Abstract: Soil magnetometry was used for detailed mapping of immission load over the territory of the Giant Mountains National Park. This project is a continuation of our previous study, which suggested that low-field magnetic susceptibility of topsoils in this region is controlled by atmospherically deposited anthropogenic ferromagnetic particles. In the present study, we have compiled a map of topsoil magnetic susceptibility on the basis of measurements on more than 460 sites. Elevated values of magnetic susceptibility can be attributed to local sources of pollution, located within and at the margins of the Park. We have identified a group of heavy metals of anthropogenic origin, present in the topsoils, and found a positive correlation between the concentration of Pb and magnetic susceptibility. Our results prove that magnetic mapping is a sensitive, fast and robust method, which can be advantageously applied to regions with relatively low degree of pollution, such as the Giant Mountains National Park.
Notes: Kapicka, A. Petrovsky, E. Fialova, H. Podrazsky, V. Dvorak, I.
Abstract: Previous investigations revealed a strong magnetic anomaly due to soil magnetic enhancement in the industrialized cross-border area of Upper Silesia (Poland) and Northern Moravia (Czech Republic). Since industrial and urban dusts contain magnetic particles, this soil magnetic enhancement is assumed to be of anthropogenic origin, caused by a high concentration of atmospherically deposited magnetic particles, accumulated in topsoil layers. This assumption is proved by investigations of vertical profiles of magnetic susceptibility along a transect crossing the border area of the two countries. The results show that the population of magnetic minerals in the organic horizon is different from that in the mineral horizons. The vertical distribution of magnetic susceptibility and thermomagnetic analysis suggests negligible lithogenic contribution. The observed relationship between magnetic susceptibility and some heavy metals, confirmed by micromorphological observations and microchemical analysis of magnetic particles separated from the organic horizons of forest topsoil, has proved the usefulness of soil magnetometry for pollution study. (C) 2008 Elsevier Ltd. All rights reserved.
Notes: Magiera, Tadeusz Kapicka, Ales Petrovsky, Eduard Strzyszcz, Zygmunt Fialova, Hana Rachwal, Marzena
Abstract: Magnetic nanoparticles encapsulated in poly(glycidyl methacrylate) microspheres were prepared and their detailed structural and magnetic characteristics given. Iron oxide nanoparticles were obtained by chemical coprecipitation of Fe(II) and Fe(III) salts and stabilized with dextran, (carboxymethyl)dextran or tetramethylammonium hydroxide. The microspheres were prepared by emulsion or dispersion polymerization of glycidyl methacrylate in the presence of ferrofluid. The microspheres were uniform both in shape and usually also in size; their size distribution was narrow. All the magnetic parameters confirm superparamagnetic nature of the microspheres. Blocking temperature was not observed, suggesting the absence of magnetic interactions at low temperatures. This is most probably caused by complete encapsulation and the absence of agglomeration. Such microspheres can be used in biomedical applications. (C) 2006 Elsevier B.V. All rights reserved.
Notes: Horak, Daniel Petrovsky, Eduard Kapicka, Ales Frederichs, Theodor
Abstract: Measurements of magnetic susceptibility of soils, reflecting magnetic enhancement of topsoils due to atmospherically deposited magnetic particles of industrial origin, are used recently in studies dealing with outlining polluted areas, as well as with approximate determination of soil contamination with heavy metals. One of the natural limitations of this method is magnetic enhancement of soils caused by weathering magnetically rich parent rock material. In this study we compare magnetic properties of soils from regions with different geological and environmental settings. Four areas in the Czech Republic and Austria were investigated, representing both magnetically rich and poor geology, as well as point-like and diffuse pollution sources. Topsoil and subsoil samples were investigated and the effect of geology and pollution was examined. Magnetic data including mass and volume magnetic susceptibility, frequency-dependent susceptibility, and main magnetic characteristics such as coercivity (Hc and Hcr) and magnetization (Ms and Mrs) parameters are compared with heavy metal contents. The aim of the paper is to assess the applicability of soil magnetometry under different geological-environmental conditions in terms of magnetic discrimination of dominant lithogenic/anthropogenic contributions to soil magnetic signature. Our results suggest that lithology represents the primary effect on soil magnetic properties. However, in case of significant atmospheric deposition of anthropogenic particles, this contribution can be clearly recognized, independent of the type of pollution source (point-like or diffuse), and discriminated from the lithogenic one. Different soil types apparently play no role. Possible effects of climate were not investigated in this study. (C) 2005 Elsevier B.V All rights reserved.
Notes: Fialova, Hana Maier, Gunter Petrovsky, Eduard Kapicka, Ales Boyko, Tetyana Scholger, Robert
Abstract: Measuring magnetic susceptibility is a method which is used to estimate the amount of magnetic particles in soils, sediments or dusts. Changes in magnetic susceptibility can be due to various reasons: input from different sources of sediments, e.g. from different soils or rocks, atmospheric fallout of anthropogenic dusts containing magnetic particles produced by fossil fuel combustion, steel production or road traffic. In the case of river sediments, input from the catchment is of primary significance. The main aim of this investigation was to test the potential of magnetic susceptibility screening in identifying the effect and significance of anthropogenic activities in an area with complex geological conditions. We investigated the magnetic susceptibility of riverbed sediments of the largest river of the Czech Republic, the Moldau river. Besides that, the magnetic signal of nearby topsoils as well as of outcropping bedrocks in the vicinity of the river was examined. In the upper 300 km of the river, the magnetic enhancement of the river sediments can be linked to anthropogenic activities. Positive correlations were found in the river sediments between the contents of Cu and Zn and magnetic susceptibility, while Fe, Mn and Ni did not show a correlation with magnetic susceptibility. However, the major geogenic magnetic anomaly in the area around the Slapy dam has made it impossible to unambiguously interpret the magnetic signal in terms of anthropogenic impact in the last 80 km downstream.
Abstract: Thermally induced reduction of amorphous Fe2O3 nanopowder (2-3 nm) with nanocrystalline Mg (similar to 20 nm) under a hydrogen atmosphere is presented as a novel route to obtain alpha-Fe and Fe3O4 magnetic nanoparticles dispersed in a MgO matrix. The phase composition, structural and magnetic properties, size and morphology of the nanoparticles were monitored by x-ray diffraction, Fe-57 Mossbauer spectroscopy at temperatures of 24-300 K, transmission electron microscopy and magnetic measurements. Spherical magnetite nanoparticles prepared at a reaction temperature of 300 degrees C revealed a well-defined structure, with a ratio of tetrahedral to octahedral Fe sites of 1/2 being common for the bulk material. A narrow particle size distribution (20-30 nm) and high saturation magnetization (95 +/- 5 A m(2) kg(-1)) predispose the magnetite nanoparticles to various applications, including magnetic separation processes. The Verwey transition of Fe3O4 nanocrystals was found to be decreased to about 80 K. The deeper reduction of amorphous ferric oxide at 600 degrees C allows alpha-Fe (40-50 nm) nanoparticles to be synthesized with a coercive force of about 30 mT. They have a saturation magnetization 2.2 times higher than that of synthesized magnetite nanoparticles, which corresponds well with the ratio usually found for the pure bulk phases. The magnetic properties of alpha-Fe nanocrystals combined with the high chemical and thermal stability of the MgO matrix makes the prepared nanocomposite useful for various magnetic applications.
Abstract: [1] In many rock magnetic studies, information on magnetic mineralogy is of crucial importance. Besides standard analytical methods, such as X-ray spectroscopy, more sensitive thermomagnetic analyses are often used. Temperature dependence of magnetic parameters can serve as basis for determination of magnetic second-order phase transition temperatures. Although limited by several drawbacks, the most serious being thermally induced transformations of the original minerals, this method provides useful information not only about the presence of magnetic minerals, but also additional knowledge on, e.g., the prevailing grain size distribution or degree of substitution. In thermomagnetic analysis, temperature dependence of two parameters, induced magnetization and magnetic susceptibility, is mostly used. However, let us say because of historical reasons, the same approach for the Curie point determination has been often used in analyzing the two parameters. In our contribution, we discuss the physical principles of the two parameters, showing that the methods developed and used for induced magnetization cannot be used also for temperature dependence of magnetic susceptibility because there is no physical justification to do so. Otherwise, the error in determining the Curie point can be some few degrees but can reach also several tens of degrees. Such an error has serious consequences for further interpretation of the data, e g., in terms of degree of Ti substitution in Ti magnetite.
Abstract: The study was performed on the area of the three countries involved in the MAGPROX project (Poland, Czech Rep., Germany). In the first stage the basic map of magnetic susceptibility based on the field topsoil measurement was compiled with an average grid density of 10 km. In the second stage of the study, vertical distribution of magnetic susceptibility of ca. 600 topsoil cores (0.3 m long), collected over central Europe, was examined with respect to the anthropogenic or lithogenic influence on magnetic susceptibility of the soil surface, with the focus being on the interpretation of the areas showing high surface susceptibility values. The maximum values were mostly observed in depths of 3-4 cm. In general seven different types of susceptibility profiles from forest areas and one typical for urban soil are presented. They are a result of a combination of natural (litho- and pedogenic) and anthropogenic contributions. Our results prove that soil profiles, dominated by anthropogenic influence due to atmospherically deposited dust, are characterized by magnetically enhanced humuous layer, corresponding to layer with the highest concentration of heavy metals. Moreover, forest soils show in these cases higher magnetic susceptibility than soils in open areas (grassland, meadows or arable soils). (C) 2005 Elsevier B.V. All rights reserved.
Abstract: In situ measurements of magnetic susceptibility of topsoils are commonly used for mapping the spatial distribution of atmospherically deposited ferrimagnetic particles. However, the surface measurements integrate signal from certain soil volume and, thus, it is not evident how deep is the magnetically enhanced layer, if there is such. This information is often required for detailed sampling. Furthermore, fast estimate of the significance of lithogenic contribution is needed for the proper interpretation of the surface data. This can be reliably done on the basis of vertical distribution of magnetic susceptibility of a soil column. Until now, there was practically no reliable, fast and sensitive enough tool to carry out these measurements in real time, directly in field. In this paper, we report on a new soil-profile kappameter SM400, which enables continuous real-time measurements, performed directly in the field. We describe its basic measurement principles. Performance parameters are discussed, showing that sensitivity is high enough to depict the soil layers with different susceptibility and a data density of 6 points per 1 mm of depth, which results in smooth curves of susceptibility, unlike field or laboratory probes used until now. Profiles acquired using different probes and instruments are compared in order to demonstrate advantages of the new approach.
Abstract: The synthesis of magnetite has been studied by mechanical alloying in an inert atmosphere of a stoichiometric mixture of micrometric particle size iron and hematite powders. The final products have been characterised by chemical analysis, SEM, TEM, XRD, Mossbauer spectroscopy as well as specific surface and magnetic measurements. The magnetite obtained in this way exhibits a high magnetic hardness. The formation of a wustite layer on the magnetite core, because of the reaction between magnetite and iron contamination coming from the bowls and grinding balls, tends to decrease the coercive force of magnetite. The formation of this phase would be avoided by controlling the grinding time. (C) 2004 Kluwer Academic Publishers.
Abstract: Industrial pollution is one of the most important environmental threats, with serious consequences for the future. Thus, its detailed study is of great importance. Apart from expensive and time-consuming chemical methods, several rapid and cheap proxy methods have been developed recently, one of them being based on rock-magnetic parameters. In the present paper we examine the use of rock-magnetic methods designed to assess the degree of pollution of recent stream sediments taken from the Arc river (Provence, France). The aim was to identify industrially-derived magnetic particles and to link this 'magnetic pollution' to concentrations of heavy metals. Geological basements allow the easy determination of magnetic particles of industrial origin. Our results clearly demonstrate that magnetic anomalies, observed in the stream sediments along the river, can be explained by human activities, as they correlate well with concentrations of lead, zinc, iron and chromium.
Abstract: A magnetite based colloid was obtained by chemical co-precipitation of iron(II) and iron(III) salts in alkaline medium and stabilized with oleic acid. Magnetic micron-size poly(2-hydroxyethyl methacrylate) (PHEMA)-based latex particles of narrow size distribution were prepared by dispersion polymerization in toluene/2-methylpropan-1-ol in the presence of three kinds of ferrimagnetic nanoparticles; chromium dioxide, maghemite, and magnetite. Cellulose acetate butyrate and dibenzoyl peroxide were used as the stabilizer and the initiator, respectively. The magnetic characteristics were examined with respect to behavior in the magnetic field and thermal stability. Our results show that chromium dioxide and derived PHEMA particles are magnetically stable in moderate temperatures up to about 100degreesC. Maghemite particles are thermally stable up to 500degreesC. Measurements of the hysteresis loops and remanent magnetization showed that embedment of magnetic particles in organic polymer has practically no effect on their magnetic hysteresis. All the samples reached magnetic saturation in fields below 0.3 T (saturation of magnetite). Regarding separation by the magnetic field, ultrafine, superparamagnetic magnetite particles show the best performance because of their magnetic susceptibility, the highest measured here and the absence of coercive force.
Abstract: Fast and cost-effective detection of industrial pollution can significantly promote its ecological, economic, and social assessment. A magnetometric method, used for qualitative determination of anthropogenic contamination, meets these requirements but needs further development in more quantitative terms. It could be used successfully in numerous cases when the heavy metals coexist with strongly magnetic iron oxide particles in the source dust. We present an integrated magnetic and geochemical study that examines the utility of magnetometric techniques for rapid, qualitative detection of metallic pollutants in soils and vegetation. The new aspect of our approach, in comparison with previously published articles on this subject, is the combined investigation (magnetic and geochemical) of both soils and vegetation, thus using an additional medium for employing the magnetometry as a pollution proxy at a site. The study area is a small (similar to3 km(2)) region in the suburbs of Sofia (Bulgaria), with the main pollution source being a metallurgical factory. Soil samples have been taken from the topmost 20 cm from private gardens, located at different distances from the factory. Vegetation samples were taken from ryegrass (both leaves and roots) and leaves from two kinds of deciduous trees (maple and acacia). The results show that both vegetation and soils are characterized by enhanced magnetic properties, compared to background material, which is due to the presence of magnetite particles of anthropogenic origin accompanying heavy metal emissions. SEM images and microprobe analyses reveal the presence of a significant amount of particles, containing heavy metals (including iron) in vegetation samples taken close to the main pollution source. Correlation analyses show a statistically significant link (correlation coefficients ranging from 0.6 to 0.7) between magnetic susceptibility and the main heavy metals (Cu, Zn, Pb) in soil samples, indicating that the magnetic susceptibility can provide a proxy method for identifying the relative contribution of industrial pollution in soils and vegetation, that is reliable, inexpensive, and less time-consuming than standard chemical analyses.
Abstract: This paper reports on magnetic and magnetomineralogical studies of forest soils from Krkonose ( Giant Mountains) National Park in the Czech Republic. Low-field magnetic susceptibility was measured in 32 soil profiles using a field probe. Thermomagnetic analysis, acquisition of remanent magnetization, alternating-field demagnetization of saturation remanence and frequency-dependent magnetic susceptibility were measured in laboratory samples from individual soil horizons as well as on their magnetic extracts. X-ray diffraction and SEM were used to identify ferrimagnetic fractions. The uppermost layer, which is dominated by magnetically soft magnetite of presumably anthropogenic origin, can be reliably identified in soil profiles over the whole region of concern. Subsoil horizons are characterised by significantly different magnetic properties.
Abstract: Experimental results of pressure-induced changes in mean magnetic susceptibility of rock samples from the main KTB boreholes are reported. It was found that susceptibility values of rocks from depths between 5200 and 7000 m show unstable behaviour upon application of pressure, showing an increase in susceptibility of between 20 and 120%. This unstable behaviour was only detected in samples from the above mentioned depth interval, which contain both ferrimagnetic and antiferromagnetic phases of pyrrhotite. On the basis of thermomagnetic analysis, magnetic field treatment, optical microscopy and domain observations of undeformed and deformed samples, reasons for this instability are discussed and interpreted in relation to redistribution of internal stresses within the ferrimagnetic phase, resulting in changes in domain wall mobility.
Abstract: A folded layer of iron ore from a Brazilian mine was taken as a structural domain to investigate the degree of interdependence of mineral preferred orientation, magnetic properties and varying strain conditions. Hematite (alpha-Fe2O3, rhombohedral) pole figures measured by means of neutron diffraction were recalculated by reducing the orientation distribution function (ODF) into a set of texture components. The degree of preferred orientation increases considerably from the limbs towards the core of the fold. Corresponding changes of magnetic susceptibility, its anisotropy and its hysteresis parameters (e.g. saturation magnetisation, saturation remanence, coercivity) indicate larger grains in the fold's nucleus due to varying deformational and texture modifying processes.
Notes: DEC xD;2 xD;S xD;APPL PHYS A-MAT SCI PROCESS
Abstract: The magnetic susceptibility of a collection of 212 archaeological samples of burnt clay of different origin (burnt soil, ovens and bricks) taken from 60 archaeological sites from Bulgaria, were studied in order to determine factors which may have affected their magnetic enhancement. The highest magnetic susceptibility values were obtained for bricks, and the lowest for burnt soils, suggesting that the firing temperature and the duration fo burning are important conditions for determining magnetic enhancement. Specific spatial pattern of the low-field magnetic susceptibility was also observed, characterized by separation of sites situated in northern and southern parts of the country, divided by the southern Bulgaria and minima in northern Bulgaria. in contrast, burnt clay plasters and bricks show the opposite picture. It is supposed that the observed pattern is due to differences in the outcropped geological formations and variable climate conditions between the two regions which determine different iron-supply during burning of initial clay material. Results from the thermomagnetic analyses show that the dominant ferrimagnetic mineral in all burnt clay materials studied, is magnetite/titanomagnetite with low Ti content and different grain-sizes. High values of frequency- dependent magnetic susceptibility indicate the presence of significant amount of fine-grained (d<0,015 <mu>m) superparamagnetic magnetite.
Abstract: In order to correlate the degree of plastic deformation and low-field magnetic anisotropy, a series of laboratory pressure experiments were carried out on a batch of grey marls. Samples were gradually deformed using triaxial high-pressure device. The confining pressure of 300 MPa was used, yielding maximum relative deformation up to 20% depending upon the uniaxial differential stress. In the range of initial deformation, irregular changes of the anisotropy parameters were typically observed. This effect is related to variable pre-deformation orientation of the anisotropy ellipsoid in the samples. At higher deformation, samples are characterized by increasing degree of magnetic anisotropy and by increasing foliation. Reorientation of paramagnetic phyllosilicate grains due to plastic deformation seems to be the most probable mechanism of the magnetic anisotropy changes.
Notes: Kapicka, A. Hrouda, F. Petrovsky, E. Polacek, J.
