variations in ferrimagnetic grain size paralleled those in particle size,χfd peaked in caly fraction and decreased with increasing particle size,irrespective of soil parent materials.The acquisition curves of IRM and demagnetization paramenter of different soil particles indicated that there were different magnetic minerals assemblages in different particle fractions.     

Mineral magnetic properties of a weathering sequence of soils derived from basalt in Eastern China

The magnetic properties and magnetic mineralogy of a weathering sequence of soils developed on basalt parent material from eastern China, were studied by rock magnetism, X-ray diffraction and soil chemical analyses to establish the connection between mineral magnetic properties and pedogenic development in a subtropical region. The magnetic susceptibility of soils formed on basalt varied greatly and did not increase with the degree of pedogenic development. The frequency-dependent susceptibility (χfd) values of soils ranged from 1.0 to 11.1% and increased with the pedogenic development. Highly significant linear relationship was found between the frequency-dependent susceptibility and the Fe_d content (R² = 0.683) and Fe_d/Fe_t ratio (R² = 0.780) in soils, indicating that pedogenic SP ferrimagnetic grains were associated with enrichment of the secondary iron oxide minerals in the weathering process of soil. Rock magnetism analysis showed that the major magnetic carriers in the weakly weathered soil profiles are magnetite and/or maghemite, and the highly developed soil profiles are generally enriched in magnetite/maghemite grains of pedogenic origin and the magnetically hard haematite, indicating that the magnetic component was transformed from a ferrimagnetic phase (magnetite) to antiferromagnetic phase (hematite) during pedogenic development. Results indicated that some of the magnetic parameters of soils, in this case χfd, can be useful for pedogenic comparisons and age correlations in the weathering sequence of soil. It is thus suggested that multiparameter rock magnetic investigations represent a more powerful approach for pedogenesis.     

澧阳平原杉龙岗遗址埋藏古水稻土磁性矿物特性

为探明埋藏古水稻土磁性矿物特征,采用环境磁学方法研究了澧阳平原杉龙岗遗址埋藏古水稻土的磁性矿物含量、组成和粒度。结果表明,埋藏古水稻土的磁化率平均值为6.2×10~(–8) m~3/kg,饱和等温剩磁平均值为16 338×10~(–5)Am~2/kg,软剩磁平均值为773×10~(–5)Am~2/kg,退磁参数S300平均值为72%。埋藏古水稻土亚铁磁性和不完全反铁磁性矿物含量随土层深度增加不断降低,其含量均低于现代耕作水稻土层;埋藏古水稻土磁化率主要来源于亚铁磁性矿物和不完全反铁磁性矿物,且亚铁磁性矿物占相对主导地位;相对于现代耕作水稻土层,埋藏古水稻土层中磁性矿物以较粗的磁铁矿颗粒为主。     

成都平原农地利用方式转变对不同母质土壤剖面磁化率的影响

[目的]分析区域土壤磁化率变化特征有助于掌握土壤环境变化规律和土壤演化特点,为区域土壤资源管理提供依据.[方法]本研究基于174个土壤剖面的675个采样数据,分析成都平原不同农地利用方式和母质条件下土壤剖面磁化率的差异,采用时空替代法探究农地利用方式转变对农田土壤剖面磁化率的影响.[结果]结果表明,研究区土壤磁化率随土...     

Changes in magnetic properties and their pedogenetic implications for paddy soil chronosequences from different parent materials in south China

It remains unknown whether there is a consistent relationship between magnetism dynamics and pedogenesis for paddy soils. In this study, three paddy soil chronosequences, derived from purple sandy shale (PS), Quaternary red clay (RC) and red sandstone (RS) in the hilly regions of south China, were studied to identify changes in magnetism during soil development and to understand their implications for pedogenesis. The results show that magnetic susceptibility (MS) and soft isothermal remanent magnetization (IRM_s) simultaneously decreased to extremely small values in the anthrostagnic epipedons during the initial stages of cultivation. In contrast, this decrease was limited in the hydragric horizons of the young paddy soils and even increased in some. These changes suggest that MS and IRM_s can be enhanced by the oxidation of Fe²⁺ in acid paddy soils (between pH 5 and 6) or be depressed by anaerobic transformations of ferrimagnetic minerals. The main influence on magnetic properties was time duration and especially reducing degree of artificial submergence, while parent materials played a supportive role. Magnetic enrichments generally occurred in the clay fraction. Ferrimagnetic clay minerals were more easily altered than minerals in the silt and sand fractions. The study also shows that there was no fixed pattern in the relationship between magnetism and paddy pedogenesis and magnetic properties should be used with care when applying them to environments in which redox processes occur.     

中国土壤颗粒研究 Ⅱ.太湖地区黄泥土型水稻土及其各级颗粒的理化特性

对太湖平原地区高产的黄泥土型水稻土的全土(<1毫米)及7个粒级(1—0.25,0.25—0.05,0.05—0.01,0.01—0.005,0.005—0.002,0.002—0.001和<0.001毫米)共8个土样,进行测定。结果表明:黄泥土粘粒部分(<0.002毫米)的粘土矿物,主要由水云母、高岭和蒙脱组成。粗粘粒级(0.002—0.001毫米)和细粘粒级(<0.001毫米)中粘土矿物的分配有明显差异;砂粒级(1—0.05毫米)中除了主要的石英外,还含有少量“铁锰砂”,所以该粒级中的SiO₂含量较粉粒级(0.05—0.002毫米)的低,而Fe₂O₃的含量则相反,容积磁化率也较高;可塑性和膨胀性都是在<0.002毫米时才始现。上述特点与作者过去所研究的白土型水稻土类似。但是,与国内外报道的几种旱地土壤的资料有所不同。