Search

The magnetic grain size, mineralogy and concentration of five ultisol sequences (lateritic soil profiles) developed on different parent rocks (syenite, dolerite, charnockite, gneiss and sandstone) in southwestern India were investigated to gain a better understanding of the pedogenic processes under tropical climate. Field investigations reveal the presence of various horizons in the lateritic profiles, such as saprolite, saprock, pallid zone, mottled zone, pebble horizon and top soil. These horizons exhibit differences in their mineral magnetic, Fourier Transform Infrared Spectroscopic (FTIR), Diffuse Reflectance Spectroscopic (redness %, amplitudes of goethite (AGt) and haematite (AHm)) and particle size properties. Magnetic susceptibility (χlf) values of the ultisol profiles varies from 5.8 to 2858.7 × 10−8m3kg−1, whereas percentage frequency dependent susceptibility (χfd %) ranges between 0.15% and 14.0%. The FTIR spectra reveal the presence of minerals like haematite, goethite, kaolinite and quartz. The upper horizons (top-soil and pebble horizon) are marked by magnetic enhancement by ultra-fine grained superparamagnetic (SP) minerals with low coercivity, most likely magnetite/maghemite. Whereas, the lower horizons (saprock, saprolite, pallid zone horizons) exhibit no magnetic enhancement and are characterized by antiferromagnetic minerals, e.g., haematite/goethite. The unweathered parent rock is characterized by low coercivity minerals of coarser magnetic grain size with a little to no superparamagnetic (SP) grains. However, the magnitude of enhancement of fine grained ferrimagnetic grains in the top soil in relation to bottom horizons varies among the five lateritic profiles. The degree of enhancement and production of the fine-grained superparamagnetic grains in topsoil decreases in the order charnockite > syenite > sandstone > gneiss > dolerite. Because the doleritic parent rock exhibits a high initial Fe concentration, it is difficult to ascertain the degree of pedogenesis, due to a strong lithogenic signature, which decreases towards the profile top. The tropical soils in the region have undergone a higher degree of pedogenesis with increased magnetic mineral concentration compared to temperate soils. However, magnetic grain size appears to be the same in both soil types. The magnetic enhancement in the topsoil may be due to the neoformation of fine-grained SP magnetite, aided by sufficient Fe supply, alternate wetting and drying cycles, dehydration, oxidation and redox conditions. [ABSTRACT FROM AUTHOR]

A comparative analysis of areal and profile measurements of magnetic susceptibility was carried out on the plots pf 100 m2 in order to improve methods of surface soil sounding for mapping purposes and for identification of anomalies associated with anthropogenic pollution or disturbance of the surface soil layer. Two sites with Haplic Chernozems and one site with Haplic Kastanozem (Endosalic, Cambic) were studied. Additionally, a catena on the Yergeni Upland with different landscape positions (eluvial, transeluvial, transeluvial–accumulative) was studied. A comparison of the areal and profile magnetic susceptibility measured to a depth of 30 cm showed a direct correlation (R2 = 0.7). The areal survey was found to correctly determine the volumetric magnetic susceptibility () to a depth of 30 cm. The variation at sites with different types of soils reflects soil–climatic zonality and spatial lithological heterogeneity expressed in different textures and mineralogical compositions of the upper (0–30 cm) soil layer within the test area of 10 × 10 m. The areal magnetic susceptibility of soils can be an important additional indicator capable of reflecting the features of soil-forming, lithological, and geochemical processes occurring in the upper soil layer. The variation at sites in different landscape positions is due to the development of sheet erosion and changes in the direction of iron oxidogenesis depending on the position of the soil profile in the relief. The set of areal and profile magnetic susceptibility measurements can be used to study soil inhomogeneities caused by anthropogenic, paleocryogenic, geomorphological, and lithogenic factors. In particular, this approach can be applied to the study of polluted soils and monitoring of agricultural lands. [ABSTRACT FROM AUTHOR]

• Magnetic enhancement in well-drained profiles is dominated by the reverse conversion of detrital hematite to maghemite. • Magnetic enhancement in poorly drained profiles is dominated by the formation of magnetite under partly anaerobic conditions. • The lowest magnetism in the transition profiles is attributed to the hydration of iron oxides into goethite before the pedogenic environment becomes anaerobic. Iron oxides and associated magnetic properties are considered good indicators of the pedogenic environment and regional climate. However, these indicators are under debate for soils developed from sediments. The accumulation of magnetic particles derived from sediments depends not only on the formation of iron oxides but also on the existence and transformation of detrital iron oxides. To explore the formation mechanism of magnetic particles accompanied by pedogenetic processes, a toposequence consisting of six profiles derived from red beds with contrasting drainage conditions under a subtropical monsoon climate is examined. We generally observed upward magnetic enhancement but inconsistent correlations between magnetism and iron oxide phases. The magnetic enhancement in the well drained profiles was dominated by the reverse transformation of detrital hematite to fine maghemite particles, whereas in the poorly drained profiles, coarse magnetite particles formed with soil organic matter enrichment in an anaerobic way. The lower magnetism in the transition profiles is attributed to the hydration of iron oxides into goethite before the pedogenic environment became anaerobic. The different magnetic enrichment mechanisms explain the nonlinear responses of magnetism and color to climate across temporal and spatial scales. These findings also suggest that soil magnetism is promising for tracing soil moisture and ecological evolution, especially in red soils and sediments across the surfaces of the Earth. [ABSTRACT FROM AUTHOR]

Changes in primary cover for agricultural crops in Amazonas region influence the phenomenon of spatial variability in soil properties. This phenomenon is still studied assuming that the spatial data is isotropic, but does not consider the anisotropic pattern of soil properties. Thus, the aim of this work was to characterize, identify and correct isotropic patterns of magnetic susceptibility (MS) measurements using anisotropic models that actually represent the spatial aspects of the data. Three cultivation areas and one under native forest, classified as Haplic Alisol, were georeferenced and sampled by a mesh system covering 192 samples per area. Texture, X-ray diffraction and frequency-dependent (χfd) and mass-specific (χlf and χhf) magnetic susceptibility analyzes were performed. Then, classical and geostatistical analyzes were applied to the data, assuming isotropy and anisotropy. All χ frequencies were shown to be spatially dependent, satisfying the isotropy hypothesis. Thereby, the application of anisotropic analysis was able to confirm the presence of all types of anisotropy in Alisols. Anisotropic correction provided an improvement in models that fit the directional trends within the areas, and provided a reduction in the nugget effect and an increase in the correlation ranges. Thus, the generated kriging maps improved the patches of zonal trends of greater or lesser χ that stand out at the level of sub-regions. These zones should, therefore, be used as indicators of variability, paying special attention during their management, especially in research related to the delimitation of specific management zones. [ABSTRACT FROM AUTHOR]

Magnetic prospecting of burial grounds is still a great challenge in the field of archaeological geophysics. Some graves appear as positive anomalies, whereas others do not generate any traces or even show up by negative anomalies. This study involves ground magnetic survey, rock magnetic and magnetic mineralogy examinations of soils to determine factors responsible for the formation of magnetic anomalies on Late Roman time burial grounds of Chernyakhiv–Sântana de Mureş archaeological culture located in the forest‐steppe of Ukraine. We surveyed these sites by a total magnetic field caesium magnetometer in order to target the archaeological excavations. We sampled infill from graves excavated under positive anomalies and profiles of background soils to analyse the enhancement of induced and remanent magnetization. In the laboratory, we examined magnetic mineralogy and measured various magnetic parameters and ratios characterizing concentration and granulometry of ferrimagnetic phase of soils. For further explanations of the magnetic anomalies, we created 3D synthetic magnetic models of the studied objects and compared the calculated total field anomalies with field measurements by their intensity and size. Here, we show how positive magnetic anomalies of destroyed burials are generated when a destruction pit remains open and later topsoil material gradually refilled it with aid of precipitation water. In this case, the infill layers acquire detrital remanence of the same intensity as the topsoil. Such burials are the best targets for magnetic survey. However, archaeological excavations revealed both intact and destroyed inhumations that caused no magnetic disturbance. Obviously, they were refilled immediately after digging/destruction, so that natural remanence of the infill remains mechanically destroyed. The study of this specific category of archaeological monuments brought us closer in the understanding the formation of magnetic anomalies in soil‐filled features and showed the potential and limitations of magnetic prospection. [ABSTRACT FROM AUTHOR]

THE interest for the application of the magnetic treatment technology in different agronomic aspects is increasing. Most agricultural studies do not take into account an important factor that may have a strong role affects the efficient application of the technology, which is the soil magnetism (SM). The magnetic susceptibility of soil is one of the measurable soil properties and utilized for different applications such as climatic information, pollution, archaeology, and agronomy. It refers to the presence of the iron oxide and oxy-hydroxide minerals, with different types and concentrations. The magnetic field (MF) affects the hydrophilic/hydrophobic character of water toward materials, soaking degree, electric conductivity, and many other properties. Many factors can affect the soil magnetism such as climate, soil drainage, Gleization, temperature, bacterial and microbial action, vegetation, and topography. This review focuses on this promising soil property and the possibility to use it as a prediction tool for a sustainable agriculture. It introduces for the subject, highlights the source of this property and measurement parameters, affecting factors, and some fields of application. It also highlights some characteristics of water when it is magnetically treated to give an overview of different topics that can be further studied to correlate the magnetism of water with the magnetism of soil for an optimum application of the magnetic technology. [ABSTRACT FROM AUTHOR]

There are few works where magnetic tracers are used for the assessment of water erosion, focusing on the traceability of sediments over the soil surface and in small areas (i.e., for laminar erosion survey). The main limitation of magnetic tracers is associated with its preparation and application, as the tracer is typically mixed with a large amount of soil and then spread manually over experimental sites susceptible to erosion. In gully erosion studies, the experimental sites (field areas where a gully is expected to develop) can be quite large. Consequently, the high volume/weight of the material (soil + tracer) to be prepared, transported, and applied renders this technique unfeasible. Moreover, eroded channels can reach a depth of several centimeters, requiring the tracer to be (re)located in the soil profile ideally at this same depth. This work presents a novel technique for the application and distribution of magnetite in the soil profile to track sediments in gully erosion assessments. Experiments were carried out in microplots, where a mixture of magnetite and water was applied over the soil surface using a backpack sprayer. Redistribution of the tracer in the soil profile was carried out with different conventional tillage implements. The control plots were subjected to the same experiments, but using a soil–tracer mixture (conventional technique). The application technique proposed herein enables a correct application of magnetite over large areas, being a promising alternative to the conventional technique. Hoeing tillage implements, such as the rotavator, ensure an approximately homogeneous redistribution of tracer in the soil profile when good soil moisture content is present. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility (MS) technique could be used as an efficient tool for management, monitoring, and analysis of soil properties. This study was conducted to investigate the relationship among the magnetic parameters and soil surface properties as well as their spatial variation in different land uses in Fars Province, southern Iran. Three dominant land uses in the study area including cropland, barren, and pasture were selected, and a total of 72 samples were collected from the soil surface (0–15 cm). Physicochemical properties, total free (Fed) and amorphous (Feo) iron forms, and MS in both high (xhf) and low (xlf) frequencies were determined. The results showed a significant difference (p˂0.05) for xlf average values among different land uses which were decreased in the order of cropland (45.31× 10−8 m3 kg−1), barren (31.68 × 10−8 m3 kg−1), and pasture (17.84 × 10−8 m3 kg−1), respectively. There was a positive significant correlation (p <0.01) between the MS values and Fed and Fed-Feo, while a negative significant correlation was observed among xlf and EC, gypsum, and Feo/Fed. The spherical model suitably described the spatial behavior of magnetic parameters and soil properties. The spatial distribution maps represented an almost parallel pattern in the spatial variations of MS, Fed, Fed-Feo, and evolution index, but an inconsistent pattern for Feo, CaCO3, gypsum, and EC in the study area. This indicates the role of diamagnetic materials in decreasing the soil magnetic properties. Results of this study clearly revealed that the MS technique is of great potential in monitoring the spatial variations of soil properties. [ABSTRACT FROM AUTHOR]

In gully erosion, the detached soil can be transported over long distances along the landscape. The eroded material can be redistributed and/or deposited on the soil surface along the landscape and then eventually be buried by newly eroded and deposited sediment. There can be significant variability of the soil conditions (e.g., texture and moisture content) over which the eroded material travels. The eroded material can be detected through the use of magnetic tracers attached to or mixed with the eroded soil. In this study we evaluated the degree to which the magnetic signal of the magnetite is conditioned by (i) burial depth of tracer, (ii) condition of soil covering the tracer and (iii) tracer concentration. In the laboratory containers were filled with a specific soil. In the filling process, a 0.5‐cm layer of a soil–magnetite mixture was interspersed in the soil profile at a certain depth. Experiments encompassed three different soil–tracer concentrations (1000:1, 200:1, 100:1), four burial depths of tracer (0 cm, 3 cm, 5 cm and 10 cm from soil surface), and two different soils. In each case, the magnetic susceptibility was measured with a susceptometer. Experiments were repeated with different soil moisture contents. If the tracer is located under the soil surface, a minimum soil–tracer concentration of 200:1 is required for its correct detection. The intensity of the magnetic signal decreases dramatically with the vertical distance of the tracer from the soil surface. The maximum detection depth for the tracer's magnetic signal is strongly dependent on the natural magnetic susceptibility of the soil, which masks the tracer's signal. Variation in soil moisture content does not significantly affect the magnetic signal. For extensive field studies, the soil–tracer volume to be handled would be very high and therefore, it is necessary to explore new tracer application techniques. [ABSTRACT FROM AUTHOR]

Fires are an integral part of many terrestrial ecosystems and have a strong impact on soil properties. While reports of topsoil magnetic enhancement after fires vary widely, recent evidence suggests that plant ashes provide the most significant source of magnetic enhancement after burning. To investigate the magnetic properties of burnt plant material, samples of individual plant species from Iceland and Germany were cleaned and combusted at various temperatures prior to rock magnetic and geochemical characterization. Mass-normalized saturation magnetization values for burnt plant residues increase with the extent of burning in nearly all samples. However, when normalized to the loss on ignition, fewer than half of ash and charcoal samples display magnetic enhancement relative to intact plant material. Thus, while magnetic mineral concentrations generally increase, changes in the total amount of magnetic material are much more variable. Elemental analyses of Icelandic samples reveal that both total plant Fe and saturation magnetization are strongly correlated with Ti and Al, indicating that most of the Fe-bearing magnetic phases originate from inorganic material such as soil and atmospheric dust. Electron microscopy confirmed that inorganic particulate matter remains on most plant surfaces after cleaning. Plants with more textured leaf surfaces retain more dust, and ash from these samples tend to exhibit higher saturation magnetization and metal concentrations. Magnetic properties of plant ash therefore result from the thermal transformation of Fe in both organic compounds and inorganic particulate matter, which become concentrated on a mass basis when organic matter is combusted. These results indicate that the soil magnetic response to burning will vary among sites and regions as a function of 1) fire intensity, 2) the local composition of dust and soil particles on leaf surfaces, and 3) vegetation type and consequent differences in leaf morphologies.

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. [ABSTRACT FROM AUTHOR]

Abstract Soil magnetic properties are sensitive indicators of pedogenetic processes. Although many of the processes that increase soil magnetism are well documented, the role of microbial communities and the metabolic characteristics of Fe-reducing bacteria are still largely unknown. For this work, two soils with contrasting magnetic properties were identified in a beech forest on Monte Zuccarello (central Italy). Samples of bulk soil and rhizosphere were obtained from A (0–7 cm), AB (7–16 cm), Bw1 (16–22 cm) and Bw2 (22–29 cm) horizons of both soils, and were analysed for their physicochemical characteristics, the amount of magnetic minerals, and the composition of total and culturable bacterial communities, focusing on siderophore-producing bacteria (SPB). Analyses confirmed that the magnetic soil (MS) have a higher content of maghemite and magnetite association, compared to non-magnetic soil (NMS). Since the formation of maghemite can occur through different processes, we investigated on the possible role of soil bacteria in the formation of this magnetic mineral. As soil maghemite generally contains small amounts of Fe2+, the formation of which has been attributed to the combustion of organic matter, SPB have been isolated and identified. MS samples showed the highest number of SPB (mainly Micrococcaceae , Bacillaceae , and Pseudomonadaceae), suggesting a significant increase in Fe-reducing bacteria. High-throughput sequencing analysis revealed a separation in terms of the total composition of the bacterial community between bulk and rhizosphere of both MS and NMS, dominated by Proteobacteria , Actinobacteria , Acidobacteria , and Verrucomicrobia phyla. Interestingly, Gamma and Delta Proteobacteria , as well as Nitrospirae , were usually more abundant in MS than in NMS, confirming that the MS was predominantly characterized by groups of magnetotactic bacteria and SPB, and potentially contributing to enhance the soil magnetic properties. Highlights • Magnetic and non-magnetic paleosols selected for different bacterial communities. • Magnetic soils were enriched in maghemite and Fe-reducing bacteria. • Rhizosphere did not promote the accumulation of magnetic minerals. • Magnetotactic and siderophore-producing bacteria increased in magnetic soils. [ABSTRACT FROM AUTHOR]

Maghemite (Mh) is a ferrimagnetic mineral that governs magnetism in the clay fraction, especially in well weathered soils from tropical and subtropical regions. In this work, we assessed different methods for Mh quantification [1: area of the reflections obtained by X-ray diffraction (XRD) (standard method); 2: Rietveld refinement; 3: selective dissolution with H 2 SO 4 and; 4: magnetic susceptibility (χ)] by application to Brazilian soils with contrasting parent materials (itabirite, basalt, gabbro, tuffite, gneiss and amphibolite). The methods based on H 2 SO 4 dissolution were found to overestimate the Mh content with respect to the standard method based on X-ray diffraction. This was particularly so with samples from gneiss and amphibolite and samples with higher contents in poorly crystalline Fe oxides. Mh contents based on magnetic susceptibility measurements or the XRD-Rietveld refinement were closer to those provided by the standard method. Mh was found to accumulate in well weathered soils and soils with a high Fe 2 O 3 content. Exception were soils from tuffite, which had high Fe 2 O 3 contents (~330 g kg −1 ), exhibited low Mh levels (~5.5 g kg −1 ). Irrespective of the parent material, Mh particles typically fall in a single domain magnetic behavior; however, they can also acquire multidomain characteristics, probably as a result of isomorphic substitution and aggregation with hematite. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that past human activities have irreversibly changed soil properties and biodiversity patterns. In the White Carpathian Mts (Central-Eastern Europe), a mosaic of hyper-species-rich and species-rich patches have developed in a regularly mown dry grassland in the area of a glassworks abandoned in the eighteenth century. We tested whether and how anthropogenically changed soils affected the distribution of extraordinary species richness. Using magnetometry we detected former furnaces, workspace, waste deposit and unaffected surrounding grasslands and compared their vegetation and environmental conditions. Archaeological features, especially furnaces and waste deposits, showed a higher pH, higher soil concentrations of exchangeable phosphorus, manganese, lead and calcium, and higher productivity. Surrounding grassland showed higher iron and sodium concentrations in the soil, higher N: P ratio in the biomass and higher species richness. Moisture was uniformly lower in soils on archaeological features, where non-trivially a more 'mesic' vegetation in terms of European habitat classification occurred. Plant compositional variation was best explained by water-extractable phosphorus. Because nutrient-richer patches were not moister as common elsewhere, and because species richness was only poorly accounted for by productivity, the occurrence of a species-poor 'mesic' vegetation on archaeological features was evidently caused by a long-lasting phosphorus oversupply which favours a comparatively small species pool of rather recently arriving species. On the contrary, surrounding phosphorus-poorer grasslands still contain the ancient species pool whose extraordinary size determines the exceptional species richness of grasslands in the study region. Its maintenance or restoration demands a persistent phosphorus deficiency. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility (χ) is a simple and quick technique to determine soil properties and to describe soil forming processes. Knowledge about factors affecting χ data helps better interpretation. Magnetic susceptibility of soils along a lithotoposequence was studied in this research in order to investigate the effects of soil forming factors (parent material and relief) and processes on the χ content and its vertical distribution. The study area is a transect from Jiroft to Kahnooj area, south Kerman Province, Iran. Rock pediment, mantled pediment, inselberg, alluvial fan, alluvial plain, and flood plain landforms with igneous parent materials (gabbro, diorite, and granite) were selected in the area. Thirteen representative pedons on different geomorphic positions were studied. Low frequency χ (χlf) values ranged from 193.1 × 10 − 8 m 3 kg − 1 to 2704.2 × 10 − 8 m 3 kg − 1 in studied soils and decreased with increasing diamagnetic material contents. Mean χlf values in soils formed on gabbro, diorite, and granite parent rock were > 1700 × 10 − 8 m 3 kg − 1 , 515.22 × 10 − 8 m 3 kg − 1 , and 352.53 × 10 − 8 m 3 kg − 1 , respectively. Frequency dependent χ of soils (in the range of 0.06 to 1.05%) showed that coarse multi domain grains inherited from igneous parent material were the main source of χlf in the area under study. Both increasing and decreasing trends of χlf with depth were observed. Decreasing trend of χlf with depth was due to illuviation of diamagnetic material into subsurface layers. On the other hand, increasing χlf with depth was attributed to the primary ferrimagnetic material inherited from igneous parent material. Alluvial plain (320.44 × 10 − 8 m 3 kg − 1 ) and mantled pediment (328.50 × 10 − 8 m 3 kg − 1 ) showed low values of χlf due to high amounts of soluble salts, anhydrite, and calcium carbonate investigated in these geomorphic positions. A positive significant relationship (R 2 = 0.018; r = 0.27, P < 0.05) between χlf and Fe o /Fe d activity ratio was found. Soil χlf decreased with development and relative dating of soils. Results of the study showed that soil χlf values were highly affected by parent material, relief, and soil development. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility investigations were conducted at an Awatixa Hidatsa village (32ME11, also known as Sakakawea Village) along a cutbank at the Knife River Indian Villages National Historic Site (KNRI) in central North Dakota, USA. This extensive exposure provided a superb opportunity to correlate magnetic susceptibility measurements with a variety of subsurface features. These features were visible in the cutbank, and also recorded in cutbank profiles completed in the late 1970s in work supervised by Robert Nickel and Stanley Ahler. The susceptibility studies are part of a larger program of geophysics at KNRI that commenced with pioneering surveys of John Weymouth and Robert Nickel, also in the 1970s, and continued with extensive surface-based magnetic surveys over the interior portion of the site in 2012 by the National Park Service. Our magnetic susceptibility study differs from other geophysical efforts in that measurements were collected from the vertical cutbank, not from the surface, to investigate different feature types within their stratigraphic context and to map small-scale vertical changes in susceptibility. In situ measurements of volume magnetic susceptibility were accomplished on the cutbank at six areas within the village and a control location off-site. Samples were collected for use in soil magnetic studies aimed at providing an understanding of susceptibility contrasts in terms of magnetic mineralogy, grain size, and concentration. Distinctive susceptibility signatures for natural and cultural soils, different feature types, and buried soils, suggest that down-hole susceptibility surveys could be usefully paired with surface-based geophysics and soil magnetic studies to explore interior areas of this and other KNRI sites, mapping vertical and horizontal site limits, activity areas, features, and perhaps even earlier occupations. This study showcases the potential of cutbank studies for future geophysical survey design and interpretation, and also underscores the importance of information gained through pioneering studies of the past. [ABSTRACT FROM AUTHOR]

In the Maya Lowlands region, along the Usumacinta River, Late Pleistocene–Holocene profiles exhibit sedimentary characteristics and soil formation processes, as a result of environmental conditions and human–environmental interactions. Here, we report a comprehensive environmental magnetic investigation on paleosols and sediments at the Tierra Blanca archaeological site which shows clear evidences of human occupation. The pedogenetical magnetic properties were characterized by rock magnetism studies to determine the composition, concentration and domain size distribution of magnetic minerals. The Late Pleistocene paleosols were formed under the influence of a humid climate, as shown by the presence of recent fine hematite formation, directly related to reduction–oxidation processes during Gleysol development. The transition from early to middle Holocene was obtained from a paleovertisol, dated as 2.34–2.3 ka, which showed a marked heterogeneity in its magnetic parameters due to continuous argilloturbation processes. The environmental conditions retrieved, indicate the presence of a drought period around 5.5 ka. The upper two paleosols were less developed and seems to be strongly affected by human activities during the Maya Classic period, dated between 1.14 and 0.97 ka. These soils were formed under more humid conditions, and yielded a magnetic mineralogy (hematite-magnetite-maghemite) due to incipient weathering and anthropic disturbance. [ABSTRACT FROM AUTHOR]

The Starunia oil-ozokerite deposit occurs in the Boryslav-Pokuttya Unit of the Carpathian Foredeep, which is the main oil- and gas-bearing part of the Ukrainian Carpathians. Starunia is of great interest in studying the relationship between the magnetic properties of rocks, soils and hydrocarbons due to extensive surface microseeps yielding oil and gas, mineral water, and clay pulp containing hydrocarbons. We identified a local negative magnetic anomaly (30-35 nT) with a width of about 700 m within the MAG1 profile. The magnetic high is associated with the area of the largest mud volcanoes in the Starunia structure. Magnetic susceptibility of the soil was measured on a site with three distinct landscape features: a patch of forest with phaeozem and mass-specific susceptibility (χ) of 20-45 × 10 m/kg for the surface topsoil; an area near the volcano and Nadia-1 well with visible hydrocarbon microseepage at the surface and the topsoil showing no visible evidence of hydrocarbon presence with χ = 20-50 × 10 m/kg; and a patch of lowland with gleysols and χ = 10-20 × 10 m/kg. Hydrocarbon-containing clays and soils from the alluvial sediments of the Velyky Lukavets River and bedrock clays near the Nadia-1 well demonstrated high χ values (up to 250-440 × 10 m/kg). [ABSTRACT FROM AUTHOR]

Magnetic iron oxide minerals, principally magnetite, maghemite, hematite, and goethite are formed in well-drained soils in response to a suite of physical, chemical, and biological factors. Despite a wide range of complexity in the pedogenic processes that lead to magnetic mineral formation, dissolution, and transformation, there are well-documented empirical relationships between various magnetic mineral assemblages in soils with environmental and climatic conditions. Recently there has been an increase in the number of quantitative magnetic paleoprecipitation proxies that have been developed, and there is great potential for magnetic methods to be used in the geologic record to develop reconstructions of past climates. Magnetic paleoprecipitation proxies have been widely utilized in Quaternary or younger loess–paleosol systems; however, they have yet to be utilized in the pre-Quaternary fossil record. Future studies of magnetic mineralogy of soils and paleosols should aim to explore non-loessic modern soils and pre-Quaternary paleosols with more focus on understanding the interaction between magnetic mineral assemblages and soil moisture. Applications of existing and novel magnetic paleoprecipitation proxies in the fossil record should prove to be a valuable resource for paleoclimatologists. [ABSTRACT FROM AUTHOR]

Among other forms, iron contained in soil is a component of magnetic minerals, both primary and secondary ones, produced by various soil forming processes. The composition of the soil magnetic fraction, characterised by a magnetic susceptibility, is the consequence of its origin. The character of susceptibility changes along the analysed chernozems’ profiles indicates a similarity of the parent rock, as well as the pedogenic processes forming the chernozems from the territories of Poland and the Ukraine. The influence of anthropogenic factors could be seen in the increased susceptibility within the humus horizon of the degraded chernozem.

• Four differences of magnetism are identified between Chinese and Serbian loess. • The first is the different contents of fine-grained ferrimagnetic minerals. • The second is the difference in the concentration of thermally unstable maghemite. • The third is the different contents of magnetic particles with single-domain phase. • The last one is the different proportion of antiferromagnetic hematite/goethite. In this study, a systematic comparison of the magnetic properties of the Xifeng loess in northern China and the Titel loess in northern Serbia was conducted. This comparison was performed to identify the causes of the different ranges of magnetic susceptibility (χ lf) enhancements from loess units to paleosol units between the two regions. Ultimately, four differences in the contents and domain states of the magnetic minerals were detected. First, the different concentration of magnetic minerals, especially fine-grained ferrimagnetic minerals between the Xifeng and Titel paleosols is the leading cause. Although the factor of pedogenesis dominated the variations in magnetic properties for each of the loess profiles, the different degrees of pedogenesis between them seemingly cannot fully explain the different contents in magnetic minerals. We consider the difference in source distances of aeolian dust or the related factors played a significant role in the contents of the included magnetic minerals. Second, the lower content of thermally unstable maghemite in the Titel paleosols is an important cause of the lower χ lf. This difference can be attributed to the varying levels of effective moisture during the pedogenesis periods, which were caused by the precipitation-evaporation difference. Third, the higher content of single-domain particles in Titel paleosols is one of the causes of the lower χ lf. This is an attractive point for promoting our understanding of the pedogenic mechanism under different geographical and climatic backgrounds; however, its origin remains unclear. Finally, the higher proportion of antiferromagnetic hematite/goethite in the Titel paleosols is an element that causes the lower χ lf , despite its weak effect. Different water and heat conditions during pedogenesis may be responsible for this difference, and the possibility of the influence of the contemporaneous Mediterranean-like climate in the Pannonian Basin should not be excluded. [ABSTRACT FROM AUTHOR]

Magnetic measurements in a number of hydrocarbon structures suggest the existence of local magnetic anomalies with certain nT amplitude reflecting the structure contours of the oil and gas deposits, which could therefore be used as a criterion for identifying hydrocarbon traps. Hydrocarbon migration and the microseepage effect changing the composition of magnetic minerals and reaching as high as the near-surface areas and soils cause local magnetic anomalies and changes in the magnetic properties of soils. Magnetic studies on the Orchovychi oil and gas field, Carpathian Foredeep, Western Ukraine, revealed specific features of the local magnetic field and the magnetic properties of soil. A local magnetic anomaly with amplitude of 6-8 nT and a width of about 4 km was detected in the structure of the magnetic field within the Outer zone of the Carpathian Foredeep. The anomaly relates to hydrocarbon deposit areas with complex morphology. Magnetic susceptibility (MS) of soils in the Orhovychi oil and gas field showed a close correlation with landscape changes. Soils were found to show magnetic susceptibility anomalies in close proximity to productive hydrocarbon areas. [ABSTRACT FROM AUTHOR]

Geophysical science offers a large range of methods that have been adapted for the detection of archaeological structures beneath the surface. Magnetometry is among others the most successful, and with respect to large survey areas, the most widely-used scientific toolkit that is used by archaeologists. New developments in instrument techniques and real-time GPS enlarged the role of magnetometer prospecting for archaeological science considerably and allow even the detailed prospecting and analysis of landscapes. An integral part of this method however should be the archaeological interpretation of the geophysical result. In this paper the rock magnetic and soil magnetic background will be discussed, which is necessary for a comprehensive understanding of survey results. The diversity of the magnetic anomalies is exemplified on the basis of selected survey results, and explains the role of magnetic prospecting in the field of archaeological science. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic enhancement of A and B horizons during soil development is a common phenomenon. To better understand the exact mechanism for the magnetic enhancement, especially the mineral transformation pathways, systematic rock magnetic studies were conducted on a Xeralf chronosequence in northwestern Spain. A positive correlation was found between the average grain size and the concentration of pedogenic maghemite particles with the exception of some A horizons, in which multiple factors seem to influence the nature and concentration of neoformed ferrimagnets. It is argued that the interaction between the positively charged iron oxides and the anionic ligands present in the solution of these acidic soils plays an important role in this respect. The time trends of the average grain size of pedogenic ferrimagnets and the strong correlation between the concentrations of hematite and maghemite in the magnetically enhanced horizons (A and B) are consistent with the hypothesis of a gradual formation of maghemite (later converted into hematite) via a precursor (most likely ferrihydrite). Therefore, this study provides strong evidence for the dynamic evolution of magnetic minerals upon pedogenesis. [Copyright &y& Elsevier]

We review the nature and importance of soil factors implicated in the formation of secondary ferrimagnetic minerals in soils and palaeosols worldwide. The findings are examined with respect to temperate regions through a comprehensive analysis of over 5000 samples of surface soil from England and Wales taken from a 5×5 km grid. Over 30 soil and environmental attributes are considered for each sample as proxies for soil forming factors. Measurements of low field magnetic susceptibility (mass specific) and frequency dependent susceptibility (mass specific and percentage) on each sample provide estimates of the concentration and grain size of ferrimagnetic minerals. Maps of soil magnetism across England and Wales show non-random distributions and clusters. One subset of data is clearly linked to contamination from atmospheric pollution, and excluded from subsequent analyses. The concentration of ferrimagnetic minerals in the non-polluted set is broadly proportional to the concentration of minerals falling into the viscous superparamagnetic domain size range (~15–25 nm). This set shows clusters of high magnetic concentrations particularly over specific parent materials such as schists and slates, mudstones and limestones. Bivariate analyses and linear multiple regression models show that the main controlling factors are parent material and drainage, the latter represented by soil drainage classes and particle size. Together these two factors account for ~30% of the magnetic variability in the complete dataset. A second group of factors, including climate (mean annual rainfall), relief (slope and altitude), and organisms (land use, organic carbon and pH) have subordinate control. Climate, as represented by mean annual temperature, and also pedogenic time are deemed not relevant at these spatio-temporal scales. The findings are consistent with a largely abiotic system where the role of iron-reducing bacteria appears minor. At coarse spatial and temporal scales, secondary ferrimagnetic mineral formation is controlled by the weathering capacity to supply Fe to the surface soil. At finer scales, soluble Fe precipitates as ferrihydrite before transformation in response to periodically anaerobic conditions into other minerals including nanoscale magnetite. [Copyright &y& Elsevier]

Mass specific magnetic susceptibility (χ) is an efficient technique to describe environmental processes and pedogenic variation patterns in soils. This study aimed to investigate the pedoenvironmental changes, including soil forming factors and processes, in Lut Watershed using the χ technique. For this purpose, three climatic sites, including site 1 (xeric/mesic soil moisture/temperature regimes), site 2 (weak aridic/mesic, weak aridic/thermic, and typic aridic/thermic regimes), and site 3 (extreme aridic/hyperthermic regimes), with different lithology and geomorphology were selected. Twenty-four pedons out of 50 which showed the maximum variations were selected as the representative pedons. Soil samples were analyzed for physicochemical properties, different iron forms, and χ measured in two frequencies 0.46 and 4.6 kHz. Results indicated that the minimum and maximum χ values were 20.6 × 10−8 m3 kg−1 and 1031 × 10−8 m3 kg−1, respectively. Mean χ values in soils formed on different rocks were in the order of sedimentary rocks < sedimentary-metamorphic rocks < felsic igneous rocks < intermediate igneous rocks < mafic igneous rocks. The frequency-dependent magnetic susceptibility percentage (χfd%) ranged from 0 to 3.38%. The vertical distribution of χ along the studied pedons showed the concomitant impact of climate, lithology, relief, drainage, soil attributes, lithological discontinuity, paleoclimate, redistribution processes, and soil evolution. The negative significant correlation among χ, χfd, and free Fe oxides (Fe d) in site 1 with igneous rocks revealed the probable conversion of primary ferrimagnetic minerals to the minerals with lower magnetic properties during pedogenesis. Moreover, the positive significant correlation (r = 0.33 and p ˂ 0.01) between soil evolution Fe o /Fe d index (ratio of soluble acid oxalate and free Fe oxides) and χ values in site 2 indicated that χ decreased during soil evolution. Due to aridity and the lack of pedogenic processes, detrital Fe-bearing minerals mainly affected χ values in site 3. Overall, the χ technique is a potential pedoenvironmental indicator for a better understanding of soil forming factors and processes in Lut Watershed. • Magnetic properties of polygenetic soils with aridic/thermic regime were preserved. • Mean χ was decreased by increasing soil evolution in xeric/mesic regime. • χ is a useful complementary technique to interpret formation of geomorphic surfaces. • Argilluviation process reduced the χ values related to the sand fraction. • The χ values in the hyperarid regime were controlled by detrital Fe-bearing minerals. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic properties of soils have negative impacts on metal detector performance during landmine clearance operations. In particular, topsoils with high concentrations of pedogenic viscous superparamagnetic minerals (magnetite/maghemite) as shown by high values of magnetic susceptibility and frequency dependent susceptibility limit the detector capability of identifying buried landmines. Thus a priori knowledge of the spatial extent of soils that may be problematic for landmine detection would aid strategic planning of clearance operations and ensure appropriate equipment is deployed. Here, we compare two approaches for estimating the broad magnetic properties of soils in Bosnia and Herzegovina: 1) an analogue approach, using data for magnetic susceptibility and frequency dependent susceptibility available for soil types from other temperate and Mediterranean regions; 2) magnetic measurements of a stratified sample of soil samples taken from the Bosnian National Soil Archive. The national soil magnetic maps produced estimate that the area of land inferred as problematic for metal detectors is 4% and 30% according to the analogue and measurement methods respectively. Combining soil type with soil parent material and climate explains the spatial variability of soil magnetic properties in terms of mechanisms of secondary ferrimagnetic mineral production and accumulation. The resulting maps indicate that the magnetic properties of dominant soils in northern Bosnia tend to be unproblematic for detectors, while in central Bosnia there is likely to be moderate detector interference. However, there is a high likelihood of dominant soils affecting detectors in southern and western Bosnia and Herzegovina, equivalent to ~30% of the total land area. The mapped outputs of susceptibility and frequency dependent susceptibility provide demining end-users with an indication of the likelihood of encountering problem soils in areas selected for clearance operations. [Copyright &y& Elsevier]

Abstract: Insights into past climate changes, and corresponding evolution of soils and the environment, can be gained by multidisciplinary studies of palaeosols. Here, we focus on palaeosols buried beneath archaeological monuments, specifically, funerary mounds (kurgans), in the Russian steppe. The kurgans were constructed, and each of the palaeosols buried, over a range of different timesteps from the mid-Holocene to ∼ 600 years before present (yr BP). Integrated magnetic, mineralogical and pedological data were used to obtain estimates of past climate (especially precipitation) changes, through both time and space. A soil magnetism-based climofunction, derived previously from modern steppe soils and modern climate, was applied to each set of palaeosols, to obtain quantitative reconstructions of annual precipitation for the time at which the soils were buried. Independent soil property data (clay mineralogy, salt content, iron mineralogy from Mossbauer analysis, and optical and electron microscopy) were also obtained, in order to test and substantiate the magnetic inferences. The data obtained indicate that the climate of the Lower Volga steppe area has varied from the mid-Holocene onwards. Precipitation minima occurred at ∼ 5000, ∼ 3800, and ∼ 1600 yr BP, with intervals of enhanced precipitation at ∼ 1900 yr BP and ∼ 600 yr BP. These rainfall variations appear to occur synchronously with changes in Middle Eastern precipitation and lake levels, suggesting they are controlled by index changes in the North Atlantic Oscillation. [Copyright &y& Elsevier]

Abstract: As geospatial technologies increasingly figure into resource management activities, there is a corresponding need to provide commensurately detailed high resolution spatial data. This study addresses the capacity of rapidly and cheaply acquired mineral-magnetic data to provide detailed spatially distributed assessments of long-term cumulative soil loss from agricultural fields. Model output from a simple distributed implementation of the Revised Universal Soil Loss Equation (RUSLE) and from a field-data-oriented soil magnetism-based erosion model are compared for a small Alabama (USA) farm lot. An undisturbed reference soil toposequence is used as input to the magnetism model, in contrast with earlier studies that relied on a single reference soil profile. Results from this procedure, while likely to be more dependable, proved primarily to further emphasize spatial patterns noted in prior studies. In addition, the use of a toposequence decreased the area over which RUSLE and magnetism models were in agreement. RUSLE underpredicted denudation relative to magnetism-model results over upper slopes, and overpredicted it on lower slopes. The locations of former access roads may explain underprediction on the upper slopes. The differences between the two method outcomes are discussed with regard to the potential for spatial variability in parent materials, the efficacies of non-fluvial soil redistribution processes, and the availability of detailed land use records for the 100+ years of agricultural activities at the site. [Copyright &y& Elsevier]

Thermomagnetic measurements, particularly measurements of the Curie or Néel temperature, are often used to identify magnetic minerals in rocks or sediments. In many samples it is impossible to determine the Curie or Néel temperature as mineral changes occur during heating. Especially in soils or sediments, iron (hydr)oxides may be transformed to ferrimagnetic iron oxides. In this study we analysed the thermomagnetic behaviour of some natural and synthetic iron minerals: goethite, haematite, ferrihydrite, lepidocrocite and siderite. The change of magnetization M with temperature was determined with a magnetic translation balance. The sample was heated in air to a maximum temperature of 700°C and subsequently cooled back to room temperature. By adding organic carbon to synthetic samples and by destroying it in natural samples, the influence of organic substance on the reactions was determined. Goethite, ferrihydrite and haematite transform to a strongly magnetic phase only if organic carbon is present. Lepidocrocite and siderite transform without organic carbon, the reaction of siderite is even weakened if organic matter is added. The transformation starts below 400°C for ferrihydrite and lepidocrocite and around 450°C for goethite. We can conclude that, though these reactions impede the identification of the ferrimagnetic oxides in many soil and sediment samples, they can be used to distinguish between the most common soil iron hydroxides in these environments. [ABSTRACT FROM AUTHOR]

Soil profiles of the Kathmandu urban area exhibit significant variations in magnetic susceptibility (χ) and saturation isothermal remanence (SIRM), which can be used to discriminate environmental pollution. Magnetic susceptibility can be used to delineate soil intervals by depth into normal (< 10−7 m3/kg), moderately enhanced (10−7–< 10−6 m3/kg) and highly enhanced (≥ 10−6 m3/kg). Soils far from roads and industrial sites commonly fall into the ‘normal’ category. Close to a road corridor, soils at depths of several centimeters have the highest χ, which remains high within the upper 20 cm interval, and decreases with depth through ‘moderately magnetic’ to ‘normal’ at approximately 30–40 cm. Soils in the upper parts of profiles in urban recreational parks have moderate χ. Soil SIRM has three components of distinct median acquisition fields (B1/2): soft (30–50 mT, magnetite-like phase), intermediate (120–180 mT, probably maghemite or soft coercivity hematite) and hard (550–600 mT, hematite). Close to the daylight surface, SIRM is dominated by a soft component, implying that urban pollution results in enrichment by a magnetite-like phase. Atomic absorption spectrometry of soils from several profiles for heavy metals reveals remarkable variability (ratio of maximum to minimum contents) of Cu (16.3), Zn (14.8) and Pb (9.3). At Rani Pokhari, several metals are well correlated with χ, as shown by a linear relationship between the logarithmic values. At Ratna Park, however, both χ and SIRM show significant positive correlation with Zn, Pb and Cu, but poor and even negative correlation with Fe (Mn), Cr, Ni and Co. Such differences result from a variety of geogenic, pedogenic, biogenic and man-made factors, which vary in time and space. Nevertheless, for soil profiles affected by pollution (basically traffic-related), χ exhibits a significant linear relationship with a pollution index based on the contents of some urban elements (Cu, Pb, Zn), and therefore it serves as an effective parameter for quantifying the urban pollution. [ABSTRACT FROM AUTHOR]

Formation of ferrimagnets in well-drained, buffered, unpolluted soils appears to be related to climate, and especially rainfall. If robust, this magnetism/rainfall couple can be used to estimate past rainfall from buried soils, particularly the multiple soils of the Quaternary loess/soil sequences of Central Asia. However, dispute exists regarding the role of climate vs. dust flux for the magnetic properties of modern loessic soils. Here, we examine the mineralogical basis of the magnetism/rainfall link for a climate transect across the loess-mantled Russian steppe, where, critically, dust accumulation is minimal at the present day. Magnetic and independent mineralogical analyses identify in situ formation of ferrimagnets in these grassland soils; increased ferrimagnetic concentrations are associated with higher annual rainfall. XRD and electron microscopy show the soil-formed ferrimagnets are ultrafine-grained (<∼50 nm) and pure. Ferrimagnetic contributions to Mo¨ssbauer spectra range from 17% in the parent loess to 42% for a subsoil sample from the highest rainfall area. Total iron content varies little but the systematic magnetic increases are accompanied by decreased Fe2+ content, reflecting increased silicate weathering. For this region, parent materials are loessial deposits, topography is rolling to flat and duration of soil formation effectively constant. The variations in soil magnetic properties thus predominantly reflect climate (and its co-variant, organic activity) – statistical analysis identifies strongest relationships between rainfall and magnetic susceptibility and anhysteretic remanence. This magnetic response correlates with that of the modern soils across the Chinese Loess Plateau. Such correlation suggests that the rainfall component of the climate system, not dust flux, is a key influence on soil magnetic properties in both these regions. [Copyright &y& Elsevier]

The Red Clay unit of northern China is a widespread Miocene–Pliocene (7.2–2.5 Ma) aeolian deposit that underlies much of the Quaternary loess–paleosol sequence in the central Loess Plateau. It comprises a sequence of highly developed soils and interbedded layers of less weathered loess-like material, here referred to as reddish loess. In common with the loess–paleosol alternations of the overlying Quaternary deposits, the soil–reddish loess alternations are interpreted to represent climatic fluctuations, in this case between warm-humid and relatively dry-cool conditions. However, while magnetic susceptibility variations in the Quaternary deposits provide a good proxy for pedogenic intensity, in the Red Clay the relationship is less clear and magnetic susceptibility data are in conflict with other measures of pedogenesis. In an attempt to resolve this issue, we have investigated a Red Clay section and overlying loess–paleosol sequence at Xifeng and have supplemented these data with samples from the Red Clay at Lingtai. Our study indicates that the Red Clay and loess–paleosol sequence have a common magnetic mineralogy comprising magnetite, maghemite and hematite (and possibly goethite), and that both sequences show a good correlation between magnetic susceptibility and the magnitude of the superparamagnetic (SP) component. This implies that susceptibility enhancement in the Red Clay is strongly related to the magnitude of the SP content, a component that is widely recognised as having a pedogenic origin in Quaternary deposits. Further support for a correlation between pedogenesis and magnetic susceptibility in the Red Clay is provided by a good correlation between magnetic susceptibility and the Rb:Sr ratio, an independent weathering index. However, differences in the magnetic mineralogy of the two units are also evident. The minimum magnetic susceptibility of the Red Clay is less than half the value of the overlying Quaternary deposits at locations such as Xifeng and Lingtai, while the maximum SP content is (relatively) larger than for the Quaternary deposits. While we cannot discount the possibility that the former difference is a reflection of different parent materials for the two units, climate may also be a contributory factor in explaining these differences. Precipitation is a major control on magnetic enhancement in paleosols [Maher and Thompson (1995) Quat. Res. 44, 383–391; Liu et al. (1995) Palaeogeogr. Palaeoclimatol. Palaeoecol. 113, 243–248], but soil anoxia and iron oxide dissolution occur if moisture exceeds some critical level. Soil moisture is therefore a critical factor in determining whether the correlation between pedogenesis and magnetic susceptibility in loess deposits is positive (central Loess Plateau, China; magnetic enhancement), negative (Alaska; Siberia; magnetic destruction) or uncertain (Pakistan; Argentina; New Zealand; cycles of enhancement and destruction). While our results indicate a generally positive correlation between pedogenesis and magnetic susceptibility in the Red Clay, they also imply that a more thorough paleoclimatic interpretation can only be achieved using complementary, but independent techniques. More work is required to deconvolve the climatic record of the Red Clay, but the reward may be the extension of the record of paleomonsoon evolution back into the Pliocene and late Miocene. [Copyright &y& Elsevier]

Magnetic susceptibility measurements on topsoils have often been used during the last few years to detect anthropogenic pollution. In most cases, a Bartington susceptibility meter for field measurements was used. However, up to now, no standard procedure has been developed for carrying out such investigations. The purpose of our study was to test the compatibility of different set-ups of instruments used for this purpose and the possible influences of subjective (human) factors. Field magnetic susceptibility measurements, carried out with four different Bartington MS2D instruments in strictly defined positions, are very consistent both for low and high values. The correlation coefficient between the magnetic susceptibility values recorded with different Bartington MS2D probes reached 97–98%. A test area was mapped independently by two groups, without any restrictions concerning the choice and distribution of the measured points, but respecting a few standard conditions (e.g., measuring at a distance from tree trunks; on the flattest place possible; recording between 10–30 values per point). The resulting susceptibility maps show the same general features in both cases, suggesting that the measuring strategy applied is suitable for topsoil magnetic screening. The methodology proposed can be used to map magnetic susceptibility on a larger scale—for example Europe—providing large sets of representative data and eliminating border-transition biases and human errors. [ABSTRACT FROM AUTHOR]

An 8 m core from the central plain of the Petit Lac d'Annecy, France, two floodplain cores, river bedload sediments and several hundred soil samples from the catchment have been studied using magnetic techniques. The soils, mainly developed on limestones and local glacial tills, show widespread magnetic enhancement with higher ferrimagnetic concentrations and contents of SP grains than found in the lake sediments. Some soils show significant concentrations of canted antiferromagnetic minerals (mainly haematite). Using magnetic quotient parameters the surface soils are classified into four mineralogical types. The lake and floodplain sediment properties over the past 6000 yrs can largely be explained by the erosion and deposition of these sources, with a smaller superimposed biogenic (magnetosomes) signal. Derived sediment-source linkages allow the construction of several hypotheses about geomorphological changes in the catchment system: (i) the long-term erosion of high altitude unweathered substrates has gradually increased towards the present day; (ii) the erosion of high altitude soils has increased within the last 1000 yrs, possibly during the period of the 'Little Ice Age'; (iii) shifts towards an increased erosion of surface lowland soil occurred ~2000 and 1000 yrs ago and may be linked to an accelerated accretion of floodplain overbank deposits; (iv) there has been a significant storage of surface soil within floodplains, which leads to an underestimation of the importance of soil erosion in the lake sediment records; (v) the sediment transported by high magnitude, low frequency flood events has shifted in source from high altitude soils before ~1000 cal. yr BP to lowland and mid-altitude free draining soils after ~1000 cal. yr BP. [ABSTRACT FROM AUTHOR]

• We evaluate soils in two agricultural fields with differing land use histories. • Soil magnetic properties positively correlate with soil organic matter in both fields. • Organic matter may limit magnetic mineral formation in some agricultural fields. • Soil magnetism can be a useful tool for soil surveys in agriculture. Magnetic properties of soil are widely utilized to study soil development in a variety of settings due to the formation of strongly magnetic iron oxides during pedogenesis. Similarly, soil organic matter (SOM) is commonly measured in soil surveys conducted on agricultural lands due to the essential role SOM plays in the soil ecosystem. Here, we present data from two agricultural fields in southeastern Minnesota that demonstrate a relationship between soil magnetic properties and SOM. In each field, we collected 100 topsoil samples along a 40 m by 20 m grid to determine spatial variability in soil magnetic properties and SOM, as well as two soil cores to constrain variability with depth (∼0–60 cm). Magnetic susceptibility, low-field remanence, and hysteresis properties were used to characterize magnetic mineral abundance and grain-size in the soils. There are strong positive correlations between SOM and three magnetic properties: the frequency dependence of susceptibility (χ fd), anhysteretic remanent magnetization (ARM), and the ratio of ARM to isothermal remanent magnetization (ARM/IRM). All three of these magnetic properties (χ fd, ARM, and ARM/IRM) are sensitive to the concentration (or relative abundance) of fine-grained (<75 nm) magnetite/maghemite known to form in well-drained soils during pedogenesis. Correlation between SOM and magnetic properties persist in each field despite differences in the management strategy over the past three decades. Our results support a functional link between SOM and soil-formed magnetite/maghemite, where increasing SOM (up to a threshold) enhances the production and stability of soil-formed magnetite due to its role in soil redox processes and iron-organic complexes. Agricultural soils seem particularly well suited to demonstrate correlations between SOM and pedogenic magnetic minerals due to their relatively low SOM and typically well-drained environments, supporting the utility of soil magnetism in agricultural soil survey studies. [ABSTRACT FROM AUTHOR]

• Soil magnetometry can help in assessing soil contamination in Fe-rich lithology. • Soil contamination can be determined by comparing topsoil and parent rock material. • SOC correlates significantly with content of S and Pb. • Frequency-dependent susceptibility discriminates anthropogenic elements in topsoil. Mineral magnetic properties are sensitive indicators for evaluating environmental changes, including environmental pressure caused by atmospherically deposited anthropogenic magnetic particles. The most commonly and easily measured magnetic parameter of soils is magnetic susceptibility, which reflects the combined ferromagnetic minerals of lithogenic, pedogenic, and anthropogenic origins. In volcanic soils rich in ferrimagnetic minerals, unfortunately, contributions of pedogenic and anthropogenic origins are masked by the lithogenic contribution. More study is therefore needed of soils developed on highly magnetic lithologies. This work aimed to determine links between magnetic susceptibility and concentration of potentially toxic elements derived from anthropogenic activities in soil (Aluandic Andosols) developed from highly magnetic parent material in a locality where contamination is not expected. The approach is based on relationships between magnetic properties and geochemical signatures of the investigated soils. Magnetic properties are represented by mass-specific magnetic susceptibility (χ) and frequency-dependent magnetic susceptibility (χ FD %). Geochemical signatures are represented by concentrations of the elements Fe, Si, Ti, Zr, Sr, Al, Nb, Mn, Ca, Rb, K, P, Zn, S, Pb, Cr, V, Ni, Cu, and As; pH in H 2 O; soil organic carbon content; and granulometry. Soil contamination was evaluated using two indexes: enrichment factor and geo-accumulation index. Our findings show that χ FD % correlates with presence of the toxic elements S and Pb, derived from human activities, while χ exhibits strong correlation with elements Al, Ti, V, and Fe, reflecting natural origin of parent material. In case of soils with well-developed humus horizon, χ FD % can be used as a proxy parameter for identifying anthropogenic influence. Our findings are beneficial also for archaeologists using magnetic susceptibility of soils as a link to chemical signatures of past settlement activities. [ABSTRACT FROM AUTHOR]

• Complete magnetic enhancement and reduction was recorded in the studied profile. • Magnetic enhancement occurred in the aerobic layer. • Magnetic reduction occurred under water-logged conditions. • Water-logged condition was caused by agriculture with a history of about 200 years. • The time required for a dissolution of iron oxides was shorter than 200 years. Previous studies have revealed that magnetic enhancement caused by the pedogenic process often occurs in aerobic soils experiencing low to moderate rainfall, while magnetic reduction caused by iron oxide dissolution often occurs in anaerobic soils experiencing high rainfall. To explore the time required for iron oxide dissolution when the soil conditions transform from aerobic to anaerobic, a typical weathering crust profile was selected. The results show the complete process of magnetic enhancement and reduction, and that the former occurred in aerobic soil due to the newborn magnetic minerals during the pedogenic process, while the latter occurred under water-logged conditions caused by rice cultivation with a history of approximately 200 years. Therefore, it can be inferred that the time required for the significant dissolution of iron oxides is probably shorter than 200 years, which is longer than that determined by indoor experiments, but much shorter than the theoretical weathering model. [ABSTRACT FROM AUTHOR]

The demand for information on the soil resource to support the establishment of public policies for land use and management has grown exponentially in the last years. However, there are still difficulties to the proper use of already existing information for soil mapping. Here we aimed to establish a protocol for soil mapping using legacy data, magnetic signature and soil attributes evaluation. A total of 493 soil samples were collected at 0-0.20 m in the geological domain of Western Plateau of São Paulo State. This work has three parts: First, we performed a classification analysis using soil mapping units (SMU) extracted from conventional soil map and Support Vector Machines algorithm (SVM). As covariates, we used categorical information, such as geology, dissection and landform maps. Second, we used soil attributes to perform a cluster analysis using k-means as partitioning method. To choose the optimal number of clusters, the same number of SMU showed in the conventional soil map (e.g. 34 clusters) were used. The last step was to compare soil and clusters maps predicted by SVM with the conventional soil map. Results showed good performance of SVM for both classifications (clusters and SMU), with overall accuracy of 0.60 and 0.90 respectively. In addition, the distribution of soil attributes within each cluster was more homogeneous and well distributed than within SMU, showing that is very possible to use numerical classification for soil mapping. Future soil surveys could use cluster analysis as a preliminary evaluation for better understanding of tropical soil variations., (Copyright © 2019 Elsevier B.V. All rights reserved.)