High Magnetic Susceptibility Values Research Articles

Development of the MIITRA QSM template: a high‐resolution magnetic susceptibility template of the older adult brain in the MIITRA atlas space

AbstractBackgroundA QSM template of the older‐adult brain is not yet available. This study constructed a high resolution QSM template of the older‐adult brain for the MITRA atlas using data from a large, diverse, community cohort of non‐demented older‐adults.MethodMagnetic susceptibility maps were generated for the 400 older‐adult paricipants used in the construction of MIITRA using the Morphology Enabled Dipole Inversion(MEDI) on the 3D 5‐echo GRE data(0.7×0.7×1.3mm3) and upsampled to 0.7×0.7×0.65mm3 using nonlocal upsampling. The first GRE echo of each participant were N4 bias field corrected, then upsampled to 0.7×0.7×0.65mm3 using non‐local upsampling and converted to synthetic T1w images using mri_synthsr. The original 3D T1w MPRAGE(1×1×1mm3) data were upsampled to 0.5×0.5×0.5mm3. The synthetic T1w images were linearly registered to the upsampled T1w data and the resulting transformations were used to forward‐map magnetic susceptibility values from the native space of each participant to exact physical locations in MIITRA space. A sparse representation based data‐fusion approach was used on the transformed signals to generate the final 0.5×0.5×0.5mm3 resolution template, denoted as MIITRA_QSM(Fig.1). Since no other magnetic susceptibility template of the older‐adult brain is currently available, we compared MIITRA_QSM to a young adult template named MuSus‐100(1×1×1mm3,100 participants,mean age 24 years) in terms of image quality and magnetic susceptibility properties.ResultVisual showed that MIITRA_QSM template includes fine details, has the expected QSM contrast, highest values in subcortical, brainstem, and cerebellar structures known for their high magnetic susceptibility(especially in older adults), lower values in the white compared to gray matter, and higher values in white matter of the frontal lobe compared to parietal and occipital lobes. When compared to MuSus‐100, MIITRA_QSM showed better delineation of cortical structures and higher image sharpness(Fig.2), as well as higher magnetic susceptibility values in most subcortical brain structures(Fig.3A), Cortical structures from the two templates exhibited more similar magnetic susceptibility values(Fig.3B).ConclusionMagnetic susceptibility values in specific subcortical, brainstem and cerebellar structures are higher in the MIITRA_QSM template compared to a young adult template, probably due to increased metal deposition in these structures with aging. The new template is expected to greatly enhance the accuracy of voxel‐wise and atlas‐based QSM studies on older‐adults.

Development of the MIITRA QSM template: a high‐resolution magnetic susceptibility template of the older adult brain in the MIITRA atlas space

AbstractBackgroundA QSM template of the older‐adult brain is not yet available. This study constructed a high resolution QSM template of the older‐adult brain for the MITRA atlas using data from a large, diverse, community cohort of non‐demented older‐adults.MethodMagnetic susceptibility maps were generated for the 400 older‐adult paricipants used in the construction of MIITRA using the Morphology Enabled Dipole Inversion(MEDI) on the 3D 5‐echo GRE data(0.7×0.7×1.3mm3) and upsampled to 0.7×0.7×0.65mm3 using nonlocal upsampling. The first GRE echo of each participant were N4 bias field corrected, then upsampled to 0.7×0.7×0.65mm3 using non‐local upsampling and converted to synthetic T1w images using mri_synthsr. The original 3D T1w MPRAGE(1×1×1mm3) data were upsampled to 0.5×0.5×0.5mm3. The synthetic T1w images were linearly registered to the upsampled T1w data and the resulting transformations were used to forward‐map magnetic susceptibility values from the native space of each participant to exact physical locations in MIITRA space. A sparse representation based data‐fusion approach was used on the transformed signals to generate the final 0.5×0.5×0.5mm3 resolution template, denoted as MIITRA_QSM(Fig.1). Since no other magnetic susceptibility template of the older‐adult brain is currently available, we compared MIITRA_QSM to a young adult template named MuSus‐100(1×1×1mm3,100 participants,mean age 24 years) in terms of image quality and magnetic susceptibility properties.ResultVisual showed that MIITRA_QSM template includes fine details, has the expected QSM contrast, highest values in subcortical, brainstem, and cerebellar structures known for their high magnetic susceptibility(especially in older adults), lower values in the white compared to gray matter, and higher values in white matter of the frontal lobe compared to parietal and occipital lobes. When compared to MuSus‐100, MIITRA_QSM showed better delineation of cortical structures and higher image sharpness(Fig.2), as well as higher magnetic susceptibility values in most subcortical brain structures(Fig.3A), Cortical structures from the two templates exhibited more similar magnetic susceptibility values(Fig.3B).ConclusionMagnetic susceptibility values in specific subcortical, brainstem and cerebellar structures are higher in the MIITRA_QSM template compared to a young adult template, probably due to increased metal deposition in these structures with aging. The new template is expected to greatly enhance the accuracy of voxel‐wise and atlas‐based QSM studies on older‐adults.

Spatiotemporal environmental monitoring of the karst-related Almyros Wetland (Heraklion, Crete, Greece, Eastern Mediterranean)

Wetlands are of great importance for providing the appropriate conditions for the diversity of species and inhabitants living in these ecosystems and for a wide range of public goods and services (fresh water, air filtering, recreational and tourism opportunities). However, despite their importance, wetlands are continuously degraded due to various human activities at an alarming rate worldwide. In the context of this study and considering the rational management of wetlands and the inevitable impact of climate change, a wetland, spatiotemporal monitoring system is proposed, implemented in the karst wetland of Almyros Stream (Heraklion, Crete, Greece). The implementation of this system is based on robust techniques from the allied fields of chemistry, earth and ecology assisted by GIS techniques. Our results indicate that this Mediterranean karst wetland of great ecological importance is under pressure because of pollution, climate change and land change. This argument is supported by (a) the high concentrations of water photosynthetic pigments and nutrients at certain times of the year, both provided by chemical analysis and partially verified by geophysical monitoring (spectral induced polarization) and (b) the high values of soil magnetic susceptibility at sites close to human infrastructures that is an indicator of heavy metals concentrations.

Magnetic Susceptibility as Proxy for Metal Concentrations and Their Risk Levels in Vaigai River Sediment, Tamilnadu, India: Horizontal and Vertical Approach

ABSTRACT Horizontal and vertical distributions of heavy metals (Al, Fe, Mg, Cd, Cr, Cu, Ni, Pb and Zn) and magnetic susceptibility of Vaigai river sediment have been assessed to know the heavy metal toxicity and magnetic behavior of the sediment. The present study intentionally shows the magnetic susceptibility as proxy for metal concentrations and their risk levels of sediment. Univariate statistical analysis is carried out to confirm the spatial distribution of the heavy metals. The metal concentrations in present sediment are compared with iportant toxic reference values such as TEL, PEL, ERL, ERM and TRV to predict the toxicity of metals. The result shows that the frequent biological effect can be possible due to Cd, Cr, Cu, Pb and Zn in all feet sediments. Some interesting pollution factors such as PLI, PER and mPEC-Q are calculated to know the pollution status of the river. High magnetic susceptibility values in S16, S18 and S25 indicate the presence of various magnetic minerals. Principal Component Analysis (PCA) is carried out to show magnetic susceptibility as proxy for measuring heavy metals and their risk levels. Since magnetic susceptibility is strongly associated with heavy metals and their risk levels, this may be proxy for determining heavy metals and their risk levels.

Mineral magnetic properties of surface soils from the Broknes and Grovnes Peninsula, Larsemann Hills, East Antarctica

This study presents the mineral magnetic, particle size, and organic content data of surface soils from Larsemann Hills, East Antarctica. The analysis of isothermal remanent magnetization and the high specific magnetic susceptibility values –mean (±S.D.) values of 117.7 (±175.0) × 10−8m3kg−1 for Broknes Peninsula and of 330.9 (±217.4) × 10−8m3kg−1 for Grovnes Peninsula– indicate high concentrations of low-coercivity magnetic minerals. The magnetic minerals are coarse-grained in the multidomain and pseudo-single domain range, and the significant correlation between some magnetic parameters suggests the dominant control of multidomain grains. The remanent acquisition coercivity H1/2 shows mean (±S.D.) values of 38.2 (±4.9) for Broknes and 38.3 (±3.7) mT for Grovnes soils suggesting magnetite dominance. The soils lie in the sand and loamy sand textural classes, and the concentration of organic matter is very low. Values of percentage frequency-dependent susceptibility indicate insignificant proportions of superparamagnetic grains, and therefore no significant evidence for pedogenic magnetic minerals was observed in these soils. The magnetic signal of Larsemann Hills soils was primarily terrigenous with no contributions from bacterial magnetite, authigenic greigite and anthropogenic magnetic minerals.

MAGNETO-MINERALOGICAL ANOMALIES AT THE PLEISTOCENE-HOLOCENE BOUNDARY IN LAKE SEDIMENTS OF NORTHEASTERN RUSSIA

The results of the study of lake sediments in the North-East of Russia are presented. The reasons for the abnormally high values of magnetic susceptibility in the transition layers from the Late Pleistocene to the Holocene are considered. The magnetic fraction of Lake Grand sediments is represented by detrital titanomagnetites and magnetites. In the sediments of the Gryazevoye, Sosednee, Vodorazdelnoye, and Sapog lakes, high values of magnetic susceptibility are due to autigenic iron sulfides, mainly greigite. The data obtained do not confirm the well-known assumption about the presence of an impact event at the boundary of the Pleistocene and Holocene.

Почвенно-микробиологические подходы к реконструкции назначения построек на древних поселениях

The aim of the article is reconstruction of purpose of ancient settlements construction using a combination of chemical and microbiological indicators. The study object is the Bagai-1 settlement of the Late Bronze Age in the northwestern part of the Crimean Peninsula. The chemical and microbiological properties of the occupation layer within the buildings of various shapes and sizes in different parts of the site have been studied. It was established that the Bagai-1 settlement is a stationary settlement of pastoralists, or was intended for living in the winter. Traces of cattle manure were found everywhere, which is confirmed by the high values of such soil indicators of livestock keeping as urease activity, the number of keratinolytic fungi and thermophilic bacteria in the cultural layer. The results of the research showed that most of the buildings in the settlement were related to livestock keeping. We cannot exclude the joint stay in the premises of both animals and humans, especially in the cold season when livestock was used as a source of heat. However, according to the complex of natural scientific data, no buildings have been identified that could be called exclusively residential, and in all cases the traces oflivestock are much more pronounced than the traces of human habitation. At the same time, vast areas without traces of stone buildings were found at the settlement, but with a high content of mineral forms of phosphates in the cultural layer and high values of magnetic susceptibility, which indicates the entry into the soil of a large amount of ceramics, ash, and pyrogenic residues. The combination of these properties can be considered as an indicator of human habitation.

Variation in magnetic susceptibility in the Bellingshausen Sea continental rise since the last glacial period and implications for terrigenous material input mechanisms

Magnetic susceptibility (MS) is routinely used as a proxy for terrigenous material input to Antarctic continental margin sediments. Variations in terrigenous input on glacial-interglacial timescales in this setting are related to a range of environmental changes; including to the cryosphere, atmosphere, and hydrosphere. However, the exact environmental factors and depositional processes that control MS values in sedimentary cores from the Antarctic continental margin remains unresolved. Here, we explore in detail sedimentary physical characteristics and MS values of core BS17-GC01 collected from Bellingshausen Sea continental rise, to understand how depositional process have varied during the late Quaternary. We found that input of terrigenous material increased markedly during Marine Isotope Stages (MIS) 2 and 4, compared to deposition during the adjacent interstadial and Holocene times. Variation in the bulk MS values were associated with changes in grain size. Size specific mass-normalized MS measurements show the fine fraction (<16 μm) has the highest MS values, followed by the coarse silt fraction (16–63 μm). However, because coarse silt is the predominant grain size, the increased bulk MS during MIS 2 and 4 are mainly driven by changes in this fraction. We propose that the coarse silt with high bulk MS values observed in glacial sediments were transported to the site as iceberg rafted debris, originating from the Bellingshausen Sea shelf region. In contrast, grains >1 mm – a commonly applied proxy for glacial transport in this setting – were observed during MIS 1 and 3 only. We conclude these contrasting signatures of iceberg rafted debris in this Bellingshausen Sea core arise from changes in the to the erosive dynamics of the adjacent ice shelf and continental shelf on glacial/interglacial timescales. • The MS in the Bellingshausen Sea co-varied with Antarctic ice core dust record. • The correlations of MS and dust record can be used for obtaining chronological points. • The MS is controlled by source/transport mechanism changes resulting in grain size change. • MS increases during MIS 2 and 4 are ascribed to increased coarse silt having high MS. • The coarse silt fraction during glacial periods was transported by icebergs.

Middle to late Holocene sedimentary filling history of the Sebkha el Melah in south‐eastern Tunisia

AbstractThe sedimentological and geochemical properties of a 146 cm long sediment core collected from Sebkha el Melah (Ml core) in south‐eastern Tunisia have been used to infer the genesis and evolution of the Sebkha el Melah over the last 5000 years. Two main sedimentary units have been defined: a huntite [Mg3Ca(CO3)4] unit at the bottom of core Ml is covered by a second unit made up of siliciclastic and evaporitic materials. The huntite level is synchronous with Holocene marine transgression, which was followed by a regression of about 5300 years bp. Geochemical data (major and trace element), magnetic analyses, grain‐size distribution and microtexture of quartz grains were performed to assess the sediment provenance. The upper unit of Ml core is characterized by alternations between fluvial, aeolian and evaporite deposits. Redox proxies displaying marked Fe/Ca and Rb/S peaks, in addition to high magnetic susceptibility (MS) values, polymodal grain‐size frequency curves, as well as sub‐angular grains with V‐shaped percussion cracks, are suggestive of palaeohydrological events. In contrast, a decreasing trend in the low MS values, bi‐modal grain‐size frequency curves as well as well‐rounded quartz grains with crescent percussion marks would indicate enhanced aeolian sand input in the sebkah el Melah sequence. Moreover, geochemical proxies suggest formation of evaporite facies under a strongly warm climate contemporary with marine intrusion.

Magnetic susceptibility in the deep gray matter may be modulated by apolipoprotein E4 and age with regional predilections: a quantitative susceptibility mapping study.

To examine the relationship between apolipoprotein E gene (APOE) mutation status and iron accumulation in the deep gray matter of subjects with cognitive symptoms using quantitative susceptibility mapping (QSM). A total of 105 patients with cognitive symptoms were enrolled. QSM data were generated from 3D gradient-echo data using an STI Suite algorithm. A region of interest-based analysis with QSM was performed in the deep gray matter. Differences between APOE4 carriers and non-carriers were assessed by analysis of covariance. Multiple regression analysis was performed to identify the factors associated with magnetic susceptibility. Clinical characters such as age, education, MMSE, vascular risk burden, and systolic blood pressure differ between APOE4 carrier and non-carrier groups. The APOE4 carrier group had higher magnetic susceptibility values than the non-carrier group, with significant differences in the caudate (p = 0.004), putamen (p < 0.0001), and globus pallidus (p < 0.0001) which imply higher iron accumulation. In a multiple regression analysis, APOE4 status was found to be a predictor of magnetic susceptibility value in the globus pallidus (p = 0.03); age for magnetic susceptibility value in the caudate nucleus (p = 0.0064); and age and hippocampal atrophy for magnetic susceptibility value in the putamen (p < 0.05). Our study demonstrates that magnetic susceptibility in globus pallidus is related to APOE4 status while those of caudate and putamen are related to other factors including age. It suggests that brain iron accumulation in the deep gray matter is modulated by APOE4 and age with differential regional predilection.

Magnetic petrology of the Neoarchean granitoids in the Vila Jussara Suite, Carajás Province, Amazonian Craton

The Vila Jussara Suite (VJS) is formed by Neoarchean (~ 2.75 Ga) granites that are located in the Sapucaia Domain of the Carajás Province (CP), Amazonian Craton. Four petrographic varieties were identified in the VJS: biotite-hornblende monzogranite (BHMzG); biotite-hornblende tonalite (BHTnl); biotite monzogranite (BMzG); and hornblende-biotite granodiorite (HBGd). In terms of magnetic signature, BHMzG has two subgroups: the first subgroup has low magnetic susceptibility (MS) values (0.16 × 10-3 to 0.81 × 10-3) and more commonly contains ilmenite with titanite rims; the second subgroup shows moderate to high MS (1.91 × 10-3 to 6.02 × 10-3) and magnetite dominant over ilmenite. BHTnl has moderate MS (0.85 × 10-3 to 1.36 × 10-3) and dominance of pyrite followed by magnetite. BMzG and HBGd have comparatively high MS (3.35 × 10-3 to 19.3 × 10-3 and 2.14 × 10-3 to 25.0 × 10-3, respectively), with magnetite dominant over pyrite. The granite varieties of the VJS were formed under different oxygen fugacity (fO2) conditions, varying from reducing (< fayalite-magnetite-quartz (FMQ)) to oxidizing conditions (nickel-nickel oxide (NNO) to NNO+1). In addition, biotite-hornblende syenogranite occurs subordinately and shows high MS values and extremely high FeOt/(FeOt + MgO) ratios, both in whole-rock and amphibole and biotite. The granites of the VJS are similar to other Neoarchean granites of the Carajás province. The reduced VJS granites are akin to the ferroan granites of Planalto suite, Estrela Complex and Vila União area and the magnesian granites of VJS approach the magnesian granites of Vila União area.

Different characteristics of barren and W–Mo–productive Cretaceous granites in the Hwanggangri mineralized district, South Korea

The Hwanggangri mineralized district (HMD) in South Korea contains a variety of ore deposits such as porphyry or skarn (Mo, Cu–Pb–Zn), carbonate replacement, and fissure–filling vein types (W–Mo, Au–Ag, fluorite). The HMD is located on the boundary of the Okcheon metamorphic belt and the Taebaeksan Basin. Most of the deposits are hosted in limestones/dolomitic limestones of the Joseon Supergroup, and the age of mineralization is Late Cretaceous (96.5–76.2 Ma) including Geumseong, Jungbo, Kwangsin, and Geumsil deposits. These granites are mainly magnetite-series biotite granites, and they can be categorized into early- and late-stage on the basis of mineral assemblage, texture, grain size, and magnetic susceptibility. Magnetite is present in some of the granites, and some of the early-stage granites retain the high magnetic susceptibility values typical of the magnetite series. However, the late-stage granites show a wide range of magnetic susceptibility values, including low ones due to fractionation. The emplacement ages of the Sokrisan, Weolaksan, Muamsa, and Susan granite bodies are 94–88 Ma, similar to the ages of mineralization in the study area. The Cretaceous granites reported to be related to W–Mo mineralization in the HMD show miarolitic, porphyritic, and micrographic textures indicating considerable hydrothermal fluid activity in a shallow environment. The rocks of the Sokrisan granite are mostly early stage, those of the Weolaksan and Muamsa granites include both early and late stages, and the studied samples of the Susan granite are entirely late stage. These four Cretaceous granites have more than 70 wt% SiO2, high Rb/Sr ratios, depletions in compatible elements, enrichments in incompatible elements, and tetrad patterns with depleted LREEs, enriched HREEs, and strong negative Eu anomalies. They all belong to the high–K calc–alkaline series, are dominantly peraluminous, and can be classified as strongly fractionated I–type granites. The Sokrisan, Weolaksan, Muamsa, and Susan granites have similar emplacement ages and geochemical characteristics that indicate the same magma source. However, the Sokrisan granite, with its mainly early-stage rocks, consistently higher magnetic susceptibility values, and relatively high Nb/Ta values, differs from the other Cretaceous granites in the HMD. This suggests that the widely exposed Sokrisan granite of batholith type has been eroded substantially, removing the late-stage rocks and ore deposits. In contrast, the stock–type Susan granite has undergone relatively little erosion, and it represents well the late-stage parts of the Cretaceous granites in the HMD. The Cretaceous granites in the HMD have mostly highly-fractionated geochemical characteristics, and the late-stage rocks that are more associated with W–Mo mineralization are more fractionated than the early-stage rocks. The respective productivities of the Susan, Muamsa, Weolaksan, and Sokrisan granites range from high to low, and the more-productive late-stage granites are still present, as they have undergone less erosion.

New insights on the Alboran Sea basin extension and continental collision from magnetic anomalies related to magmatism (western Mediterranean)

In the Alboran Sea there are a few well exposed Neogene and Quaternary volcanic zones, often geographic highs, that are generally associated with magnetic anomalies. In this paper, we present a characterization of these magnetic anomalies based on a recent and accurate magnetic data compilation for the Abloran Sea area. The anomalies reveal the distribution of magmatism and shed light into the discussion about the origin and evolution of the westernmost Mediterranean. One of the most relevant magnetic anomalies is the Nador dipole, which extends from the Gourougou volcano to the Chafarinas Islands, and is related to an E-W crustal scale intrusion. However, the main NE-SW elongated continuous dipoles of the central Alboran Sea are not related to any surface structure, but they are parallel to the Alboran Ridge, which is the main volcanic high in the Alboran Sea, and are located to the north of it. These anomalies extend discontinuously eastward along the NW-SE dipoles located along the Yusuf fault zone. The results of our 2D magnetic forward modeling suggest that the causative bodies of these main magnetic dipoles are deep igneous bodies. According to the tectonic evolution of the region, and the high magnetic susceptibility values obtained, these igneous bodies probably are made of a basic igneous rocks. Their emplacement may represent the westward tip of the rift axis of the AlKaPeCa Domain, which is related to the Oligocene-Miocene NW-SE extension, and associated with the southern slab retreat stage and oceanic spreading of the Algerian basin. Afterwards, these bodies were displaced toward the west, together with the Alboran Domain, and affected by the STEP fault located at its southern limit. Since the Late Miocene, the north Alboran Ridge elongated intrusions acted as a backstop that conditioned the folding and uplift of the Alboran Ridge in a tectonic indentation setting. In this setting, the STEP fault is deformed and the eastern part of the bodies were segmented along the Yusuf transtensional fault system. Simultaneously, the E-W crustal body related to the Nador magnetic dipole was emplaced, possibly evidencing a slab tearing process. The deep seated basic igneous bodies constitute main crustal heterogeneities that reveal and drive the Alboran Sea tectonic inversion.

Application of biomagnetic analysis technique using roadside trees for monitoring and identification of possible sources of atmospheric particulates in selected air pollution hotspots in Delhi, India

With increasing atmospheric pollution and health issues associated with size of the particulate matter, it has become important to look for techniques that may improve the monitoring resolution. Magnetic bio-monitoring of particulate matter has been used in recent years in some countries as an approach for better spatial resolution that provides proxy indicators for the measurements over large areas. Delhi, which is one of the most polluted cities of not just India, but the whole world, is still probing to understand the possible sources. The present magnetic biomonitoring study was therefore, carried across different land use areas in some air pollution hotspots of Delhi, using common roadside tree species Morus alba, Ficus religiosa, Ficus virens and Ficus benghalensis to understand the magnitude and nature of the particulate pollution, and possible sources by studying magnetic properties (Magnetic susceptibility, Frequency-dependent susceptibility, S-ratio, and SIRM) of the dust deposited on leaves. Mass specific magnetic susceptibility (10−8 m3 kg−1) values were found to follow the order: Traffic intersection area (25.6–66.5) > Industrial area (25.4–41.3) > Residential area (13.2–30.1) > Institutional area serving as control (2.7–6.6). High magnetic susceptibility values indicated particulates with ferrimagnetic grains of anthropogenic or technogenic origin. Frequency-dependent Susceptibility indicated dominance of coarse multidomain (MD) and Pseudo Single Domain (PSD) +MD grains in industrial area and major traffic intersection. Average S ratio across all study sites ranged from 0.92 to 0.99 indicating presence of soft magnetic mineral with low coercivity. High SIRM values (10−5Am2 kg−1) from 58.1 to 862.3 suggested prevalence of magnetite dominating atmospheric particulates particularly in traffic intersection and industrial area, and to some extent in residential area. Morus alba and Ficus religiosa were found more suitable bio-monitors and the technique provided useful information on size, mineralogy and possible source of the particulates.

Methanogens and Their Syntrophic Partners Dominate Zones of Enhanced Magnetic Susceptibility at a Petroleum Contaminated Site

Geophysical investigations documenting enhanced magnetic susceptibility (MS) within the water table fluctuation zone at hydrocarbon contaminated sites suggest that MS can be used as a proxy for investigating microbial mediated iron reduction during intrinsic bioremediation. Here, we investigated the microbial community composition over a 5-year period at a hydrocarbon-contaminated site that exhibited transient elevated MS responses. Our objective was to determine the key microbial populations in zones of elevated MS. We retrieved sediment cores from the petroleum-contaminated site near Bemidji, MN, United States, and performed MS measurements on these cores. We also characterized the microbial community composition by high-throughput 16S rRNA gene amplicon sequencing from samples collected along the complete core length. Our spatial and temporal analysis revealed that the microbial community composition was generally stable throughout the period of investigation. In addition, we observed distinct vertical redox zonations extending from the upper vadose zone into the saturated zone. These distinct redox zonations were concomitant with the dominant microbial metabolic processes as follows: (1) the upper vadose zone was dominated by aerobic microbial populations; (2) the lower vadose zone was dominated by methanotrophic populations, iron reducers and iron oxidizers; (3) the smear zone was dominated by iron reducers; and (4) the free product zone was dominated by syntrophic and methanogenic populations. Although the common notion is that high MS values are caused by high magnetite concentrations that can be biotically formed through the activities of iron-reducing bacteria, here we show that the highest magnetic susceptibilities were measured in the free-phase petroleum zone, where a methanogenic community was predominant. This field study may contribute to the emerging knowledge that methanogens can switch their metabolism from methanogenesis to iron reduction with associated magnetite precipitation in hydrocarbon contaminated sediments. Thus, geophysical methods such as MS may help to identify zones where iron cycling/reduction by methanogens is occurring.

Geochemical Compositions and Magnetic Susceptibility of Soils from Different Origins: A Case Study in South Lampung, Indonesia

DOI:10.17014/ijog.7.3.267-272The study of rock weathering into soil is very important in geophysics. The geochemical and magnetic characteristics of soil were investigated in South Lampung using magnetic susceptibility and X-ray Fluorescence (XRF) measurements to identify the rock origin of the soil. The samples consisted of three soil types, those are granite soil, tuff soil in front of ITERA (Institut Teknologi Sumatra, South Lampung), and tuff soil inside ITERA. The tuffs (in front of and inside ITERA) and granite were taken in and around ITERA. The result showed that granite had the highest magnetic susceptibility value, while tuff soil in front of ITERA had the highest FeO content. Each sample can be distinguished by magnetic susceptibility and FeO content to prove that it can be used as a tool to distinguish the rock origin of soil.

A multi-proxy approach for reconstructing environmental dynamics since the mid Holocene in Lake Ismarida (Thrace, N. Greece)

The paleoenvironmental evolution of Lake Ismarida in Thrace (Northern Greece) is revealed by the combined lithological, micropaleontological (benthic foraminifera, pollen and NPPS), molluscan analyses, magnetic susceptibility measurement and radiocarbon dating of a 5.8-m long sediment core. The mid Holocene evolution of the lake area is evidenced by the documentation of four sedimentary Units in the core ISMR-2, corresponding to four distinct evolutionary stages: (1) during ∼5500-3500 cal yr BP the lake area was a shallow marine environment characterized by an Ammonia beccarii, small rotaliids, miliolids, Bittium reticulatum and Veneridae spp. assemblage, marine dinoflagellate cysts, and low magnetic susceptibility values; (2) during ∼3500-3000 cal BP the environment is gradually tending to more isolated conditions forming an open lagoon, characterized by marine and euryhaline fauna and low magnetic susceptibility values; (3) during 3000 cal yr BP, the open lagoon presented a transition to an oligohaline inner lagoon, characterized by an Ammonia tepida, Haynesina germanica, Aubignyna perlucida, Pirenella conica, Cerastoderma glaucum and Abra spp. assemblage, sedges and aquatic vegetation. This restricted, entirely isolated from the sea inner lagoon could be definitely used as the landmark of the Lake Ismaris from Heorodotus, while describing the march of Xerxes through Thrace in 480 B.C.; (4) since ∼2000 cal yr BP to the present, the Lake Ismarida is formed, characterized by fresh-water indicators and aquatic pollen, Pseudoschizaea and high magnetic susceptibility values. Finally, the progradation of the Filiouris River deltaic deposits resulted to a 4 km wide deltaic plain between Lake Ismarida and the nowadays coastline. Pollen assemblages record the dominance of a rather rich deciduous forest in the area with traces of human presence in the lower part of the sequence, whereas the opening of the plant landscape under the increasing human pressure is evidenced after ∼ 3000 cal yr BP. Finally, an open vegetation pattern, contemporaneous with the retreat of forest vegetation, is evidenced in the area already before 2000 cal yr BP.

Steel Slag Characterisation—Benefit of Coupling Chemical, Mineralogical and Magnetic Techniques

Steel-making slag is largely used today in road construction and other applications, but significant volumes are landfilled and cannot be recycled for excessive contents in hazardous metals, such as chromium or vanadium. The long-term behaviour of this material is still little known, and the characterisation of large volume slag dumps remains an environmental challenge. In this study various analytical techniques are used to characterise Electric Arc Furnace (EAF) slag landfilled for several decades and exposed to chemical weathering and erosion. Coupling chemical, mineralogical and magnetic techniques helps to understand the relations between hazardous metals and mineral phases. A special interest is given to Fe-bearing minerals microstructure so as to link the magnetic properties of the material to its mineralogical composition. The studied slag presents high amounts of chromium (between 1 and 3 wt. %) and very high magnetic susceptibility values (near 60 × 10−6 m3/kg), explained by the presence of magnetite and a spinel solid solution. Some correlations are found between magnetic susceptibility and potentially hazardous metals, providing new perspectives for future environmental investigations.

Geostatistical approach to the study of the magnetic susceptibility variation: Lamas de Olo Pluton case study

The Lamas de Olo Pluton, in northern Portugal, is a post-tectonic pluton located in the northern part of the Central Iberian Zone of the Iberian Variscan belt. It is a composite massif comprising different granites: Lamas de Olo, Alto dos Cabecos and Barragem. Magnetic susceptibility was measured in 349 oriented cores from 48 sampling sites across the pluton. The measured magnetic susceptibility (Km) values range between 21 µSI (or 21 × 10− 6 SI) and 2769 µSI for all studied granites. The application of the geostatistical methodologies leads to a more detailed mapping of the magnetic susceptibility data and provided a quantification of its spatial dispersion. Kriging interpolation allows the visualization of two different areas in the Lamas de Olo Pluton: (1) areas with higher magnetic susceptibility values, typical of magnetite-bearing granites (Km ≥ 1200 µSI) and (2) areas with lower values, which correspond to ilmenite-type behavior granites (21 µSI < Km < 1200 µSI), showing the heterogeneity of their granites, with a predominance of ilmenite-type granites. Alto dos Cabecos and Barragem are classified as ilmenite-type granites and Lamas de Olo granite presents both behaviors. The mineralogical and geochemical study of the Lamas de Olo granite with different behaviors does not show significant differences between the two types, allowing us to conclude that the Lamas de Olo granite was originated by the same magma and its mineralogical composition varied during the rise and emplacement of the magma implying the alteration of magnetite into hematite.

The estimation of an anthropogenic depth boundary using the magnetic susceptibility method in Kogi State, North-Central Nigeria

Magnetic susceptibility measurements remain one of the most reliable methods used to investigate the pollution of both surface and subsurface soil from metallic anthropogenic sources. Most of the geological rocks within the study area increase the susceptibility of the soil; however, knowing the natural background susceptibility of the parent rocks will give an idea of the anthropogenic influence on the susceptibility of the soil. This study was carried out in Kogi State, North Central Nigeria, with the aim of determining the depth of the boundary between the anthropogenic influences on soil magnetic susceptibility from those of a lithogenic origin. Magnetic susceptibility measurements were carried out on 1,760 soil samples, collected from 220 soil profiles at a depth of 80.0 cm and at intervals of 10.0 cm. From the spatial distribution of magnetic susceptibility maps at different depths, the boundary between the basement complex and the sedimentary basin was clearly demarcated. The result further shows the highest magnetic susceptibility values of 350–650 × 10−5 SI, which dominates the surface soil to a depth of 40.0 cm. At the depth of 40–50 cm, the result indicates the combination of a natural anthropogenic influence on soil magnetic susceptibility with an average of 250 × 10−5 SI. Furthermore, no evidence of layering along the depth sections was observed, suggesting that the soil profiles indicate areas mainly covered by anthropogenically influenced susceptibility, which were localized and restricted to commercial places within the state. This study reveals that the average depth of soil affected by anthropogenic pollutants is between 40–50 cm in commercial places and 20–30 cm in other places with less commercial activities.