Use Of Magnetic Susceptibility Research Articles

Fractionations of heavy metals and their correlations with magnetic susceptibility in soil from a typical alluvial island in the lower yangtze river, China

The use of magnetic susceptibility (χ) as a means of assessing heavy metal pollution in soils has been explored by researchers, yielding varying results in terms of the correlations between χ with heavy metals. The efficacy of χ as an indicator of soil heavy metal pollution remains a topic of debate. This study aims to elucidate the inter-relationships between χ, iron oxides, and heavy metals in soil through the application of a modified 5-step sequential extraction procedure (SEP), and to identify an effective approach for assessing metal concentrations in soil using magnetic susceptibility measurements. The soil samples were collected from a typical alluvial island in the lower Yangtze River, China, and a total of 6 forms (exchangeable and acid soluble fraction, easily reducible fraction, oxidizable fraction, amorphous iron oxide, crystallized iron oxyhydroxides and residual fraction) were partitioned and their heavy metal concentrations and χ were analyzed. The results show that crystalline Fe oxyhydroxides and residual fractions are the two uppermost fractions of heavy metals. By combining the fractionation of elements with the variation of χ of the soil during the processing of SEP, it was inferred that the external input of Fe, Pb, Cr and Cd in the soil likely originated from the vicinal steel production. The correlation analysis revealed a significant correlation between heavy metal concentrations and χ in the residual fraction, whereas no significant correlations were observed between the concentrations of heavy metals and χ in the bulk soil samples. It is recommended that the evaluation of heavy metal contamination in the soil neighboring industrial sites can be conducted via magnetic susceptibility measurements subsequent to the elimination of crystalline iron oxyhydroxides.

Feasibility study on the use of magnetic susceptibility for recovery of vanadium component in magnetite

ABSTRACT Vanadium in the vanadium-bearing titanomagnetite (VTM) exist by replacing iron in the magnetite crystal, and magnetite should be recovered separately from titanium components in the vanadium-bearing titanomagnetite. In the present study, a sensing system was proposed by measuring magnetic susceptibility of magnetite because the magnetic susceptibility can be easily and quickly measured. The effects of mixing ratio of magnetite and ilmenite with silica and the distance between the magnetic susceptibility meter and the sample bed on the magnetic susceptibility were investigated. The magnetic susceptibility of the mixture of magnetite and ilmenite with 0.1 g or 0.2 g of silica decreased with increasing the ratio of ilmenite in the mixture, but the effect of silica addition was not significant. When the distance between the magnetic susceptibility meter and the sample bed increased, the magnetic susceptibility of magnetite decreased, but the magnetic susceptibility decreased with increasing the thickness of magnetite sample bed of magnetite. Because the magnetic susceptibility depended strongly on the content of magnetite, the sensing system using the magnetic susceptibility measurement could be successfully applied to detect magnetite.

The Use of Magnetic Susceptibility as a Technique to Measure the Impact of Wildfires on Archaeological Heritage

Wildfires are one of the main threats of natural areas and often fires can affect protected or heritage areas and properties, in which the preservation requirements demand the use of non-destructive techniques (NDTs). The magnetic susceptibility is an NDT that provides information on the mineralogical composition of the materials but has never been applied to the evaluation of fires. Here, we combine laboratory with field analysis to test the applicability of the magnetic susceptibility for the assessment of the impacts of wildfires. The laboratory results showed an increase in the magnetic susceptibility with the temperature, more evident in the samples heated to 600 °C and above. The in situ measures revealed a spatial variation in the magnetic susceptibility, which was related to the behaviour of the fire in the area. The samples were later analysed with other magnetic destructive techniques that were used to confirm the mineralogical processes that occurred in the materials. The increase in the susceptibility values were due to the formation of iron oxides. The destructive analysis also showed the presence of minerals such as hematite and magnetite in the samples. Overall, the study allowed a first approach to test the magnetic susceptibility as a simple and fast way to measure the impacts of wildfires.

The use of magnetic susceptibility and chemical analysis data for characterizing heavy metal contamination of topsoil in Denizli city, Turkey

Denizli is one of the most rapidly growing cities in Turkey having experienced fast urban and industrial development in the last decades, engendering a serious threat to the environment and the population health. Therefore, this study used the magnetic susceptibility method to evaluate the contamination degree of most parts of Denizli city. X-ray fluorescence (XRF) analysis was performed on samples chosen from different parts of the study area to identify the quantity and origins of the heavy metals present in the study area corresponding to the magnetic susceptibility measurements. Multivariate statistical analysis such as Cluster analysis (CA) and the principal component analysis (PCA) was performed for the best understanding of the relationship between heavy metal contamination, magnetic susceptibility measurements and XRF analysis results. The environmental status of the study area was evaluated by the aid of elaboration and interpretation of the contamination factor (CF), geoaccumulation index (Igeo), Enrichment factor (EF) and the pollution load index (PLI) which allowed the comparison between the different polluted parts of the study area. The results obtained as maximum values from the calculation of the contamination factor were found as follows: Fe (30.98), Cr (25.86), Ni (14.71), Zn (9.24), Cu (7.96), Pb (5.86). The mean values obtained for the implemented geoaccumulation index were found for each element as follow; Fe (4.39), Cr (4.12), Ni (3.29), Cu (2.44), Pb (2.01) Zn (2.62) while the enrichment factor's results were found as follow Fe (11.80), Cr (11.07), Ni (5.90), Cu (3.87), Pb (2.71) Zn (4). The average value of the pollution load index reflects the heavy pollution of the study area by reaching a value of 7.7. The contour maps plotted for the distribution of heavy metals concentration and magnetic susceptibility measurement showed similar pollution degrees in the city industrial zone and near the main highway (Antalya Highway), which passes through the city. This high heavy metal load gradually decreases toward the city borders. Furthermore, the content of heavy metal and the PLI are notably positively correlated with the magnetic susceptibility measurements. Overall, results testify to the effectiveness of the magnetic susceptibility method for applications in determining environmental contamination caused by heavy metals.

Petrography, geochemistry and magnetic susceptibility of the Isortoq Fe-Ti-V deposit, Isortoq Giant Dykes, South Greenland

The Isortoq Giant Dykes in the Proterozoic Gardar Province, South Greenland, include the Isortoq South giant dyke and the Isortoq North giant dyke. The fine-grained Fe-Ti-V deposit hosted by the Isortoq South giant dyke, referred to as the Isortoq Fe-Ti-V deposit, is considered a good test site for the use of magnetic susceptibility for the mapping of ore grades. Here, we test this and show that the Fe, Ti and V distribution is controlled by titanomagnetite disseminated throughout fine-grained troctolite. The deposit displays a clear correlation between magnetic susceptibility and Fe, Ti and V grades in bulk samples of consecutive 2 m sections from 11 drill cores, totalling 2671 m in length. We observe that Fe, Ti and V are almost entirely hosted in titanomagnetite, which controls the magnetic susceptibility. Field measurements of the magnetic susceptibility can thus be considered as a reliable exploration tool for this type of mineralisation. We further consider the origins of the deposit by reconnaissance petrography, mineral and bulk rock chemistry of the large mass of aphanitic Fe-rich troctolite in the Isortoq South giant dyke. We suggest that the deposit may represent the base of a basanitic to trachybasaltic magma chamber, in which Fe-rich immiscible melts accumulated, crystallised and fractionated. The processes suggested here may apply to other giant dykes and intrusions of the Gardar Province.

Concentration of Mobile Forms of Heavy Metals and Magnetic Properties of Soils in the Town of Volsk, Saratov Region, Russia

Aim. Magnetic susceptibility is a fast, inexpensive and reliable technique for estimating and monitoring anthropogenic contamination of soil with heavy metals. However, certain factors affecting magnetic susceptibility need to be determined before applying this technique to environmental studies. The objectives of this study were to investigate: (1) the effect of parent materials and land use on magnetic susceptibility and concentrations of Ni, Pb, Cr, Cd, Cu and Zn; and (2) the possible use of magnetic susceptibility as an indicator of anthropogenic heavy metals contamination of soil in the city of Volsk, Saratov region, Russia.Material and Methods. Fifty (50) composite surface soil samples (0–10 cm) were selected. 1M HNO3 extractable concentrations of Ni, Pb, Cr, Cd, Cu and Zn were analyzed using atomic absorption spectroscopy. Concentrations of organic matter in the soil were determined. Magnetic susceptibility at low and high frequency (χlf and χhf) were measured and frequency dependent susceptibility (χfd) was calculated.Results. Magnetic susceptibility varied from 1.34 to 29.6 × 10−7 m3 kg−1. A positive strong correlation (P value = 0.01, r = 0.55) was obtained between Pb and χlf. Significant correlational relationships were observed between Pb with χlf, most likely due to significant effects of anthropogenic activities on magnetic susceptibility, therefore enhancing Pb concentrations in urban soils.Conclusions. In the soils studied, magnetic susceptibility could be employed as an indicator of anthropogenic contamination of soil with heavy metals.

Distribution and dispersal of surface sediments on the continental margins of India

Abstract The vast area, varying climate regimes, diverse source terrain lithology of the mainland India generate complex weathering and erosional patterns and leads to diverse sediment distribution and dispersal on the surrounding continental margins of India. Thus, to delineate the sources, distribution and sediment dispersal pathways around India, 254 sediment cores from the eastern and western continental margins of India were investigated for physical properties using non-destructive, whole core logging technique combined with grain-size analyses. The distribution of magnetic susceptibility, gamma ray density and grain-size traces the sources in the Indian landmass which contribute sediments to the margins and demarcates their extent of influence. The results from the magnetic susceptibility distribution indicate that the dominant influx of modern high susceptibility sediment into the margins of India originates from the weathering of Deccan Basalts and its subsequent transportation by Narmada and Tapti Rivers in the west coast and Krishna and Godavari Rivers in the east coast. Though the Himalayan sources are the second largest supplier of magnetic minerals to the shelf, their contribution, when compared to the Deccan sediments is not significant. The lack of present-day sedimentation in the outer shelf regions of margins of India is evident from the gamma ray density distribution and is confirmed by the discrete sample grain-size analysis. Gamma ray density variations in the margins follow the same pattern as the grain size variations and demarcate the boundary between inner shelf modern clayey sediments and the outer shelf relict carbonate sands. Regional distribution maps of physical properties and grain-size for both the margins of India are presented and geographical limits of each provenance are defined, thus providing a comprehensive picture of sediment distribution and dispersal patterns in the area and highlights the use of magnetic susceptibility as a powerful tool in deciphering the source to sink pathways of sediments.

Magnetic susceptibility as indicator of anthropogenic disturbances in forest topsoil: A review of magnetic studies carried out in Central European forests

Abstract Forest topsoil is subjected to physical and chemical degradation due to the deposition of urban and industrial dust and landfill, as well as physical disturbances including a relic of former cultivation, clearcutting, and afforestation. Such disturbances are observed in all natural and semi-natural forests across Europe, but most intensively in urban forests surrounding cities and industrial areas. Magnetic susceptibility constitutes a convenient physical parameter that is used for both, determination of levels of industrial and urban dust deposition alongside relevant potentially toxic elements (PTEs), and for the precise localization of polluted areas (so-called “hot spots”). Deposited on the soil surface, technogenic magnetic particles (TMPs) contained in different kinds of anthropogenic dusts increase the magnetic susceptibility of polluted topsoil. This effect can easily be measured “in situ” by applying a geophysical (geomagnetic) technique – soil magnetometry – for which magnetic susceptibility is the basic parameter. This technique can be performed inexpensively and rapidly with high spatial resolution at local (e.g., for individual trees, and forest stand areas around pollution sources) and regional (for whole regions or countries) scales. The application of combined magnetic-chemical analyses together with geostatistical methods (especially cokriging methods) can deliver more significant results regarding the spatial distribution of pollution than chemical testing alone. A high degree of correlation between magnetic susceptibility and PTEs content (expressed in the form of Pollution Load Index) significantly improves the level of precision in localizing polluted areas. Knowledge of forest topsoil quality and the use of magnetic susceptibility for the precise delineation of areas with considerable anthropogenic physical and chemical disturbances may facilitate the management application of the ecosystem service concept at local and regional scales.

Using magnetic susceptibility measurements to differentiate soil drainage classes in central Iran

We examine the potential of magnetic susceptibility measurements to discriminate different soil drainage classes in the Gandoman region, central Iran. Four soil drainage classes, comprising poorly drained (PD), somewhat poorly drained (SPD), moderately well drained (MWD) and well drained (WD), were identified, and a total number of 48 soil profiles were excavated and studied. The soil samples were collected from all studied profiles from the genetic horizons individually. Magnetic susceptibility was measured at both low (0.46 kHz) and high (4.6 kHz) frequencies. The crystallized and amorphous iron forms were also measured using citrate-bicarbonate-dithionite solution and oxalate-ammonium extracts, respectively. The highest magnetic susceptibility was observed in WD soils, whereas the lowest susceptibility was observed in PD soils. The results of the predictor models developed by discriminate analysis showed that the use of magnetic susceptibility and iron forms could correctly predict about 90.9, 78.6, 85.7 and 88.9% of all profiles in WD, MWD, SPD and PD classes, respectively. Overall, the results indicate that magnetic susceptibility could be applied as a marker for the discrimination of drainage classes in the study area. Magnetic susceptibility is thus a quickly accessible and low-cost indicator for soil drainage classes for landownerships and subsequent analyses.

Using magnetic susceptibility to evaluate pollution status of the sediment for a typical reservoir in northwestern China.

Intensive anthropogenic activities may add to pollution risks to lakes and rivers, which can be revealed by the magnetic characteristics of sediments. The present study aims to assess the pollution status of the sediment of a typical reservoir in northwestern China by application of magnetic susceptibility. The values of magnetic susceptibility exhibited significant positive correlations with trace metals (Co, Cu, Mn, Ni, and V) and natural radionuclides (232Th and 40K). Multivariate statistical analysis indicated common sources and similar deposition characteristics of magnetic particles and trace metals. It was conformed that magnetic susceptibility could be used as an indicator to identify industrial sources of trace metals, but was not suitable to indicate the traffic or natural sources. Linear regression equations between the low-frequency magnetic susceptibility and the integrated pollution index as well as annual effective dose rate indicated a potential for using magnetic susceptibility in semi-quantitative assessment of trace metal pollution and radiological hazard in sediments. A three-step procedure is proposed for the use of magnetic susceptibility in pollution monitoring, which provides a fast and effective method for estimating the pollution extent and tracing the major sources of trace metals in the sediment of lakes and rivers.

Use of magnetic susceptibility to assess metals concentration in soils developed on a range of parent materials

This research was conducted to evaluate the utilization of magnetic susceptibility measurements in the assessment of metal concentrations in soils developed on a range of parent materials in northwestern Iran. Eighty surface soil samples were collected from eight parent rocks including ultrabasic rocks, basalt, andesite, granite, marl, limestone, Qom formation, and shale. The collected samples were assessed to determine magnetic susceptibility at low frequency (χlf) and concentrations of some metals comprising chromium (Cr), iron (Fe), copper (Cu), nickel (Ni), zinc (Zn), cobalt (Co), and manganese (Mn). The results showed that the highest levels of metals and χlf were observed in basic and ultrabasic soils. Strong positive correlations (P < 0.01) detected between χlf and Fe (0.87), Mn (0.78), Zn (0.74), Ni (0.90), Co (0.78), and Cr (0.90) in all samples indicated a potential for using magnetic susceptibility in semi-quantitative estimation of metal concentrations in soils of natural ecosystems. Multiple linear regression between metal contents and χlf showed that Ni, Zn, Mn, and Co could explain 77% of the total variance in χlf in the study area. K-means cluster analysis categorized the studied soils into three groups based on metals and χlf variability. Clustering of soils based on their parent rocks and use of further magnetic measures, i.e., saturation isothermal remanent magnetization (SIRM), isothermal remanent magnetization (IRM100mT) and natural remanent magnetization (NRM) are expected to improve the accuracy of metal concentration predictions in natural soils of the study area.

Magnetic mapping of distribution of wood ash used for fertilization of forest soil

The effect of wood-ash fertilization on forest soils has been assessed mainly through geochemical methods (e.g., content of soil organic matter or nutrients). However, a simple and fast method of determining the distribution of the ash and the extent of affected soil is missing. In this study we present the use of magnetic susceptibility, which is controlled by Fe-oxides, in comparing the fertilized soil in the forest plantation of pine and oak with intact forest soil. Spatial and vertical distribution of magnetic susceptibility was measured in an oak and pine plantation next to stems of young plants, where wood ash was applied as fertilizer. Pattern of the susceptibility distribution was compared with that in non-fertilized part of the plantation as well as with a spot of intact natural forest soil nearby. Our results show that the wood-ash samples contain significant amount of ferrimagnetic magnetite with susceptibility higher than that of typical forest soil. Clear differences were observed between magnetic susceptibility of furrows and ridges. Moreover, the dispersed ash remains practically on the surface, does not penetrate to deeper layers. Finally, our data suggest significant differences in surface values between the pine and oak plants. Based on this study we may conclude that magnetic susceptibility may represent a simple and approximate method of assessing the extent of soil affected by wood-ash.

Evaluation of the influence of cultivation period on soil redistribution in northeastern China using magnetic susceptibility

Magnetic susceptibility has been shown to be a reliable, economic and rapid method for tracking soil redistribution; however, more case studies are necessary to verify the link between soil movement and magnetic susceptibility. In this study, we sought to evaluate soil redistribution in northeastern China using magnetic susceptibility on the basis of data collected from croplands with different cultivation periods. The results showed that the magnetic susceptibility values, whether low-frequency magnetic susceptibility (χlf) or frequency-dependent magnetic susceptibility (χfd), were markedly different between forestland and cropland, with larger differences for longer cultivation periods. The magnetic susceptibility increased dramatically in topsoils on forest slope, whereas the difference in magnetic susceptibility between topsoils and subsoils decreased in cropland as the cultivation period increased. The magnetic susceptibility values varied significantly across sites on a given slope, increasing gradually from the upperslope to the lowerslope, regardless of whether the slope was forestland or cropland. Longer cultivation periods resulted in larger differences between the upperslopes and lowerslopes which were particularly notable when the cultivation period was longer than 50 years. For middleslopes and lowerslopes, the soil loss of an 110-year cultivated slope was approximately two times higher than that of a 30-year cultivated slope. These findings suggest that the use of magnetic susceptibility is feasible for tracking soil redistribution and soil loss.

Magnetic susceptibility as a simple tracer for fluvial sediment source ascription during storm events

Sediment tracing using a single tracer, low frequency magnetic susceptibility (Xlf), was used to apportion suspended sediment to geologically defined source areas and to interpret sediment source changes during flood events in the degraded catchment of the Vuvu River, a headwater tributary of the Mzimbubu River, South Africa. The method was tested as a simple tool for use by catchment managers concerned with controlling erosion. The geology of the 58 km2 catchment comprises two distinct formations: basalt in the upper catchment with a characteristically high magnetic susceptibility and shales with a low magnetic susceptibility in the lower catchment. Application of an unmixing model incorporating a Monte Carlo uncertainty analysis showed that Xlf provided a means to assign the proportion of each geological province contributing to the river's sediment load. Grab water samples were collected at ten-minute intervals during flood events for subsequent analysis of suspended sediment concentration and the magnetic susceptibility of the filtered sediment. Two floods are presented in detail, the first represents a significant event at the start of the wet season (max. discharge 32 m3 s−1); the second was a smaller flood (max discharge 14 m3 s−1) that occurred a month later. Suspended sediment concentrations during the twelve monitored events showed a characteristic decline over the wet season. The main source of suspended sediment was shown to be from the mudstones in the lower catchment, which contributed 86% of the total measured load. The sediment dynamics during the two floods monitored in detail were quite different from each other. In the first the sediment concentration was high (11 g L−1), peaking after the flood peak. The Xlf value increased during the event, indicating that contribution to the sediment load from basalt in the upper catchment increased during the recession limb. In the second, smaller flood the sediment peak (6 g L−1) coincided with the flood peak. Low Xlf values indicated that mudstones in the lower catchment soils dominated the sediment load throughout the entire event. Sediment tracing using a single property (Xlf) was thus used effectively to study changing sediment sources both between and during a flood event in a catchment with strongly contrasting magnetic signatures in different areas. The results support the use of magnetic susceptibility as a simple and cheap tool to determine sediment provenance that can be used to guide catchment restoration in similar environments.

Magnetic susceptibility for characterizing areas with different potentials for sugarcane production

Abstract The objective of this work was to evaluate the use of magnetic susceptibility for characterizing the spatial variability of soil attributes and identifying areas with different potentials for sugarcane (Saccharum spp.) production. Samples were collected at 110 points (1 per 7 ha) in the layers of 0.00-0.20 and 0.20-0.40 m, to determine the magnetic susceptibility and physical and chemical attributes of the soil. Fiber content, sucrose polarization (POL), and sugarcane yield were determined in 33 points. The spatial variability model for magnetic susceptibility was 63 and 22% more accurate in delimiting soil potential for sugarcane production than soil physical and chemical attributes at the 0.0-0.2 and 0.2-0.4-m layers, respectively. The spatial variability map for magnetic susceptibility was strongly correlated with clay (0.83 and 0.89, respectively, for the layers) and sand contents (-0.84 and -0.88); moderately correlated with organic matter (-0.25 and -0.35), sum of bases (-0.46 and 0.37), cation exchange capacity (0.22 and 0.47), pH (-0.52 and 0.13), and POL (0.43 and 0.53); and weakly correlated with sugarcane yield (0.26 and 0.23). Magnetic susceptibility can be used to characterize the spatial variability of soil attributes and to identify areas with different potentials for sugarcane production.

Magnetic susceptibility mapping of the Sudbury area, Ontario, Canada: evaluating pollution distributions decades later

This study evaluates the use of magnetic susceptibility and magnetic parameter measurements in assessing spatial and temporal variations of pollutants that emanated from mining industries in and around Sudbury, Ontario, Canada. For this purpose, in situ magnetic susceptibility (κin situ) was measured at 106 sites on a grid of 10 km × 10 km and 5 km × 5 km. The κin situ values ranged from 2 × 10−5 to 149 × 10−5 SI, and the highest κin situ values were observed near the active (Copper Cliff) and inactive (Coniston) mining sites. The lowest κin situ values were measured at increased distances from possible pollution sources; therefore, mapping of in situ magnetic susceptibility values is a proxy to polluted areas in and around Sudbury. To evaluate potential anthropogenic and (or) lithogenic input to κin situ, low-frequency mass specific magnetic susceptibility (χlf) variations with depth were classified into four different types of profiles. For further investigation of magnetic minerals in the samples, laboratory measurements of magnetic susceptibility, frequency dependence of magnetic susceptibility, hysteresis properties, thermosusceptibility curves, anhysteretic and isothermal magnetizations, and scanning electron microscopy – energy-dispersive X-ray spectroscopy (SEM–EDS) were also conducted on the soil samples. Laboratory measurements indicated that ferrimagnetic minerals (e.g., magnetite) of variable grain size were the dominant magnetic minerals, with the exception of one site that contained an iron sulfide (greigite) phase near a mine waste site. Magnetic spherules observed in SEM micrographs are of variable sizes (6–60 μm), suggesting that suspended particulate matter (PM10) is present, and may be a health concern. At some sites, EDS analysis showed that heavy metals (Co, Al, and Ni), which threaten human health, are also present in the study area.

Detecting and Correcting for Paleomagnetic Inclination Shallowing of Sedimentary Rocks: A Review

Magnetic anisotropy and the elongation/inclination (E-I) approaches have been increasingly employed as two important means for detecting and correcting the paleomagnetic inclination shallowing in sedimentary rocks that was first recognized sixty years ago. Both approaches are based on certain assumptions, and thus have advantages and intrinsic limitations in investigating shallow inclinations in sedimentary rocks. The E-I approach is relatively easy to use, but it needs a large dataset to adequately sample paleomagnetic directions due to paleosecular variation of the geomagnetic field. Also, slow sediment accumulation rates and local tectonics could lead to under- or over-corrections using the E-I approach. For the magnetic anisotropy technique, labor-intensive, sophisticated laboratory rock magnetic experiments are required in order to accurately determine both bulk magnetic anisotropy of remanence-carrying grains and magnetic anisotropy of an individual particle, i.e., “a” factor, of samples. Our review shows that, despite the intensive laboratory work necessary for applying anisotropy-based inclination corrections, it is worth investing the effort. In addition, the joint use of magnetic susceptibility and remanence anisotropy measurements as well as detailed rock magnetic measurements for determining the particle anisotropy “a” factor have the advantage of retrieving direct evidence of inclination shallowing and correcting for it with high confidence. We caution against use of either of the two approaches without full appreciation of the underlying assumptions and intrinsic limitations of each technique. The use and comparison of both techniques could provide the most robust inclination shallowing correction for sedimentary rocks.

Quantitative Susceptibility Mapping Suggests Altered Brain Iron in Premanifest Huntington Disease.

In patients with premanifest (nonsymptomatic) and advanced Huntington disease, changes in brain iron levels in the basal ganglia have been previously reported, especially in the striatum. Quantitative susceptibility mapping by using MR phase imaging allows in vivo measurements of tissue magnetic susceptibility, which has been shown to correlate well with iron levels in brain gray matter and is believed to be more specific than other imaging-based iron measures. The purpose of this study was to investigate the use of magnetic susceptibility as a biomarker of disease progression. Fifteen subjects with premanifest Huntington disease and 16 age-matched healthy controls were scanned at 7T. Magnetic susceptibility, effective relaxation, and tissue volume in deep gray matter structures were quantified and compared with genetic and clinical measures. Subjects with premanifest Huntington disease showed significantly higher susceptibility values in the caudate nucleus, putamen, and globus pallidus, indicating increased iron levels in these structures. Significant decreases in magnetic susceptibility were found in the substantia nigra and hippocampus. In addition, significant volume loss (atrophy) and an increase effective relaxation were observed in the caudate nucleus and putamen. Susceptibility values in the caudate nucleus and putamen were found to be inversely correlated with structure volumes and directly correlated with the genetic burdens, represented by cytosine-adenine-guanine repeat age-product-scaled scores. The significant magnetic susceptibility differences between subjects with premanifest Huntington disease and controls and their correlation with genetic burden scores indicate the potential use of magnetic susceptibility as a biomarker of disease progression in premanifest Huntington disease.

FERRAMENTAS MATEMÁTICAS, SUSCETIBILIDADE MAGNÉTICA E MODELOS DE PAISAGEM APLICADOS NA DELIMITAÇÃO DE ÁREAS DE MANEJO ESPECÍFICO

A identificação de padrões de variabilidade dos atributos do solo permite o uso e a ocupação do solo de maneira sustentável. O objetivo deste trabalho foi delimitar áreas de manejo específico utilizando ferramentas matemáticas, suscetibilidade magnética e modelos de paisagem. A área de estudo localiza-se no município de Guariba, SP. Escolheu-se uma área de 110 ha, onde foram identificadas e mapeadas três superfícies geomórficas (I, II e III). Na área, foram coletadas 204 amostras de solo em uma transeção, nas profundidades de 0,00-0,20 e 0,60-0,80 m. Foram determinados o pH em CaCl2, os teores de areia, argila, matéria orgânica, P, Ca, Mg, K, H+Al, e calculados SB, CTC e V. A suscetibilidade magnética (SM) foi medida com o auxílio de uma balança analítica. Os limites matemáticos da técnica Split Moving Windows Dissimilarity Analysis (SMWDA) utilizando as informações da suscetibilidade magnética ficaram próximos aos limites de campo identificados com base nos modelos de paisagem. A utilização conjunta da suscetibilidade magnética, dos modelos matemáticos e de paisagem permitiu identificar diferentes áreas de manejo, locais com diferentes teores de argila e níveis de fertilidade do solo. A susceptibilidade magnética pode ser adotada como alternativa para identificar e mapear unidades de manejo.

Uso de parámetros indirectos para la evaluación de la contaminación de suelos por metales pesados en una zona minera de San Luis Potosí, México

Tailings are a significant source of arsenic and heavy metals. When mining wastes are subjected to wind dispersal and water erosion, they may be the cause of widespread soil contamination. In this work, a mining area in the state of San Luis Potosi, Mexico, was selected to evaluate the use of magnetic susceptibility (MS), electrical conductivity (EC) and pH as alternative indicators for the delimitation of the spatial distribution of arsenic and heavy metals in mine wastes and soils contaminated by their dispersal. The MS, EC, pH and the total concentration of potentially toxic elements (PTE), such as arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn) and iron (Fe), were determined in 107 waste and soil samples. Moreover, the concentration of major ions in solution was analyzed and XRD and SEM analyses were carried out. Finally the hazard index (HI) was assessed as a value showing the effect of joint presence of As, Cd and Pb in the area. The results indicate that higher values of MS, EC and total concentrations of PTE and