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Brantas River is a largest urban river supplying raw water and drainage in Jawa Timur Province, Indonesia. Dense population along the river is a threat of pollution due to anthropogenic pollutants. In this study, we characterize the magnetic properties and heavy metal contents of surface sediments in various locations along the Brantas River. This study aims to enhance our understanding of the relationship between magnetic parameters and heavy metal contents in surface sediments from river. Surface sediment samples were taken and measured by a series of magnetic measurements, mineralogical analysis and heavy metal contents. The results show that magnetic minerals in surface sediments of Brantas River are dominated by PSD magnetite mineral. This relatively coarser grain size can be caused by magnetic particles produced by erosion around the river. Surface sediments have very high mass-specific magnetic susceptibility varying from 844.0 to 7231.4 × 10−8 m3kg−1 (on average of 3022.9 × 10−8 m3kg−1) because influenced by the surrounding volcanic environment. Magnetic susceptibility can identify and classify enrichment of heavy metals. Based on the Pearson correlation analysis, magnetic susceptibility has strong positive correlation with the heavy metal contents of ferromagnetic elements such as Fe and Co so that it can potentially be used as an indicator of pollution of both these heavy metals in the Brantas River. This present work shows the novelty of the relationship between magnetic susceptibility and heavy metal contents in surface sediments from river in volcanic and tropical environment. Unlabelled Image • Surface sediments of Brantas River have very high magnetic susceptibility. • Ferrimagnetic mineral of surface sediments mainly presents in the form of magnetite. • Heavy metals exhibit strong positive correlation with magnetic susceptibility. • Magnetic susceptibility can be used as an indicator of heavy metal pollution. [ABSTRACT FROM AUTHOR]

Between 22 and 17 cal ka BP, five large meltwater events from within the Laurentian Channel Ice Stream deposited mud beds meters thick across a large area of the Laurentian Fan and adjacent continental slopes. This study determines the sources of these event beds and relates them to the glaciological evolution of the retreating Laurentian Ice Stream. We analyzed major element and magnetic mineral contents of these event beds and compare them with a new collection of 80 source reference samples from the Gulf of St. Lawrence area. Element ratios suggest a steady compositional change from older to younger outburst event beds, while element-specific offsets from reference sample compositions indicate grain-size and mineral/element partitioning during suspension transport. Their magnetic properties place event beds on the source mixing trend of four reference samples groups, which represent two magnetite-rich sources (Canadian Shield and/or Southern Newfoundland) and two hematite-rich sources (Appalachian red beds). Using a deterministic linear source mixing model based on IRM 100mT , HIRM and Ca%, we find that the earlier two outburst events had higher contributions from granitic and calcareous sources than the later three events. Combining materials, timing and scenarios of the outburst events with ice-sheet retreat and ice-stream dynamics, we argue that the subglacial sediment depocenter of the earlier two event beds was located in the lower Laurentian Channel while that of the later three events was upstream from Cabot Strait. • Event bed sediments unmixed from new Gulf of St. Lawrence reference sample data. • Hematite, magnetite and calcite are most indicative tracer minerals for provenance. • Quantify contributions from surrounding red-bed, granite and carbonate rock provinces. • Demonstrate element partitioning by subglacial outwash and hyperpycnal plume transport. • Sediments premixed in subglacial depocenters above outer and inner Laurentian Moraines. [ABSTRACT FROM AUTHOR]

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To evaluate the mechanics of mid‐Proterozoic environmental iron transport and deposition, we coupled microscale textural and bulk rock magnetic techniques to study the ~1.4‐Ga lower Belt group, Belt Supergroup, Montana and Idaho. We identified a pyrrhotite‐siderite isograd that marks metamorphic iron‐bearing mineral reactions beginning in subgreenschist facies samples. Even in the best‐preserved parts of the basin, secondary overprints were common including recrystallization of iron‐bearing sulfides, base metal sulfides, and nanophase pyrrhotite. Despite these overprints, a record of redox chemistry was preserved in the early diagenetic framboidal pyrite and detrital iron oxides including trace nanoscale magnetite that remained after sulfidization in anoxic and sulfidic sedimentary pore fluids. Based on these results, we interpret the Belt Basin as having oxic waters, at least in shallow‐water environments, with no indication of abundant ferrous iron in the water column; this is consistent with the cooccurrence of early eukaryotic fossils within the same strata. Plain Language Summary: Observing iron chemistry and mineralogy in sedimentary rocks is one of the primary methods for understanding ancient redox environments; today, iron is poorly soluble in seawater due its high dioxygen levels, but some iron‐based metrics suggest that ocean and lakes were rich in soluble iron for a billion years after the rise in atmospheric oxygen 2.3 Ga. Using a novel approach for evaluating iron environmental processes, we analyzed the iron‐bearing minerals within 1.4‐Ga rocks and were able to untangle which minerals were primary, containing information about the ancient environment, and which minerals were secondary, telling the story of later alteration through fluids carrying new elements into the rock or higher temperatures/pressures from burying the sediments. Primary detrital iron minerals implied that the Belt Basin waters were oxygenated, at least in shallow‐water environments, contrary to prior work but consistent with the rich fossil record of eukaryotes in the same strata. Key Points: A pyrrhotite‐siderite isograd was identified within the ~1.4‐Ga lower Belt group, Belt Supergroup in subgreenschist facies samplesDiagenetic overprints include recrystallization of iron sulfides, base metal sulfides, nanophase pyrrhotite, and iron‐bearing carbonatesEarly diagenetic pyrite and detrital iron oxides suggest the Belt Basin had oxic waters, consistent with cooccurring eukaryotic fossils [ABSTRACT FROM AUTHOR]

Abstract The paleomonsoonal variations and their impact on the weathering patterns in the source regions of sediments of the Andaman Sea were investigated from a 21 kyr sedimentary record using environmental magnetic, clay mineralogical and geochemical techniques. The sediment provenance of the study area determined from the geochemical discrimination diagrams and available ε Nd records indicates that the Western Andaman Sea receives a considerable contribution from the Indo-Burman ranges (IBR) and local sources compared to the central and eastern Andaman Sea. The results illustrate a strong Indian Summer Monsoon (ISM) during the late glacial (16–13 kyr), early (10.5–8.5 kyr) and middle Holocene (5–3.5 kyr) and a weak ISM during the Younger Dryas (12.9–11.7 kyr) and late Holocene (3.5–0 kyr) periods. The mineral magnetic grain size parameters (χ ARM /SIRM, SIRM/χ LF , χ ARM /χ LF) show finer grain sizes during the strong ISM periods indicating the increased chemical weathering while cold and dry periods are marked by an increase in magnetic grain size indicating the shift from chemical to physical weathering in the source regions. The results from our study are in agreement with the global and local records of paleoclimate and weathering and exhibit a close correlation with the solar insolation data suggesting the major role played by the solar forcing on the ISM variability. Highlights • A 21 kyr high resolution record of provenance, weathering and Indian Summer Monsoon (ISM) in the Indo-Burman ranges • Magnetic grain size tracks increased chemical weathering and ISM during the late glacial, early- and mid-Holocene. • Younger Dryas and late Holocene periods witnessed reduced ISM and increased physical weathering • Good coherency of this record with local and global records illustrates the role of solar forcing on the ISM variability. [ABSTRACT FROM AUTHOR]

Changes in the Earth's magnetic field can deeply modify the polar caps and auroral zones, which are the regions of most frequent precipitation of energetic particles. The present field is characterized by a dominant dipole plus weaker multipolar components. The field varies greatly in time, with the most drastic changes being polarity reversals that take place on average every ∼200 000 yr. During a polarity transition the field magnitude may diminish to about 10 per cent of its value prior to the reversal due to a decreasing dipolar component and by becoming mostly multipolar in nature. Polar caps depend on the geomagnetic field configuration so changes in their morphology are expected as a consequence of the variation and reversal of this field. We model polar caps' location by considering a superposition of the internal geomagnetic field and a uniform external field and then following the open field lines to the Earth's surface. Polar caps' location and shape for different magnetic field reversal scenarios are analysed in this work. Two polar caps near the present dipole axis intersection with the Earth's surface prevail for a dipole decrease to a certain extent, below which the southern hemisphere polar cap moves to mid-latitudes. An axial dipole collapse gives a pair of polar caps both at mid-latitudes of the southern hemisphere, while in a dipole rotation scenario the polar caps reside at the equator. If reversals occur due to an energy cascade from the dipole to higher degrees, more than two polar caps may appear. In our energy cascade scenario, four polar caps at various latitudes of both hemispheres prevail. These results indicate that during reversals auroral zones may reach mid- and low-latitude regions, and the atmosphere may become more vulnerable to the direct effect of energetic particle precipitation. This vulnerability is particularly striking at the southern hemisphere where reversed flux patches appear on the core–mantle boundary and weak intensity characterizes the present field at the Earth's surface. [ABSTRACT FROM AUTHOR]

Abstract The previous studies applied "wind intensity" model to explain the corresponding variations of magnetic susceptibility and particle size curves in Tienshan Mountain loess. Most of these studies focused on low altitude loess, due to their high deposit rate, and ignored the high-altitude loess. In this study, we investigated characteristics of lithological and pedogenic magnetic particles to systemically understand their paleoclimatic implications. The result suggested high mountain loess in Tienshan region exhibits that, not only lithologic magnetic particles, but also pedogenic present the variable contents. The magnetic susceptibility has a complex implication. In contrast, the fine-grained magnetite exhibits a close link with pedogenesis. Therefore, the relative parameters can be used to recover moisture variation. The evidences from particle size and their dependence of magnetic susceptibility suggested particle-size effect on lithological magnetic susceptibility is weak. The "wind intensity" model can be an important factor for variations of lithologic magnetic susceptibility of Tienshan Mountain loess rather than a dominant factor. It still needs more study to determine the implication of magnetic susceptibility of lithologic materials. [ABSTRACT FROM AUTHOR]

Abstract The vertical and horizontal contamination profile of the loess sediments located in the vicinity of the highway Novi Sad-Belgrade, with the intense frequency of vehicles, has been assessed. The heavy metal content (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) and hydrocarbon content were determined for the samples collected from two loess profiles in broad ranges of depth (0.15–4.50 m at 0.15 m intervals) and horizontally deeper in the sediment (0.01, 0.05 and 0.10 m). For all loess samples the contents of heavy metals were lower than the remediation intervention values. Hydrocarbon content in all analyzed sediment samples was below limit of quantification of 50 mg/kg. Magnetic susceptibility of the samples revealed the occurrence of one weak paleosol in one loess profile as well as the anthropogenic loess like deposits in the upper part of the second profile. The polynomial regression was successfully applied to estimate relationship between magnetic susceptibility of the loess and heavy metal content, total organic carbon and grain-size distribution. The developed second order equations are a responsive method with the calculated multiple R higher than 94%. The proposed statistical approach greatly simplifies the analysis of loess profile as a record of pollution, and it may serve to estimate the extremely high values of magnetic susceptibility influenced by small increase in heavy metal content, total organic carbon and grain size distribution. [ABSTRACT FROM AUTHOR]

In order to verify if the magnetic parameters can be indicators of soil contamination, the relationship between magnetic parameters and the concentration of heavy metals in soil samples from the Almendares-Vento basin was studied. Measurements of magnetic susceptibility, chemical determinations of heavy elements and remanent magnetization, were made. The concentration values in the samples of the heavy elements (Cr, Fe, Ni, Mn, Cu, Zn and Pb) were determined by mass spectrometry with inductively coupled plasma. Magnetic susceptibility yielded higher values towards the upper part of the soil, up to 20 cm deep, which can be attributed to the presence of magnetic material of anthropogenic origin on the soil surface, generated by productive processes at the facilities of the region. It is concluded that increases in the values of magnetic susceptibility are indicators of the increase in the concentration levels of heavy elements for soils of the basin as a consequence of human contamination. [ABSTRACT FROM AUTHOR]

Abstract Urban air quality is strongly affected by the surrounding local traffic and emission compounds such as particulate matter (PM) and heavy metals, which pose a serious health risk globally. These compounds are known to be traffic related, but fairly few studies have focused on point source emissions of traffic flow. In this study we applied magnetic biomonitoring using moss bags (Sphagnum papillosum) to study the point source emissions caused by stop-and-go traffic. Moss bags were placed alternately at traffic light crossings (n = 19) and midway areas between the crossings (n = 29) along four street transects and one separate traffic light crossing in the city of Turku, Finland. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. The PM was composed of fine-grained pseudo-single-domain (PSD) magnetite and the concentrations of χ, Cu, Mo and Sb significantly differed between traffic light crossing areas compared to midway areas. The elements Ba, Cu, Fe, Mo, Ni, Pb, Sb and Ti showed moderate to high levels of accumulation and correlated strongly with χ and saturation magnetisation (M S). Our results show that a high volume of stop-and-go traffic is a major source of harmful PM pollution especially along busy main roads. To improve urban air quality and public health we strongly advice the municipal administrations to pay more attention to urban planning and traffic management to reduce stop-and-go traffic and decrease the levels of urban PM pollution. Highlights • Magnetic biomonitoring is an effective and low-cost method to monitor air quality. • Stop-and-go traffic a major source for magnetic particles and heavy metals. • Pollution levels more elevated at traffic light crossings than in midway areas. • Urban planning and traffic management needed to reduce PM from stop-and-go traffic. [ABSTRACT FROM AUTHOR]

The abrupt, millennial-scale climatic fluctuations have been identified in a worldwide region. However, it lacks of such record in central Asia which is climatically characterized by arid and sensitive to climate change. Here, we present the results of magnetic analysis of a loess section in Tajikistan which reveals 22 millennial-scale climate oscillations and 5 Heinrich events during the last glacial-interglacial cycle. In particular, millennial-scale climate variations are strongly evidenced for the interval from 50 to 30 ka. The systemic investigation suggests the magnetic enhancement mechanism is same between Tajikistan loess and Chinese Loess Plateau (CLP) loess which are both due to increasing pedogenic fine-grained maghemite and magnetite. In turn, the magnetic results support the climatic variation presents an in-phase pattern between central Asia and Monsoon Asia during last glacial, with humidity increased during interstadials and decreased during stadials. The magnetic records reveal the humidity in central Asia is sensitive to millennial-scale climate oscillations during Last Glacial. [ABSTRACT FROM AUTHOR]

Ultrafine grains of magnetic minerals provide reliable recordings of both naturally occurring and anthropogenically generated particulate matter in polluted air; magnetic data can be used to understand biogenic iron-cycling in anaerobic environments, as well as pedogenesis and palaeoclimate studies of loess soils. The ultrafine fraction is produced under specific conditions and can be easily recognized by its superparamagnetic (SP) behaviour. Many proxies have been proposed to account for the SP contribution by measuring its susceptibility dependency with frequency (frequency effect) or the magnetization loss after removing an external inducing field. Here we introduce the Superparamagnetic Concentration and Dipole Moment (SPCDM) procedure for quantitative interpretation of SP magnetization. This procedure is well suited to SP carriers with a fast magnetization decay (<1 s), as would be expected for magnetic minerals with a grain size distribution lying below the blocking volume for stable, single-domain (SD) magnetization. SPCDM requires a dedicated experimental procedure to isolate the SP response from the paramagnetic and remnant effects, as observed in samples with mixed contributions. The proposed technique was tested using synthetic, nanoparticles of magnetite and then to characterize the magnetic properties of air particulate matter (PM) sampled at Jânio Quadros tunnel in São Paulo, Brazil. For nano-sized magnetite, SPCDM estimates for dipole moment are invariable with mass concentration and consistent with the published results; estimates for particle concentration are strongly correlated with true mass concentration (R 2= 0.96). For air PM, SPCDM estimates a particle size with a diameter of 7.7 ± 0.1 nm, a kind of ultrafine magnetic material not previously recognized in air pollutants. [ABSTRACT FROM AUTHOR]

The Holocene environmental evolution in coastal area, including deltas and estuaries, is vital to the Neolithic colonization in the eastern China. A 29-m long sediment core XL was obtained from the region between the Taihu Lake and Qiantang Estuary, and multiple analyses on the core sediments have been done to investigate the evolution history of the inner coastal zone of Hangzhou Bay during the Holocene. Six sedimentary facies are identified since the late Pleistocene, including the paleosol at the bottom, overlain by tidal-flat-channel complex (TFC), tidal-distributary-channel (TDC), inner estuarine basin (IEB), subtidal-to-intertidal-flat, and fluvial-plain facies. The TFC and TDC facies are dated to be formed before 8500 cal yr BP, featured by relatively coarse sediments, high magnetic properties and less abundant foraminifera, denoting the tide-influenced setting with large terrestrial inputs. The IEB facies characterized by the most abundant foraminifera fossils and the lowest sediment magnetic properties, is inferred to be deposited during the maximum flooding period between 8500 and 7900 cal yr BP. The branch estuary was then infilled by local sediments with a shallowing-upward subtidal-to-intertidal sequence during 7900-4300 cal yr BP. At last the fluvial plain system developed since no later than 4300 cal yr BP, favouring the rapid development of Neolithic cultures in the region. [ABSTRACT FROM AUTHOR]

The Iranian Plateau was once occupied by the Neotethys Sea, which connected with the Indian Ocean in the southeast and the proto-Mediterranean in the west during most of the Cenozoic era. However, the Neotethys Sea has undergone a stepwise retreat, and the Tethyan Seaway also closed in the Miocene driven by both Arabia-Eurasia collision and global eustatic sea-level drop. Changes in the land-sea distribution and uplift of the Zagros Mountain belt must have affected paleoclimatic changes in Iran. To date, a high-resolution paleoclimatic record is lacking for Iran. In this paper, we present new environmental magnetic and color parameter data for terrestrial sediments in the Qom back-arc basin, Central Iran from the middle to late Miocene (17–11.5 Ma). All of our parameters indicate an abrupt climatic change at ∼13 Ma. We suggest that the less reddish color and a shift in environmental magnetic parameters after ∼13 Ma implies weakened chemical weathering under a colder/drier climate. Enhanced aridification was mainly controlled by closure of the Tethyan Seaway and shrinkage of the Neotethys Sea after ∼13 Ma, which greatly reduced moisture transport to the downwind Central Iran by westerlies, whereas the rain shallow effect of the initially uplifted Zagros Mountain belt and reduced seawater evaporation related to lower sea-surface temperatures after the Mid-Miocene Climatic Transition only played minor roles. Therefore, our results provide a window to discuss relationships between plate tectonic movements, land/sea distribution, and climatic change in a tectonically active region during the late Cenozoic. • Mid-Miocene environmental magnetic records of Central Iran. • Paleoclimatic parameters indicate a remarkable climatic shift at ∼13 Ma. • Enhanced aridification in Central Iran since ∼13 Ma. • Closure of the Tethyan Seaway played a major role in the enhanced aridity. [ABSTRACT FROM AUTHOR]

The Cryogenian nonglacial epoch (CNE) spans from the termination of the Sturtian snowball Earth (ca. 659 Ma) to the initiation of the Marinoan snowball Earth (ca. 649.2 Ma). The carbonate sequences formed in low latitudes record paleoclimatic and paleoceanographic changes during the CNE. Three negative carbon isotope (δ13C) excursions, named Rasthof, Tayshir and Trezona, are present at the bottom, middle, and top of the carbonate sequences, bracketing two intervals with highly positive δ13C values. Uranium isotope (δ238U) data from Mongolia reveal ocean redox changes linked to δ13C variations during the CNE, marked by the development of anoxic deep ocean to extensive oxygenation and subsequent deoxygenation. However, the timing and duration of these paleoceanographic events and δ13C excursions have not been adequately investigated. Here, we report new environmental magnetic results of the higher paleo-latitudinal, siliciclastic-dominated Datangpo Formation (Fm) in South China that may help constrain the age and correlation of the CNE geochemical events. We identified four segments of the Datangpo Fm based on the magnetic susceptibility (MS) profile and other environmental magnetic parameters, which are, in ascending order, the ascent segment (Da), lower stable-segment (Db), transition segment (Dc), and upper stable-segment (Dd). These segments are dated by the astronomical time scale as 659–655.6 Ma (Da), 655.6–653.3 Ma (Db), 653.3–652.3 Ma (Dc), and 652.3–649.2 Ma (Dd). Environmental magnetism analyses show that the highest magnetite concentration but lowest fine-grained magnetite contents are present in "Da", followed by "Dd" and "Db". These results suggest a sea-level fall and a potential decrease in oxygenation after the deposition of the transition segment (Dc), implying that a cooling climate started ∼4 Myr before the Nantuo glaciation (Marinoan snowball Earth). Ocean redox variations revealed by environmental magnetism in the Datangpo Fm are consistent with those reported from the low-latitudinal carbonate sequences. "Da" likely corresponds to the Rasthof δ13C excursion and "Dc" corresponds to the Tayshir δ 13C excursion; whereas "Db" and "Dd" probably correspond to the two intervals with positive δ 13C values. • Four segments of the Cryogenian nonglaciatial epoch in South China are identified and the time of each segment is constrained. • Environmental magnetism analyses show a climate cooling ∼4 Myr before the Nantuo glaciation (or Marinoan snowball Earth). • Siliciclastic depositions in South China are linked to carbonate depositions in low-latitude continents. [ABSTRACT FROM AUTHOR]

Reconstruction of oceanic redox conditions across the Palaeocene-Eocene Thermal Maximum (PETM, ∼55.93 Ma) provides crucial information on potential PETM triggers and biotic turnover. Widespread oceanic deoxygenation has been documented to occur during the PETM, but the exact timing and regional variability is poorly understood. Here we document well-preserved magnetofossils with large variations in magnetic properties and crystal morphologies at International Ocean Discovery Program (IODP) Sites U1409 (∼2913 m palaeodepth) and U1403 (∼4374 m palaeodepth) across the PETM, and use these proxies to trace Northwest Atlantic palaeoredox changes. Our records suggest that deep-sea oxygenation at these sites decreased gradually, starting several hundred thousand years before the PETM, reaching a minimum ∼50 ky before the PETM, followed by a broad increase. This pattern in palaeoredox conditions likely reflects changes in deep-sea circulation and ocean temperature. We thus provide evidence for the existence of precursors to PETM warming, and suggest that ocean circulation changes might have played an important role in triggering carbon release to the ocean-atmosphere system at the PETM onset. • Magnetofossils are variable across the PETM at different North Atlantic palaeodepth. • Magnetofossil components with morphologies are used to trace palaeoredox conditions. • Deep-sea deoxygenation started several hundred thousand years before the PETM onset. • Atlantic deep-sea circulation played a key role in climatic changes before the PETM. [ABSTRACT FROM AUTHOR]

The Great Barrier Reef (GBR) located along the northeastern margin of Australia is the largest coral reef system in the world. Modern climatic alterations are quickly changing the GBR ecosystem. To understand the implications of these changes it is important to reconstruct the geological history of GBR. Here we use geochemical and magnetic proxies to evaluate past climatic fluctuations and their consequences on sediment deposition along the GBR margin. IODP Expedition 325 – Hole M0058A, drilled on the uppermost slope at ca. 170 m water depth, reveals the depositional history of the GBR margin during the interval of MIS 7 to 5 and MIS 1. Magnetic and geochemical variations along the core section reveal detailed information on sediment accumulation and on the variations in terrigenous input in relation to sea-level fluctuations and climate change. Sea-level variations influenced margin deposition between MIS 7 and 6 impacting shoreline progradation/retrogradation and siliciclastic redistribution, resulting in a mixture of finer to coarser magnetic assemblages with no significant changes in terrigenous input. At the end of MIS 6 a decline in the deposition of carbonate sediments concomitant with the deposition of fine-grained magnetite-rich terrigenous sediments suggests an intensification of the monsoon in response to global warming trends. Arid periods over NE Australia were established after the glacial/interglacial transition (the MIS 6-5e) and at the middle Holocene (after the MIS 2–1 transition at ca. 7 ka), which favored dust deposition over the region. Enhanced dust fertilization subsequently promoted primary productivity at these intervals resulting in the presence of biogenic magnetite at Hole M0058A produced by magnetotactic bacteria. • IODP Expedition 325 - Hole M0058A data reveal changing sedimentation accumulation in response to past climate changes. • A mixture of magnetic assemblages resulted from the redistribution of siliciclastic sediments. • Fine-grained magnetite indicates surface runoff, while biogenic magnetite is related to dust input. [ABSTRACT FROM AUTHOR]

A test site located along a 12-lane motorway east of Montpellier, France, is used to evaluate the potential of biomagnetic monitoring on traffic-related particulate matter (PM) to parametrize a computational fluid dynamics (CFD) simulation of the local airflow. Two configurations were established on the site with three vegetated flat-top earth berms of a basic design, and a fourth one was located windward to the traffic roofed with a 4-m-high precast concrete wall. As a first step, PM deposition simultaneously on plant leaves, on low-cost passive artificial filters, and on soils was estimated from proxies supplied by magnetic and X-ray fluorescence measurements on both sides of the motorway. These latter revealed that traffic-related pollutants are present on soils samples highlighted with a clear fingerprint of combustion residues, and wears of breaks, vehicles, and highway equipment. Maximum PM accumulations were detected in the lee of the berm–wall combination, while no significant deposition was observed on both sides of the flat-top earth berms. These results are in line with measurements from PM µ-sensors operated by the regional state-approved air quality agency. Finally, we compared the experimental measurements with the outcomes of a computational fluid dynamics (CFD) modeling based on the Reynolds-Averaged Navier–Stokes (RANS) equations that consider the traffic-induced momentum and turbulence. The CFD modeling matches the experimental results by predicting a recirculated flow in the near wake of the berm–wall combination that enhances the PM concentration, whereas the flat-top berm geometry does not alter the pollutants’ transport and indeed contributes to their atmospheric dispersion.

The main objective of this research was the determination of the geochemical and mineralogical properties of particulate matter: TSP (total suspended particles) and, especially PM1 (particles with aerodynamic diameter not greater than 1 µm) suspended in the air of a selected urban area in southern Poland. Identification of the emission sources of metals and metalloids bound in TSP and PM1 as well as the assessment of potential risk of urban ambient air to human health using hazard indices was an additional aim of this investigation. The daily TSP and PM1 quartz fiber filters collected during heating season were subjected to mass magnetic susceptibility (χ) measurements, SEM (Scanning Electron Microscopy) observations and geochemical analyses. Obtained results revealed that the concentration of TSP and PM1 well correlated with their mass-specific magnetic susceptibility. The good relationship between the PM concentration and χ suggests that magnetic susceptibility measurements can be a good proxy of low-level atmospheric dust pollution. The rank order of potentially toxic elements (PTE) based on average concentration was Ba > Zn > Al > Fe > Pb > Mn > Ti > Cu > Cr > Ni >As > Cd > V > Tl, both for TSP and PM1. PM1/TSP ratios for PTE concentrations and χ were around or slightly above unity, which indicated that PM1 was the main carrier of PTE (with the exception of cadmium, copper and lead) and technogenic magnetic particles. The non-carcinogenic and carcinogenic risks were confirmed by very high values of human health indices.

We used a novel approach of applying magnetic analyses to investigate the material released from the receding glacier Werenskioldbreen on Spitsbergen, Svalbard, Arctic Norway. Surface sediments were taken from the bay Nottinghambukta and the Werenskioldbreen foreland, along two main proglacial streams. Magnetic analyses, namely the low-field mass magnetic susceptibility, anhysteretic susceptibility mass normalized and hysteresis parameters, served to determine magnetic properties and identify the magnetic composition of the study material. We selected two distinct types of sediments. The first group, consisting of magnetite and pyrrhotite, has more single-domain grains in comparison to the second one, containing only magnetite. In the second group, multi-domain particles dominate. Deposits from the north stream, glacier river and an area close to the estuary of Nottinghambukta include magnetite and pyrrhotite. Magnetite was found in the south stream and in the outside part of the bay. Magnetic composition reflects different source rocks of sediments. This study demonstrates the utility of the magnetic method in analysing the current state of glacier environments.

Abstract The loess-palaeosol record on the island of Susak in Croatia is a unique archive of Late Glacial climate changes in the Adriatic region, possibly even in the wider area. On Susak up to 90 m of thick Quaternary sediments were deposited, and are accessible for detailed palaeoclimate reconstructions. In this paper, the results of a high-resolution grain-size and rock magnetic investigation on the Last Glacial (Upper Pleniglacial) Sand Pit section from Susak are presented. In spite of its significant thickness, the Sand Pit section does not represent a continuous record; it is a result of a very dynamic environment. There, the deposition of dust and formation of loess has been interrupted by pedogenesis, periods of increased sand accumulation, erosion due to slope wash and water activity, redeposition and wildfires, and all in the time period of about 10.000 years of the Upper Pleniglacial, as seen from the IRSL dating results. The grain-size data clearly show a shift towards coarser grain sizes which differs from typical loess regions. Such predominance of the coarser-grained over the fine-grained fraction, very likely resulted from the predominance of deposition over pedogenesis, increased wind activity and proximal source of material. The rock magnetic signal preserved in the sediment also differs compared to loess-palaeosol records from other regions. The susceptibility values are several times higher than in the records from the Pannonian basin and from typical Eurasian loess. Both the increased susceptibility values and the grain-size are very likely the result of a significant proximal material input from the Po River plain. [ABSTRACT FROM AUTHOR]

The aim of this study was to establish a method for predicting heavy metal concentrations in PM 2.5 (particulate matter with a diameter of less than 2.5 μm) using support vector machine (SVM) models combined with magnetic properties of leaves. In this study, PM 2.5 samples and the leaves of three common evergreen tree species were collected simultaneously during four different seasons in Nanjing, China. A SVM algorithm was used to establish models for the prediction of airborne heavy metal concentrations based on leaf magnetic properties, with or without meteorological factors and pollutant concentrations as input variables. Results showed that the annual average PM 2.5 concentration was 58.47 μg/m 3 . PM 2.5 concentrations, leaf magnetic properties, and nearly all airborne heavy metals had higher concentrations in winter than in spring, summer, or fall. Ferrimagnetic minerals preponderant in dust-loaded leaves were sampled from the three tree species. Models using magnetic properties of leaves from Ligustrum lucidum Ait and Osmanthus fragrans Lour yielded better prediction effects than those based on the leaves of Cedar deodara G. Don , showing relatively higher correlation coefficient (R) values and lower errors in both training and test stages. Fe and Pb concentrations were well-simulated by the prediction models, with R values > 0.7 in both training and test stages. By contrast, the concentrations of V, Co, Sb, Tl, and Zn were relatively poor-simulated, with most R values < 0.7 in both training and test stages. Predictions for the main urban areas of Nanjing showed that the highest heavy metal concentrations occurred near industrial and traffic pollution sources. Our results provide a cost-effective approach for the prediction of airborne heavy metal concentrations based on the biomagnetic monitoring of tree leaves. [ABSTRACT FROM AUTHOR]

Environmental magnetic applications to topsoil have proved useful for investigating roadside pollution. However, such magnetic monitoring has been avoided in volcanic regions due to the high magnetic content in volcanic ash. Environmental magnetic studies are reported for the volcanically active Mt. Hakusan National Park in Japan. In‐field magnetic susceptibility measurements along the park's major road show higher magnetic susceptibilities in topsoils within 1.5 m from the roadside. However, laboratory mass susceptibility measurements fail to show a similar susceptibility trend to the field measurements. Based on rock magnetic analyses, the major magnetic mineral is pseudosingle‐ to multidomain (MD) magnetite that is both increased in abundance in MD and oxidized magnetite near the roadside, indicating that passing vehicles are evidently the main pollutant source. Therefore, even in an active volcanic region where magnetic susceptibility may not be an efficient tool, detailed magnetic measurements can provide the basis for the discrimination of roadside pollution. [ABSTRACT FROM AUTHOR]

Environmental magnetism, and the magnetic leaf signal in particular, is amply investigated and applied as proxy for atmospheric particulate matter pollution. In this study, we investigated the magnetic signal of annual segments of tree branches, and the composition of particles deposited hereon. Branches are, contrary to leaves of deciduous trees, available during leaf-off seasons and exposed to air pollution year-round. We examined the intra- and inter-tree variation in saturation isothermal remanent magnetization (SIRM) of branch internodes of London plane ( Platanus x acerifolia Willd.) trees in an urban environment. The branch SIRM, normalized by surface area, ranged from 18 to 650 × 10 −6 A; the median amounted to 106 × 10 −6 A. Most of the branch magnetic signal was attributed to the epidermis or bark, and the presence of metal-containing particles on the branch surfaces was confirmed by SEM-EDX. The location of the trees and the height, the depth in the crown and the age of the branches significantly influenced the branch SIRM. The median branch SIRM was up to 135% higher near a busy ring road than in quiet environments (city park and quiet street canyon), and was linked to the presence of Fe-rich particles with co-occurrence of trace metals such as Cr, Cu, Zn and Mn on the branch surface. Within the tree crowns, the branch SIRM generally decreased with increasing height, and was 22% higher in the interior than at the periphery of the crowns. Within the branches, the SIRM increased with each year of exposure, but did not relate to year-to-year variation in particle concentrations due to branch surface changes (epidermis shedding). Our results provide indications that branches can be a valuable alternative for biomagnetic monitoring of particulate pollution, but intra-tree variability in branch SIRM can be substantial due to the branch's location in the tree and branch age. [ABSTRACT FROM AUTHOR]

Proxy records from radial sand ridge fields are essential for understanding sedimentary environmental changes forced by climate-driven coast and sea level variations that affect large river inlets. We conducted a systematic environmental magnetic study on sediments from a radial sand ridge field in the South Yellow Sea, eastern China. From 41.6 to 0 m, the sediments of core YZ07 derive from river mouth, littoral and modern tidal flat environments. Magnetic measurements indicate that magnetite and hematite dominate the studied magnetic mineral assemblages. Magnetic mineral contents are highest in the river mouth environment and lowest in the modern tidal flat environment. The magnetic minerals in the core YZ07 sediments can be attributed primarily to detrital inputs rather than biogenic sources. The highest χ and SIRM values and lowest χ ARM /SIRM and χ ARM /χ values reflect relatively warm and humid climate conditions respectively during the period ∼7000 to 2900 a B.P. (41.6–24.73 m). Compared with the period ∼7000 to 2900 a B.P. (41.6–24.73 m), the period between ∼2900 and 870 a B.P. (24.73–5.14 m) is characterized by lower χ, χ ARM and SIRM values and higher χ ARM /SIRM and χ ARM /χ values, which indicate cool and dry climatic conditions. Our results reconfirm known regional climatic events that demonstrate Holocene climatic instability. Gradual decreases in χ and SIRM and increases in χ ARM /SIRM, χ ARM /χ and χ fd characterize the sediments after 870 a B.P. (5.14–0 m). As indicated in previous studies, these changes were influenced by diversion of the Yellow River. Additionally, spectral analysis of the χ and χ ARM /SIRM records reveals rapid climatic fluctuations on millennial and centennial scales that coincide with those recorded in marine sedimentary records from adjacent regional seas. These results are important for investigations into the interactions between regional systems and global change in monsoonal climatic regions, thus providing an example of the evolution of a large scale geomorphic feature resulting from river-sea interaction. [ABSTRACT FROM AUTHOR]

Hysteresis, thermomagnetic and low-temperature magnetic experiments on particle-size fractioned samples from the Chinese Loess Plateau (CLP) can be used to better characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/palaeosols. However, a systematic study of the grain-size-dependent magnetic mineralogy of the Central Asian loess deposits has not been undertaken. In this paper, four size fractions of 17 loess and palaeosol samples from Central Asia and the CLP were subjected to aforementioned rock magnetic measurements. Our findings are as follows: (1) In Central Asia, the fractionated samples from loess and palaeosol couplets exhibit no obvious differences in their magnetic mineralogy due to weak pedogenesis. (2) Thermomagnetic analyses suggest that the content of maghemite in the clay fraction of palaeosols from the CLP is one or two orders of magnitude larger than that of the loess samples from the CLP and Central Asia. This result does not support the view that maghemite in the loess/palaeosol sequences of the CLP originated mainly from eolian sources. (3) Both hysteresis and low-temperature magnetic experiments demonstrate that detrital ferrimagnetic grains are mostly enriched in the 20–75 μm fraction of loess/palaeosols from Central Asia and the CLP. The relative paucity of coarser magnetic grains in the >75 μm fractions indicates that a positive correlation does not always exist between the magnetic concentration parameters and the sedimentological particle size in Chinese loess deposits. (4) The regional variations in the magnetic properties of the 20–75 μm fraction suggest that the supply of clastic sediments is the main control on the magnetic properties of loess deposits in Central Asia. [ABSTRACT FROM AUTHOR]

Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dating back to 9.4 cal ka BP were carried out for discriminating and correlating tephras and laminated sediments in four different cores. Six tephra units (T0, T1, T2, T3, T4 and T5) with distinct magnetic properties were identified in the cores. The tephra units are characterized by ferrimagnetic material, with a grain size in the pseudo single domain (PSD) range. There is no significant correlation between magnetic susceptibility peaks of the different tephra units except for the tephra T1 and T2. On the contrary ARM profiles show significant correlations as remanent magnetization indicators. The tephra units T1 and T2, have a higher magnetic susceptibility and a higher intensity of remanent magnetization, and finer grain size than the other tephra units. The results suggest that there is a clear difference between the magnetic properties of the different tephra units and the lake sediments. Our findings show that also differential deposition of volcanic material including magnetic mineral occurs during the transport with distance from the volcanic source. [ABSTRACT FROM AUTHOR]

This study investigates the magnetic mineralogy of palaeosol S5 from Xifeng (XF), Linyou (LY) and Baoji (BJ) sections with increasing annual precipitation from north to the south on the Chinese Loess Plateau. Palaeosol S5 samples from these three localities are further prepared as magnetic extracts and separation residues. Low-temperature magnetic measurements including field cooled and zero field cooled (FC/ZFC) remanence, in-phase magnetic susceptibility, thermal remanent magnetization and room temperature saturation isothermal remanence magnetization (RTSlRM), with X-ray diffraction measurements are carried out for all magnetic extracts and separation residues samples. The asymmetric rounded 'hump' in cooling curves on RTSlRM and the 'tilted' Verwey transition on ZFC/FC curves suggest that partially oxidized magnetite is the dominant magnetic contributor, not pure maghemite or magnetite. Furthermore, The Verwey transitions on cooling curves slightly decrease and the increased slope of 'tilted' Verwey transition on ZFC remanence curves show that the degree of oxidation of magnetite between localities increases in the order XF-LY-BJ. Hard isothermal remanent magnetization, X-ray diffraction data and the difference of magnetization in warming curves of RTSlRM suggest that both hematite concentration in magnetic extracts and goethite concentration in separation residues increase from XF to BJ. Frequency-dependent susceptibility and ZFC/FC curves show that BJS5 layer formed under high palaeoprecipitation has less superparamagnetic (SP) but more single domain to pseudo-single domain particles, because SP maghemite was dissolved and transformed into goethite by temporary waterlogging. The increase in hematite concentration is interpreted as due to SP maghemite oxidation or original goethite dehydration within dry soil environment. Therefore, transformation of maghemite to goethite in waterlogged phases of the S5 palaeosol led to the loss of magnetization. [ABSTRACT FROM AUTHOR]

Abstract: Eolian dust is a major terrigenous component in North Pacific Ocean pelagic sediments and is an important recorder of Asian terrestrial environmental evolution and Northern Hemisphere atmospheric circulation. In order to extract and quantify wind‐borne mineral signals and develop a reliable eolian dust proxy for pelagic sediments, we investigated sediments from Ocean Drilling Program Hole 885A, North Pacific Ocean, by integrating results from environmental magnetism, transmission electron microscopy, and diffuse reflectance spectroscopy (DRS). Our results indicate that ferrimagnetic and antiferromagnetic minerals coexist in the sediments. The former includes biogenic magnetite, nano‐sized single domain (titano) magnetite inclusions embedded in silicate hosts, submicron vortex state magnetite, and ultrafine superparamagnetic maghemite. The latter includes hematite and goethite. Our results indicate that magnetic properties can be used to determine an overall trend of increased eolian dust inputs, with additional significant influence from biogenic and volcanogenic components. In contrast, a newly proposed parameter RelHm+Gt (combined hematite and goethite concentration) obtained from DRS measurements extracts precisely the eolian signal and precludes other components. Our DRS results indicate that hematite/goethite and siliceous fractions deposited at Hole 885A were jointly delivered to the North Pacific Ocean from Asian dust sources. Therefore, we suggest that RelHm+Gt is a reliable eolian dust proxy for pelagic sediments in this region. [ABSTRACT FROM AUTHOR]

Low-field mass-specific magnetic susceptibility (MS) measurements using multifrequency alternating fields are commonly used to evaluate concentration of ferrimagnetic particles in the transition of superparamagnetic (SP) to stable single domain (SSD). In classical palaeomagnetic analyses, this measurement serves as a preliminary assessment of rock samples providing rapid, non-destructive, economical and easy information of magnetic properties. The SP--SSD transition is relevant in environmental studies because it has been associated with several geological and biogeochemical processes affecting magnetic mineralogy. MS is a complex function of mineral-type and grain-size distribution, as well as measuring parameters such as external field magnitude and frequency. In this work, we propose a new technique to obtain quantitative information on grain-size variations of magnetic particles in the SP--SSD transition by inverting frequency-dependent susceptibility. We introduce a descriptive parameter named as 'limiting frequency effect' that provides an accurate estimation of MS loss with frequency. Numerical simulations show the methodology capability in providing data fitting and model parameters in many practical situations. Real-data applications with magnetite nanoparticles and core samples from sediments of Poggio le Guaine section of Umbria--Marche Basin (Italy) provide additional information not clearly recognized when interpreting cruder MS data. Caution is needed when interpreting frequency dependence in terms of single relaxation processes, which are not universally applicable and depend upon the nature of magnetic mineral in the material. Nevertheless, the proposed technique is a promising tool for SP--SSD content analyses. [ABSTRACT FROM AUTHOR]

Pre-Quaternary terrestrial climate variability is less well understood than that during the Quaternary. The continuous eolian Red Clay sequence underlying the well-known Quaternary loess-paleosol sequence on the Chinese Loess Plateau (CLP) provides an opportunity to study pre-Quaternary terrestrial climate variability in East Asia. Here, we present new mineral magnetic records for a recently found Red Clay succession from Shilou area on the eastern CLP, and demonstrate a marked East Asian climate shift across the Miocene-Pliocene boundary (MPB). Pedogenic fine-grained magnetite populations, ranging from superparamagnetic (SP)/single domain (SD) up to small pseudo-single domain (PSD) sizes (i.e., from <30 nm up to ~1000 nm), dominate the magnetic properties. Importantly, our mineral magnetic results indicate that both pedogenic formation of SP grains and transformation of SP grains to SD and small PSD grains accelerated across the MPB in the Shilou Red Clay, which are indicative of enhanced pedogenesis. We relate this enhanced pedogenesis to increased soil moisture availability on the CLP, associated with stronger Asian Summer Monsoon precipitation during an overall period of global cooling. Our study thus provides new insights into the Miocene-Pliocene climate transition in East Asia. [ABSTRACT FROM AUTHOR]

Eastern Canadian margin sediments bear testimony to several catastrophic deglacial meltwater discharges from the retreating Laurentide Ice Sheet. The reddish-brown plumite layers deposited on the levees of the Laurentian Fan valleys have been recognized as indications of multiple outburst floods between Heinrich events 2 and 1. Five event layers have been consistently recorded in three new gravity cores retrieved on the SW Grand Banks slope and comply with the previously published Laurentian Fan core MD95-2029. The apparently huge extent of these outburst plumes around the Laurentian Fan as well as their causes and consequences are investigated in this study using physical properties, rock magnetic and grain-size analyses, together with seismoacoustic profiling. We provide the first detailed 14 C ages of the outburst event sequence and discuss their recurrence intervals in the context of regional ice retreat. Compared to the hemipelagic interlayers, event layers have overall uniform and systematic changes of rock-magnetic properties. Hematite contents increase over time and proximally while magnetite grain sizes fine upwards and spatially away from the fan. Based on the sediment composition and load, we argue that these plumites were formed by recurrent erosion of glacial mud deposits in the Laurentian Channel by meltwater outbursts. Three alternative glaciological scenarios are evaluated: in each case, the provenance of the transported sediment is not an indicator of the precise source of the meltwater. [ABSTRACT FROM AUTHOR]

A detailed environmental magnetic investigation has been performed on a sub-alpine sedimentary succession deposited over the past 15,400 years in Daping Swamp in the western Nanling Mountains of South China. Magnetic parameters reveal that fine grains of pseudo-single domain (PSD) magnetite or titanomagnetite are the dominant magnetic minerals in the lake sediments and surface soils collected from the catchment, which suggests that magnetic minerals in lake sediments mainly originated from surface soil erosion of the catchment. Variation of surface runoff caused by rainfall is interpreted as the main process for transportation of weathered soils into the lake. In the Last Deglacial period (LGP, 15,400–11,500 cal a BP), the influx of magnetic minerals of detrital material may have been significantly affected by the severe dry and cold conditions of the Last Glacial Maximum. Stabilised conditions of the catchment associated with increased vegetation coverage (e.g., 8000–4500 and 2500–1000 cal a BP) limited the input of magnetic minerals. Intensive soil erosion caused by increased human activity may have given rise to abnormal increases in multiple magnetic parameters after 1000 cal a BP. Because changes in runoff and vegetation coverage are closely related to Asian summer monsoon (ASM) intensity, the sedimentary magnetism of Daping Swamp provides another source of information to investigate the evolution of the ASM. [ABSTRACT FROM AUTHOR]

Sediments from continental shelves are sensitive to changes in both oceanic and terrestrial conditions, and, therefore, magnetic minerals in such sediments are affected strongly by depositional and diagenetic processes. Here, we investigated systematically an N-S transect of three sediment cores from the central South Yellow Sea (SYS) muddy area. Magnetic data indicate the presence of a horizontally distributed thick greigite-bearing layer. From an age model based on published magnetostratigraphy, accelerator mass spectrometry 14C dating ages, sedimentary characteristics and foraminiferal analysis, this layer was deposited within marine isotope stages (MIS) 17-13, following an enhanced sulphidic period over MIS 21-19 when the YS Warm Current and the associated YS Cold Water Mass were strong and where underlying sediments have higher total organic carbon, total sulphur and trace element molybdenum contents. Trace element cadmium enrichment in the greigite-bearing layers is documented for the first time, which indicates that weakly sulphidic (i.e. with trace levels of free H2S) conditions existed before greigite formed in a sulphidic environment during early diagenesis. It also indicates that subsequent conditions free of oxygen and H2S after greigite formation are more favourable for its preservation. We propose that organic matter supply was controlled over an extended period by moderate primary productivity. The combined effects of palaeoclimate and local tectonic subsidence were crucial for the formation and preservation of the identified greigite. In brief, our study improves understanding of the formation and preservation mechanisms of greigite in continental shelf sediments and reveals mid-Pleistocene palaeoenvironmental changes in the SYS. [ABSTRACT FROM AUTHOR]

The soils in the Yellow River Delta (YRD) were formed through the deposition of the Yellow River sediments under complicated hydrodynamic conditions, resulting in large variability in soil properties. In this study, environmental magnetic analyses were conducted on four typical soil profiles and one high resolution soil profile with distinct soil layers to examine the soil formation process and to track the environmental changes. The results showed that the red clay layer (RCL) in the YRD soil profiles had unique magnetic properties, which could be clearly separated from the yellow silt layer (YSL) at frequency dependent susceptibility (χ fd %) > 6%, susceptibility of anhysteretic remanent magnetization (χ ARM ) > 250 × 10 − 8 m 3 kg − 1 , χ ARM /magnetic susceptibility (χ lf ) > 5, χ ARM /saturated isothermal remanent magnetization (SIRM) > 45 × 10 − 5 m A − 1 and SIRM/χ lf < 12 × 10 3 A m − 1 . The magnetic enhancement of the RCL could be attributed to the presence of fine superparamagnetic (SP)/single domain (SD) ferrimagentic grains sourcing from hydrodynamic sorting of old sediments (e.g., paleosol in the Chinese Loess Plateau). It was hard to discriminate the RCL and YSL in the < 2 μm fraction by magnetic bi-plots, suggesting that the abundance of clays with higher contents of secondary ferrimagnetic minerals contributed significantly to the magnetic variability of different soil layers in the YRD. Three units were identified in a high resolution soil profile based on the changes of magnetic curves, including a steady deposition process in the upper unit, a strong hydrodynamic process with varied provenance in the middle unit and a heterogeneous deposition process in the lower unit with the RCL. The three units were closely linked to the variation of nutrients (carbon and nitrogen) and metals (chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), titanium (Ti) and zirconium (Zr)) in the soil profile, indicating the influence of provenance and sorting during sediment transportation and deposition. The magnetic method is sensitive to characterize soil formation and environmental changes in the coastal zone. [ABSTRACT FROM AUTHOR]

The presence or absence, degree and variation of heavy metal contamination in New Zealand soils is a matter of ongoing debate as it affects soil quality, agriculture and human health. In many instances, however, the soil heavy metal concentration data do not exist to answer these questions and the debate is ongoing. To address this, magnetic susceptibility (a common proxy for heavy metal contamination) values were measured in topsoil (0-30 cm) and subsoil (50-70 cm) at grid sites spaced at 8 km intervals across ca. 20 000 km² of southern New Zealand. Samples were measured for both mass- and volume-specific magnetic susceptibility, with results being strongly, positively correlated. Three different methods of determining anomalies were applied to the data including the topsoil-subsoil difference method, Tukey boxplot method and geoaccumulation index method, with each method filtering out progressively more anomalies. Additional soil magnetic (hysteresis, isothermal remanence and thermomagnetic) measurements were made on a select subset of samples from anomalous sites. Magnetite is the dominant remanence carrying mineral, and magnetic susceptibility is governed by that minerals concentration in soils, rather than mineral type. All except two anomalous sites have a dominant geogenic source (cf. anthropogenic). By proxy, heavy metal contamination in southern New Zealand soils is minimal, making them relatively pristine. The provenance of the magnetic minerals in the anomalous sites can be traced back to likely sources in outcrops of igneous rocks within the same catchment, terrane or rock type: a distance of <100 km but frequently <1 km. Soil provenance is a key step when mapping element or isotopic distribution, vectoring to mineralization or studying soil for agricultural suitability, water quality or environmental regulation. Measuring soil magnetic susceptibility is a useful, quick and inexpensive tool that usefully supplements soil geochemical data. [ABSTRACT FROM AUTHOR]

A detailed magnetic analysis has been done on sedimentary core of the International Ocean Discovery Program (IODP) Site U1433A during Leg 349 in the South China Sea (SCS). Results show that dominant carriers of the natural remanent magnetization are greigite and (titano) magnetite. The major shift in both declination and inclination at ~ 185 mbsf is assigned to the Matuyama-Brunhes reversal boundary (~ 0.773 Ma). Constrained by biostratigraphic ages, variations in magnetic parameters of the core can be well correlated to the marine oxygen isotope record at glacial/interglacial cycles. Low values of concentration-dependent magnetic parameters correspond to the interglacials, and vice versa. During the interglacial periods, the dominant magnetic minerals are detrital (titano) magnetite and have relatively coarser grain sizes, while fine-grained greigites dominate the glacial periods. This indicates that during the glacials, greigite prevails at the anoxic condition with amount of terrigenous iron oxide caused by the disconnection between the SCS and the Indian Ocean and the exposure of shelf, but digenesis is suppressed at the opposite environment by the high sea level (interglacials). Thus, the preservation/sulfide process of (titano) magnetite is intimately related to the transformation of sea level changes with the monsoon-related rainfall caused by the glacial/interglacial variation. [ABSTRACT FROM AUTHOR]

Abstract: Recent investigations have discovered an unexpected abundance of magnetofossils in oxic pelagic red clays. These have potential to serve as paleoenvironmental tracers in otherwise nonfossiliferous sediments. Here, we report on variations in the abundance and morphology of magnetofossils in red clay from the western North Pacific. Magnetic measurements revealed that magnetofossils dominate the magnetic mineral assemblage of the sediments. An endmember analysis of isothermal remanent magnetization acquisition curves, supplemented by an analysis of S ratios, indicates that the magnetic assemblage can be unmixed into three endmembers, two corresponding to magnetofossils and one to terrigenous magnetic minerals. Direct counting of magnetofossil morphologies under a transmission electron microscope shows that the two magnetofossil endmembers differentiate equant magnetofossils and bullet‐shaped magnetofossils, respectively. The stratigraphic variation of the endmember contributions revealed that the equant magnetofossils are dominant for the most part, while an interval at around 7 m in core depth shows higher abundance of the bullet‐shaped magnetofossils. This may reflect enhanced organic carbon flux to the sediments. The organic carbon content is low throughout the sediments, and it does not show any change corresponding to the increase of bullet‐shaped magnetofossils, pointing at extensive remineralization of the organic carbon. On the basis of lithostratigraphic correlation to nearby drilling sites, we tentatively estimate the age of the bullet‐shaped magnetofossil increase as sometime between ∼75 and 25 Ma. These results suggest that environmental information can be obtained from magnetofossils in pelagic red clay. [ABSTRACT FROM AUTHOR]

The use of mineral magnetic techniques as pollution proxy for road deposited sediment was explored using various statistical approaches. Standard techniques were adopted for measurement of mineral magnetic and geochemical parameters. The analyses of magnetic parameters revealed that the samples were dominated by ferrimagnetic minerals and multidomain grains. This implied that the magnetic fractions in the samples might be of anthropogenic origin. Results also indicate that the samples were dominated by low coercive, magnetically soft minerals. Thermomagnetic curves confirmed magnetite as the remanence bearing magnetic mineral having a Curie point temperature of ~580 °C. The strong association observed between magnetic susceptibility, susceptibility of anhysteric remanent magnetization and saturation isothermal remanent magnetization and aluminum, titanium, manganese, iron, chromium and lead demonstrated that these metals occurred as ferrimagnetic particles of technogenic origin resulting from vehicular sources. Assessment of pollution status of the road deposited sediment identified silicon and lead as the priority pollutants of concern. Generally, pollution load index was <1 (mean, 0.66 ± 0.14), indicating that the samples were not polluted in the overall, but the metals were in the buildup stage requiring constant monitoring. The sources of pollutants from principal component and cluster analyses identified the sources of pollution to be mainly from vehicular emissions such as brake linings, exhaust materials, tire wear, corroded metal parts, abrasion of lubricating oil and road construction materials. This study found that mineral magnetic techniques offer great potential as pollution proxy for soil pollution studies. [ABSTRACT FROM AUTHOR]

The Miocene is a key transitional period for the Asian monsoon evolution and establishment of modern-like geomorphic landscapes in the northern Tibetan Plateau. Elucidating the Miocene paleoenvironmental changes and their relationships with climate and tectonics are significant in understanding future hydrological changes in the northern Tibet under a warming climate. In this study, detailed lithological and rock magnetic investigations were conducted on a Miocene fluvial-lacustrine sediment sequence from the Linxia Basin in Northeast Tibet, to understand the paleoenvironmental and palaeohydrological response to the tectonics and global climatic change, especially to the effects of the Middle Miocene Climatic optimum (MMCO). The results demonstrated that strong waterlogged reducing environments during MMCO precluded the occurrences of pedogenesis in the Linxia Basin owing to highly humid climates. As the precipitation decreased significantly before and after MMCO, pedogenesis occurred increasingly owing to temperate and well-drained conditions. A synthesis of the lithological and magnetic variations in Miocene fluvial-lacustrine sediments further indicated that climate humidification prevailed in most areas of the northern Tibetan Plateau during MMCO. These observations demonstrate that global climate change, rather than the tectonic uplift, significantly influenced the Mid-Miocene paleoenvironmental evolution in northern Tibet. • Rock magnetic analysis of Miocene sediments in the Linxia Basin was performed. • Mid-Miocen climate humidification prevailed in the northern Tibetan Plateau. • Global climate change drove the paleoenvironmental evolution in the northern Tibet. [ABSTRACT FROM AUTHOR]

The main body of Hebi City is located in the transition zone between the mountain and the plain on the north bank of the Yellow River. It includes two major geomorphological units, the bedrock uplift area of the Taihang Mountain and the sedimentary area of the North China Plain. The Shinaimiao (SNM) core locates in Hebi City of China, belongs to the accumulation plain of the eastern foothills of the Taihang Mountains which is part of the North China Plain, and composed by quaternary alluvium and flood deposits in lithology. The SNM core is 126.64 m deep. Environmental magnetism and ESR dating method are used to divided the lower and middle Pleistocene, and determine the quaternary bottom boundary. OSL and radiocarbon (14C) dating methods are used for the division of the middle and upper Pleistocene, and Holocene. Quaternary stratum of SNM core is divided by multiple dating methods, which have provided the basic data for the study of urban active fault detection and environmental evolution in Hebi City and its vicinity. [ABSTRACT FROM AUTHOR]