城市道路尘埃的磁性特征及其环境意义

城市环境磁性研究表明,道路尘埃中的粗颗粒磁性载体(频率磁化率系数χ′FD＜5%)多为人为源,磁性矿物以单畴和多畴状态的磁铁矿为主,同时含有少量的赤铁矿和其他磁性矿物;细颗粒磁性载体(χ′FD为7%～11%)多为自然源,磁化率较低(小于100×10-8 m3/kg).磁性物质在迁移时往往与粗一级粒径的尘埃颗粒相伴生,磁性参数(如磁化率)和重金属元素(如铅、锌)质量分数之间呈相关关系,它们之间的关系可以用回归分析方法确定.利用电镜分析、因子分析和聚类分析方法可以识别道路尘埃物质的污染源.因此,道路尘埃的磁性特征研究在城市环境评价中具有潜在的重要意义.     

黄土高原-阿拉善高原典型断面表土磁学特征研究

在黄土高原-阿拉善高原区域沿接近降水量最大梯度线方向系统采集了表土(包括沙漠和土壤)样品,详细研究了其环境磁学、粒度和有机质含量等环境替代指标的变化特征.结果表明,整个断面表土中的强磁性矿物主要为磁铁矿和磁赤铁矿,并含有赤铁矿.阿拉善高原表土中磁性矿物颗粒多为多畴(MD),总体含量偏低,磁性矿物中硬磁组分含量较高;黄土高原区表土中磁性颗粒多为准单畴(PSD),总体含量偏高,磁性矿物中软磁组分含量较高.进一步分析发现,在干旱地区,频率磁化率与降水有良好的相关性,而常用的磁化率不能较好地反映降水量变化.本研究指示在干旱地区应用单一磁化率指标解释环境变化需要谨慎.     

东海陆架平北地区残留沉积磁性特征及其油气指示意义

本文利用1994－1995年在东海陆架平北地区获取的370个柱状样,对该区残留沉积物作磁性测试和磁性矿物鉴定,以进行陆架残留沉积物磁性特征与深部油气渗漏关系的研究。磁性测试显示本区存在磁化率异常和饱和等温剩磁异常两种磁性异常现象。根据磁性参数特征和多种矿物物理学鉴定结果,确定导致本区磁化率异常的矿物为陆源碎屑磁铁矿,导致剩磁异常的矿物为自生或次生铁硫化物胶黄铁矿和磁黄铁矿。证据显示本区剩磁异常是油气渗漏的产物;而磁化率异常则主要指示古滨海砂的分布。作者提出在本区的油气化探中,剩磁参数是有效的化探磁性指标。     

火电厂粉煤灰的矿物磁性及其环境意义

火电厂排放的粉煤灰是重要的大气颗粒污染物之一,利用粉煤灰的磁性监测环境污染是新近发展的新手段。应用矿物磁测技术和X射线衍射对浙江省主要电厂排放的粉煤灰的矿物磁性特征和磁性矿物学,以及与重金属元素的关系进行了研究,结果表明粉煤灰具有较高的磁化率（X）、软剩磁（IRM20mT）和饱和等温剩磁（SIRM）值,粉煤灰频率磁化率（Xfd）的平均值为2．5％,磁性矿物以多畴（MD）颗粒存在,粉煤灰的剩磁矫顽力（BCR）在42～53mT之间。矿物测试结合X射线衍射分析表明粉煤灰中的氧化铁矿物以FeO4和Fe2O3-α为主,粉煤灰的磁化率与Fe、Mn、Pb、Zn、Cu、CA含量呈显著线性正相关,相关系数（r）分别是0．924,0．866,0．725,0．756,0．945和0．867,磁化率可作为粉煤灰中重金属元素含量的代用指标。     

东海陆架平北地区残留沉积物磁性特征及其油气指示意义

利用1994～1995年在东海陆架平北地区获取的370个柱状样，对该区残留沉积物作磁性测试和磁性矿物鉴定，以进行陆架残留沉积物磁性特征与深部油气渗漏关系的研究。磁性测试显示本区存在两种磁性异常，即磁化率异常和饱和等温剩磁异常。根据磁性参数特征和多种矿物的物理学鉴定结果，确定导致本区磁化率异常的矿物为陆源碎屑磁铁矿，导致剩磁异常的矿物为自生或次生铁硫化物胶黄铁矿和磁黄铁矿。证据显示本区剩磁异常是油气渗漏的产物；而磁化率异常则主要指示古滨海砂的分布。由此提出，在本区的油气化探中剩磁参数是有效的化探磁性指标。     

中亚地区现代表土磁学特征及其古环境意义*

在中国西北地区主要沙漠、绿洲和戈壁及蒙古国南部戈壁等亚洲中部粉尘源区采集了表土(包括沙漠和土壤)样品,系统分析了样品的磁学性质(包括磁化率、无磁滞磁化率、等温剩磁、磁滞回线和热磁曲线)。结果表明,中亚地区表土样品中主要磁性矿物是铁磁矿,含有赤铁矿和磁赤铁矿,并伴有少量顺磁性矿物;磁性矿物粒度主要是准单畴(PSD)和多畴(MD),超顺磁性颗粒含量较低,接近于中国西部黄土地层含量。中亚地区表土磁性矿物含量总体都较低,磁性矿物含量在空间上与降雨量成正比。研究结果指示西部地区(准噶尔盆地和南部塔里木盆地)表土样品较北部地区(鄂尔多斯高原、阿拉善高原以及蒙古高原)表土样品,其粗颗粒磁性矿物含量高,而细颗粒磁性矿物含量低。本研究结果为黄土地层古土壤磁性增强源自成土过程提供了最直接的证据。     

武汉东湖现代沉积物磁组构特征及意义

采自武汉东湖现代沉积物的0．86m长的样品被用于研究湖泊现代沉积物的磁性各向异性，研究发现，东湖的现代沉积可划分为3个阶段，不同阶段的沉积特征与磁学性质反映了不同的沉积环境物源差异，通过分析样品沉积特征，磁化率K值特征并结合磁性矿物在各层面间的差别，从而分析得出磁化率K值可作为地层划分的有效辅助手段，磁铁矿广泛存在于所有砂质及泥质沉积物中，是引起东湖现代沉积物磁化率变化的主导性物质。     

渭河流域典型黄土剖面的环境磁学特征及其古气候意义

对黄土高原南部耀县全新世黄土地层的形成及保存环境进行了研究.结果表明:地层中磁性矿物主要为软磁性矿物,硬磁性矿物对地层的磁学性质贡献小;随着成壤强度的增加,硬磁性矿物的相对含量在减少.本区全新世地层的形成和保存环境为氧化环境,适宜用磁学手段反演全新世古气候.对磁化率和频率磁化率、无磁滞剩磁磁化率的对比分析,可以看出:成壤强度较低时,细粒磁性矿物相对于磁性矿物总量的增加速率相对较快;成壤强度较高时,细粒磁性矿物的相对含量会达到或趋近饱和,相对于磁性矿物总量的增加速率相对较慢.研究表明,在黄土地层中,χfd%和χARM/χ等指示细粒磁性矿物的磁学参数可以显示更细微的气候变化;在古土壤中,χlf的气候指示意义相对更好.     

渭河流域典型黄土剖面的环境磁学特征及其古气候意义

对黄土高原南部耀县全新世黄土地层的形成及保存环境进行了研究. 结果表明: 地层中磁性矿物主要为软磁性矿物, 硬磁性矿物对地层的磁学性质贡献小; 随着成壤强度的增加, 硬磁性矿物的相对含量在减少. 本区全新世地层的形成和保存环境为氧化环境, 适宜用磁学手段反演全新世古气候. 对磁化率和频率磁化率、无磁滞剩磁磁化率的对比分析, 可以看出: 成壤强度较低时, 细粒磁性矿物相对于磁性矿物总量的增加速率相对较快; 成壤强度较高时, 细粒磁性矿物的相对含量会达到或趋近饱和, 相对于磁性矿物总量的增加速率相对较慢. 研究表明, 在黄土地层中, χfd%和χARM/χ等指示细粒磁性矿物的磁学参数可以显示更细微的气候变化; 在古土壤中, χlf的气候指示意义相对更好.     

直流场和交变场对泥岩磁化率的影响

磁化率值不仅受控于天然岩石和环境物质中磁性颗粒的组合特征,还与实验室内的处理过程有关,包括热处理过程和加场处理过程.热处理过程通常改变磁性矿物的类型,使样品的磁化率值发生明显变化,因而备受关注.但加场处理过程对样品磁化率的影响在于改变其中所含磁性颗粒的磁畴结构,这种变化是微观的,目前尚未受到应有的重视.本文选择8块泥岩样品进行了加场处理对其磁化率影响的研究.样品取自松辽盆地松科1井青山口组一段,主要携磁矿物为准单畴( PSD)或多畴(MD)磁铁矿.在逐步获得等温剩磁直至饱和的过程中,逐步测量样品的磁化率值.随后对其进行单轴系统交变退磁,逐步测量剩磁后,完成磁化率测量.结果发现:1)直流场使样品的磁化率值增大.在低于50mT的外加场中,随外加场的增强,样品的磁化率值快速增大;之后,随外加场的增强,样品的磁化率值基本不变,直到600mT; 600mT ～ 1T之间样品的磁化率值又大幅增大;最终,样品的磁化率较初始值(x0)增大0.84％ ～ 3.40％.这种磁化率值的增大受控于样品内PSD或MD磁铁矿磁畴结构的改变,与磁铁矿的含量无关.2)样品获得SIRM后进行的逐步交变退磁使其磁化率值有所降低,随交变场的增强,其降低的幅度也增大,但是,交变场达到100mT时,样品的磁化率值仍较x0高.经逐步交变退磁后,样品的磁化率较x0增加0.03％ ～ 2.42％.因而,天然样品在进行磁化率测量之前,不能将其置于任何直流场或交变场中处理.     

武汉市东湖沉积物的磁性特征与重金属含量之间的关系

对武汉市东湖主湖区的郭郑湖和塘林湖114个沉积物样品的磁化率与代表性样品的频率磁化率系数、磁滞回线参量和重金属元素进行系统分析, 综合区域环境背景, 探讨应用岩石磁性方法技术评价大型城市内陆湖泊沉积物污染程度的可行性及其效果.结果表明, 在主成分中, 郭郑湖沉积物没有一个主成分占绝对优势, 仅有少数重金属元素含量与磁化率相关, 磁化率χ与重金属富集强度的相关性较差; 而塘林湖沉积物有一个“工业源”的主成份占绝对优势, Fe (全铁)、Co、V、Mn、Ti、Ba、Cr、Ni、Cu等元素与饱和等温剩磁SIRM、χ关系密切(相关系数大于0.87).郭郑湖与塘林湖的沉积物的饱和等温剩磁与重金属富集强度的相关程度高于磁化率, 因此, 可以用其(SIRM) 作为环境污染程度的指示参量.      

The role of hematite–ilmenite solid solution in the production of magnetic anomalies in ground- and satellite-based data

Remanent magnetization (RM) of rocks with hematite–ilmenite solid solution (HISS) minerals, at all crustal levels, may be an important contribution to magnetic anomalies measured by ground and satellite altitude surveys. The possibility that lower thermal gradient relatively deep in the crust can result in exsolution of HISS compositions with strong remanent magnetizations (RM) was studied for two bulk compositions within the HISS system. Samples from granulite-terrane around Wilson Lake, Labrador, Canada contains titanohematite with exsolved ferrian ilmenite lamellae. Other samples from the anorthosite-terrane of Allard Lake, Quebec, Canada contain ferrian ilmenite with exsolved titanohematite lamellae. In both cases, the final exsolved titanohematite has similar Ti content and carries dominant magnetic remanence with REM (=NRM/SIRM, where NRM is the natural remanent magnetization and SIRM is the saturation isothermal remanent magnetization) that is comparable to the Ti-free end member. The RM was acquired prior to exsolution and the ilmeno-hematite-rich rock possesses thermal remanent magnetization (TRM), whereas rocks with hemo-ilmenite possess chemical remanent magnetization (CRM). In both cases, we found fairly large homogeneous grains with low demagnetizing energy that acquired intense RM. The magnetism of the ilmeno-hematite solid solution phases is not significantly perturbed by the continuous reaction: ilmeno-hematitetitanohematite solid solution. Hence, the occurrence of HISS in rocks that cooled slowly in a low intensity magnetic field will have an intense magnetic signature characterized by a large REM.     

Characterization of diamictons on the basis of their mineral magnetic properties in Murchisonfjorden,Nordaustlandet, Svalbard

Different grain-size fractions of 12 lithologically defined and 2 non-defined Weichselian glacial stage diamicton units from Nordaustlandet, Svalbard were studied for their mineral magnetic properties. The applied measurements included magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), ‘backfield’ isothermal remanent magnetization (IRM) and several of their parametric ratios. The results indicated a poor correlation between the magnetic fingerprint of dry-sieved and wet-sieved diamicton samples. The dry-sieved samples had higher χ, ARM and SIRM values, suggesting a higher concentration of ferrimagnetic grains. This was probably because washing of the samples resulted in the loss of the most fine-grained ferrimagnetic material. Both sieving methods seem to be capable of discriminating different diamictons, but they cannot be used contemporaneously. The results only partially support previous findings of the chronostratigraphic correlation of diamictons. They indicate that in suitable conditions and within a limited area it is possible to discriminate (and group) glacigenic sequences based on the magnetic signature of their fine-grained fractions in the sample. For example and based on the mineral magnetic fingerprint, a diamicton unit that was described from the marine core (MUR 09/sor1/125–150) obtained from Isvika region most probably represents diamicton material that were derived from provenance areas related to the Middle Weichselian glacial stage. It was also noted that certain mineral magnetic parameters, such as SIRM/χ and SIRM/ARM ratio, had greater potential in discriminating diamicton units than others.     

罗布泊自生胶黄铁矿对磁性参数χARM/SIRM指示意义的影响

沉积物中磁性矿物的颗粒大小具有重要环境指示意义,是环境磁学研究的重要内容。磁性参数非磁滞剩磁磁化率/饱和等温剩磁（χ_ARM/SIRM）常被用于指示磁性颗粒大小,当沉积物磁性特征为较粗的多畴（MD）颗粒主导时表现为低值,而为较细的单畴（SD）颗粒主导时表现为高值。本研究对罗布泊盐湖LB剖面的沉积物进行了系统环境磁学测试,结果发现剖面中含有5个χ_ARM/SIRM值低于上覆层和下伏层的层位,指示其磁性颗粒较粗。但磁滞参数和扫描电镜结果显示这5个层位磁性颗粒明显细于上覆层和下伏层沉积物,显示χ_ARM/SIRM在这5个层位的指示意义失真。矿物鉴定结果显示这5个层位的主导磁性矿物为早期成岩成因的SD胶黄铁矿,赋存形态主要为颗粒团聚体、单颗粒或颗粒团聚体附着于硅酸盐矿物表面以及分布于薄片状硅酸盐内,这种赋存形态导致其具有较强的磁相互作用,并限制了χ_ARM的增加,最终造成χ_ARM/SIRM下降,指示意义失真。本研究显示当沉积物中存在胶黄铁矿等自生矿物时,利用比值参数χ_ARM/SIRM判断磁性矿物颗粒特征需谨慎。     

Relationship between magnetic properties and heavy metals of urban soils with different soil types and environmental settings: implications for magnetic mapping

Two types of soil (fluvisols and anthrosols) were collected from different environmental settings (suburb and industrial area) in Wuhan, central China, aiming to examine the applicability of magnetic mapping for heavy metal pollution of urban soil in a large region. Magnetic measurements and chemical analysis indicated elevated magnetization and heavy metal concentrations of topsoils in the industrial area. Magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM) and saturation isothermal remanent magnetization (SIRM) of fluvisols are much higher than those of anthrosols, but contrary for frequency-dependent susceptibility, indicating that soil magnetism strongly depends on the soil type/condition. Predominant magnetic carrier in topsoils in industrial area is pseudo-single-domain/multi-domain magnetite. Environmental scanning electron microscope/energy dispersive X-ray examination of the magnetic extracts from these topsoils revealed abundant spherical particles with diameters of 10–50 μm that are rich in iron-oxides, and could be attributed to the nearby industrial activities (e.g., steel work and power generation). Significant correlations were observed between magnetic concentration-related parameters (e.g., χ, ARM and SIRM) and concentrations of Cu, Pb, Zn, Hg and Tomlinson pollution load index. These results proposed that magnetic proxy mapping of soil pollution is an effective, fast and inexpensive tool for delineation of heavy metal pollution. However, interpretation of magnetic properties for such a purpose must be done on a site-specific basis, taking into account the possibilities of pedogenic enhancement/depletion under the specific soil conditions.     

东海外陆架浅孔沉积物的岩性和磁性特征及成因讨论?

利用东海外陆架的10根柱状样，进行磁性、粒度、氯离子含量和粘土矿物分析。结果表明：在东海外陆架扬子浅滩前缘，浅部沉积地层自上而下可分为两层。上层为砂泥混合物，含大量贝壳碎片，磁化率与饱和等温剩磁较强，主要是磁铁矿富集所致，反映了冰后期海侵对晚更新世沉积物的强烈改造。研究还发现，现代海底表层沉积物中存在铁硫化物，它是浅海还原环境中铁磁性矿物次生变化的产物。下层为坚硬致密的黄褐色泥质粉砂和粉砂质泥（硬土层），磁化率与饱和等温剩磁较弱，但局部存在剩磁异常高，从矫顽力等磁性特征证明它是硫复铁矿的富集所致。另外，在硫复铁矿富集层中绿泥石和氯离子含量明显富集，反映该硬土层是早期海侵沉积物在末次冰期干冷气候条件下的风化产物。     

Investigating the potential of using environmental magnetism techniques as pollution proxy in urban road deposited sediment

The use of mineral magnetic techniques as pollution proxy for road deposited sediment was explored using various statistical approaches. Standard techniques were adopted for measurement of mineral magnetic and geochemical parameters. The analyses of magnetic parameters revealed that the samples were dominated by ferrimagnetic minerals and multidomain grains. This implied that the magnetic fractions in the samples might be of anthropogenic origin. Results also indicate that the samples were dominated by low coercive, magnetically soft minerals. Thermomagnetic curves confirmed magnetite as the remanence bearing magnetic mineral having a Curie point temperature of ~580 °C. The strong association observed between magnetic susceptibility, susceptibility of anhysteric remanent magnetization and saturation isothermal remanent magnetization and aluminum, titanium, manganese, iron, chromium and lead demonstrated that these metals occurred as ferrimagnetic particles of technogenic origin resulting from vehicular sources. Assessment of pollution status of the road deposited sediment identified silicon and lead as the priority pollutants of concern. Generally, pollution load index was <1 (mean, 0.66 ± 0.14), indicating that the samples were not polluted in the overall, but the metals were in the buildup stage requiring constant monitoring. The sources of pollutants from principal component and cluster analyses identified the sources of pollution to be mainly from vehicular emissions such as brake linings, exhaust materials, tire wear, corroded metal parts, abrasion of lubricating oil and road construction materials. This study found that mineral magnetic techniques offer great potential as pollution proxy for soil pollution studies.     

The influence of particle size variations on the magnetic properties of sediments from the north-eastern Irish Sea

This paper considers the magnetic properties of a range of recent and contemporary sediments from the north eastern part of the Irish Sea. Principal component ordinations of the results show a close link between magnetic property variations and particle size. The magnetic properties of a subset of samples, particles sized by a combination of sieving and pipette analysis, confirm that variations in ferrimagnetic (‘magnetite’) grain size parallel those in particle size, despite the fact that the magnetic grains in the fine grades have diameters 1–2 orders of magnitude smaller than those of the particle size fraction in which they occur. This is best explained by postulating that the fine magnetic grains occur in the clay fraction but are present in declining concentrations in the coarser grades up to 4ø as an artefact of the pipette method. Most samples have a biomodal distribution of magnetic minerals, with a coarse mode associated with heavy minerals in the sands or coarse silts, and a fine mode in the clays. Magnetic susceptibility (x) and saturation isothermal remanent magnetization (SIRM) largely pick out the coarse mode where present; anhysteretic remanent magnetization (ARM) largely picks out the fine mode. The results open up the possibility of normalizing samples from these environments for particle size and, more specifically, clay content, by means of ARM or ARM/x values. The most likely source for the uniform and almost exclusive stable single domain magnetite, which dominates the magnetic properties of the clays, is thought to be bacterial magnetosomes. The measurements as a whole do not appear to hold much promise for discriminating sediment source types.     

Magnetic characteristics of topsoil from Xinjiang, Northwestern China, and their implications

In this study, a set of environmental magnetic parameters (_{χlf, χfd}%, _χARM , SIRM, HIRM, SOFT and SIRM/_{χlf, χARM} /SIRM and _χARM /_χlf) of 331 top-soil samples from Xinjiang Uygur Autonomous Region of China were systematically measured and the magnetic characteristics and its environmental significance were discussed. Our results indicate that the main magnetic minerals of these top-soils are single-domain magnetite. The content of magnetic minerals in top-soils from north Xinjiang is higher than that from south Xinjiang; however, the content of hard magnetic minerals is higher in the topsoils from south Xinjiang. The top-soils from Yili region contain similar magnetic minerals as that from south Xinjiang, but with much stronger magnetic SP content due to higher pedogenic processes. The differences in magnetic characteristics among top-soils from different regions of Xinjiang might reflect the differences of regional climatic factors, especially the precipitation.