Sediment Components Research Articles

Occurrence Characteristics and Risk Assessment of Microplastics in Water and Sediments of Anhui Section of Huaihe River Basin

The occurrence characteristics and ecological risk level of microplastics in the water and sediments of the Anhui section of Huaihe River Basin were analyzed via field sampling, stereomicroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), risk index (H), and pollution load index (PLI) model. The current situation of microplastics in the water and sediments of the basin was analyzed, and the ecological risk assessment of microplastics was conducted. The results showed that the detection rate of microplastics at each site in the basin was 100%. The average abundance of microplastics in surface water and sediments was (39800±3367) n·m-3 and (5078±447) n·kg-1, respectively. The average abundance of microplastics in the downstream was higher than that in the upstream and midstream. The particle size of microplastics in water and sediments was primarily 20-150 μm, accounting for 82.96% and 80.77%, respectively. The microplastics were primarily fiber (water 76.05%, sediment 84.53%), film (water 21.83%, sediment 15.43%), and debris (water 2.12%, sediment 0.04%). The microplastics in water and sediments were primarily transparent, accounting for 63.31% and 83.69%, respectively. Polyethylene (65.74% in water and 80.62% in sediment) and polypropylene (18.43% in water and 9.71% in sediment) were the major components of water and sediments. Microplastics were primarily derived from agricultural films, abandoned fishing gear and nets, and artificially abandoned plastic bags in ports. The microplastic risk index (H) model assessment revealed that the risk index of some sites was high, and the risk level of microplastics in the Anhui section of Huaihe River Basin was grade II. The pollution load index (PLI) model assessment revealed that the ecological risk of surface water and sediments in the basin was generally low.

Prediction of metformin adsorption on subsurface sediments based on quantitative experiment and artificial neural network modeling

Metformin (MET), a widely employed hypoglycemic pharmaceutical agent, has been frequently detected within groundwater, which has posed a threat to ecosystems and human health. However, the adsorption behavior of MET onto distinct constituent aquitards and aquifers sediments remains shrouded in uncertainty. To reveal the adsorption capacities and mechanisms of diverse sedimentary matrices, we delved into a series of adsorption experiments involving MET on 37 subsurface sediment samples obtained from four boreholes (ranging from 0 to 30 m in depth) in the Jianghan Plain. The quantitative analysis revealed that a majority of the sedimentary compositions consisted of clay minerals (mainly chlorite, montmorillonite and albite), with MET exhibiting considerable variability in across different sediment components (ranging from 15.5 to 489.4 mg/kg). In general, MET adsorption declined in proportion to an increase in quartz composition and depth. Consequently, an artificial neural network model was constructed (R2 = 0.971) to assess the influence of sediment composition on MET adsorption, and thereby elucidating the dominant roles played by chlorite and montmorillonite in this process. Notably, electrostatic attraction, cation exchange, and chemical bonding emerged as the primary mechanisms governing MET adsorption on sediments, particularly those rich in clay minerals. By shedding light on the adsorption mechanism of MET on clay-dominated subsurface sediments, our findings have contributed to a quantitative understanding of MET's adsorption capacity and have highlighted the associated environmental risks.

Multi-proxy evidence of unprecedented hydroclimatic change in a high Arctic proglacial lake: Linnévatnet, Svalbard

ABSTRACT Svalbard is at the forefront of sea ice, marine, and terrestrial environmental change in the Arctic and so can be viewed as an example of what may be expected in other high latitude regions influenced by the North Atlantic Current. However, there are few highly resolved (subdecadal) paleoclimate records from this area that provide a long-term perspective on recent climatic changes. Here, we investigate a new composite sedimentary sequence from Linnévatnet, western Spitsbergen, spanning the last ~2,000 years. The chronology of this new composite laminated sequence is supported by four radiometric dates. Prior to conducting paleoclimate investigations on these lake sediments, we investigated the sediment sources entering Linnévatnet. Sediment samples collected around the lake’s watershed indicate that the main sediment sources come from the eastern carbonate valley wall as well as Linnéelva, the main river system. Micro-X-ray fluorescence (µ-XRF) results indicate that calcium is the largest component of sediment delivered to the delta-proximal basin, where the sedimentary record was collected. Percentage organics deduced from loss-on-ignition measurements reveal an antiphased relationship with calcium and magnetic susceptibility, implying that the sediment loading at the core site is largely modulated by the alternation of calcium derived from carbonates of the eastern flanks of the valley and by coal-bearing sandstone from Linnéelva, derived from the main river inflow that drains the central valley. Linnéelva is mainly fed by snow and glacier meltwaters from Linnébreen, the small valley glacier now located 7 km south of Linnévatnet. Because Linnébreen is underlain by coal-bearing sandstone, organic content in Linnévatnet lake sediments can be used as an indicator of glacier activity. Annually resolved parameters—that is, calcium and grain size—were found to be strongly correlated to temperature inferred from nearby Lomonosovfonna δ18O ice record as well as the wider reconstructed Northern Hemisphere winter temperature. The coarsest grain size, highest calcium values, and lowest concentration of organics occurred just in recent years, suggesting that glacier influence on the sedimentary input to Linnévatnet is now at an all-time low in the context of the past millennia.

Decoupled local climate and chemical weathering intensity of fine-grained siliciclastic sediments from a paleo-megalake: An example from the Qaidam basin, northern Tibetan Plateau

Clay mineralogy and elemental geochemistry of lacustrine sedimentary records have been widely used in paleo-weathering and paleo-climate studies. However, different paleo-climatic interpretations may be produced via analyses on siliciclastic sediments and other sedimentary components (e.g., authigenic minerals and organic materials), especially for megalake systems. To test this hypothesis, we focus on late Cenozoic lacustrine fine-grained deposits from the northwestern Qaidam basin and combine clay mineralogical and geochemical data (including neodymium isotope) to interpret sediment provenance, reconstruct paleo-weathering history and characterize sediment-climate feedback processes. Provenance analysis results show that the lacustrine siliciclastic sediments were derived from lithologically similar sources that provided dominant felsic parent-rocks. The kaolinite/illite ratio, illite chemistry index, Chemical Index of Alteration (CIA) values are low and demonstrate overwhelmingly mild-moderate chemical weathering intensity, seemingly matching well with the middle–late Miocene regional arid climate. However, these weathering intensity index values are also highly fluctuant and display increasing trends during ~13.4–12 Ma and ~8.8–8.4 Ma. The reconstructed paleo-weathering history is discrepant with local intensified aridity conditions documented by previously published sedimentary carbonate oxygen isotope, evaporite mineral, biomarker and sporopollen data. Given the occurrence of a middle–late Miocene megalake in the Qaidam basin, the intense exhumation at ~13–12 Ma and the ~9 to ~7 Ma intensified East Asian summer monsoon precipitation in northeastern Tibet regions, we suggest that the lacustrine fine-grained siliciclastic compositions and corresponding weathering records were likely influenced by tectonic and climatic changes in far regions to the east. The observed clay mineralogical and geochemical variations reflect weathering conditions involving sediment sources and transport pathways, not merely the depositional areas. Our findings verify the possible differences in paleo-climate reconstruction results from different lacustrine sediment indicators. This study emphasizes the importance of a sediment source-to-sink perspective for paleo-climate study based on siliciclastic materials in megalake systems.

Interfacial interactions controlling adsorption of metal cations on montmorillonite

Abstract Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+ tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multiden-tate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research.

RECONSTRUCTION OF SEDIMENT RUNOFF FORMATION FEATURES IN THE LAKE KHORLAKEL (NORTH CAUCASUS) CATCHMENT FOR THE LAST 8 THOUSAND YEARS (ACCORDING TO GEOMORPHOLOGICAL AND LITHOSTRATIGRAPHIC DATA)<a href="#FN2"><sup>2</sup></a>

The change in sediment yield is an important indicator of the natural environment dynamics, depending on the combination of landscape, tectonic and climatic conditions. Assessment of sediment yield often based on the results of studying the bottom sediments of mountain lakes with relatively compact catchments. However, for correct reconstructions, in addition to analyzing lake sediments, it is necessary to study the causes and mechanizm of sediment redistribution in their catchments, to identify sediment delivery pathways to the reservoir and their possible changes over different time windows. The drainless Lake Khorlakel, located at the altitude of 2045.0 m above sea level on the northern macroslope of the Greater Caucasus. It is a suitable testing ground for complex research: on the one hand, the relict reservoir is an ideal sedimentation trap, and on the other, it is located with in an area of intensive exogenous processes and tectonic activity. The two boreholes were drilled in 2017 in the deepest (≈8 m) part of the lake and 17 samples collected taken from the cores for radiocarbon dating, which made it possible to build an age model for the range from 8000 to 500 yr. BP. Complex geological and geomorphological studies were carried out in 2021 to interpret the obtained data. It was found that sedimentation in the lake is associated with runoff and sediment redistribution in the Elbashi creek catchment. A number of episodes of proluvial activation with the formation of an outflow cone, followed by lake accumulation, have been traced for the last 8 kyr. The connection between lake and catchment ceased only in the last 1 kyr. BP. Two main stages of lake sedimentation with a boundary of 3 kyr. BP and 10 episodes, that are characterized by different proportions of mineral and organic components in bottom sediments were established. Some of the lithostratigraphic boundaries correlate with strong earthquakes that occurred in the Elbrus region, and some – with climatic events.

Middle to late Holocene environmental evolution and sea level change on the west coast of Bohai Bay

Bohai Bay is a typical area of global change research in East Asia, due to its unique geographical location and shallow water environment. In this paper, we present the results of a study of grain-size, geochemistry, pollen and algae of a middle to late Holocene sediment core from Haixing wetland, which located on the west coast of Bohai Bay. The results show that: 1) Prior to 6700 cal a B.P., the content of Cl, Sr/Ca ratio were the highest, end-member analysis of grain size suggested EM2 were dominant, which is characteristic of marine sediment and the concentrations of Pediastrum and Typha (indicating a freshwater environment) pollen were lowest, overall indicating the maximum of relative sea level; 2) During 6700–5000 cal a B.P., and the Ti and K contents, EM1 (lacustrine sedimentary component) increased substantially, EM2 decreased, and EM3 (fluvial sedimentary component) began to appear. The concentrations of Pediastrum, Dinophyceae and Typha pollen began to increase. All these indicating that the relative sea level began to fall and the study area became a lagoon environment; 3) During 5000–3500 cal a B.P. the Ti and K content increased further; EM1 was dominant, EM2 was rare, indicating that the relative sea level decreased further and the lagoon gradually became enclosed; 4) After 3500 cal a B.P., the Ti content reached its maximum and the Cl content and Sr/Ca ratio decreased to their lowest levels. EM1 was dominant and EM2 was virtually absent; dinoflagellate cysts almost disappeared and there was large increase of Typha pollen, indicating the complete exclusion of a marine influence during most of this period. However, during 2500–2000 cal a B.P. the Cl and the Sr/Ca ratio increased slightly once again, indicating a transient transgression.

Lead Components of Bulk Sediments from Dahu Swamp in Nanling Mountains (South China): Implications for the Climatic and Environmental Changes Since the Last Deglaciation

Lead Components of Bulk Sediments from Dahu Swamp in Nanling Mountains (South China): Implications for the Climatic and Environmental Changes Since the Last Deglaciation

The Modern Nile Delta Continental Shelf, with an Evolving Record of Relict Deposits Displaced and Altered by Sediment Dynamics

The most extensive coverage of surficial sediment samples collected to date on Egypt’s Nile Delta coast and shelf is needed to better define sediment dispersal patterns across this setting’s rapidly eroding margin. Changes in time are now induced by River Nile sediment cutoff by dams, sea level rise, marked shelf subsidence, and regional climate changes, which have altered the amounts and components of sediments; these require replacement, along with the implementation of more effective coastal protection measures. Multiple computer-generated offshore maps depict the distributions and proportions of sand, silt, and mud; the mean grain size and standard deviation (sorting); heavy mineral concentrations; and carbonate content. Heavy mineral lobes at the coast and offshore identify former Nile branch sites. Channel lobes extending seaward resulted from their progradational phase and from the delta’s altered sedimentation from the early to late Holocene. The progressive deposition and erosion of these fossil fluvial lobes, and of two active Nile channels, selectively removed their quartz and less dense minerals, thus concentrating heavy minerals on the coast and inner shelf. The prolonged dispersal of original sediment effluence from relict and recent Nile tributaries induced variable depositional patterns on the present shelf. These coastal depocenters, along with extensive sand, silt, and mud from shelf sediments, were reworked further seaward and dispersed by bottom currents, thus masking most previous onshore-to-offshore transport patterns. The major surficial features document long-term responses to the diverse dispersal that influenced the shoreline to the outer shelf deposits from the Pleistocene to the present.

Carbon burial potential of the surface sediment and its associated anthropogenic impacts in the semi-closed area of Bohai Bay

Carbon burial potential in marine sediments plays an important role in global warming. However, they are easily disturbed by human activities in coastal areas. In this study, marine sediment samples were collected from the coastal area of Bohai Bay, and the effects of exogenous inputs on the carbon content and forms were evaluated. Results showed that the carbon content in sediments ranged from 12.45 g/kg to 19.14 g/kg, with an average of 16.23 g/kg ± 2.78 g/kg, and the average organic carbon (C-Org) content is 12.68 ± 1.14 g/kg, which accounts for about 75% of the total carbon storage in sediment. The content of inorganic carbon (CaCO3) did not change significantly, but the content of C-Org in the estuary area was significantly higher than that in other areas. The proportions of active components in C-Org such as light organic carbon (LOC) and neutral organic carbon (NOC) were relatively low, accounting for approximately 9.49% and 18.15% of the total organic carbon, respectively. The spatial distribution characteristics of LOC and NOC were similar to that of C-Org in the study area. This indicates that human activities have increased the content of C-Org and its active components in marine sediments. Although C-Org and its active components are of relatively low abundance, both are easily affected by human activities which increase pollutants associated with the active components of organic carbon in coastal sediments. Therefore, further consideration should be given to reducing the pollutants carried by exogenous inputs, so that cleaner carbon can be buried in the sediments of Bohai Bay.

Carbonate-silicate interaction in subducting slabs recorded by Zn isotopes in western Alps metasediments

Carbonate-silicate interaction within subduction channels influences the chemical and physical properties of subducting carbon and is crucial to understanding the fate of carbonates in subduction zones. However, geochemical evidence for such interaction is still limited. Here we investigate zinc isotopes (expressed as δ66ZnJMC-Lyon) to decipher potential carbonate-silicate interaction in subducting slabs given the remarkable Zn isotopic difference between silicate and carbonate components. A suite of high- to ultrahigh-pressure metasediments containing variable amounts of carbonates from the Schistes Lustrés nappe (western Alps) record subduction processes to various depths (∼15–90 km) in a cool geothermal condition (∼8°C/km). Despite a broad range of metamorphic grades (0.8–2.9 GPa and 300–630°C) and carbonate contents (0–49 wt%), the bulk metasediments have nearly constant δ66Zn values (av. 0.21±0.05‰, 2sd, n=12), which are indistinguishable from their putative protoliths (0.25±0.07‰, 2sd, n=5). The lack of systematic variation of bulk sediment δ66Zn with metamorphic grades implies a limited transfer of Zn during prograde metamorphism. Therefore, sediments will preserve their original Zn isotopic compositions after subduction into the mantle. By contrast, the carbonate components in sediments obtained by leaching exhibit a progressive decline in δ66Zn from 0.82±0.01‰ to 0.20±0.04‰ and a modest increase in Zn concentration with pressure. These variations are best interpreted as a result of prolonged closed-system Zn isotopic exchange between isotopically heavy carbonates and light silicate components in the subducting slab. Our results demonstrate that a considerable amount of carbonates in subducting sediments can be retained at least down to the depths of the sub-arc mantle (>90 km). The strong pressure-dependent Zn isotopic fractionation (R2=0.87) during carbonate-silicate interaction makes Zn isotopes a novel proxy for the storage depth of subducting carbonates.

Surface microtextures of quartz grains and minor sedimentary components across the Paleolithic Jeongok‐ri sediments, Yeoncheon, South Korea

ABSTRACTThe Jeongok‐ri Paleolithic site in the central Korean peninsula is known as the first findspot of Acheulean‐type hand axes in East Asia. Although many previous studies have investigated the depositional environments of Jeongok‐ri sediments across the Paleolithic occupation, they remain controversial. In this study, we collected an 11‐m‐long core to obtain evidence from systematic surface microtextures of quartz grains (SMQs) concerning depositional environments in the Jeongok‐ri archeological site. SMQs in the Jeongok‐ri sediments are characterized by dominant angular to subangular outlines and small to large conchoidal fractures with arcuate steps, as well as sparse V‐shaped percussion cracks; these features suggest short distances and subaqueous transportation with grain‐to‐grain collisions and violent impacts of quartz grains. On the basis of simultaneous sedimentation of the hosting silt deposits, our SMQ results suggest that Jeongok‐ri sediments were originally fluvial, regardless of their intermediate sedimentary history. This evidence from quartz grain microtextures is consistent with minor sedimentary components found in the Jeongok‐ri core sediments, such as diatom grains as microfossil constituents, along with macroscopic charcoals and titanium‐bearing detrital magnetite grains. The geological and geomorphological conditions of the Jeongok‐ri site are also favorable for floodplain environments given the position adjacent to river terraces formed by the previous lateral erosion of a meandering channel in the nearby Hantan River. Our findings will help to understand environmental conditions during the development of Paleolithic cultures in East Asia.

A detective duo of apatite and zircon geochronology for East Avalonia, Johnston Complex, Wales

The Johnston Complex represents a rare inlier of the Neoproterozoic basement of southern Britain and offers a window into the tectonomagmatic regime of East Avalonia during the assembly of Gondwana. This work presents in situ zircon (U–Pb, Lu–Hf), apatite (U–Pb), and trace element chemistry for both minerals from the complex. Zircon and apatite yield a coeval crystallization age of 570 ± 3 Ma, and a minor antecrystic zircon core component is identified at 615 ± 11 Ma. Zircon Hf data imply a broadly chondritic source, comparable to Nd data from East Avalonia, and T DM 2 model ages of c. 1.5 Ga indicate source extraction during the Mesoproterozoic. Zircon trace element chemistry is consistent with an ensialic calc-alkaline continental arc setting and demonstrates that magmatism was ongoing prior to terrane dispersal at 570 Ma. Apatite trace element chemistry implies a sedimentary component within the melt consistent with voluminous S-type granite production during the formation of Gondwana. The similarity of the ɛHf and geochemistry between both zircon age populations suggest derivation from a uniform source that did not undergo significant modification between 615–570 Ma. Time-constrained apatite–zircon chemistry addresses complexities in dating S-type granitoids (zircon inheritance) and permits inferences on post-magmatic thermal histories. Supplementary material: Zircon U–Pb, Lu–Hf and trace element data, and apatite U–Pb and trace element data are available at https://doi.org/10.6084/m9.figshare.c.6484464

The nature of the Karoo mantle source region from the perspective of olivine in the Luenha picrites: an oxygen isotopic and chemical study

The Karoo large igneous province has been divided into rift zone and basin-related groups, with picrites from the Luenha river, Mozambique, representing an end-member of the latter. New O isotope, major and trace element data for olivine have been combined with MELTS crystallisation modelling to deconvolve compositional diversity associated with magma differentiation from source-derived heterogeneity. Three olivines populations have been discerned as follows: (1) the ‘main trend’, which records crystallisation from a variety of magma compositions; (2) the ‘low Cu trend’, which is inferred to represent xenocrysts or antecrysts; and (3) the ‘high CaO’ olivines, which record polybaric crystallisation of a primitive, little fractionated magma. The trace element variability in olivine phenocrysts relates partially to sampling of different parts of the same overall magma transport and storage systems, and partly to heterogeneity of parental magmas and their mantle sources. When the measured δ18Oolivine values have been converted into δ18Omelt values, the mean δ18Omelt values for the ‘main trend’ and ‘low Cu’ groups are indistinguishable from each other (5.7 ± 0.1‰, 2σ); however, the mean δ18Omelt value of 6.1 ± 0.1‰ for the ‘high CaO’ group is distinctly enriched. These data record source heterogeneity and suggest contributions from two mantle sources, one with elevated δ18O, and another with more ‘typical’ mantle δ18O. Combining these data with previously reported trace element and Nd and Sr isotope data support derivation from a mantle source similar to non-chondritic bulk silicate earth, but with minor contributions (1–2% for the enriched magmas) from a recycled sedimentary component. This points to the importance of a primitive mantle source for the basin-related successions in Karoo.

Biocalcification crisis in the continental shelf under ocean acidification

Ocean acidification (OA) is a persistent challenge for humans and is predicted to have deleterious effects on marine organisms, especially marine calcifiers such as coral and foraminifera. Benthic foraminifera is an important component of sediment in the continental shelf, while little is known about the impact of ocean acidification on benthic foraminifera both at the community and individual level and associated calcium carbonate deposition. We conducted eight months continued culture experiment under the scenario of 400, 800, 1200 and 1600 ppm pCO2 gradients on living benthic foraminifera from four stations in the continental shelf of the West Pacific Ocean. Statistic results showed OA had a negative effect on the abundance of benthic foraminifera. In contrast, the diversity increased roughly under OA conditions implying OA might stimulate the emergence of rare species and promote community diversity to some extent. In addition, we confirmed that the offshore area wasn’t the refuge for benthic foraminifera while the nearshore one had more resistance to moderate acidification. Calcareous species Protelphidium tuberculatum was the dominant species occupying on average 75% in all treatments and its shell diameter, weight and thickness showed a decrease, indicating the decrease of calcification of benthic foraminifera. A relationship between the weight of P. tuberculatum and pCO2 (R2 = 0.96) was established. Based on the present work, calcareous benthic foraminifera deposited 8.57 × 104 t calcium carbonate per year and this might reduce by nearly half and 90% under 800 and 1200 ppm scenarios, which indicates a biocalcification crisis under ongoing OA. This work shows an analogy for palaeoceanic OA and also provides new insights into the sediment of calcium carbonate in the future.

Plume–lithosphere interactions and LIP-triggered climate crises constrained by the origin of Karoo lamproites

We identified a ca. 180 Ma diamondiferous lamproite event in Zambia, establishing a link between ultrapotassic volcanism and the early Jurassic Karoo flood basalt province of sub-Saharan Africa. The cratonic lamproites erupted through the Permo–Triassic Luangwa Rift structure, but MgO-rich ultrapotassic magma formation was unrelated to rifting and triggered by plume–lithosphere interactions during the Karoo LIP event. Elevated Li–Zn–Ti concentrations in magmatic olivine (up to 18.5 ppm Li at 86–90 mol.% forsterite) and strong Sr–Nd–Hf–Pb isotopic enrichment of the host lamproites (87Sr/86Sr = 0.70701–0.70855, εNd = −10.8 to −10, εHf = −20.3 to −19.1, 206Pb/204Pb = 16.8–17.5) suggest partial melting of phlogopite-metasomatized lithospheric mantle domains, at approximately 180–200 km depth. The mantle-like δ7Li values (+2.8 to +5.7‰) of the most pristine lamproite samples are compatible with source enrichment by asthenosphere-derived melts, without significant involvement of recycled sedimentary components. This geochemical fingerprint stands in sharp contrast to the negative δ7Li compositions of primitive K-rich volcanic rocks from collision zone settings, where the shallow mantle sources contain recycled sediment.Isotope modelling demonstrates that the sub-Saharan lamproites originate from a MARID-style metasomatized peridotitic mantle source that underwent incompatible element enrichment at ca. 1 Ga, during tectonic activity associated with Rodinia supercontinent formation. Plume-sourced basaltic and picritic magmas of the 180 Ma Karoo LIP interacted with such K-rich hydrous lithospheric mantle domains, thereby attaining enriched incompatible element and radiogenic isotope compositions. Nd–Hf isotope mass balance suggests that up to 25% of MARID-sourced lamproite melt component contributed to some of the high-Ti flood volcanic units.Although large quantities of volatiles can be transferred from Earth’s mantle to the atmosphere via plume–lithosphere interactions, it is unlikely that outgassing of mantle-sourced sulphur can exceed the climatic impact caused by the release of much more abundant carbon from thick continental roots. Thus, the excess SO2 required to account for transient atmospheric cooling during the early Jurassic, coincident with the Karoo LIP event, must have had a thermogenic origin near the surface of Earth.

An Image Recognition Method for Urine Sediment Based on Semi-supervised Learning

Because there are many categories, large morphological differences and few labels of urinary sediment components, and uneven data in urine sediment images recognition, the accuracy and recall rate of the existing urine sediment images recognition methods are not ideal. The main purpose of this paper is to improve the accuracy and recall of urine sediment image recognition by proposing a urine sediment image classification method based on semi-supervised learning. This paper proposes a method based on semi-supervised learning to classify urine sediment images. This algorithm designs a re-parameterization network (US-RepNet) for low-resolution urine sediment microscopic images to extract complex features of urine sediment images. The dual attention module is introduced on Us-RepNet to increase the extraction of fine-grained features from urine sediment images. And the cross-entropy loss (C.E. loss) function is optimized to train an unbiased classifier to improve long-tailed distribution image classification. The experimental results show that the accuracy of proposed method can reach 94% with only a small amount of labeled data for 16 types of urine sediment images under long-tail distribution. The algorithm can recognize most types, and reduces the need for labeled information, while achieving excellent recognition and classification performance. Comprehensive analysis shows that it can be used as a practical reference for urine sediment analysis. • Re-parameterization network is used to recognize low-resolution microscopic images. • Re-parameterization network can effectively extract the features of urine sediment images. • CSAM increases the extraction of fine-grained features. • Unbiased classifier is trained under the improved C.E. loss function.

Interactions between micaceous minerals weathering and cesium adsorption

The environmental behavior of radioactive cesium (RCs) in contaminated areas is generally governed by soil and sediment components and natural weathering conditions. In this study, desorption tests and spectroscopic approaches were used to explore the interaction between the weathering of micaceous minerals (i.e., biotite and phlogopite) and the adsorption of Cs+ and the critical role of weathering in the environmental behavior of RCs. Results showed that the reaction sequence between weathering and Cs+ adsorption significantly affected the surface species of Cs+ and the structure of biotite and phlogopite. Regardless of whether it occurred before, after, or during Cs+ adsorption, weathering generated more high-affinity adsorption sites, namely, interlayer sites (ITs) and frayed edge sites (FESs), to different extents, and then facilitated the uptake of Cs+ at FESs and ITs on micaceous minerals in a poorly exchangeable state. Cs+ stabilized the micaceous mineral structure once it was absorbed within collapsed interlayers by hindering cation exchange and preventing further destruction during weathering. As important weathering factors, high temperature and Ca2+ content promoted the binding of Cs+ in the interlayers of biotite and phlogopite by enhancing interlayer cation exchange. These findings are beneficial for a better understanding of the environmental behaviors of RCs in the hydrosphere and pedosphere.

Storm-driven variations in depositional environments modify pyrite sulfur isotope records

The sulfur isotopic composition of marine pyrite (δ34Spyr) is one of the major geochemical tools to reconstruct global changes in Earth's surface environment. Storm-driven variations in depositional environments, however, can play key roles in modifying the δ34Spyr signal. Here we present δ34Spyr values in a complete Holocene muddy storm deposit on the East China coastal plain, which is identified by comprehensive analyses of sediment components, organic matter composition, bulk organic carbon isotopic ratios, carbon and oxygen isotopic ratios of carbonates and trace element concentrations. We find that positive (+5.8‰ to +15.8‰) and negative (−9.0‰ to −19.7‰) δ34Spyr values were preserved in two successive intervals of the muddy storm deposit (ca. 62 cm long), corresponding to the high-energy storm peak phase (HESPP) and the waning-energy late storm phase (WELSP), respectively. We propose that the 34S enrichment in pyrite from the HESPP is most likely due to a combination of storm reworking of sediments and high sedimentation rates, which involves various physical and chemical processes leading to the accumulation of 34S-enriched pyrite, such as oxidation of near-surface sulfides, reduced exchange of sulfate between sediment pore fluids and the overlying water column, and/or input of excess reactive iron minerals. In contrast, lower sedimentation rates and limited sedimentary remobilization during the WELSP allow the isotopic signal of early-formed 32S-enriched pyrite to be preserved. The striking shift in δ34Spyr values, therefore, reflects a dramatic change in the local depositional environment between the HESPP and WELSP, suggesting that non-steady-state deposition induced by storm activity facilitates the formation of isotopically “heavy” pyrite. This sharp shift can be further generalized as a characteristic feature of δ34Spyr values in storm deposits. Our work highlights the critical impact of weather- and climate-event-driven depositional variations on δ34Spyr values, adding to the growing evidence emphasizing the local environmental and diagenetic controls on these records.

Chemolithotrophic biosynthesis of organic carbon associated with volcanic ash in the Mariana Trough, Pacific Ocean

Volcanic ash is a major component of marine sediment, but its effect on the deep-sea carbon cycle remains enigmatic. Here, we analyzed mineralogical compositions and glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in submarine tuffs from the Mariana Trough, demonstrating a fraction of organic carbon associated with volcanic ash is produced in situ. This likely derives from chemolithotrophic communities supported by alteration of volcanic material. Tuff GDGTs are characterized by enrichment of branched GDGTs, as in chemolithotrophic communities. Scanning electron microscope, Raman spectrum and nano secondary ion mass spectrometry analysis demonstrates organic carbon exists around secondary heamatite veins in the altered mafic minerals, linking mineral alteration to chemolithotrophic biosynthesis. We estimate organic carbon production of between 0.7 − 3.7 × 1011 g if all the chemical energy produced by ash alteration was fully utilized by microorganisms. Therefore, the chemolithotrophic ecosystem maintained by ash alteration likely contributes considerably to organic carbon production in the seafloor.