Magnetic Minerals Research Articles

Reconstruction of late Holocene palaeoenvironmental and palaeohydrological changes using multi-proxy analysis of Sattal lake sediments, Kumaun lesser Himalaya, India

The present study aims to investigate the palaeoenvironmental changes around Sattal Lake, Kumaun Lesser Himalaya spanning the last 1670 years. Based on multi proxy analysis (i.e., grain size, mineral magnetism, clay mineralogy, Total Organic Carbon (TOC) and carbon isotopes), supported by a robust radiocarbon chronology, three major environmental phases were identified. Warm, wet phases occurred between 1,150–650 cal yr BP and 260 cal yr BP to the present. These phases coincide closely with the Medieval Climatic Anomaly (MCA) and modern warming, respectively. These warm/wet events were due to elevated precipitation, resulting in high lake levels and an expansion of the lake margin, which were marked by lower δ13C values, comparatively higher sand concentration, TOC values and magnetic susceptibility (χlf). The inference of a modern warm phase is supported by high resolution instrumental data. The MCA, which is marked by elevated amounts of coarse grained (sand) detrital material, is inferred to be an interval of strengthened of monsoonal intensity, which correlates with available monsoon records from various continental paleoclimate archives. Following the MCA a cold and dry phase was observed to occur between 610 and 260 cal yr BP, corresponding to the Little Ice Age (LIA). The LIA, which was characterized by high silt and clay concentration, high δ13C, low TOC and reduced magnetic susceptibility (χlf), is inferred to represent an interval of low lake levels, likely reflecting an episode of weakened monsoonal intensity.

Environmental magnetic records derived from lacustrine sediments in the Western Guangdong Province, China: Implications for Late-Holocene climatic/environmental changes

The western Guangdong Province (WGDP) in China, influenced by both the East Asian and the Indian summer monsoon, is a pivotal region for exploring the Asian summer monsoon (ASM) evolution. So far, there still lacks detail studies on late Holocene climatic/environmental changes here. In this study, multiple magnetic parameters were measured on the lake sediments of Hedong section in this area. Results indicated a dominance of pseudo-single-domain detrital (titano-)magnetite or maghemite mixed with paramagnetic and anti-ferromagnetic minerals in sediments, and the impacts of authigenic greigite, bacterial activity, post-depositional dissolution, and dilution effects were trivial. Changes in rainfall-induced surface erosion intensity were determined as a role in sediment magnetic properties. Intensified surface erosion deduced by increased rainfall favored enhanced concentrations and more coarse-grained magnetic minerals in sediments, and vice versa. Thus, the magnetic parameters can be used to reflect varying ASM strength in the past ~4300 years. They revealed four relatively humid (strengthened ASM) (i.e., 4300–4000 cal. yr BP, 3500–3130 cal. yr BP, 2640–1950 cal. yr BP, and 1250–850 cal. yr BP), and three dry periods (weakened ASM) (i.e., 4000–3500 cal. yr BP, 3130–2640 cal. yr BP, and 1950–1250 cal. yr BP) which coincided with the Bond events 3, 2, and 1 respectively. In combination with the three significant cycles (i.e., 1250-, 75-, and 65-year) revealed by spectral analysis on SIRM record, we inferred both the external forcing (e.g., solar activity) and internal hemispheric-scale atmospheric processes (e.g., ENSO, North Atlantic Oscillation) have played an integral role in late Holocene climate changes in the study region.

Nonnegligible contribution of terrigenous sediment inputs from local small watersheds to west regions of the Pearl River Estuary, northern South China Sea shelf

As a crucial “sink” for terrigenous material entering the ocean, provenance of sediments within the coastal zone and continental shelf sea regions holds significant scientific importance in the investigation of global material cycling. Environmental magnetism was proved as an effective and rapid approach for sediment source identification. Detail and systematic magnetic measurements were performed for surface sediment samples collected from the mega Pearl River, local small rivers (Tan, Moyang and Jian rivers) of west Guangdong, coastal zone (CZ) and continental shelf (CS) to analyze the contribution of local small watersheds to marine sediments. The results indicate that detrital river input magnetite and hematite are coexisted in both CZ and CS sediments. Compared to CZ sediments, relatively higher concentration of hematite and finer grain size of magnetite are appeared at CS sediments. By comparing of magnetic parameters, it was inferred that magnetic minerals from the Pearl and Tan rivers are transported and deposited on the coastal zone by Guangdong longshore current. Meanwhile, sediment magnetic parameters in the Moyang and Jian Rivers are similar to the CS sediments, implying the two rivers-sourced materials were directly transported and deposited at the CS due to their narrow and restricted estuaries, and/or the CS preserves the residual deposits from the two rivers formed during the Last Glacial. Except for the Pearl River, sources of local small rivers significantly contribute to marine sediments at the coastal zone and continental shelf.

Vortex Magnetic Domain State Behavior in the Day Plot

AbstractThe ability of rocks to hold a reliable record of the ancient geomagnetic field depends on the structure and stability of magnetic domain‐states contained within constituent particles. In paleomagnetic studies, the Day plot is an easily constructed graph of magnetic hysteresis parameters that is frequently used to estimate the likely magnetic recording stability of samples. Often samples plot in the region of the Day plot attributed to so‐called pseudo‐single‐domain particles with little understanding of the implications for domain‐states or recording fidelity. Here we use micromagnetic models to explore the hysteresis parameters of magnetite particles with idealized prolate and oblate truncated‐octahedral geometries containing single domain (SD), single‐vortex and occasionally multi‐vortex states. We show that these domain states exhibit a well‐defined trend in the Day plot that extends from the SD region well into the multi‐domain region, all of which are likely to be stable remanence carriers. We suggest that although the interpretation of the Day plot and its variants might be subject to ambiguities, if the magnetic mineralogy is known, it can still provide some useful insights about paleomagnetic specimens' dominant domain state, average particle sizes and, consequently, their paleomagnetic stability.

Insights Into a Correlation Between Magnetotactic Bacteria and Polymetallic Nodule Distribution in the Eastern Central Pacific Ocean

AbstractThe Clarion–Clipperton Fracture Zone (CCFZ) in the eastern central Pacific Ocean is the world's largest area for potential deep‐sea polymetallic nodule mining and is attracting increased scientific and commercial interest. Recent studies indicate that biogenic magnetite, generated intracellularly by magnetotactic bacteria (MTB), can carry a biogeochemical remanent magnetization in polymetallic nodules, although whether biogenic or physical‐chemical processes are responsible for nodule formation remain poorly constrained. Here, we report a combination of magnetic, electron microscope and geochemical analyses on seafloor surface sediments from the eastern CCFZ to understand the spatial distribution of biogenic magnetite and possible relationships between MTB and polymetallic nodules. Experimental results indicate that sedimentary magnetic minerals from the northern and southern regions are dominated by detrital (eolian loess and volcanic material) and biogenic magnetic minerals (magnetosomes), respectively. Sediments from the intermediate region contain both detrital and biogenic magnetic minerals. Quantitative first‐order reversal curve‐principal component analysis indicates that biogenic magnetite has the highest concentration in the intermediate CCFZ region, coincident with the highest polymetallic nodule density. Combined with previous research, we speculate that MTB growth on the CCFZ seafloor is driven mainly by local redox conditions. Manganese nodule surfaces are rich in organic biofilms, which results in a relatively thick oxic‐anoxic transition zone in high‐abundance manganese nodule regions, which generates an optimal microenvironment for both MTB growth and magnetite biomineralization. This study provides new clues for understanding the ecological distribution of MTB and the biogeochemical remanent magnetization recorded by biogenic magnetite in deep‐sea sediments.

Holocene paleoclimatic records from Chakrata area, Northwest Himalaya

We present monsoon variability records for the Holocene using multi-proxy approach (environmental magnetism, carbon isotope, and total organic carbon) from a 146 cm thick sedimentary profile in the Kotikanasar meadow (Chakrata), Northwest Himalaya. The chronology of the record was constrained by five AMS 14C ages. The carbon isotope (δ13C) and Total Organic Carbon (TOC) data highly variable which vary between -26.62‰ and -22.46‰ (C3-plants) and 0.1 to ∼4%, respectively, indicating paleo-vegetation history and productivity of the studied area. The environmental magnetics indicates highly fluctuating in the Early Holocene with high concentrations of magnetic minerals during high monsoon conditions and vice-versa. Intense Indian Summer Monsoon (ISM) phases were identified during the Early and Late Holocene i.e., ∼9.2 to 7.4 ka, and ∼4.8 ka to Modern which shows warm and wet climate. While decline in the ISM intensity during ∼7.4 to 4.8 ka which indicates cold and dry climatic condition in the Northwest Himalayan regions. From ∼9.2 to 7.4 ka highly fluctuating climate linked with the Early Holocene warming. Sediment profile exhibits aridity in climate accompanying with the high influence of mid-latitude westerlies during ∼7.4 to 4.8 ka from Northwest Indian regions (Enzel et al., 1999). Hence the long-term fluctuation in the climate governed by the changes in the North Atlantic Ocean circulation as well as variations in the incoming solar radiations.

Changes in the magnetic properties of a tropical red soil following the conversion of forest into agricultural land

Land uses have a large impact on the magnetic properties of soil. Understanding the changes in such properties caused by different land uses will help to correctly explain and apply magnetic parameters. In this study, the magnetic susceptibility, magnetic mineral types, and magnetic domain state of iron oxide particles in soil after the transformation of a forest into a tea garden and cornfield in a tropical area were compared. 1)The vertical distribution characteristics of soil magnetism under the three land uses in tropical red soil area were similar. The magnetic properties of soil in the 0–20 cm surface layer was significantly different, but there were no significant differences below 20 cm. The low-frequency mass magnetic susceptibility and anhysteretic susceptibility of topsoil were largest in the cornfield, followed by the forest and tea garden, and the magnetic susceptibility of the topsoil in the cornfield was significantly higher than in the tea garden and forest. 2)The magnetic minerals in tropical red soil area were mainly ferrimagnetic minerals (maghemite and magnetite). The content of ferrimagnetic minerals decreased with depth, while the content of antiferromagnetic minerals (hematite) increased. 3)The magnetic particles were mainly composed of superparamagnetic (SP), single domain (SD), and pseudo single domain (PSD) particles. The magnetic differences in the topsoil were mainly caused by changes in the ferrimagnetic mineral concentration of SD particles. Tea garden and cornfield are the two main agricultural land in the study area. Through the correct application of magnetic parameters, it is helpful to monitor the influence of land use change on soil properties, so as to provide the necessary reference for the rational use of soil.

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity.

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Mineral Magnetism in Relation to Thermal Thellier Palaeointensity Experimental Results of the Deccan Basalt Flows Along the Deep Drill Hole in Western India and Their Significance

Mineral Magnetism in Relation to Thermal Thellier Palaeointensity Experimental Results of the Deccan Basalt Flows Along the Deep Drill Hole in Western India and Their Significance

Quantifying the mineral magnetic signature of petroleum systems and their source rocks: a study on the Inner Moray Firth, UK North Sea

SUMMARY This study aims to expand on existing connections between magnetic minerals and hydrocarbons within petroleum systems. Previous studies have focussed on single-source petroleum systems whereas this study, for the first time, analyses a multi-source petroleum system to investigate potential correlations between different kerogen type source rocks and magnetic minerals. To do this, the study investigates the magnetic mineral characteristics of the Inner Moray Firth (IMF), UK North Sea, through room-, low- and high-temperature techniques, and correlates this to published basin and petroleum systems modelling results that show a three-source hydrocarbon mix. Magnetic mineral analysis identifies extensive evidence for magnetite, goethite and siderite, alongside more minor lepidocrocite and iron sulphides. Although we find that magnetite is ubiquitous within the IMF, its abundance is relatively low, and, in contrast, the relatively magnetically weak goethite is more likely the most abundant magnetic mineral throughout the IMF. In agreement with previous studies, we find magnetic enhancement at oil-water contacts (OWCs); however, here, we identify two different magnetic enhancement processes at OWCs in wells, which are dependent on the amount of sulphur available in the local environment. Wells with low levels of sulphur have increasing levels of magnetite towards the OWC, with the magnetic enhancement occurring at the top of the water-saturated section. Sulphur-rich environments display an increase in iron sulphides near the OWC at the bottom of the oil-saturated sediments. Additionally, we confirm the presence of siderite as indicator of upward vertical migration. Combining with petroleum system model predictions, we find direct links between iron hydroxide presence and Type I and II–III kerogen source rocks, and iron sulphide presence with Type II kerogen source rocks. This study shows the potential for further utilization of magnetic mineral analysis within hydrocarbon exploration and petroleum system definition.

High-resolution relative paleointensities over the last 40 ka from marine sediments in the western equatorial pacific: Magnetic events and interhemispheric correlation

Core MD01-2385 retrieved in the western equatorial Pacific (Northwest of Papua-New Guinea) has been sampled every 2 cm for paleomagnetic and radiocarbon measurements. The age model, well constrained by 47 14C ages (both new and former), indicates that our record spans approximately the last 38 ka. The average sedimentation rate is ∼30 cm/ka. Analysis of the magnetic mineralogy revealed that the natural remanent magnetization (NRM) is predominantly carried by magnetite. A relative paleointensity record (RPI) was derived, allowing us to estimate a lock-in depth of approximately 18 cm, corresponding to ∼600 years in our case, by comparing it with the CALS10k.2 model. Comparison with two other western Equatorial Pacific RPI, selected for their geographical proximity (∼1000 km) and high resolution, allowed us to compile a regional reference record (WEPEQ). Several intervals of lower intensities have been identified and may correspond to the known events of Mono Lake (∼34 ka), Rockall (∼27 ka), Hilina Pali (∼18 ka) and possibly Tianchi (∼5–8 ka). Overall, our equatorial curve exhibits strong similarities with RPI curves from mid to low latitudes, such as those from the Iberian Margin and Black Sea. A detailed investigation hints at the presence of non-dipolar structures in the Earth's magnetic field at the shorter time scale, especially during the low intensity intervals. In contrast, notable differences are observed when compared to high-latitude stacks, especially from the North Atlantic (NAPIS). This points to the potential climatic bias that may affect high-latitude records during the glacial maximum and glacial-interglacial transition.

Effect of temperature and particle size on dielectric property of vanadium-titanium magnetite

The current body of research on microwave-assisted grinding of vanadium-titanium magnetite (VTM) predominantly focuses on the analysis of changes in particle size and dissociation degree of the grinding products. Nonetheless, the microwave heating mechanism of the ore remains inadequately explored. In this study, the dielectric property of VTM with different particle sizes were measured at a frequency of 2.45 GHz and temperatures ranging from ambient to 800 °C. The results indicate that the dielectric constants (ε′) and dielectric loss factors (ε″) of VTM increase with temperature. The loss tangent coefficients (tan δ) initially increase and then decrease, reaching a maximum value of 0.44 at approximately 500 °C. The values of dielectric property parameters increase as the particle size decreases. By calculating the penetration depth equation, it can be determined that the optimal particle size for uniform heating in microwave of VTM is approximately 15 ∼ 30 mm. The heating rate of the ore in the microwave field is divided into two stages. Initially, the heating rate is very fast due to the ore being a strong magnetic mineral. However, when the ore temperature reaches 500 °C, the tan δ of the ore decreases, leading to a decrease in the heating rate.

A Geochemical Mechanism for >10 m Apparent Downward Offsets of Magnetic Reversals Inferred From Comparison of Two Scotia Sea Drill Sites

AbstractWe document an apparent downward displacement of the Matuyama‐Brunhes magnetic reversal by ∼20 m at Scotia Sea International Ocean Discovery Program Site U1538 (Pirie Basin) by comparison with the well‐defined paleomagnetic record at nearby Site U1537 (Dove Basin). Detailed stratigraphic correlation between the two sites is possible due to similar lithologic variations. However, the two sites have distinctly different porewater geochemistry. Notably, Site U1538 indicates a greater demand for electron acceptors to oxidize organic carbon and Fe2+ enrichment below the depth of SO42− depletion. Magnetic parameters indicate enrichment of an authigenic magnetic mineral with strong remanence properties around the depth of SO42− depletion (∼46 m at Site U1538) relative to magnetic parameters at correlative depths at Site U1537. Fe2+ enrichment below the depth of SO42− depletion is not predicted based on the energetically favorable order of electron acceptors for microbial respiration but is documented here and in other depositional settings. This indicates Fe2+ production exceeds the production of H2S by SO42− reduction, providing a geochemical environment that favors the production and preservation of ferrimagnetic remanence‐bearing iron sulfides over paramagnetic pyrite and, thus, a mechanism for deep chemical remanent magnetization acquisition at depths of tens of meters. The influence of authigenic ferrimagnetic iron sulfides on paleomagnetic signals can be difficult to demonstrate with magnetic properties alone; therefore, this finding has implications for evaluating the fidelity of magnetostratigraphic records with complementary geochemical data. Such situations should be considered in other depositional environments with similar porewater Fe2+ accumulation below the SO42− reduction depth.

Anti-phase variation of long eccentricity and precipitation in inland Asia during the Middle Miocene Climatic Optimum

The mechanisms and pace of orbital forcing on precipitation in inland Asia during the Cenozoic remain poorly understood. Many previous studies using magnetic proxies for precipitation have shown a consistent signal of long eccentricity (405 kyr) in hydrological records of central China that are younger than ca. 11 Ma. Most studies suggest that variations in rainfall amount were controlled by Northern Hemisphere summer insolation, and the peak of precipitation is associated with eccentricity maxima. Here, we report multiple magnetic records dating back to the Middle Miocene Climatic Optimum (MMCO, ∼14−17 m.y. ago), including a detailed record from a new section in the Qaidam Basin, which was dated using magnetostratigraphy, U-Pb geochronology, and apatite low-temperature thermochronology. Our records show the exact opposite: 405 kyr wet-dry cycles dominated, but the wetter intervals correspond to eccentricity minima and ice-volume maxima during the MMCO. Taken at face value, these results question the origin—monsoonal or westerly-derived—of the precipitation that reached central China during the middle Miocene and the mechanisms that enhanced monsoonal penetration of inland Asia. We also suggest that this anti-phase relationship could also reflect biases in magnetic proxies for precipitation during the wettest climatic phases, which can result in the dissolution of magnetic minerals and a significant underestimation of past rainfall.

Magnetic properties and load of potentially toxic heavy metals carried by the coarse and fine fractions of indoor dust

The granulometric fractions of indoor dust, categorized as coarse (grain size of 1.00–0.071 mm) and fine (grain size <0.071 mm), were investigated to discern variations in their magnetic properties and contents of potentially toxic heavy metals. Monthly dust samples were gathered from January 2021 to December 2022 from a private apartment situated on the outskirts of a large urban agglomeration (Warsaw, Poland). To assess indoor dust, several magnetic parameters, including mass-specific magnetic susceptibility, were employed. Portable X-ray fluorescence measurements were utilized to evaluate the enrichment of granulometric fractions in harmful heavy metals. The study reveals a comparable composition of magnetic minerals irrespective of grain size (magnetite and metallic iron), with variations observed in the domain state of magnetic particles (contribution of single-domain (SD) grains to multi-domain (MD)). Seasonal fluctuations were predominantly noted in the distribution of the fine fraction's mass during the warm season (May–July). A notable increase was observed in the fine fraction's mass contribution to the total dust mass compared to the winter season (December and February). The fine fraction was highly enriched in toxic metals, including Pb, Cr, Cu, Mn, Fe, and Sr. Pollution Load index is 6–8 for the fine fraction and 2–8 for the coarse fraction. The increase in the fine fraction mass induces linear changes in magnetic susceptibility, likely associated with the rise in anthropogenic magnetic particles. This finding holds significant implications for human health, as fine particles laden with toxic heavy metals can enter the human respiratory tract causing adverse health effects.

Iron Age ceramics from Thracian rock-cut complexes from Bulgaria – Mineral magnetic relics of technological production and use

The Gluhite kamani Thracian rock-cut complex in the Eastern Rhodopes Mountain is famous with its more than 500 rock niches carved in the rock at heights up to 20 m. Continuous habitation starting from the final Chalcolithic (the second quarter of the 4th millenium BCE) until the Late Classical – Early Hellenistic period (late 5th – 4th century BCE) provides unique opportunity for studying diachronic changes in pottery production and use. In this contribution, systematic analysis of a collection of 135 ceramic sherds from five archaeological periods at the site was carried out using a combined mineral magnetic and geochemical approach. Magnetic susceptibility (χ), frequency-dependent magnetic susceptibility (χfd%) and firing temperature (Tfire), determined using the magnetic susceptibility method, were combined with data from elemental XRF analyses. Thermomagnetic measurements, employed for identification of magnetic minerals revealed the dominant presence of (titano)magnetite with low Ti-content and/or a fraction of single-domain magnetite and in few cases hematite. Although varying in a wide range, median χ values of ceramic sherds from the Early Iron Age (EIA) periods show similar distribution, while for Late Iron Age (LIA) with the introduction of the wheel-thrown pottery, χ values are higher, presumably due to decreased amount of silica-rich clastics in the clay. Concurrently, χfd% values decrease in ceramics from the LIA, indicating predominant presence of stable single-domain magnetite in the iron oxide composition of the ceramics. Firing temperatures (Tfire) estimations display a systematic pattern of two groups – higher (Tfire between 760 and 800 °C) and lower (Tfire ∼ 400–––600 °C). During the EIA periods both Tfire groups are present, characterized by systematic gradual decrease of the median value of the low Tfire when going from EIA1 towards the EIA2. Wheel-thrown pottery from the LIA show low Tfire ∼ 400 °C only. Based on the differences in thermomagnetic properties of ceramics, their magnetic parameters and Tfire estimates, two possible hypotheses are suggested to explain the observed changes in EIA ceramic characteristics: i) utilization of two differently sourced clay materials (illite-dominated and montmorillonite-dominated) for production of ceramics fired at higher and lower temperatures, respectively; and ii) utilization of one raw clay source, while using two firing regimes – firing at higher temperature for prolonged time, and fast firing to high temperature with successive stage of longer firing at lower temperature. Differences in thermomagnetic properties of wheel-thrown pottery from the LIA period leads to the assumption for utilization of diverse clay source for their production, as compared clay sources for the Early Iron Age periods.

Exploring the astrobiological potential of rock varnish from a mars analogue field site of Ladakh, India

Rock varnish, a dark-coloured natural feature rich in manganese (Mn), iron (Fe), and clay minerals that forms on rock surfaces and subsurface rock fractures in extremely dry and cold environments, is believed to provide nutritional support to microbiota. Because varnish supports an extensive microbial community, this rock coating is considered a substrate for potential microbial life to thrive in extreme environments on Earth. Although research in the past decades have advanced understanding of the varnish microbiome, little is known about this microbial community in settings that are high altitude (lower oxygen), dry, and cold. We present here new morphological, chemical, and rock magnetic results of rock varnish from this environmental setting, the Ladakh, a potential analogue site for life in extreme environments. Our results include the presence of putative magnetofossils-in the form of nanochains present in the rock varnish layer. Further, the higher concentrations of oxidised Mn4+ and carboxylic acid functionality on the varnish surface revealed organic signatures. These collective results point towards the enriched concentration of magnetic minerals on the varnish layer that are possibly sourced through biotic forms. Consequently, the rock varnish can serve as an archive of ancient environmental records, as well as a potential geomaterial for astrobiological studies from the Martian analogue field location of Ladakh, which needs to be explored further for extensive biogeochemical studies.

Characterization of the inhalable fraction (< 10 μm) of soil from highly urbanized and industrial environments: magnetic measurements, bioaccessibility, Pb isotopes and health risk assessment

Soil in urban and industrial areas is one of the main sinks of pollutants. It is well known that there is a strong link between metal(loid)s bioaccessibility by inhalation pathway and human health. The critical size fraction is < 10 μm (inhalable fraction) since these particles can approach to the tracheobronchial region. Here, soil samples (< 10 μm) from a highly urbanized area and an industrialized city were characterized by combining magnetic measurements, bioaccessibility of metal(loids) and Pb isotope analyses. Thermomagnetic analysis indicated that the main magnetic mineral is impure magnetite. In vitro inhalation analysis showed that Cd, Mn, Pb and Zn were the elements with the highest bioaccessibility rates (%) for both settings. Anthropogenic sources that are responsible for Pb accumulation in < 10 μm fraction are traffic emissions for the highly urbanized environment, and Pb related to steel emissions and coal combustion in cement plant for the industrial setting. We did not establish differences in the Pb isotope composition between pseudo-total and bioaccessible Pb. The health risk assessment via the inhalation pathway showed limited non-carcinogenic risks for adults and children. The calculated risks based on pseudo-total and lung bioaccessible concentrations were identical for the two areas of contrasting anthropogenic pressures. Carcinogenic risks were under the threshold levels (CR < 10–4), with Ni being the dominant contributor to risk. This research contributes valuable insights into the lung bioaccessibility of metal(loids) in urban and industrial soils, incorporating advanced analytical techniques and health risk assessments for a comprehensive understanding.

Enhancing PHGMS performance for recovery of ultra-fine ilmenite from tailings

In southwest China, the Panzhihua area annually produces about 80 million tons of tailings with a TiO&lt;sub&gt;2&lt;/sub&gt; grade of around 5.0%, which causes serious waste of titanium resources as well as environmental and safety issues. The ilmenite contained in these tailings is ultra-fine in size, so it is difficult to recover under the regular operating conditions of pulsating high gradient magnetic separation (PHGMS). In this study, an SLon-100 PHGMS separator was applied to concentrate an ultra-fine titanium tailing under a wide range of operating conditions. The experimental results indicated that a combination of high pulsating frequency, large pulsating stroke, and low feed velocity was favorable for the highly efficient recovery of ultra-fine ilmenite from the tailings. The TiO&lt;sub&gt;2&lt;/sub&gt; grade in the optimal concentrate was enhanced from 4.33% to 13.64%, at a recovery of 66.55% and an enrichment ratio of 3.15 through a one-stage PHGMS process. The size analysis of the optimal concentrate showed that the TiO&lt;sub&gt;2&lt;/sub&gt; recovery in -25+18 µm and -18+10 µm fractions exceeded 70%. To further understand this PHGMS performance, the optimal ultra-fine ilmenite and larger-size ilmenite concentration conditions were compared. This study provides a valuable reference in the PHGMS operation for recovering ultra-fine weakly magnetic minerals, including ilmenite.

Magnetic Hydrocycloning of Weakly Magnetic Mineral Slime

Magnetic Hydrocycloning of Weakly Magnetic Mineral Slime