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Unmixing of remanent magnetization curves, either isothermal remanent magnetization (IRM) or backfield IRM, is widely used in rock magnetic and environmental magnetic studies to discriminate between magnetic coercivity components of different origins. However, the wide range of physical properties of natural magnetic particles gives rise to an ambiguous interpretation of these components. To reduce this ambiguity and provide a straightforward interpretation of coercivity components in terms of domain state, interactions, and constituent magnetic phases, we combined backfield IRM unmixing with unmixing of nonlinear Preisach maps for two typical mid‐latitude northern hemisphere loess‐paleosol sequences. Both backfield IRM and nonlinear Preisach maps unmixing are based on the same non‐parametric algorithm, and provide similar endmembers (EMs) in the two sections studied. The first EM (EM1) has a low median coercivity (∼21 mT) and is a non‐interacting single domain (SD) magnetite/maghemite of pedogenic origin. The second EM (EM2) has a moderate median coercivity (∼60 mT) and is a mixture of pseudo‐single domain/multidomain, SD magnetite/maghemite and non‐interacting SD hematite, all of eolian origin. The same EM1 found in both sections suggests that this component's grain size and coercivity are independent of pedogenesis intensity. The same EM2 indicates that a similar magnetic population is being transported and deposited, irrespective of the dust source area and loess granulometry. The approach outlined here provides strong evidence that non‐parametric backfield IRM unmixing isolates physically realistic EMs. Unmixing nonlinear Preisach maps elucidates these EMs in terms of domain states and their constituent magnetic phases. Plain Language Summary: Magnetic minerals occurring in natural materials carry crucial information about environmental processes. However, since a given material typically contains several magnetic components, the environmental signals it encodes are convoluted. Due to different physical properties of natural magnetic particles, recovering information about each individual process can be a challenging task. One popular method used to differentiate magnetic populations with different origins is numerical unmixing of their coercivity distributions because they are sensitive to characteristics of individual magnetic populations. Coercivity distributions represent the first derivatives of IRM acquisition curves, which are built by exposing a sample to a series of magnetic fields in the laboratory. Generally, there is ambiguity in the interpretation of coercivity components. Therefore, we devised an unmixing method using data sets called non‐linear Preisach maps, built from a sequence of IRM curves that are processed into two‐dimensional diagrams. These data sets give us additional information to that gleaned from coercivity distributions, such as magnetic domain states and particle interaction signatures. We tested this approach on two loess‐paleosol sections located in Southeastern Europe, because they developed in different climatic conditions, and had different dust source areas. Key Points: Non‐parametric remanent magnetization curves unmixing provides physical, though ambiguous, componentsNon‐parametric Preisach maps unmixing resolves this ambiguity by allowing the identification of mineral phases and domain statesIn loess‐paleosol deposits the pedogenic and eolian components are respectively independent of pedogenesis intensity and dust source areas [ABSTRACT FROM AUTHOR]

The chronic exposure to particulate matter (PM) pollution causes societal and environmental issues, in particular in urban areas where most citizen are regularly exposed to vehicular traffic. Since almost two decades, environmental magnetic monitoring has demonstrated its efficiency to successfully map relative concentrations of airborne particle deposition on accumulative surfaces. A better understanding of the magnetic results requires discriminating the main traffic-related sources of the observed signal on particle collectors. To meet this objective, we investigated a sample set of exhaust and non-exhaust sources with respect to their magnetic fingerprints inferred from hysteresis loops, first-order reversal curve (FORC) diagrams, temperature dependency of initial susceptibility and unmixing of isothermal remanent magnetization acquisition curves. The source sample set comprises 14 diesel and gasoline exhaust smoke residues, 12 abrasive-fatigue wear test pieces from worn brake-pads, brake powders, worn tire-tread and three resuspension products: asphalt concrete, street dust and Saharan mineral dust deposited by precipitation after long-range eolian transport. Magnetic properties of the source samples were compared to those from various accumulative surfaces exposed to urban traffic (passive collectors, filters of facemasks for cycling, plant leaves and tree barks). We found some fingerprints of exhaust pipes and brake wear products on these collectors. The findings highlight the relevance of environmental magnetism tools to characterize different traffic-related source signals in accumulative surfaces in urban environment. [ABSTRACT FROM AUTHOR]

Purpose: Iron-bearing magnetic minerals in the sediments of the water-level fluctuation zone (WLFZ) in large reservoirs play critical roles in the burial and release of organic carbon and pollutants. This study aims to reveal the spatial distribution of magnetic minerals across different elevations and reaches within the WLFZ of the Three Gorges Reservoir (TGR), the largest reservoir in the world, and their links to sediment provenance and hydrodynamic conditions. This study will provide a fundamental basis for future investigations in the roles of magnetic minerals in the circulation processes of pollutants and organic carbon within the WLFZ of fluvial-reservoir systems. Materials and methods: ~ 300 sediment samples and nearby side-slope soils were collected from various altitudes within the WLFZ at ten different sites of the TGR. The magnetic properties of these sediments and soils were examined using environmental magnetism. Additionally, previously reported data on magnetic properties of suspended sediments from upstream rivers flowing into the TGR were assembled. Nearby side-slope soils and suspended samples were used to represent magnetic properties of potential sources for the sediments within the WLFZ. Results and discussion: Our findings reveal that magnetite/maghemite and hematite particles dominate the sediments within the WLFZ of the TGR. Relatively higher concentration of hematite particles in the upper part (> 165 m) of WLFZ mainly originates from or are nearby side-slope soils, whereas higher concentration of magnetite/maghemite particles in the lower part of WLFZ is primarily due to sediment supply from upstream of the Yangtze River. The dominance of coarser magnetite/maghemite within the WLFZ of the upper reach of the TGR, from Jiangjin district to Fuling district, is due to strong water flow velocity. An increase in the concentration of nanosized fine-grained magnetic particles within the WLFZ of the middle and lower reaches of the TGR can be attributed to a combination of reduced water dynamics and intense regional soil erosion of nearby side slopes. Conclusions: Our findings indicate that the concentration and grain size of magnetic minerals exhibit spatial variations within the WLFZ of reservoirs under the influences of sediment provenance and hydrodynamics. These findings provide fundamental insights on future exploration into the crucial roles of iron-bearing magnetic minerals in the accumulation, migration, and transformation of pollutants and organic carbon within the WLFZ of reservoirs and their response to changes in sediment sources and water dynamics. [ABSTRACT FROM AUTHOR]

The relationship between initial Homo sapiens dispersal from Africa to East Asia and the orbitally paced evolution of the Asian summer monsoon (ASM)--currently the largest monsoon system--remains underexplored due to lack of coordinated synthesis of both Asian paleoanthropological and paleoclimatic data. Here, we investigate orbital-scale ASM dynamics during the last 280 thousand years (kyr) and their likely influences on early H. sapiens dispersal to East Asia, through a unique integration of i) new centennial-resolution ASM records from the Chinese Loess Plateau, ii) model-based East Asian hydroclimatic reconstructions, iii) paleoanthropological data compilations, and iv) global H. sapiens habitat suitability simulations. Our combined proxy-and model-based reconstructions suggest that ASM precipitation responded to a combination of Northern Hemisphere ice volume, greenhouse gas, and regional summer insolation forcing, with cooccurring primary orbital cycles of ~100-kyr, 41-kyr, and ~20-kyr. Between ~125 and 70 kyr ago, summer monsoon rains and temperatures increased in vast areas across Asia. This episode coincides with the earliest H. sapiens fossil occurrence at multiple localities in East Asia. Following the transcontinental increase in simulated habitat suitability, we suggest that ASM strengthening together with Southeast African climate deterioration may have promoted the initial H. sapiens dispersal from their African homeland to remote East Asia during the last interglacial. [ABSTRACT FROM AUTHOR]

Abstract Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level.

An urgent environmental problem in the Perm region is the increased concentration of some heavy metals in soils. This paper presents the results of studying the ecological and geochemical role of the magnetic fraction of soils in the Middle Cis-Urals. The study used magnetometry, geostatistical and geochemistry methods. It has been established that the magnetic fraction is a geochemical barrier in soils and accumulates potentially toxic elements (Mn, Ni, Cu, Co, and Pb). The total content of Mn, Zn, Ni, Cu, Co, and Pb in the soils of the agricultural landscapes of the taiga-forest zone of the Middle Cis-Urals exceeds the clarke of world soils. The ecological-magnetic subprofile of the studied soils is subdivided into ecological-magnetic layers: accumulation, destruction, and stable state of magnetic particles. The environmental organizations of the Perm region are recommended to use methods of ecological magnetism for carrying out soil-ecological monitoring and identifying land contaminated with heavy metals. The obtained information about the elemental chemical composition of soils of the Middle Cis-Urals can be used in the management of land resources and the development of the concept of land policy in the region. [ABSTRACT FROM AUTHOR]

Recent research has suggested that East Asia has experienced a prevailing monsoon climate since the Eocene. However, there is little knowledge about the development of the East Asian monsoon system before the Miocene, particularly in southern China, due to a lack of well‐dated continuous sediment records. Here, we present new magnetic proxy records from International Ocean Discovery Program Site U1501 in the northern South China Sea. We conducted rock magnetic experiments, made scanning electron microscopy observations and performed diffuse reflectance spectrum analysis on the late Eocene‐early Oligocene core sediments. The magnetic signal of the sediments is dominated by detrital magnetite and titanomagnetite formed during the silicate weathering and erosion processes, which were used to infer the evolution of summer monsoon precipitation in southern China. Our results along with geochemical and clay mineral data from Site U1501 strongly indicate that the East Asian summer monsoon generally weakened across the Eocene‐Oligocene transition. This change was linked to coeval global cooling rather than tectonic processes. Prior to the Eocene‐Oligocene transition, the summer monsoon intensified, likely due to the latest Eocene warming event caused by the enhancement of the Atlantic Meridional Overturning Circulation, which may have preconditioned the Earth system for the greenhouse‐to‐icehouse transition. Plain Language Summary: To date, there is little knowledge regarding the long‐term evolution of monsoon climate in South China before the Miocene due to a lack of well‐dated continuous sediment records. The recent International Ocean Discovery Program Expedition 368 retrieved continuous late Eocene‐early Oligocene sediments at Site U1501 within the northern South China Sea, thus providing an opportunity to fill this gap. In this study, we investigate the evolution of the East Asian summer monsoon in South China during the late Eocene‐early Oligocene through a comprehensive analysis of the magnetic properties of the sediments. The results strongly indicate that the summer monsoon generally weakened across the Eocene‐Oligocene transition, which was linked to coeval global cooling. A short‐term strengthening of the summer monsoon prior to the Eocene‐Oligocene transition was also recorded. This change is attributed to the warming caused by the latest Eocene strengthening of the Atlantic Meridional Overturning Circulation, which may have preconditioned the Earth system state before causing a transition into an icehouse Earth. Key Points: The environmental magnetic record in the northern South China Sea indicates monsoon evolution during the late Eocene to early OligoceneThe East Asian summer monsoon weakened across the Eocene‐Oligocene transitionGlobal cooling drove the long‐term weakening of East Asian summer monsoon [ABSTRACT FROM AUTHOR]

Located at the modern junction of the Asian Summer Monsoon and the Westerlies, the northeastern Tibetan Plateau and western Chinese Loess Plateau are in distinct climatic setting from the middle and eastern Chinese Loess Plateau. Besides, Holocene climate variations near the Asian Summer Monsoon margin are highly debated with different models proposed. We carried out environmental magnetic analyses on the Minle loess section, with continuous deposition between 13.3–0.5 ka, located near this margin. Results show that the magnetic susceptibilities of palaeosols are dominantly contributed by superparamagnetic (SP) and single-domain (SD) maghemite and/or magnetite produced by pedogenesis. Limited changes in the content of haematite indicate that dust origin hardly influenced the magnetic mineral variations. The section is divided into four substages according to the changes in magnetic indices and provides a full scene of Holocene climatic evolutions. During the coldest and driest Late Glacial (13.3–11.7 ka), it displays the weakest pedogenesis, as suggested by the lowest SP and SD concentration. The strongest pedogenesis in the Minle section produced higher magnetic susceptibility than the loess records in the Chinese Loess Plateau during the early Holocene Optimum (11.7–8.1 ka). The subsequently declined summer insolation, equatorward migrated Westerlies and the weakened Asian Summer Monsoon led to weak pedogenesis during the middle Holocene (8.1–5.3 ka). Stronger pedogenesis during the late Holocene (5.3–0.5 ka) than the middle Holocene might be due to lower evapotranspiration from weaker insolation and/or to the enhanced winter Westerlies. We attribute the spatiotemporal differences in climatic records of the Chinese loess to precipitation, effective humidity and aeolian geomorphological processes. [ABSTRACT FROM AUTHOR]

Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level. [ABSTRACT FROM AUTHOR]

Detailed and systematic analyses of the magnetic and grain-size properties of the Weihe River sediments were conducted to explore effective proxies that could reflect variations in the runoff. Ultimately, the magnetic parameter χARM/χlf was considered a reliable proxy owing to the close relationship with grain-size fraction larger than 63 μm, with a correlation coefficient of 0.90. By combining accelerator mass spectrometry radiocarbon (AMS 14C) dating, a timescale ranging from 12,900 year BP to the present was established for the section. Accordingly, the reconstructed runoff variations showed that, from 12,900 to 9,600 year BP, the hydrodynamic force of the river was relatively strong, and the runoff was large. From 9,600 to 7,500 year BP, these two parameters varied from weak to strong, and the trend continued to increase from 7,500 to 5,300 year BP. At 5,300 year BP, the sediments shifted from the fluvial to the continental environment, indicating a marked decrease in the runoff. Although the resolution and pattern of this reconstruction were rough, this is a significant analysis among the historical runoff studies based on floodplain sediments, and the results showed trends that to some extent coincide with the variations in the intensity of the East Asian Summer Monsoon. HIGHLIGHTS An integrated study of Weihe River sediments using environmental magnetism and particle size analysis.; Establishing a chronological framework for the Weihe sedimentary profile using AMS14C dating.; The magnetic ratio parameter χARM/χlf is extracted as an effective proxy for indicating river runoff.; The results show that the runoff process of the Weihe River is mainly controlled by the East Asian summer winds.;

Purpose: This study is aimed at analyzing the spatial distribution of magnetic susceptibility and the content of potentially toxic elements (PTEs) in the surface layer of bottom sediments in the Vistula estuary (Gulf of Gdańsk, Poland) in relation to local sedimentary conditions. We also assessed the usefulness of magnetic susceptibility measurements to identify changes in sediment properties caused by anthropogenic factors. Materials and methods: Bottom sediments were collected along three transects using the Van Veen grab sampler. The following properties were determined: granulometric composition, organic matter and carbonate content, pH, electrical conductivity, and heavy metal content (Cd, Cr, Cu, Fe, Ni, Pb, and Zn). Specific (mass) magnetic susceptibility (χ) was measured using the MS2 Bartington® laboratory magnetic susceptibility meter. To characterize the conditions of the sedimentary environment in the study area, statistical analysis was performed on selected parameters of grain size distribution, such as mean grain diameter (Mz) and sorting (σ1) indices. Results and discussion: The research showed significant differences in the sedimentary environment (erosion vs. deposition processes) along the studied transects which were controlled by the wave regime, sea currents, and river water inflow. Open-water sediments were richer in organic matter and more saline than deltaic sediments, which in turn were characterized by higher pH and higher carbonate content. The highest mean total content of Pb, Cu, Ni, and Zn and the highest magnetic susceptibility (χ) were determined in open-water sediments, while the highest Fe and Cr values were obtained for deltaic sediments. Statistically significant differences between these sediments were found only for organic matter (LoI), Pb, Cu, and Cd content. Magnetic susceptibility showed a moderate correlation with Pb, Cu, Cd, and Zn (rs 0.4–0.6). Conclusion: PTE content and magnetic susceptibility of sediments showed a very high heterogeneity within the study area, depending mainly on the location (delta vs. open waters), grain size composition, and organic matter content. Our results demonstrated that magnetic susceptibility analysis is an easy method that can be used to complement the identification of technogenic changes in the marine environment. [ABSTRACT FROM AUTHOR]

While there is a general sense that reservoirs can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. Here multiple-proxy analyses including 210Pb, grain size, heavy metals, magnetic parameters, and spheroidal carbonaceous particles (SCPs) were conducted for a sediment core from a typical subtropical reservoir in South China (Huangkeng Reservoir). 210Pb dating revealed that the core spans from ~ 1964 to 2019, with the sedimentary rate increasing during recent years. The sedimentary environment was mainly influenced by natural process (especially precipitation), along with the accumulation of Cr, Ni, Cu, V, As, Sb, and Co and most magnetic particles. However, four heave metals (Cd, Pb, Tl, and Zn) were found mainly from atmospheric deposition from industrial/agricultural activities in Huizhou City, which was also indicated by SCPs, S-ratio, and χARM/SIRM. According to temporal variation of SCPs, the atmospheric pollution history of nearby city (Huizhou City as the most close one) from 1964 was reconstructed. The study shows that reservoir sediments, especially in areas with few or no natural lakes, are high-efficacy and high-resolution achieves for research on environmental evolution in the Anthropocene related to global change and intensifying human activities. [ABSTRACT FROM AUTHOR]

We report the first complete loess–paleosol record spanning the last 130 kyr from the southern extremity of the Hunshandake Sandy Land (HSL) in central‐eastern Mongolia. Our combined mineral magnetic and geochemical results demonstrate that during the last interglacial, the front of the East Asian summer monsoon (EASM) extended to central‐eastern Inner Mongolia, consistent with modern observations of climate change. However, during the last glacial, typical magnetic parameters (e.g., magnetic susceptibility and anhysteretic remanent magnetization and their ratios), which have been successfully adopted to denote the EASM variations on the Chinese Loess Plateau (CLP), show only muted temporal variations and cannot be readily correlated with equivalent records from the main body of the CLP. Remarkably, the Zr/Rb ratio, a robust geochemical indictor of the winter monsoon, is positively correlated with saturation isothermal remanent magnetization and saturation magnetization during the last glacial, demonstrating the strong control of wind vigor on high‐field magnetization signals dominated by lithogenic ferrimagnetic minerals. In contrast to the variable response of magnetic parameters to regional paleoclimatic fluctuations, the Rb/Sr and Ba/Sr ratios (two summer monsoon indicators) faithfully track weak chemical weathering processes and fine‐scale monsoon oscillations, especially during the last glacial. Additionally, we found that higher proportions of pedogenic high‐coercivity magnetic minerals were formed during the last interglacial, which may reflect relatively low rainfall but higher evapotranspiration in the southern extremity of the HSL compared with the CLP. We therefore attribute this complex magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia. Plain Language Summary: Located at the present‐day northern limit of the East Asian summer monsoon (EASM), the arid and semi‐arid central‐eastern Inner Mongolia is highly sensitive to the advance and retreat of the EASM. To date, paleoclimatic history over the last interglacial–glacial cycle in this region is poorly documented due to the spatial scarcity of reliable sedimentary archives. Here, we present mineral magnetic, diffuse reflectance, and geochemical results for a well‐preserved loess–paleosol record from the southern extremity of the Hunshandake Sandy Land since the last interglacial, aimed at furthering our understanding of paleoclimatic history and possible forcing mechanisms in this region. Our results clearly demonstrate that during the last interglacial the EASM could penetrate to the studied site, and weaker precipitation but higher evapotranspiration compared with that on the Chinese Loess Plateau led to a lower degree of ferrimagnetic enhancement but higher proportions of pedogenic hematite. During the last glacial, we propose that the combination of mineral magnetic and geochemical analyses is critical to discriminating the weakest soil forming processes from strong lithogenic signals controlled by wind vigor/advance of sandy land margin. We attribute this "atypical" mineral magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia. Key Points: We report the first loess–paleosol record since the last ∼130 kyr in the southern Hunshandake Sandy Land, central‐eastern Inner MongoliaGeochemical ratios yield less ambiguous paleoclimate interpretations in the northern limit of the East Asian summer monsoon (EASM) compared with magnetic parametersWe attribute this atypical mineral magnetic record in monsoonal margin to a threshold response to the EASM variations [ABSTRACT FROM AUTHOR]

Abstract We report the first complete loess–paleosol record spanning the last 130 kyr from the southern extremity of the Hunshandake Sandy Land (HSL) in central‐eastern Mongolia. Our combined mineral magnetic and geochemical results demonstrate that during the last interglacial, the front of the East Asian summer monsoon (EASM) extended to central‐eastern Inner Mongolia, consistent with modern observations of climate change. However, during the last glacial, typical magnetic parameters (e.g., magnetic susceptibility and anhysteretic remanent magnetization and their ratios), which have been successfully adopted to denote the EASM variations on the Chinese Loess Plateau (CLP), show only muted temporal variations and cannot be readily correlated with equivalent records from the main body of the CLP. Remarkably, the Zr/Rb ratio, a robust geochemical indictor of the winter monsoon, is positively correlated with saturation isothermal remanent magnetization and saturation magnetization during the last glacial, demonstrating the strong control of wind vigor on high‐field magnetization signals dominated by lithogenic ferrimagnetic minerals. In contrast to the variable response of magnetic parameters to regional paleoclimatic fluctuations, the Rb/Sr and Ba/Sr ratios (two summer monsoon indicators) faithfully track weak chemical weathering processes and fine‐scale monsoon oscillations, especially during the last glacial. Additionally, we found that higher proportions of pedogenic high‐coercivity magnetic minerals were formed during the last interglacial, which may reflect relatively low rainfall but higher evapotranspiration in the southern extremity of the HSL compared with the CLP. We therefore attribute this complex magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia.

Effective moisture (EM) distribution in the Indian summer monsoon (ISM) region is strongly related to regional topography. An understanding of climate change and the interactions between climate variables can help predict future climate variations. Here, we reconstruct a stack EM record for Southwest China over the past 90 kyr using environmental magnetism in lake sediment. The EM in Southwest China at the orbital scale was closely linked to precession‐induced change in North Hemisphere solar insolation, as well as the ISM variability. However, at the glacial‐interglacial scale, it was decoupled with ISM intensity, being wetter during glacial periods (weakened ISM) and drier during interglacial periods (enhanced ISM). Combined with modern meteorological observations, we suggest that the topographical barrier effect and temperature induced dryness are responsible for the decoupling between ISM intensity and EM. The terrestrial topography and temperature strongly influence EM distribution by altering the dynamics of onshore airflow and evapotranspiration. Plain Language Summary: Effective moisture (EM) directly affects hydrological cycle and wider‐scale socio‐economic development. Reconstruction of prehistoric EM levels is essential for deeper understanding of the global climate system, developing climate models and improving prediction of future climate variations. Here, we reconstruct a high‐resolution EM record over the past ∼90,000 years from lake sediments in Tengchong, Yunnan province, Southwest China. We found that the variation of precession (shifts in the rotational axis of the Earth) and solar insolation are the key contributors to the EM variability at the orbital scale. Unusually, a wetter climate during the glacial period and relatively drier interglacial periods were observed in our records, which is opposite to those found in previous studies (arid glacial and humid interglacial) in monsoon regions, indicating a decoupling pattern between monsoon intensity and EM in study region. Based on a comprehensive analysis of the modern meteorological observations, we conclude that the topography and temperature exert a considerable role in modulating EM distribution and response to the decoupling pattern. Key Points: The long‐term effective moisture (EM) record in Southwest China since ∼90 kyr was reconstructedThe EM variability at the orbital scale in terrestrial Indian summer monsoon region is primarily dominated by precessionThe topographic barrier and temperature induced aridification contribute to the decoupling of monsoon intensity and EM [ABSTRACT FROM AUTHOR]

The cave system in the Sierra de Atapuerca holds one of the most important archaeological sites for the understanding of early human occupation in Europe. Among the different cavities and galleries, the Gran Dolina cave yielded a new hominin species coined as Homo antecessor of an Early Pleistocene age. Encouraged by our previous results in Gran Dolina, we carried out a study to extend and deepen our rockmagnetic investigation of the paleoenvironmental reconstruction of the upper Gran Dolina cave based on experiments that include composition, relative concentration, and grain size of the magnetic iron oxides present in the sediments. Based on the rockmagnetic experiments, we identified magnetite, hematite, goethite, and possibly maghemite in changeable amounts along the profile, which allows us to complement the existing shortage in the literature on the palaeoenvironmental reconstruction of the site. We tentatively interpret the rockmagnetic changes recorded in the cave sediments in terms of glacial/interglacial conditions, furnishing the base for a better understanding for the formation conditions of this unprecedented archaeological site. [ABSTRACT FROM AUTHOR]

In well‐buffered modern soils, higher annual rainfall is associated with enhanced soil ferrimagnetic mineral content, especially of ultrafine particles that result in distinctive rock magnetic properties. Hence, paleosol magnetism has been widely used as a paleoprecipitation proxy. Identifying the dominant mechanism(s) of magnetic enhancement in a given sample is critical for reliable inference of paleoprecipitation. Here, we use high‐resolution magnetic field and electron microscopy to identify the grain‐scale setting and formation pathway of magnetic enhancement in two modern soils developed in higher (∼580 mm/y) and lower (∼190 mm/y) precipitation settings from the Qilianshan Range, China. We found that both soils contain 1–30 μm aeolian Fe‐oxide grains with indistinguishable rock magnetic properties, while the higher‐precipitation soil contains an additional population of ultrafine (<150 nm) magnetically distinct magnetite grains. We show that the in situ precipitation of these ultrafine particles, likely during wet‐dry cycling, is the only significant magnetic enhancement mechanism in this soil. These results demonstrate the potential of quantum diamond microscope magnetic microscopy to extract magnetic information from distinct, even intimately mixed, grain populations. This information can be used to evaluate the contribution of distinct enhancement mechanisms to the total magnetization. Plain Language Summary: Reconstructing how natural climate variations in the past influenced rainfall patterns is important for understanding how rainfall would respond to our current changing climate. The amount and properties of microscopic, magnetic minerals in soil can change due to variation in soil moisture; therefore, characterizing the magnetic properties of soils can aid in quantifying past rainfall. We use the quantum diamond microscope (QDM), a device that allows micrometer‐scale mapping of magnetic sources in rock and soil samples, to investigate the magnetic properties of two soils formed in low‐ and high‐rainfall environments. We find that, although both soils contain wind‐blown, magnetic dust, only the high‐rainfall soil contains an abundant, highly magnetic population of magnetite grains formed in soil pore spaces during repeated cycles of wetting and drying. These observations demonstrate the dominant pathway by which soil magnetism responds to rainfall and showcase the ability of QDM mapping to reliably identify the mechanism of magnetism modification in soils. Key Points: Both high and low precipitation soils contain aeolian grain population with indistinguishable magnetic propertiesHigh precipitation soil alone contains anhysteretic remanent magnetization‐susceptible, <150 nm magnetites inferred to be formed from wet‐dry cycling in pore spacesMagnetic field microscopy is able to quantify rock magnetic properties of intimately mixed grain populations and pinpoint their locations [ABSTRACT FROM AUTHOR]

Prior work on rotational remanent magnetization (RRM) and rotational anhysteretic remanent magnetization (ARMROT) has demonstrated promise for magnetic mineral identification in earth materials. One challenge has been to calibrate the measurements to magnetic mineral types and microstructural controls, since previous studies have used differing spin rates, alternating field (AF) intensities and decay times, which hinders a comparison of data sets. Using a RAPID magnetometer we show that the range of usable practical rotation rates is 0.25–3 Hz [rps] which allows a wide range of RRM and ARMROT characteristics to be utilized (at 100 mT AF field, 100 μT bias field). Sets of magnetic mineral extracts from sediments, and well characterized rock samples that contain the key magnetic minerals magnetite, pyrrhotite and greigite are used for a calibration of the RRM-ARMROT behaviour. Detrital pyrrhotite and pyrrhotite-bearing phyllites have largely small positive effective field (Bg) values (up to 6 μT), with differences in Bg and ARMROT ratios at 0.5 and 2.5 Hz [rps] allowing grain size discrimination. The positive Bg values, and changes in RRM and ARMROT with rotation rates allow distinction of pyrrhotite from magnetite and diagenetic greigite. Diagenetic greigite has Bg values of –83 to –109 μT (at 0.5 Hz [rps]) and unusual RRM variation at low rotation rates caused by anisotropy affects. In contrast to previous work, based on crushed and sized natural magnetite at high spin rates, Bg for single domain magnetite from intact bacterial magnetofossils from Upper Cretaceous Chalk has some of the lowest Bg (0–1 μT) and displays a steep decline in ARMROT with increasing rotation rates. A simple tool for particle size characterization of magnetite may be the ratio of ARMROT at spin rates 2.5 and 0.5 Hz [rps]. Stability of RRM is better studied using RRM acquisition with increasing AF field intensity, since static demagnetization imparts a nuisance gyroremanence along the field axis. Mineral microstructure, dislocations and particle interactions are likely additional effects on RRM behaviour that need more investigation. [ABSTRACT FROM AUTHOR]

This paper reports the results of an environmental magnetism research carried out with the main objective of determining the spatial variation of pollution in the urban area of Metropolitan Area of the Aburrá Valley (Colombia). A two-dimensional sampling was designed in which 99 sampling sites were defined, each site was georeferenced and described by categorical factors of land use, road hierarchy, road surface, soil group or geological unit, plant species collected and city or municipality. A total of 307 environmental samples were collected, of which 110 were of urban surface soil, 99 of urban dust and 98 leaves of public ornamental plants. Rock magnetism techniques were performed to determine the nature of the magnetic minerals present in the samples. A non-parametric analysis of variance was made to relate the magnetic parameter values to the categorical factors and reveal the possible sources of the magnetic particles. After that, using the magnetic magnification factor in the dust and surface soil samples, the area and sample zone specific contamination reference values were defined. From the calculated and geo-referenced values, maps were designed showing descriptive models of the environmental contamination for each urban area according to the nature of environmental sample and magnetic parameters. The results reveal that the magnetic signal in the sites with the highest concentration of magnetic minerals is dominated by ferrimagnetic minerals of anthropogenic origin. Non-parametric analyses of variance show that a higher relative concentration of these minerals has a strong relationship with road hierarchy and a lesser degree with land uses. The maps show that most of the urban area studied has some level of contamination. [ABSTRACT FROM AUTHOR]

Abstract Effective moisture (EM) distribution in the Indian summer monsoon (ISM) region is strongly related to regional topography. An understanding of climate change and the interactions between climate variables can help predict future climate variations. Here, we reconstruct a stack EM record for Southwest China over the past 90 kyr using environmental magnetism in lake sediment. The EM in Southwest China at the orbital scale was closely linked to precession‐induced change in North Hemisphere solar insolation, as well as the ISM variability. However, at the glacial‐interglacial scale, it was decoupled with ISM intensity, being wetter during glacial periods (weakened ISM) and drier during interglacial periods (enhanced ISM). Combined with modern meteorological observations, we suggest that the topographical barrier effect and temperature induced dryness are responsible for the decoupling between ISM intensity and EM. The terrestrial topography and temperature strongly influence EM distribution by altering the dynamics of onshore airflow and evapotranspiration.

High-temperature susceptibility (HT-χ) data are routinely measured in Earth, planetary, and environmental sciences to rapidly identify the magnetic mineralogy of natural systems. The interpretation of such data can be complicated. Whilst some minerals are relatively unaltered by heating and are easy to identify through their Curie or Néel temperature, other common magnetic phases, e.g., iron sulphides, are very unstable to heating. This makes HT-χ interpretation challenging, especially in multi-mineralogical samples. Here, we report a review of the HT-χ data measured primarily at Imperial College London of common magnetic minerals found in natural samples. We show examples of “near pure” natural samples, in addition to examples of interpretation of multi-phase HT-χ data. We hope that this paper will act be the first reference paper for HT-χ data interpretation.

Abstract In well‐buffered modern soils, higher annual rainfall is associated with enhanced soil ferrimagnetic mineral content, especially of ultrafine particles that result in distinctive rock magnetic properties. Hence, paleosol magnetism has been widely used as a paleoprecipitation proxy. Identifying the dominant mechanism(s) of magnetic enhancement in a given sample is critical for reliable inference of paleoprecipitation. Here, we use high‐resolution magnetic field and electron microscopy to identify the grain‐scale setting and formation pathway of magnetic enhancement in two modern soils developed in higher (∼580 mm/y) and lower (∼190 mm/y) precipitation settings from the Qilianshan Range, China. We found that both soils contain 1–30 μm aeolian Fe‐oxide grains with indistinguishable rock magnetic properties, while the higher‐precipitation soil contains an additional population of ultrafine (

SK-2 borehole in Songliao Basin provides unprecedented geological materials for investigating the Early Cretaceous continental paleoenvironment and paleoclimate in northeastern China. The lacustrine successions of the lower Shahezi (K1sh) Formation at the depth from 4,542 to 5,695 m was systematically studied using environmental magnetism and cyclostratigraphy in this study. Magnetic analysis reveals an inverse correlation between magnetic susceptibility (MS) and lithological ranks in fine clastic sediments, with the highest values in mudstones and the lowest in sandstones. The main magnetism carriers in the lower K1sh are pseudo-single-domain (PSD) and/or multi-domain (MD) magnetite with minor presence of hematite. MS was used to further explore the genesis of the environmental and climatic variations through cyclostratigraphic analysis. Sedimentary cycles of 113 m, 34 m, 13 m and 6 m can be identified in the power spectrum, which were interpreted as long and short eccentricity, obliquity, and precession cycles, demonstrating the impact of astronomical cyclicity on sedimentary rhythmicity. Floating astronomical time scale (FATS) of 4,090 kyr and 4,148 kyr were established by tuning the inferred long and short eccentricity cycles to the artificial 405-kyr and 105-kyr orbital eccentricity curves respectively. The estimated sediment accumulation rate around 28 cm/kyr confirms the rapid deposition process within the faulted lacustrine basin. Based on this study, the lake level oscillations in Songliao Basin are assumed to be shaped by long and short eccentricity, precession and semi-precession cycles during Early Cretaceous. This study also indicates that the sand-mudstone alternations deposition in K1sh is most likely driven by the seasonal discrepancies of summer insolation during semi-precession periods.

As an important global water vapor source, the Western Pacific warm pool (WPWP) influences precipitation changes in middle and low latitudes. The low-latitude water cycle is a key climate parameter at different time scales, as it contributes to various feedback processes. However, at present, indicators of precipitation variability in the equatorial western Pacific are limited. In this work, we used the sedimentary record of the southern margin of the WPWP to study the precipitation variability over the western equatorial Pacific since MIS8. The age framework based on plankton-foraminifera δ18O was used to analyze changes in geochemical elements, clay minerals, and magnetic parameters of a marine sediment core H10. As new precipitation records, our precipitation records (TiO2, χ, and SIRM concentration without carbonate base) are closely related to monsoon and Intertropical Convergence Zone and generally in inverse phase with the oxygen isotope records of stalagmites from caves in China. A spectral analysis showed an obvious precession period. The southern margin of the WPWP water cycle is closely related to the East Asian monsoon in the last four climate cycles, and is influenced by both high and low latitudes.

Magnetic measurement was combined with geochemical analysis to investigate the trace metal pollution of atmospheric dustfall from rural areas of Inner Mongolia and urban regions of Hebei province in northern China. It is found that the type of magnetic mineral within atmospheric dustfall samples in Inner Mongolia is similar to those found in Hebei province, but the atmospheric dustfall samples in Inner Mongolia have lower magnetic mineral concentrations and finer particles. Linear multiple regression analyses show that the relationship between magnetic parameters and trace metals is found to vary between the contrasting rural and urban areas, and is controlled by the different source magnetic minerals. The concentration- and type-dependent magnetic properties of the particles correlated strongly with the concentrations of trace metals derived from natural processes, and the grain size-dependent magnetic parameters correlated negatively and significantly with the concentrations of trace metals derived from anthropogenic activities. [ABSTRACT FROM AUTHOR]

In this study, dustfall samples were systematically collected in various regions of Shanghai before and after the occurrence of COVID-19 in December 2019 and December 2020. The magnetic response, content and pollution status of relevant heavy metal elements in the samples were analyzed using environmental magnetism, geochemistry, scanning electron microscopy (SEM) and the enrichment factor (EF) method. The results show that the magnetic particles in the dustfall samples are mainly pseudo-single-domain (PSD) and multi-domain (MD) ferrimagnetic minerals, and Fe, Zn, Cr, and Cu are mainly concentrated in the districts with intensive human activities. Due to restrictions on human activities following the COVID-19 epidemic, both the values of magnetic parameters and the heavy metal pollution level in 2019 are more significant than those in 2020, which is consistent with the Air Quality Index (AQI) results. In addition, magnetic susceptibility (χlf), non-hysteresis remanence (χARM) and saturation isothermal remanence (SIRM) have different degrees of correlation with heavy metal elements, and the correlations with Fe, Pb, Cr and Zn are extremely prominent. The magnetic parameters can effectively and quickly reflect the level of particulate matter pollution, making them a useful tool for monitoring urban air quality. [ABSTRACT FROM AUTHOR]

Sediment source fingerprinting using environmental magnetism has successfully differentiated between sediment sources in several studies in the Eastern Cape Province of South Africa. The method was applied in this study to the near‐natural landscape of southern Kruger National Park (Mpumalanga Province) to trace sediment and determine sediment yields by lithology in four reservoir catchments that were underlain by igneous, metamorphic, and sedimentary rocks. The Park area has no history of cultivation and is a conservation area, so catchment sources were dominated by underlying lithologies. One sediment core was collected in the assumed deepest area of the reservoir. Source discrimination and apportionment were estimated using a common statistical protocol that includes a Mann–Whitney U or Kruskal–Wallis H test, mass conservation test, discriminant function analysis, and an (un)mixing model. A contribution from each lithology‐defined source was estimated. Sediment yield by lithology was estimated by using published catchment area‐specific sediment yields in combination with the (un)mixing model. Underlying lithology determined vegetation type and density, and vegetation appeared to play a crucial role in protecting soils and reducing erosion. Proximity to reservoir, that is, travel distance for eroded sediment, and connectivity were also important factors controlling the relative contribution from each potential source. The contributing area for sediment was found to be dynamic through time and was probably dependent on runoff and temporal variations in vegetation cover. [ABSTRACT FROM AUTHOR]

Whether the East Asian summer monsoon (EASM) migrated westward into the Asian interior during past warm periods is still unclear but is important for predicting precipitation variability in the Asian interior under future warming. Recent precipitation records from the Qaidam Basin in the Asian interior suggest that the EASM further migrated westward into the western Qaidam Basin during the middle Piacenzian warm period (mPWP: 3.264–3.025 Ma), indicating that precipitation in this ecologically fragile region was greater than it is currently. However, these precipitation records reveal weak sensitivity to insolation forcing, which is inconsistent with records from monsoon-influenced regions, hindering our understanding of orbital timescale precipitation variations in the Qaidam Basin during this Pliocene warmth. In this study, we report high-resolution (∼3 kyr) magnetic parameter-based records and medium grain size records from the GS section of the western Qaidam Basin during 3.25–2.95 Ma. We interpret magnetic parameters and grain size as precipitation proxies based on their sensitivity to precipitation variations. Our precipitation records suggest that the EASM precipitation was likely the precipitation source for the Qaidam Basin during the mPWP. At the orbital timescale, precipitation records reveal dominant 20-kyr precessional cycles, consistent with records from the Chinese Loess Plateau and the South China Sea, suggesting that the June insolation gradient controlled precipitation variations in the Qaidam Basin during the mPWP. At the 40-kyr band, precipitation records show in-phase relationships with ice sheets, and we infer that Antarctic ice sheet forcing seems to also influence Qaidam precipitation via atmospheric or marine processes. These results provide the first evidence demonstrating that Qaidam precipitation was extremely sensitive to the June insolation gradient and ice sheets during the mPWP, improving our understanding of orbital timescale precipitation variations in the Asian interior during past warm periods. • The Qaidam precipitation was dominated by the 20-kyr cycles during 3.25–2.95 Ma. • The Qaidam precipitation was also characterized by the 40-kyr cycles. • The forcing mechanism may be related to insolation and ice sheets. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Paleoenvironmental archives in East Antarctica have revealed significant changes during the Holocene, marked by ice sheet retreat leading to the isolation of submarine basins. These basins offer valuable insights into past climate, glaciology, and oceanography shifts that impact sedimentary processes. In this study, environmental magnetism and biogeochemical proxies to investigate the Mid-to-Late-Holocene transitions in Pup Lagoon, a coastal isolation basin is presented. Our findings reveal distinct stratigraphic zones reflecting shifts from marine to lacustrine environments. The results reveal predominant mechanical weathering in the Stornes region, producing coarse-grained “soft” ferrimagnetic minerals. Notably, a period of warm oceanographic conditions between 6000 and 4722 cal. yr BP was characterized by mixed magnetic grain sizes and ultrafine superparamagnetic grains, indicating relatively oxic open waters in the basin. Subsequent shifts to reducing conditions coincide with persistent marine sea ice cover from 4722 to 2634 cal. yr BP, favoring the retention of coarse-grained ferrimagnets. Finer magnetic grain sizes between 2634 and 2185 cal. yr BP was attributed to the increased freshwater inputs associated with the Mid-Holocene Hypsithermal. Further, diagenetic changes under persistent sea ice cover between 2185 and 1970 cal. yr BP led to the selective dissolution of fine-grained ferrimagnets. Transitioning to freshwater isolated basin conditions between 1970 and 588 cal. yr BP, fine ferrimagnet precipitation indicate oxic to suboxic conditions alongside drier conditions. Biogenic productivity increased post-isolation, which was reflected in increased (Total Organic Carbon) TOC and (Total Nitrogen) TN percentages. Additionally, the presence of greigite in the isolated phase sediment indicates reducing conditions owing to organic matter decomposition. Notably, χfd% exhibits an inverse trend to sea ice concentration, potentially indicating anoxic-dysoxic conditions due to the presence of sea ice. These observations align with broader regional sea ice concentration changes, emphasizing the interconnected behavior of local and regional factors shaping Antarctic coastal environments. [ABSTRACT FROM AUTHOR]

Uplift of the Tibetan Plateau, expansion/shrinkage of the Paratethys Sea, and global climate are three major forcings for central-east Asian climatic and environmental variations during the Cenozoic. However, knowledge of expansion/shrinkage history of the Paratethys Sea is much less well known in comparison with the other two forcings. Here, we present a first multiple-parameter environmental magnetic and diffuse reflectance spectroscopy study of the Eocene eolian Red Clay deposits (∼51–40 Ma) in the Xorkol Basin of the northeastern Tibetan Plateau, which is near the easternmost maximum boundary of the Eocene Paratethys Sea. The first detailed Eocene expansion/shrinkage history of the Paratethys Sea was reconstructed based on the hematite content of the Eocene Red Clay, which shows remarkable consistency with the previous low-resolution Paratethys Sea paleowater depth record in the southwestern Tarim Basin. These results demonstrate that the Paratethys Sea experienced a three-stage (shrinkage-expansion-shrinkage) evolution between ∼51 and 40 Ma, with boundaries at ∼46.2 and 42 Ma. Superimposed on this framework, the Paratethys Sea experienced four times of rapid shrinkages at the expansion phase (shows 400-kyr cycles) during ∼44–42 Ma modulated by eccentricity forcings. These new results are of great significance to evaluate respective role of Tibetan uplift, global climate, and Paratethys Sea area variations in Asian climate and environmental change over the Eocene.

We present millennial to centennial-scale monsoon variability during the Late-Pleistocene to Holocene using multi-proxy data from 100 cm thick peat deposit in the Baspa Valley, northwest Himalaya. Based on high-resolution mineral magnetism, carbon isotope, and total organic carbon data supported by radiocarbon dating, four climatic phases of alternating strengthened and weakened Indian summer monsoon (ISM) are identified for the last 20 kyr in the higher central Himalaya. Periods of strengthened ISM are dated to ~15 to ~14 ka, ~10 to ~7 ka, ~2.4 to ~1.3 ka, and 243 yr BP to present, which is ascribed to the post-Older Dryas associated with an increase in solar insolation. The phases of weakened ISM are bracketed between ~20 and ~15 ka, ~14 to ~10 ka, ~7 to ~2.4 ka, and ~1300 to ~243 yr BP. These phases are attributed to global cooling events, i.e., the Last Glacial Maximum (LGM), Younger Dryas (YD), and the Middle to Late Holocene. They govern by changes in the solar insolation. [ABSTRACT FROM AUTHOR]

Children's exposure to air pollution affects both their health and learning skills. Fine and ultrafine particulate matter (PM2.5, PM1), notably issued from traffic sources in urban centers, belong to the most potential harmful health hazards. However their monitoring and the society's awareness on their dangers need to be consolidated. In this study, raising teacher and pupil involvement for air quality improvement in their schools environment is reached through developing a passive monitoring technique (bio‐sensors made of tree bark). The experiment was implemented in two urban elementary schools situated close to a main traffic road of the city of Toulouse (South of France). Magnetic properties, carbonaceous fraction measurements, and scanning electronic microscopy (SEM‐EDX) investigations were realized both on passive bio‐sensors and filters issued from active sampling. We find that traffic is the main PM1 source for both outdoors and indoors at schools. Higher levels of outdoor PM in the school's environments compared to urban background are reached especially in the cold period. The schools proximity to a main traffic source and lack of ventilation are the main causes for observed PM1 accumulation in classrooms. The co‐working experiment with educational teams and pupils shows that the use of bio‐sensors is a driver for children empowerment to air pollution and therefore represents a potential key tool for the teachers though limiting eco‐anxiety. As PM accumulation is observed in many scholar environments across Europe, the proposed methodology is a step toward a better assessment of PM impact on pupil's health and learning skills. Plain Language Summary: Children's exposure to air pollution affects both their health and learning skills. Monitoring airborne particles in school environments from a knowledge co‐production perspective seems essential to address air pollution in schools. Here we use tree bark and filter samples to monitor air quality in schools. Teachers and pupils are involved in the implementation process. The experiment was set up in two schools in Toulouse (France), close to the busy ring road. Traffic is the main source of air pollution both inside and outside of the classrooms. Quantities of airborne particles are higher during cold periods. The proximity of the highway and poor ventilation in the schools are the main cause of airborne particles accumulation inside classrooms. Collaboration with school staff and students shows that the use of tree has been a driving force for children to embrace the project and understand the context of air pollution, limiting anxiety related to this topic. Key Points: Magnetic methods and carbon analyses evidence high concentrations of indoor and outdoor PM1 due to traffic sourcesProximity of traffic source and absence of ventilation favorize accumulation of PM indoor threatening children's health and learning skillsPassive monitoring using vegetal media facilitates teacher and pupil involvement and prevents eco‐anxiety [ABSTRACT FROM AUTHOR]

The Paleocene‐Eocene Thermal Maximum (PETM, ∼56 Ma) presents a past analog for future global warming. Previous studies provided evidence for major loss of dissolved oxygen during the PETM, although understanding the degree and distribution of oxygen loss poses challenges. Magnetofossils produced by magnetotactic bacteria are sensitive to redox conditions in sediments and water columns, and have been used to reconstruct paleoredox conditions over a range of geological settings. Here, we present records of well‐preserved magnetofossils from cores along Walvis Ridge in the Southeast Atlantic that span the PETM across a depth transect (∼1,500–3,600 m paleodepth). Hysteresis, isothermal remanent magnetization curves, first‐order reversal curve diagrams, and low‐temperature magnetic measurements document large variations in magnetic properties of magnetofossils, which relate to time and water depth. Abundant magnetofossil grains are present within the studied sediments, and their morphologies change with paleodepth, as shown by transmission electron microscope observations. Magnetofossils from samples within the PETM onset at the deeper sites (∼2,600–3,600 m paleodepth) have lower coercivity values, a higher oxidation degree, and smaller grain sizes than those from shallower sites (∼1,500–1,800 m paleodepth), likely reflecting changes in paleoredox conditions at different paleodepths. We use the magnetofossil records to reconstruct relative changes in dissolved oxygen content at different water depths through the PETM, and suggest that ocean deoxygenation likely expanded downwards in the early stages of the PETM. We thus demonstrate the value of magnetofossil records for paleoenvironmental reconstructions over time and space, particularly for sediments that lack carbonate fossils. Plain Language Summary: The Paleocene‐Eocene Thermal Maximum (PETM, ∼56 Ma) was the most severe global warming event over at least the last 65 million years. Understanding environmental perturbations across this interval can provide insights into our current and future warming world. Magnetofossils may be preserved in sediments after the death of magnetotactic bacteria or other microorganisms, and may record critical paleoenvironmental information, including on marine productivity and oxygenation. Here, we use a newly proposed magnetofossil‐based proxy to reconstruct ocean oxygenation along a water depth transect (∼1,500–3,600 m) spanning the PETM in the Southeast Atlantic (Walvis Ridge). Our paleoenvironmental reconstructions indicate that deoxygenated seawater expanded downwards during the early warming stages of the PETM, and demonstrate the use of magnetofossils as paleoredox proxies. Key Points: Large variations in magnetofossil signatures at different South Atlantic paleodepths during the Paleocene‐Eocene Thermal Maximum (PETM)Magnetic properties combined with morphological data of magnetofossils trace paleoredox changes at different water depths during the PETMMagnetofossil records suggest lowered ocean oxygenation during the PETM in intermediate and deep waters [ABSTRACT FROM AUTHOR]

Hematite concentration is an important climatic proxy for environmental (climatic) studies of soils and sediments. However, the accurate quantification of naturally occurring hematite has always been a difficult question, especially for those areas with lower hematite concentrations. Diffuse reflectance spectroscopy (DRS) is an effective method for hematite identification and quantification with lower detection limits. In this study, we synthesized a set of samples with well-determined concentrations to explore the exact detectable range of hematite and propose the most effective transfer function between the DRS proxy and hematite concentration. In addition, natural sediments from Inland Asia and the Western Pacific Ocean were used to further test the feasibility of the new transfer function. Results show that the lowest DRS detection limit for hematite could reach ~0.00078%, but is affected by the natural matrix. We also find that the second derivative of the Kubelka–Munk (K–M) function is monotonically correlated with the hematite concentration (0.00078%–100%), but ambiguities exist for the first derivative. Therefore, the second derivative of the K–M function is highly suggested for the hematite quantification, especially when concentration exhibits a wide range of variations. This study provides important references for the application of hematite proxy and promotes the popularization and development of the DRS method. [ABSTRACT FROM AUTHOR]

This study investigates the sedimentological evolution of the South Danamandıra Lake (SDL) lake in Çatalca Peninsula, 70 km west of İstanbul, using Georadar data and multiproxy analyses of five sediment cores. The lake is a 1.3-m deep, endorheic freshwater peatland, heavily colonised by common reed (Phragmites sp.). The multiproxy core investigations include a lithological core description and environmental magnetism, physical properties (gamma density and magnetic susceptibility), geochemical elemental, pollen and radiocarbon dating analyses. The lithological sequence in the lake consists of an upper peat unit and a lower sand-silt-clay unit. The peat unit is characterized by lower magnetic susceptibility, density and lithophile elements (K, Fe, Ti, and Zr) concentrations than the sand-silt-clay unit. Overall interpretation of the multiproxy data and the age-depth model suggest that the SDL was formed in a shallow depression of a fluvial channel at ca 10.9 cal kyr BP, and became a eutrophic lake at 8.1 cal kyr BP during the early Holocene warm period. Redox-sensitive element (i.e. Mn) distribution and mineral magnetic properties indicate that the peat unit has accumulated under anoxic conditions below a thin oxic surficial layer. Increase in the Taraxacum, Asteraceae, and Poaceae pollen percentages, together with high siliciclastic inputs in the lake, indicate that anthropogenic influence in the area started at 5.4 cal kyr BP [ABSTRACT FROM AUTHOR]

This study is close to an earlier urban soil survey carried out for a rapidly growing city with a high traffic density in Aurangabad city, India. Consequently, it aims to use the environmental magnetism approach to assess roadside emissions at a known polluted site. Magnetic measurements have been successfully implemented in soil studies and seem to be a suitable approach for pollution assessment in industrial and roadside areas of the study area. The present study was accomplished for magnetic susceptibility, isothermal remanent magnetization, coercivity, hysteresis measurements, thermomagnetic curves, scanning electron microscopy, and energy-dispersive spectroscopy analysis to evaluate the absolute fraction of magnetic minerals in bulk soil samples. The soils displayed variation in magnetic susceptibility values, which was influenced by concentration, domain states, and morphological characteristics of magnetic minerals. Substantial variation in the mineralogical composition of soils deriving from different industrial activities was noticed. The results indicate that industrial and roadside soil samples with mostly coarser and irregular-shaped show ferrimagnetic minerals. The presence of iron–titanium combination in most of the samples is due to titanomagnetite accompanying the titanium-bearing grains. In soils, a higher amount of ferrimagnetic minerals (magnetite, titanomagnetite, maghemite) with a minor content of antiferromagnetic minerals (hematite/goethite) was noticed. These studies reveal that magnetic and morphological characterization of soils can be used as an appropriate tracer for industrial and roadside soil pollution, which leads to new avenues for more detailed chemical mapping. [ABSTRACT FROM AUTHOR]

This study presents new evidence for long-term variability in the late Holocene North American Monsoon (NAM), Pacific coast of Mexico. We have carried out a rock magnetic study on two deep-sea sediment cores from the Pacific coast Pescadero Basin. The magnetic intensities estimate total magnetic material and are a proxy for total clastic sediment. Ratios of magnetic intensities estimate the grain size of magnetic material. The rock magnetic data show a decimeter scale, multi-decadal oscillation with fourteen cycles (A-N) over the last 1200 years. These oscillations reflect alternating intervals of stronger/coarser magnetic/clastic flux to the coastal ocean and intervals of weaker/finer magnetic flux. We think these variations are caused by variations in long-term dominance of the NAM; summer (wet) monsoons produce rainy conditions (with runoff) while winter (dry) monsoons produce significant offshore winds, increased upwelling/biological productivity. We can correlate our variability to two other published studies southeast of Pescadero Basin, coastal lake sediments in Laguna de Juanacatlan and a Juxtlahuaca Cave stalagmite. Both of these studies estimate local rainfall. We see evidence of the same pattern of multi-decadal rainfall-runoff variability in these records as we see in Pescadero Basin, which is synchronous to within ±25 years over the last 1200 years. The multi-dacadal pattern of hydrologic variability in all three records varies in cycle duration from ~90-years wet/dry cycles in the Little Ice Age (1400–1850 AD) to ~60-years cycles in the Medieval Climate Optimum (1100–1400 AD). This variability in cycle duration suggests some chaotic nature to the regional NAM climate pattern or some long-term non-linear forcing (PDO?).

Abstract Children's exposure to air pollution affects both their health and learning skills. Fine and ultrafine particulate matter (PM2.5, PM1), notably issued from traffic sources in urban centers, belong to the most potential harmful health hazards. However their monitoring and the society's awareness on their dangers need to be consolidated. In this study, raising teacher and pupil involvement for air quality improvement in their schools environment is reached through developing a passive monitoring technique (bio‐sensors made of tree bark). The experiment was implemented in two urban elementary schools situated close to a main traffic road of the city of Toulouse (South of France). Magnetic properties, carbonaceous fraction measurements, and scanning electronic microscopy (SEM‐EDX) investigations were realized both on passive bio‐sensors and filters issued from active sampling. We find that traffic is the main PM1 source for both outdoors and indoors at schools. Higher levels of outdoor PM in the school's environments compared to urban background are reached especially in the cold period. The schools proximity to a main traffic source and lack of ventilation are the main causes for observed PM1 accumulation in classrooms. The co‐working experiment with educational teams and pupils shows that the use of bio‐sensors is a driver for children empowerment to air pollution and therefore represents a potential key tool for the teachers though limiting eco‐anxiety. As PM accumulation is observed in many scholar environments across Europe, the proposed methodology is a step toward a better assessment of PM impact on pupil's health and learning skills.

The Indian monsoon is an important part of the global monsoon system, allowing important transfers of moisture at a large geographical scale and deeply affecting human populations and economic prosperity of regions. The tropical summer monsoon in the Northern Hemisphere is generally considered to be driven by low latitude solar radiation. Therefore, the summer monsoon strength is near zero-phase to the maximum of Northern Hemisphere Summer Insolation (NHSI). However, records from the Arabian Sea and some other parts of the Indian Ocean (e.g., Andaman Sea) show that a ∼8 kyr phase difference exists between the Indian summer monsoon (ISM) strength and the northern Hemisphere Summer Insolation maxima, which is obviously different from the records of stalagmites in the East Asia and other marine sediments (e.g., Bay of Bengal). This leads to the “sea-land precession phase paradox” in indian summer monsoon research. This paper systematically summarizes the Indian monsoon variability on orbital scale indicated by various records from the Indian monsoon regions (including oceans and continents) since the late Quaternary. The orbital forcing of Indian monsoon, the potential phase difference between indian summer monsoon and northern Hemisphere Summer Insolation and its possible forcing mechanism(s) are further discussed. The observed phase lag between indian summer monsoon and northern Hemisphere Summer Insolation may be controlled by the Atlantic Meridional Overturning Circulation (AMOC), latent heat transfer between the southern Indian Ocean and the Asian continent, or caused by the lack of tightly coupling between the Arabian Sea summer monsoon proxies and the monsoon intensity. In addition, it is still unclear whether previous monsoon proxies can provide a strong constraint on the intensity of summer monsoon. Environmental magnetism has been widely used in high-resolution dating and the analysis of paleoclimate variabilities in marine and terrestrial sediments, due to its high sensitivity on the rainfall and temperature. Therefore, in order to solve these issues, it is necessary to combine magnetic parameters with geochemical and paleontological parameters for more systematic work in the future.

The cave system in the Sierra de Atapuerca holds one of the most important archaeological sites for the understanding of early human occupation in Europe. Among the different cavities and galleries, the Gran Dolina cave yielded a new hominin species coined as Homo antecessor of an Early Pleistocene age. Encouraged by our previous results in Gran Dolina, we carried out a study to extend and deepen our rockmagnetic investigation of the paleoenvironmental reconstruction of the upper Gran Dolina cave based on experiments that include composition, relative concentration, and grain size of the magnetic iron oxides present in the sediments. Based on the rockmagnetic experiments, we identified magnetite, hematite, goethite, and possibly maghemite in changeable amounts along the profile, which allows us to complement the existing shortage in the literature on the palaeoenvironmental reconstruction of the site. We tentatively interpret the rockmagnetic changes recorded in the cave sediments in terms of glacial/interglacial conditions, furnishing the base for a better understanding for the formation conditions of this unprecedented archaeological site.

Characterization of magnetic, morphological, chemical properties and source apportionment of environmental transporters (dust and soil) around Mejia Thermal Power Station (MTPS), West Bengal, India were performed. Rock magnetic measurements combined with scanning electron microscopy (SEM) and X-ray fluorescence (XRF) study distinguish the mineral magnetic phases and identify their environmental implications concerning anthropogenic and natural factors. Findings of this study strengthen detection of anthropogenic magnetite, contributed by traffic and MTPS emission in dust and soil, respectively. However, presence of antiferromagnetic minerals in residential areas confirms their lithogenic and/or pedogenic origin. Existence of a low amount of anthropogenic magnetite in residential areas indicates their onset from fly ash emission due to prevailing north-easterly wind direction. Both soil and dust samples are categorized into three types of ferrimagnetic particles (spherules, irregular, and aggregate) with diverse morphologies and enriched iron concentration. Soil and dust were influenced by quartz, while the average concentrations of potentially toxic elements (PTEs) occurred in decreasing order of Ba>Zr>Cr>V>Sr>Zn>Y>Nb>Pb>Co>Sc>Ga>Ni. Sampling sites near ash pond with higher concentrations of PTEs than those situated at distance suggest that PTEs association with fly ash happened during coal combustion. This explains the observed correlation between magnetite particles and proxies for multiple pollution sources (like MTPS and traffic). It also reveals the necessity for attention when detecting abundance of anthropogenic magnetite using environmental magnetic methods. Thus, the identification of magnetite using environmental magnetic measurements can be used as a tracer for natural loading within anthropogenic background. [ABSTRACT FROM AUTHOR]

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