Frequency-dependent Magnetic Susceptibility Research Articles

Vertical distribution of magnetic susceptibility as affected by pedoenvironmental factors along an arid and semi-arid transect, Fars Province, Iran

Soil magnetism provides valuable information about soil-landscape relationships and soil evolution. However, only limited number of studies on the relationship between soil magnetic properties and soil forming factors and processes, especially in arid and semi-arid regions, are available. The aim of this study was to determine vertical distribution of soil magnetic susceptibility and selected pedoenvironmental parameters and to interpret them in terms of the soil evolution. Eight representative soil profiles were selected on different geomorphic surfaces including alluvial fan, piedmont plain and flood plain. Soil samples were collected from different diagnostic horizons and analyzed for routine physico-chemical properties, different iron forms and magnetic susceptibility. The average values of magnetic susceptibility (χlf) and relative frequency-dependent magnetic susceptibility in the studied soils are 53.1 × 10−8 m3 kg−1 and 2.62%, respectively, with the latter ranging from 0 to 6.88%. The negative significant correlation (with correlation coefficient R = −0.48 and statistical significance p < 0.01) between soil evolution index (ratio of acid oxalate soluble and free Fe oxides — Feo/Fed) and χlf values indicated that χlf increased with soil evolution. A positive significant correlation between χlf and Fed (and Fed — Feo) values, and a negative significant correlation between χlf and CaCO3 values were observed. The vertical distribution of χlf along the studied profiles showed different patterns (uniform, non-uniform, ascending and descending) with depth. Overall, the results indicated that the χlf distribution along the soil profiles was affected by topography, distribution of different iron forms, soil evolution, and weathering rate in different soil layers.

Tracing of traffic-related pollution using magnetic properties of topsoils in Daejeon, Korea

The present study was designed to explore the possibility of roadside pollution screening using magnetic properties of topsoil samples in Daejeon, South Korea. Low-field magnetic susceptibility, frequency dependence of magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRM were determined for roadside topsoil samples. Magnetic susceptibility measured on 238 samples from the upper 5 cm of the topsoils ranged from 8.6 to 82.5 × 10–5 SI with a mean of 28.3 ± 10.8 × 10–5 SI. The proximal zone, 55 m wide area situated on either side of the main street, exhibited an enhancement of magnetic susceptibility. In areas distant from the main street, low magnetic susceptibility (< 50 × 10–5 SI) was observed. The topsoil samples exhibited significant susceptibility contrasts, suggesting that two dimensional magnetic mapping was effective in identifying traffic-related pollution. A few magnetic hotspots with intensities of magnetic susceptibility near or over 50 × 10–5 SI might reflect the difference in topographic elevation and surface morphology. Among various IRM-related parameters, remanence of coercivity was most significant statistically. In most samples, IRM component analysis provided dual coercivity components. Thermal demagnetization of composite IRM and morphological observation of magnetic separates suggest angular magnetite produced by vehicle non-exhaust emissions spherical magnetite derived from exhaust emission to be the dominant contributors to the magnetic signal. It is likely that lower- and higher-coercivity components represent the presence of coarse-grained angular magnetite and fine-grained spherical magnetite, respectively.

Moisture evolution in Central Asia since 26 ka: Insights from a Kyrgyz loess section, Western Tian Shan

Central Asia (CA) is located in the hinterland of the Eurasian continent, and faces an extreme risk of continued aridification under the current global warming trend. To predict future climate change in CA, paleoclimate studies provide essential references. However, the mechanisms underlying climate changes in CA remain relatively poorly known. Here, we investigate moisture variations in CA, as recorded in a 6-m loess section in the Western Tian Shan, Kyrgyzstan, which has accumulated since ∼26 ka based on the radiometric AMS 14C dating. We reconstructed the evolution of the wind regime and moisture conditions in the Western Tian Shan with a modified grain size index (GSIm) and a new L∗ proxy (ΔL∗). While the frequency-dependent magnetic susceptibility (χfd), redness (a∗) and yellowness (b∗) did not provide reliable paleoclimatic indicators, due to weak pedogenesis and other controlling factors. The GSIm records demonstrated a precipitation maximum in summer before ∼15 ka, shifting to a maximum in spring after ∼15 ka, probably associated with large-scale modulation of the latitudinal climatic zones and atmospheric circulation in response to retreat of the Northern Hemisphere ice sheets. Based on the ΔL∗ records, we place emphases on the important role of temperature-modulated evaporation in moisture evolution across CA; however, this has only influenced moisture evolution in spring and summer, with little effect on winter moisture conditions. Moreover, the ΔL∗ records may also indicate that atmospheric humidity can partly affect the long-term effective moisture variations.

Imprints of paleo-environmental conditions and human activities in mineral magnetic properties of fired clay remains from Neolithic houses

Fire as a global phenomenon plays crucial role in the Earth’s climate feedbacks and forcing. However, human’s influence is becoming increasingly important during the Anthropocene epoch. Burnt Neolithic houses are among the most impressive remains from fire-related ancient human activities. Mineral magnetic properties and firing temperature estimates using magnetic susceptibility method were carried out on a collection of burnt clay remains from house destructions originating from 18 Neolithic sites from Bulgaria. All of the sites/dwellings ended their existence after extensive fire. The general aim of the study was to explore the mineral magnetic properties of fired clay materials against the most important environmental factors. The main magnetic minerals identified in the burnt structures were magnetite, maghemite and hematite, as well as recently reported in several studies ε-Fe2O3. The latter evidences high intensity fire since this specific mineral can be synthesized at temperatures exceeding 900 °C. Magnetic susceptibility and percent frequency dependent magnetic susceptibility at site level were considered in relation to the climatic conditions, as defined in the published anthracological studies involving most of the sites. The major difference in lithology of the outcropping rock formations between North and South Bulgaria may influence variations in magnetic enhancement of the burnt clay across the sites at similar other conditions. Firing temperature estimates vary in wide range – between 580 °C and 1050 °C. Estimated average firing temperatures at site’s level showed higher values in Early Neolithic sites (Tfire average = 815 °C) as compared to Late Neolithic ones (Tfire average = 746 °C and 713 °C). We suggest that possible hypotheses for the trend observed could be: difference in climate regimes across the territory, leading to different “fire weather”; or difference in the vegetation fuel used in house construction; and intentional burning of Early Neolithic houses.

Variations of Thermally and Optically Stimulated Luminescence Sensitivity of Loess and Pedocomplex Samples from Southern Tajikistan, Central Asia

To better understand the factors controlling the quartz luminescence sensitivity in loess deposits, samples from two loess sections in southern Tajikistan are investigated. Both pattern and amplitude in the variations of quartz luminescence sensitivity of these two sections are similar, showing higher values in pedocomplex units and lower values in the loess units. Similar trends of variation are found between the quartz luminescence sensitivity and climate proxies, including frequency-dependent magnetic susceptibility, median grain size and IRSL/[post-IR] OSL ratio. Laboratory experiments involving thermal activation and repeated bleaching/irradiation cycles reveal much larger sensitivity enhancement for samples with initial lower sensitivity from loess units than those from pedocomplex units with higher sensitivity. The observed systematic contrast in quartz luminescence sensitivity between the loess and pedocomplex units are interpreted as resulting from the differentiation of the weathering products from the source area and subsequent sensitization during the sedimentary transfer prior to deposition.

Archaeomagnetic investigations in Bolgar (Tatarstan)

The objective of this study is to provide a well-dated point for a future palaeosecular variation (PSV) reference curve for western Russia. For this purpose archaeomagnetic and magnetic property analyses were carried out on a pottery kiln unearthed at the UNESCO World Heritage site of ancient Bolgar, having a rather precise age dating. The archaeological context provided an age between 1340 and 1360 C.E. The characteristic remanence vector was determined through alternating field demagnetisation and Thellier-Thellier palaeointensity experiments. Some innovations were introduced regarding palaeointensity. The check testing the equality of blocking and unblocking temperature was redefined. This allowed waiving the commonly used additional zero-field cooling steps during the Thellier-Thellier experiment. Another innovation concerns the calculation of archaeointensity at structure level. A Bayesian approach was introduced for averaging individual specimen archaeointensities using a prior probability distribution of unknown uncertainties. Next, an additional prior probability distribution was used to correct for cooling rate effects. This resulted in a lower uncertainty compared to common practice and in eluding time consuming cooling rate experiments. The complex magnetic mineralogy consists of maghaemite, multi-domain haematite and Al-substituted haematite. Some samples contained also some non-stoichiometric magnetite. The magnetic mineralogy was determined through hysteresis loops, backfield and remanence decay curves, measurements of the frequency dependence of magnetic susceptibility and through low temperature magnetisation curves. Accompanying high-temperature thermomagnetic analyses revealed an excellent thermo-chemical stability of the studied specimens. Directions obtained from alternating field demagnetisation and those extracted from archaeointensity experiments are congruent and have low uncertainties. The obtained archaeomagnetic results are fairly in agreement with global geomagnetic field models and contemporary PSV data of the wider area. The geomagnetic field vector obtained for ancient Bolgar is of high quality, deserving thus its inclusion in a future PSV reference curve for European Russia.

Soil and dust magnetism in semi-urban area Truskavets, Ukraine

The objective of this paper was to study pollution in the semi-urban area of Truskavets (Ukraine) using low-cost and energy-efficient magnetic measurements. Soil magnetic properties were measured near a railway station (transect) and near a road (transect and grid). To compare the magnetic properties of the soils from the urban areas, we sampled in a forest area located 2–3 km from Truskavets. Additionally, ten dust samples were taken 150 cm above the ground from the smooth surface of the tree bark. Near the Stebnyk Ring (the end of the second transect), we established a grid (20 × 20 m) and measured the soil magnetic susceptibility MS (mass-specific χ, and volume κ). There were taken 55 soil samples within the upper 0–5 cm of the topsoil. The results showed that low-frequency MS of the natural soil was within the range of 8–10 × 10–8 m3/kg, a low value for the Ukraine soils. The urban soils collected near the roadway and the railway had high MS values. Soil pollution was confirmed by the frequency dependence of magnetic susceptibility: χfd = 2–3%. Our results, based on the thermomagnetic, hysteresis, isothermal (IRM), and anhysteretic remanent magnetization (ARM) measurements, suggested that magnetite is responsible for the increase in the magnetic signal of the urban soils. Natural soils normally contain a single domain (SD) grains. It has also been found that the high coercivity haematite and goethite are stable pedogenic minerals in the Truskavets natural soil. Overall, the magnetic measurements have proven to be a rapid, low cost, non-destructive and efficient technique for soil monitoring and air quality assessment.

Characteristics of magnetic susceptibility on cropland and pastureland slopes in an area influenced by both wind and water erosion and implications for soil redistribution patterns

Many areas are influenced by both wind erosion and water erosion, and the overlap of wind and water erosive forces results in serious land degradation. Magnetic susceptibility (MS) is an effective tool for quantifying soil redistribution. This method has been applied successfully in wind and water erosion research, but not in research on soil erosion induced by both wind and water yet. This study attempts to investigate the characteristics of MS in different land uses in a wind and water eroded area and explore their implications for wind and water erosion. A cropland and a pastureland slope in the Bashang area of the Agro-Pastoral Transition Zone of North China were selected, and samples from the two transects were measured for mass-specific low-frequency MS (χlf), frequency-dependent MS (χfd), particle size distribution and the MS of five aggregate size classes. The results show that there is a high value concentration of χlf in the middle slope of the cropland, indicating that the soil is transported by water and accumulated on the slope. The correlation between χlf and χfd in the cropland is obviously weaker than the pastureland, which is a result of SP loss due to wind erosion in the cropland. The mean χlf of the surface pastureland is half that of the cropland, which suggests there is deposition of exogeneous wind eroded particles with low MS in the pastureland, and they include coarse particles by saltation and creep from local areas and fine particles transported from remote areas. Due to the different sources of the soil particles, the contribution mechanisms of MS on the two slopes are distinct. Human activities associated with tillage also influence the soil redistribution in the cropland. These preliminary results indicate that MS could be applied to the study of soil erosion induced by both wind and water to provide a supplementary perspective achieving spatially explicit results.

ОЦІНКА АНТРОПОГЕННОГО ЗАБРУДНЕННЯ ПОВЕРХНЕВИХ ВІДКЛАДІВ МІСТА ЧЕРНІВЦІ ЗА МАГНІТНОЮ СПРИЙНЯТЛИВІСТЮ ТА ВМІСТОМ ВАЖКИХ МЕТАЛІВ

The paper is devoted to spatial distribution of low-frequency magnetic susceptibility (χ) of surface sediments in Chernivtsi city as an informative indicator of geochemical contamination of the topsoil. The bulk content of heavy metals in urban soils and the correlations between the χ, frequency dependence of magnetic susceptibility (kfd) and the content of Cd, Mn, Cu, Ni, Pb, Zn were studied. Χ vary from 10∙10-8 to 1286∙10-8 m3/kg with a median value of 66∙10-8 m3/kg. In 20 % of samples χ exceeds the median value three times or more, indicating that the soil is contaminated with iron dust and magnetic particulate matter derived from anthropogenic aerosols. Priority contaminants of city soils are metals such as Pb and Zn, the bulk content of which exceeds the trigger concentration in the vast majority of samples. The χ revealed strong correlation with bulk content of Pb and Zn and the weaker one, but still statistically significant, with Cu and Cd. An additional criterion for the common anthropogenic origin of heavy metals and magnetic minerals in soils is the significant negative correlation coefficients between kfd and content of Zn, Pb, and Cu. So, it can be argued that the increase in Zn, Pb, and Cu content is accompanied by an increase in concentration of magnetic minerals in the multidomain state. The maps were produced, showing spatial distribution of χ and Pollution Load Index (PLI), calculated by three metals (Zn, Pb, and Cu). For 51 % of the samples, the PLI indicates no contamination, 35 % indicate moderate contamination,14 % are strongly contaminated. These results prove that surface sediment over a large area of the city require measures to reduce their toxicity. The correlation coefficient between χ and PLI makes 0.88, indicating χ as a quick indicator of geochemical soil contamination in the city of Chernivtsi.

Elemental and magnetic analyses, source identification, and oxidative potential of airborne, passive, and street dust particles in Asaluyeh County, Iran

One of the most important environmental issues in arid and semi-arid regions is deposition of dust particles. In this study, airborne, passive, and street dust samples were collected in Asaluyeh County, in August 2017, September 2017, and February 2018. The PM2.5 and PM10 concentrations for the sampling period ranged between 19.7 and 76.0 μg/m3 and 47.16–348 μg/m3 with an average of 46.4 μg/m3 and 143 μg/m3, respectively. Monthly dust deposition rates ranged from 5.2 to 26.1 g/m2 with an average of 17.85 g/m2. Positive Matrix Factorization (PMF) applied to the dust compositional data indicated that Sb, Zn, Pb, Mo, Cu, and As come from anthropogenic sources while Al, Fe, Ti, Mn, Ni, Cr, and Co originate mostly from geogenic sources. The PMF results indicated that the geogenic material was the major source of passive and airborne dust samples. Elemental compositions were similar for passive dust and local surface soil. Frequency-dependent magnetic susceptibility (χIf and χfd%) showed that the local soil is entisol. Isothermal remanent magnetization (IRM-100mT/IRM1T) versus saturation IRM (SIRM) demonstrated that the background sample contains ferrimagnetic minerals, but with increasing SIRM, the concentration of soft magnetic magnetite-like phases increases and the magnetic particles are larger. Mrs./Ms. versus Bcr/Bc indicated that the magnetic particles sizes were probably between 120 and 1000 nm. Eu values and the mean Eu/Eu* and La/Al values clearly show that the airborne dust is most affected by oil industries, while passive dust samples primarily originated from local surface soils. These assumptions were confirmed by Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model results. The samples display a moderate level of oxidation towards ascorbic acid (OPAA) and glutathione (OPGSH). Regarding the passive and airborne dust samples, backward Generalized Estimating Equations (GEE) modeling results display a significant positive relationship between geogenic material and oxidative potential (OP). It includes many redox-active transition metals. Alternatively, the street dust OP is strongly related to geogenic and industrial sources and OPAA is marginally related to urban sources. It was shown that measured magnetic parameters can be used for OP estimation.

Diversity and peculiarities of soil formation in eolian landscapes – Insights from the mineral magnetic records

Magnetic properties of loess-paleosol sequences are widely utilized as sensitive, easily-obtained and reliable proxy archives of past climate change in continental settings. However, soil formation in aeolian landscapes may occur under different and changing conditions of dust sedimentation, which will affect the growth and development of the pedogenic magnetic component. This phenomenon is explored in our study by analyzing depth variations of the following magnetic characteristics: frequency dependent magnetic susceptibility, anhysteretic magnetic susceptibility and the ratio between anhysteretic susceptibility and isothermal remanent magnetization acquired in a 100 mT back field (χarm/IRM-100 mT), along three loess-paleosol profiles from NE Bulgaria. A conceptual model for the time evolution of the grain size of the pedogenic magnetic fraction with soil depth is proposed, which is build upon the mechanism of soil formation – accretional or in stable land surfaces, or a combination of the two. Another magnetic ratio – isothermal remanence acquired in a 300 mT back field divided by low field magnetic susceptibility (IRM-300 mT/χ) is utilized as a proxy for the changes in the ratio of silt to clay fractions, indicative of changes in dust sedimentation regimes during glacial-interglacial transitions. According to the proposed conceptual model, verified by the magnetic signature of three Holocene soils from NE Bulgaria, discrimination between accretional soils and soils developed without dust additions during soil forming period can be done. Accretional soils are characterized by parallel changes in grain size sensitive magnetic proxies. Soils, developed at stable landscape conditions show gradation of the depths at which maximum enhancement of various proxies occurs with deepest occurrence of the maximum in χfd, followed by depth of maximum χarm and χarm/IRM-100 mT. Another implication of the new conceptual model is that the mean coercivity of the pedogenic component of accretional soils will be higher than that of soils developed without eolian input at equal temperature conditions because of the soils' thermal gradient and different depths, at which pedogenic minerals form in the two settings. The results revealed that the Holocene soils (So) has developed under different soil-forming conditions than paleosols from the same sites.

Review of magmatic iron-ore mineralization in central-western Mexico: Rock-magnetism and magnetic anomaly modelling of Las Truchas, case study

Las Truchas deposits formed by contact metasomatism in a Mesozoic volcano-sedimentary sequence intruded by a batholith. Later, post-mineralization hydrothermal alteration affected minerals and magnetic properties. For this study, we sampled the host rocks and iron ores. The mineralogy and magnetic domain states of oxide minerals were characterized by reflected light and scanning electron microscopy together with rock magnetic experiments such as thermomagnetic measurements, frequency dependence of magnetic susceptibility, hysteresis, first-order-reversal-curves and UnMix curves.Qualitative and quantitative forward modelling of the subsurface structure was inferred by processing of magnetic anomaly maps. Induced and remanent magnetization (intensity and direction) and the Königsberger ratio were used as input parameters for the quantitative modelling process to adjust our calculated anomaly with the observed magnetic anomalies. We attempt to understand the geological factors that control the magnetic signatures, which can be used to improve the geological interpretation of magnetic studies.

Slow Magnetic Relaxation, Antiferromagnetic Ordering, and Metamagnetism in MnII (H2 dapsc)-FeIII (CN)6 Chain Complex with Highly Anisotropic Fe-CN-Mn Spin Coupling.

Reactions of [Mn(H2 dapsc)Cl2 ]⋅H2 O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K3 [Fe(CN)6 ] and (PPh4 )3 [Fe(CN)6 ] lead to the formation of the chain polymeric complex {[Mn(H2 dapsc)][Fe(CN)6 ][K(H2 O)3.5 ]}n ⋅1.5n H2 O (1) and the discrete pentanuclear complex {[Mn(H2 dapsc)]3 [Fe(CN)6 ]2 (H2 O)2 }⋅4 CH3 OH⋅3.4 H2 O (2), respectively. In the crystal structure of 1 the high-spin [MnII (H2 dapsc)]2+ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2 dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (Ueff /kB ) of 36.0 K with τ0 =2.34×10-11 s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [FeIII (CN)6 ]3- and [MnII (H2 dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII (CN)6 ]3- complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.

Metal-Organic Frameworks as Playgrounds for Reticulate Single-Molecule Magnets.

Achieving fine control on the structure of metal-organic frameworks (MOFs) is mandatory to obtain target physical properties. Herein, we present how the combination of a metalloligand approach and a postsynthetic method is a suitable and highly useful synthetic strategy to success on this extremely difficult task. First, a novel oxamato-based tetranuclear cobalt(III) compound with a tetrahedron-shaped geometry is used, for the first time, as the metalloligand toward calcium(II) metal ions to lead to a diamagnetic CaII-CoIII three-dimensional (3D) MOF (1). In a second stage, in a single-crystal-to-single-crystal manner, the calcium(II) ions are replaced by terbium(III), dysprosium(III), holmium(III), and erbium(III) ions to yield four isostructural novel LnIII-CoIII [Ln = Tb (2), Dy (3), Ho (4), and Er (5)] 3D MOFs. Direct-current magnetic properties for 2-5 show typical performances for the ground-state terms of the lanthanoid cations [7F6 (TbIII), 6H15/2 (DyIII), 5I8 (HoIII), and 4I15/2 (ErIII)]. Analysis of the χMT data indicates that the ground state is the lowest MJ value, that is, MJ = 0 (2 and 4) and ±1/2 (3 and 5). Kramers' ions (3 and 5) exhibit field-induced emergent frequency-dependent alternating-current magnetic susceptibility signals, which is indicative of the presence of slow magnetic relaxation typical of single-molecule magnets.

Low field frequency dependent magnetic susceptibility inversion

In this work we present an open source implementation of the procedure proposed by Ustra et al. (2018) to invert frequency dependent susceptibility (FDS) data to obtain quantitative information on grain-size variations of magnetic particles in the transition of superparamagnetic (SP) to stable single domain (SSD). The software provides the inversion parameters (FDS asymptotes) as well as the limiting frequency effect and transition factor, which provide information regarding contribution of the SP particles to magnetic susceptibility as well as relative variation of the particle grain-size in the SP-SSD transition. Numerical simulations show the procedure's capability in retrieving modeled parameters and fitting data, and its limitation regarding the range of variation of relaxation times. Real data application illustrates the reliability of the procedure for a mineral assemblage in the SP-SSD range.

Development and magnetic properties of loess-derived forest soils along a precipitation gradient in northern Iran

In order to investigate the development of forest soils formed on loess, six representative modern soil pedons were selected along a precipitation gradient extending from eastern Golestan (mean annual precipitation, MAP = 500 mm) to eastern Mazandaran Provinces (MAP = 800 mm). Physiochemical, micromorphological and magnetic properties, as well as clay mineralogy of soils were studied using standard methods. Soils are mainly classified as Alfisols and Mollisols. Downward decalcification and the subsequent clay illuviation were the main criteria of soil development in all study areas. Pedogenic magnetic susceptibility of pedons studied varied systematically across the precipitation gradient in Northern Iran, increasing from 14.66 × 10−8 m3 kg−1 at the eastern part to 83.75 × 10−8 m3 kg−1 at the western margin of this transect. The frequencydependent magnetic susceptibility showed an increasing trend with rainfall as well. The micromorphological study of soils indicated that there is a positive relationship between climate gradient (increasing rainfall) and the micromorphological index of soil development (MISECA). The area and thickness of clay coatings showed an increasing trend with rainfall. Grain size analysis indicates that pedogenic processes are responsible for changing original grain size distribution of loess in our soils. The correlation achieved among modern soil properties and precipitation could be applied to the buried paleosols in the whole study area to refer degree of paleosol development and to reconstruct the paleoclimate.

Assessment of areal water and tillage erosion using magnetic susceptibility: the approach and its application in Moroccan watershed.

Soil erosion constitutes a serious threat for sustainable agriculture in many countries. Magnetic susceptibility of soil is a fast, cheap, and non-destructive technique that could be used to quantify soil erosion or soil redistribution on a long-term scale. This study attempts to analyze the variation of magnetic susceptibility in soil profiles having the same lithology and climatic conditions, but different land uses and slope gradients in a subcatchment in northern Morocco. Soil cores were collected on forested, cultivated, and pasture lands. Each core was associated to a field unit (also called a homogeneous unit) characterized by a set of four cited erosion factors. The samples were measured for mass-specific low-frequency magnetic susceptibility (χlf) and frequency-dependent magnetic susceptibility (χfd). The linear correlation of χlf and χfd indicates the homogeneity of magnetic population in soil. It supports the use of empirical models based on comparisons of χlf to predict the value of magnetic parameter after tillage homogenization and removal of soil material from the surface, and to estimate soil erosion or redeposition. The study built a methodology improving these empirical models and enabling a quantitative approach of the phenomenon. Two models, namely "tillage homogenization" (as improved in this study) and the proposed "simple correlation" result in globally similar estimates of erosion, while another model, the "simple proportional" model, underestimates it. The results give an estimate of long-term erosion (deposition) in sampled units and allow drawing of an areal soil redistribution map in the watershed.

Analysis of magnetic properties rocks and soils around the Danau Diatas, West Sumatra

The magnetic characteristics of the rocks have different magnetic properties of each kind. If this rock experiences weathering, then the rock material will be carried around the area such as the lake, through the wind, the water is then sedimentated. These sediments can also come from dust from volcanic eruptions (volcanic ash) where the magnetic properties that come from surrounding rocks are different from the magnetic properties derived from dust from volcanic eruptions. This study was used to determine the magnetic characteristics of rocks and soil around the Danau Diatas West Sumatra, which is one source of sediment. This the magnetic properties can be determined using rocks magnetism method that are commonly used to determine the magnetic properties of a material nature. Characteristics magnetic determined through test susceptibility magnetic using Bartington MS2B (Magnetic Suceptibility sensor B) dual frequency of 470 Hz and 4.7 kHz. Results this study shows values χ LF (susceptibility low frequency), χhf (susceptibility high frequency) and χfd % (susceptibility frequency dependent ). Value of susceptibility of rocks and soil obtained variations in the range of 23.77 × 10−8 m3 / kg - 2791.6 × 10−8 m3 / kg and 17.4 × 10−8 m3 / kg - 2804.4 × 10−8 m3 / kg. The value of magnetic suceptibility of rock and soil is included in the ferromagnetic mineral group and the types of minerals contained there in are ilmenite (FeTiO3) and hematite (Fe2O3). The value of frequency-dependent magnetic susceptibility χfd (%) ranges from 0.4% to 13.5%. For the value of χfd (%) 0.4% - 1.1% means that there is no or contains less than 10% superparamagnetic grain, for the value of χ fd (%) 3.3% means the mixture of superparamagnetic grain and coarser non-superparamagnetic grain, or superparamagnetic grain measuring < 0.005μm, and for the value of χ fd (%) 13.5%, meaning that the whole or consists of more than 75% superparamagnetic grains.

МАГНІТНА СПРИЙНЯТЛИВІСТЬ ҐРУНТІВ У СКЛАДІ ЕРОЗІЄЗНАВЧИХ ДОСЛІДЖЕНЬ

Water erosion of the soil is a major factor in the degradation of agricultural land in Ukraine. About 13 million hectares of arable land need additional protection. The study of the influence of the mentioned hazard processes is important both for the scientists and land endusers. The purpose of the paper is to demonstrate the possibilities of soil magnetic susceptibility mapping in erosion studies. The comparison with traditional methods is implemented. The studies were carried out at the territory of Farm Enterprise "Phoenix" of the Bliznyukovsky district of the Kharkiv region at the distance of 6 km to the southeast of the Lozova. The study site is used for crop production. The relief of the site is complicated by the developed ravine network. The soil is ordinary chernozems (Haplic Chernozems in WRB classification). We have registered high correlation between magnetic susceptibility (MS) of the studied chernozems and humus content (organic matter). The Spearman correlation coefficient slightly depends on the frequency magnetic susceptibility coefficient. The results give the opportunity to recommend soil MS studies as the additional tool in soil erosion mapping. The magnetic measurements are expensive and fast for the humus (organic matter) identification of eroded soil. The relation of the values of soil MS and the value of potential soil loss at the studied area was low. The study of the magnetic mineralogy confirmed the absence of the anthropogenic soil pollution. We confirmed this by the values of the frequency dependence of magnetic susceptibility which were above 6. The domination of the superparamagnetic (SP) grains with the size less than 20 nm was confirmed by the values of the frequency dependence of magnetic too. The majority of the MS values are 10-20. The magnetic minerals of the studied soil have been formed in real time under the pedogenic (natural soil formation) process.

Magnetic susceptibility of Entisols and Aridisols great groups in southeastern Iran

This study was performed to explore the variability of magnetic susceptibility between soil great groups in an arid region including seven soil great groups of south-eastern Iran. In the studied area 126 soil profiles were described and classified in seven soil great groups according Soil Survey Staff. Soil samples were collected from control sections and some soil properties such as organic matter (OM), calcium carbonate equivalent (CCE), gypsum, pH, electrical conductivity (EC), dithionite extractable iron (Fed), oxalate extractable iron (Feo), magnetic susceptibility at low and high frequencies (χlf and χhf) and frequency-dependent magnetic susceptibility (χfd) were measured in the laboratory. The lowest χlf was obtained for Torriorthents and Torripsamments soil groups with lowest soil development degree. The highest magnetic susceptibility was observed for Calcigypsids and Haplocalcids soil great groups. Similar trend to χlf was observed for seven studied soil great groups in respect to Fed and inversely trend to χfd. Correlation analyses revealed that Fed was significantly related with χlf and low value of χfd in all soil profiles revealed the formation of stable single domains (SSD) due to pedogenic processes. Achieved negative correlations between χlf and carbonates, organic matter and gypsum confirmed diamagnetic behaviors of these soil components. The results of discriminant analysis indicated that combining magnetic measures such as magnetic susceptibility and dependent susceptibility and iron forms could not successfully predict all soil great groups in the studied area and average 57% accuracy was achieved.