Sediment Cores Research Articles

Geochemical Profiles of Deep Sediment Layers from the Kolubara District (Western Serbia): Contamination Status and Associated Risks of Heavy Metals

Global awareness of the harmful effects of heavy metal contamination in soil has increased significantly. Understanding the vertical distribution of oxides and elements is vital for tracing the history of potential contamination. Thus, this study focuses on deep sediment cores primarily composed of quartz and clay minerals from a small village in the western Tamnava Basin of Serbia. The aim was to assess the vertical distribution of 11 oxides and 21 elements and the ecological risks of eight heavy metals by analyzing 250 sediment samples from 18 boreholes at depths ranging from 5 to 58.5 m. Deep sediment core samples were analyzed using energy-dispersive X-ray fluorescence spectrometry (ED-XRF). Potential contamination levels were evaluated within the study area. Additionally, samples were analyzed for total carbonate and organic carbon contents and particles retained on a 0.063 mm sieve. Higher than permitted concentrations of vanadium (V), thallium (Tl), and barium (Ba) were found. Notably, this zone is located above a proposed lithium and boron mine in Gornje Nedeljice, making it crucial for monitoring efforts. Even if mining operations do not commence, examining the deep sediment layers in this rural area remains important. This study offers novel and valuable data on the concentrations of potentially toxic elements in undisturbed deep sediment, serving as a benchmark for future comparisons.

Wetland Ecosystem Service Preservation? Geochemical Changes in Systems with Mangroves and Shrimp Farms in the Northern Ecuadorean Coast

Mangrove sediments serve as paleoenvironmental records of organic matter and nutrient accumulation. Ecuador, the world’s largest producer of whiteleg shrimp Penaeus vannamei in brackish waters, lost 43% of its continental mangroves between 1969 and 1999. Currently, more than 70,000 hectares of shrimp farms operate in estuaries with mangroves and within mangrove reserves. Variations in mangrove coverage and the extent of shrimp farms are described for the period 1996–2020 for two mangrove reserves, REMACAM and RVSMERM, with an observed increase in the extent of shrimp farms in both reserves. Four sediment cores obtained from mangrove drains and drains transformed into shrimp farm infrastructures were analyzed to observe the impact of this activity on the cumulative changes in total organic carbon (TOC) content and total nitrogen (TN) content, the fractionation of stable isotopes δ13C and δ15N, as well as the TOC/TN ratio. The mangrove drains in REMACAM had 3.8 times more TOC and 2.3 times more TN than drains transformed into shrimp farms in RVSMERM, with lower TOC/TN ratios. The organic matter in sediments from sectors with a higher proportion of shrimp farms mainly came from particulate organic matter of freshwater and freshwater algae compared to mangrove drains. Increases in TOC and TN content were recorded in all analyzed sectors, which could be attributed to the cumulative impact of population growth, the development of other agricultural crops, and continental deforestation, despite the fact that proportionally, the highest increases occurred in the sector with a greater influence of shrimp farms.

Trace elements in the sediment cores of lakes on King George Island, Antarctica

Primary studies of the concentrations of rare elements in the sediments of two lakes on King George Island (Kitezh and Glubokoe) showed that their geochemistry reflects the geological features of the area. Compared to the upper part of the Earth's crust, the studied sediments are enriched in Cu, Cd, V, Tl, Mn, Ti and P. Similar patterns have been identified in the geochemistry of volcanic and sedimentary rocks of the Fildes Peninsula. Trends in REE changes generally follow their behavior in rocks, but the overall REE concentration in sediments of lakes is higher, which may be due to the presence of organic matter accumulating in sediments of water bodies. Unlike the aquatic environment, the chemical composition of sediments does not reflect the significant influence of the activities of polar stations. However, small increases in Pb and Sb concentrations in the upper sediments suggest the influence of long-range atmospheric transport of the contaminants.

Paleoecological History of Maplecrest Fen, Catskill Mountains (NY, USA) From Deglaciation to the Industrial Age

ABSTRACTAimTo develop the palaeoecological and palaeoclimatic history of Maplecrest Fen, Greene County, NY.LocationCatskill Mountains, New York.Time Period13,500 calendar years to present (ybp, present = 1950).TaxonAngiosperms, gymnosperms and bryophytes.MethodsWe used pollen and spore analysis, macrofossil analysis, loss‐on‐ignition (LOI) and X‐ray fluorescence (XRF) analysis of a 7.8 m sediment core from the Fen along with AMS radiocarbon dates retrieved from the identified terrestrial macrofossils.ResultsLate‐glacial and Holocene vegetational change from ice withdrawal reveals the development of a shallow lake and then fen to the present. The boreal spruce (Picea), fir (Abies) and paper birch ((Betula papyrifera) pollen signature near the base of the core (Zone M2) suggest a Younger Dryas (YD) signal overtopping warmer Allerod aged basal sediments. The early Holocene white pine (Pinus strobus) is followed by increases in hemlock (Tsuga) and beech (Fagus), ushering in a moister climate. About 5200 ybp drought is indicated by the well‐known hemlock biostratigraphic decline in the Northeast. Drepanocladus moss and stonewort (Chara) shift to sedges (Carex) and violets (Viola) locally present. For the next 5000 years, the vegetation will remain relatively stable with lower temperatures suggested by the return of spruce and fir. Ragweed (Ambrosia) rise along with other weedy taxa marks European settlement near the top 50 cm of the core, along with a striking increase in anthropogenic lead, as seen using X‐ray fluorescence.Main ConclusionsDeglaciation began in the Catskills at a high elevation about 13,500 years ago and recession of ice from the Laurentide margin proceeded at about 0.1 km/year. Temperature shifts promoted changes in the boreal forest including warming and cooling, and drought and wetter intervals both appear in the Holocene history but do not appear to be easily forecast as climate continues to warm.

The Paleochrono-1.1 probabilistic model to derive a common age model for several paleoclimatic sites using absolute and relative dating constraints

Abstract. Past climate and environmental changes can be reconstructed using paleoclimate archives such as ice cores, lake and marine sediment cores, speleothems, tree rings, and corals. The dating of these natural archives is crucial for deciphering the temporal sequence of events and rates of change during past climate changes. It is also essential to provide quantified estimates of the absolute and relative errors associated with the inferred chronologies. However, this task is complex since it involves combining different dating approaches at different paleoclimatic sites and often on different types of archives. Here we present Paleochrono-1.1, a new probabilistic model to derive a common and optimized chronology for several paleoclimatic sites with potentially different types of archives. Paleochrono-1.1 is based on the inversion of an archiving model: a varying deposition rate (also named growth rate, sedimentation rate or accumulation rate) and also (for ice cores) a lock-in depth of air (since, in the absence of significant surface melt, the air is trapped in the ice at about 50–120 m below the surface) and a thinning function (since glacier ice undergoes flow). Paleochrono-1.1 integrates several types of chronological information: prior knowledge of the archiving process, independently dated horizons, depth intervals of known duration, undated stratigraphic links between records, and (for ice cores) Δdepth observations (depth differences between events recorded synchronously in the gas and solid phases of a certain core). The optimization is formulated as a least-squares problem, assuming that all probability densities are near-Gaussian and that the model is nearly linear in the vicinity of the best solution. Paleochrono-1.1 is the successor of IceChrono, which produces common and optimized chronologies for ice cores. Paleochrono-1.1 outperforms IceChrono in terms of computational efficiency, ease of use and accuracy. We demonstrate the ability of Paleochrono-1.1 in an experiment involving only the MSL speleothem in Hulu Cave (China), and we compare the resulting age model with the Speleothem Isotope Synthesis and Analysis version 2 (SISALv2) age models. We then demonstrate the multi-archive capabilities of Paleochrono in a new ice-core–speleothem dating experiment, which combines the Antarctic Ice Core Chronology 2023 dating experiment, based on records from five polar ice cores, with data from two speleothems from Hulu Cave, dated using uranium / thorium radiometric techniques. We analyze the performance of Paleochrono-1.1 in terms of computing time and memory usage in various dating experiments. Paleochrono-1.1 is freely available under the open-source MIT License.

Holocene onshore/offshore tephra correlation of Mt. Etna, Sicily

The volcanic history of Mt. Etna is mainly known from studies of subaerial deposits and stratigraphy. However, little is known about the offshore deposits, which can provide a more detailed insight into geological and sedimentological processes affecting the flanks of Mt. Etna. During RV Meteor Cruise M178, eight gravity cores were taken offshore across the continental margin east of the volcanic edifice to re-evaluate the volcanic history of pre-historic eruptions and mass wasting events in the area. In total, we investigated 87 marine tephra layers in order to build a marine tephrostratigraphic framework. Based on major element compositions of glass shards, sediment componentry, and petrographic characteristics, 27 layers were identified as primary pyroclastic flow and fall deposits, i.e., directly related to an explosive volcanic eruption. However, most of the remaining tephra layers are interpreted to represent deposits of secondary density currents and are not necessarily related to a volcanic eruption. The marine dataset is complemented by twelve onshore samples taken from major explosive eruptions. Applying geochemical fingerprinting of volcanic glass shard compositions, we correlated eleven marine tephra deposits to seven well-known Mt. Etna eruptions (FV, FF, FG, FL, FS, TV, and M1 eruptions) within the last 12 kyr, which provide valuable time markers in the marine sediment record. Furthermore, we correlated ten marine tephra layers between the marine cores (four individual eruptions) and identified another six primary layers in single cores. In total, we discovered 17 widespread volcanic events in the marine record, including four previously unknown eruptions between 10 and 7.7 ka, which indicate that Mt. Etna was more active than previously thought during this time period.

Delayed environmental pollution caused by transient landscape storage - An example from the Lesser Antilles.

The strong pest pressure on intensive banana cultivation in the French West Indies led to the intensive use of chlordecone (an organochlorine insecticide) between 1972 and 1993. Due to its high toxicity for the population and the environment, many studies were conducted on the transfer of chlordecone over the last 20 years. However, most studies focused on the dissolved fraction of chlordecone, while the particle-bound fraction was understudied. Therefore, this study reconstructs pluri-decadal erosion rates (i.e. 1980-2023) and associated chlordecone particle-bound transfers from soil and sediment cores sampled in a cultivated headwater catchment (Saint-Esprit, Martinique). Based on sediment accumulation analysis in an agricultural reservoir, high erosion rates (i.e. 10 t ha-1 yr-1) were found in the investigated catchment during the study period, with values exceeding the estimated tolerable soil loss rate in tropical context (i.e. 2.2 t ha-1 yr-1). Based on the analysis of soil cores sampled along a banana plantation hillslope, this study highlights the formation of colluvial deposits with high levels of chlordecone contamination. When these areas are affected by erosion processes, this leads to massive remobilization of particle-bound chlordecone to water bodies. Indeed, in sediment sampled in the downstream reservoir, we observed a drastic increase in these transfers since 2006, synchronous with changes in agricultural practices. This study therefore highlighted the occurrence of legacy contamination at toeslope positions, which was estimated to potentially persist for 4000 to 11,000 years. Such a residence time highlights the need to implement changes in land management to effectively reduce agricultural soils erosion, particularly in areas identified as "temporary deposition zones" for chlordecone contamination, in order to protect downstream water bodies from chlordecone transfer. To achieve this, agricultural practices that may increase soil erosion, such as herbicide application or intensive ploughing, should be minimized. Overall, this study improved our understanding of erosion and associated chlordecone transfers in tropical environments.

Paleomagnetic inclinations and relative paleointensity variations during the upper Aptian to middle Albian in Sergipe-Alagoas Basin, South Atlantic Ocean (NE Brazil)

Summary During the Jurassic and Early Cretaceous, Earth's magnetic field experienced a high frequency of polarity reversals. This hyperactivity period is followed by a ∼38 Myr prolonged period of stable normal polarity from the Aptian until the Santonian, known as the Cretaceous Normal Superchron (CNS; chron C34n, from 121.4 to 83.65 Ma). However, the CNS might have been characterized by more variability than previously thought, but the current databaseis uneven in its spatial and temporal distribution. In this study, we integrate paleomagnetic and biostratigraphic data from the SER-03 sedimentary core, drilled onshore in the Sergipe-Alagoas Basin, NE Brazilian margin, South Atlantic Ocean. The 183-meter cored interval spans 5.2 Myr (114.7–109.5 Ma), including the Aptian–Albian transition. It records the evolution from restricted marine settings to the complete opening of the South Atlantic Ocean. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization, were measured. Rock magnetic analyses indicated that primary magnetizations were preserved throughout the interval, with detrital magnetite identified as the primary magnetic carrier, predominantly in the pseudo-single domain and low-coercivity states. Normalizations by χ, ARM15mT, and IRM15mT were used to determine relative paleointensity curves and were compared to the curve resulting from the pseudo-Thellier method. The SER-03 relative paleointensity record shows marked changes in both intensity and inclination. Inclination instability results are comparable with those found in volcanic rocks from surrounding the region. The high-resolution SER-03 magnetic record revealed that the field variability was higher than expected during the CNS, but remaining substantially lower than during other periods, such as thelate Jurassic. The new SER-03can serve as a dating and correlation tool for coeval records.

Substantial invasion of Antarctic Intermediate Water into the Arabian Sea during Younger Dryas and Heinrich Stadials

Antarctic Intermediate Water (AAIW) is an important component of the global thermohaline circulation and an essential limb of the Atlantic Meridional Overturning Circulation (AMOC), which redistributes heat, oxygen, and nutrients in the global ocean. Understanding the dynamics of intermediate water circulation over a millennial timeframe is essential to determine the impact of AMOC changes on ocean heat transport during abrupt climatic events. However, the precise relationship between global ocean intermediate water circulation and abrupt climate events, such as the Younger Dryas (YD) and Heinrich Stadials (HS), is not yet fully understood, particularly in tropical regions. Here, we present a ∼29 ka high-resolution record of Neodymium isotope (ƐNd) in authigenic phases, a water mass tracer, of a sediment core collected from the intermediate depth (840 m) in the eastern Arabian Sea (off Goa) to understand the past variability in AAIW circulation in the northern Indian Ocean on a millennial time scale. Our new ƐNd record reveals the pronounced temporal variation (−9.5 to −6.1) throughout the core, marked with enhanced radiogenic Nd signature during the YD, HS1, and HS2. These episodes of enhanced radiogenic Nd signatures signify an increased northward penetration of Antarctic Intermediate Water into the Northern Indian Ocean. The intervals of northward progression of AAIW coincide with the Northern Hemisphere cold events which could have resulted from the enhanced formation of AAIW in the Southern Ocean that occurred due to the warming-induced deceleration of the AMOC. This correlation underscores a robust connection between the formation of North Atlantic Deep Water (NADW) and Southern Ocean climate dynamics through the "bipolar seesaw" mechanism. Our study emphasizes that tracking changes in AAIW in the Arabian Sea can provide insights into the past and future variations in AMOC.

Iceberg-rafted debris events from the glacial Kamchatka in the southwestern Okhotsk Sea over the past 110 kyrs

High-resolution analyses of ice-rafted debris (IRD) and its light and heavy minerals in a sediment core sample from the SW Okhotsk Sea reveal the varying sources of terrigenous material and iceberg discharge events from the Kamchatka Peninsula into the SW Okhotsk Sea since the last interglacial period (Marine Isotope Stage (MIS) 5). Our results suggest the dominance of seasonal and mobile sea ice since 110 ka BP, with occasional perennial sea ice in the SW Okhotsk Sea, which is the most important agent for the basin-wide dispersal of land-sourced terrigenous material. Between 33 ka BP and 14 ka BP (MIS 2), prevalent sea ice formed on the northern shelves. Since 14 ka BP, instead, the IRD originated mainly from the Sakhalin Gulf, with a substantial increase in near-source material input. Thirteen events of IRDKamchatka were identified between 87 and 27 ka BP (mainly in MIS 4–3), with debris definitely originating from the Kamchatka Peninsula. Among these events, the four most prominent types of iceberg/ice sheet rafting occurred at ∼63 ka, ∼53 ka, ∼40 ka, and ∼33 ka BP. Simultaneously, they are consistent with the IRDiceberg events that occurred in the core of western Kamchatka and are also close to the age of H6, H5, H4 and H3 in the Heinrich Events. The initial source areas and transportation pathways of these iceberg armadas varied considerably over time. During ∼87–53 ka BP, icebergs originated from the western Kamchatka Peninsula and migrated southward. During ∼53–27 ka BP, IRDKamchatka inputs likely originated from the eastern Kamchatka Peninsula. This suggests that during MIS 4/3, the mountain glaciers of the Kamchatka Peninsula experienced a reduction in scale and retreated from the western to the eastern part of the peninsula. The event at 27 ka BP marks the last major IRDKamchatka contribution to the Okhotsk Sea from the Kamchatka Peninsula. Since 14 ka BP, the input of IRDKamchatka into the SW Okhotsk Sea has become very weak.

A Northgrippian sedimentary magnetic enhancement along the western margin of India

Sedimentary magnetic records of shelf region contains complex environmental evolution information, necessitating records from various global regions to accurately interpret its significance. A sediment core (SSD-39/GC-01) retrieved from the eastern Arabian Sea was analyzed to elucidate the geologic and climatic controls on the sediment rock magnetic and grain size properties. We report the first record of high energy sediment deposits linked with intense monsoon phases, sea level variations, and extreme natural events during the Northgrippian period (8.27 ka to 4.20 ka). The compilation of magnetic susceptibility profiles of six sediment cores from the western margin of India revealed the presence of multiple sedimentary intervals of enhanced magnetic susceptibility and most likely reflect periods of high sedimentation events controlled by the regional geologic and climatic processes. We identified two anomalous sedimentary magnetic zones (Z-II, Z-IV) marked by an elevated magnetite content and sediment grain size, which reflect the periods of high-sedimentation events on the shelf off Goa. A shift in the magnetic mineral composition, clastic grain size, calcium carbonate, and organic carbon content at ~1.8 ka (Z-I) indicate a abrupt change in monsoon intensity. The elevated organic content within Z-I indicate efficient preservation of labile organic matter which survived oxidation due to rapid sediment deposition. End-member modeling of rock magnetic and grain size properties enabled us to discriminate and quantify the contributions of terrigenous fluxes and post-depositional mineral phases to the bulk magnetic mineral assemblage. We demonstrate that rapid scanning of magnetic susceptibility of sediment cores has the potential to precisely detect the periods of increased continental (magnetic flux) inputs into the marine shelf system. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of how shelf sedimentation responded to past geological and climatic conditions globally.

Coupled Impact of Climate Change and Anthropogenic Activity on the Changes of Terrestrial Organic Carbon Accumulation in the River‐Dominated Coastal Margin

AbstractRiver‐dominated marginal seas play a crucial role in the global carbon cycle. However, the centennial burial record of organic carbon (OC) remains unclear. In this study, we conducted a comprehensive analysis of bulk OC, its isotopic composition (δ13C and Δ14C), biomarkers (lignin and n‐alkanes), and sedimentological evolution based on sediment core from the Yellow River‐dominated Bohai Sea (BS). We also compiled several published OC burial records from other river‐dominated coastal margins. Our findings indicated that since the 1950s, the accumulation of terrestrial OC in central BS has shown a concurrent decline, as evidenced by a ∼50% decrease in terrigenous/aquatic ratio of n‐alkanes (TAR), which accompanied by a significant reduction in sediment load due to the watershed human activities. More intense erosion and resuspension due to stronger hydrodynamic condition under the increasing frequency of winter storms could account for the observed sediment coarsening and concomitant increase of the degraded lignin and old‐OC since the 1980s, suggesting that delta erosion‐induced sediment redistribution could influence the selective transport and accumulation of the more woody allochthonous OC components. The temporal profiles of lignin records indicated a spatial heterogeneity of recent terrestrial OC burial among the large river‐dominated coastal margins under the enhanced global delta erosion. Compared to the fluvial input‐dominated OC burial in the Yangtze River, Pearl River and Mississippi River delta margins, a more hydrodynamic forcing impact on the terrestrial OC burial was discerned in the BS due to the coupled effect of recent climate change and substantial decline in sediment load.

Untangling the coupling effect of water quality and quantity on lake algal blooms in Lake Hulun from a dual perspective of remote sensing and sediment cores

Algal blooms and sediment diatoms are crucial indicators of lake water ecology, influenced by water quantity and quality. However, the coupled effects of water quality and quantity changes on algal blooms are still unclear, especially for lakes in cold and arid regions. This study assessed the long-term variations in algal blooms in Hulun Lake using a novel approach combining remote sensing and sediment core samples for diatom analysis. Two mutation points from the structural change test were identified in approximately 2000 and 2010 for algal bloom area (MBE) and sediment diatom richness, indicating asynchronous algal blooms. A structural equation model (SEM) demonstrated that water level (WL) changes were the dominant influencing factor, co-driving the variations in algal blooms and sediment diatoms in conjunction with total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD). The results revealed nonlinear relationships between the lake WL, TN, Chla, and COD. The water level of 543 m emerged as a critical threshold affecting the relationship between water quality and quantity. Distinct differences in this relationship were observed when water levels were above or below this threshold. These variations became particularly pronounced during periods of high and low water levels. The results provide novel insights into the dynamics of algal blooms and can further support lake ecosystem conservation and management.

Spatial and Temporal Bayesian Hierarchical Model Over Large Domains With Application to Holocene Sea Surface Temperature Reconstruction in the Equatorial Pacific

AbstractWe present a novel space‐time Bayesian hierarchical model (BHM) to reconstruct annual Sea Surface Temperature (SST) over a large domain based on SST at limited proxy (i.e., sediment core) locations. The model is tested in the equatorial Pacific. The BHM leverages Principal Component Analysis to identify dominant space‐time modes of contemporary variability of the SST field at the proxy locations and employs these modes in a Gaussian process framework to estimate SSTs across the entire domain. The BHM allows us to model the mean field and covariance, varying in space and time in the process layers of the hierarchy. Using the Markov Chain Monte Carlo (MCMC) method and suitable priors on the model parameters, posterior distributions of the model parameters and, consequently, posterior distributions of the SST fields and the attendant uncertainties are obtained for any desired year. The BHM is calibrated and validated in the contemporary period (1854–2014) and subsequently applied to reconstruct SST fields during the Holocene (0–10 ka). Results are consistent with prior inferences of La Niña‐like conditions during the Holocene. This modeling framework opens exciting prospects for modeling and reconstruction of other fields, such as precipitation, drought indices, and vegetation.

Multi-proxy reconstructions of paleotemperature in the southern South China Sea since the last deglaciation

The accuracy of paleothermometers is a prerequisite for understanding the past sea surface temperature (SST) changes in the tropical seas. Here, we analyzed the SST estimates reconstructed by four lipid proxies with common linear and newly advanced models in parallel in a sediment core collected from the southern South China Sea (SCS). After excluding the impact of terrestrial input, all of the four proxies-inferred SSTs displayed a gradually warming pattern since 18.3 ka. Our long-chain alkenones-derived annual SST at seawater depth of 0–30 m (SST 0–30 m) record closely matched the regional synthetic SST record from the entire southern SCS, corresponding to high-latitude climate events during the deglaciation. The temperatures reconstructed by long-chain diols (LCDs) showed an upper limit of 27 °C, and we thus proposed that they reflected the optimal survival temperature for organisms producing LCDs when SST was higher than 27 °C. Isoprenoid and hydroxy glycerol dialkyl glycerol tetraethers (iGDGTs and OH-GDGTs)-derived temperatures likely reflected the subsurface temperature (subT) at seawater depth of 30–125 m and SST towards the warm season in the tropical sea, respectively.

Decadal trends of black carbon and heavy metal accumulation in a lake sediment core from central China: A historical perspective

Black carbon (BC) and heavy metal are vital indicators of historical human activities. This study investigates the historical pollution trends of BC, char, soot, and heavy metals in lake sediments from Yinjia Lake (YJL). BC, char, and soot concentrations exhibit similar historical trends, with average values of 1.59, 1.27, and 0.32 mg/g, respectively. Char, constituting 67.25–85.85 % of BC, indicates a dominant fraction in the lake. A notable increase in BC, char, and soot was observed post-1955, peaking in 2005, followed by a decline, reflecting local economic development and anthropogenic activities. Heavy metals, including Cu, Cd, Zn, Pb, Cr, Co, Ni, and Mn, also displayed a significant increase post-1950, with Cd showing an exceptionally high concentration. The average deposition fluxes of BC, char, and soot were consistent with their concentrations, peaking in 2005. The correlations between BC, char, soot, and heavy metals suggest BC’s role as a metal carrier, influenced by industrial and anthropogenic emissions. The char/soot ratio analysis indicates predominant biomass burning pre-1950 and increased fossil fuel combustion post-1950, with regional variations observed. The study highlights the impact of industrialization, urbanization, and policy changes on pollution trends in YJL.

Global Warming – Our Greatest Challenge

The current state of Earth’s climate is the result of a long-lasting, continuous development: it is a snapshot from a film of the Earth’s history that has lasted around 4.5 billion years and is still running. Climate fluctuations are documented by geological findings (marine sediment cores: several million years; ice cores: 800,000 years), by tree rings (10,000 years), historical records (1000 years) and by modern instruments (e.g. thermometers and barometers, 250 years). These data reveal pronounced changes as a characteristic feature of Earth’s climate, which extend over time scales ranging from months to millions of years. In recent decades, climate scientists have analysed many of these data sets and developed dynamic models that have been successfully tested against modern observations and are used to project the future of our climate. Data analysis and climate modelling show that a pronounced impact of human activities on current climate change is apparent.

Understanding sediment and carbon accumulation in macrotidal minerogenic saltmarshes for climate resilience

Coastal saltmarshes play an essential role in providing services such as sediment and carbon storage, coastal protection and support for biodiversity. Despite their importance, understanding the factors controlling sediment and carbon accumulation in these minerogenic saltmarshes remains challenging due to their diversity and site-specific characteristics. Understanding the respective role of these drivers is essential for effective coastal management, particularly for mitigating the impacts of climate change. This study evaluates the control of forcing factors on the lateral and vertical morphological evolution and carbon burial rates of three minerogenic saltmarshes located on the French Atlantic coast (Pertuis Charentais region). By focusing on these sites, the study isolates specific factors such as wind and wave exposure, inundation frequency, and sediment availability, while minimizing confounding influences like climate and tidal range. Results reveal significant lateral expansion of saltmarsh boundaries towards the sea across all sites, with the highest rates of progradation observed in the protected areas influenced by geomorphological features such as sand spits and sheltered bay heads. Sediment and mass accumulation rates (SAR; MAR), derived from 210Pb and 137Cs profiles of sediment cores (n = 14), range from 0.48 to 2.22 cm yr−1, among the highest reported globally, with notable variability within and between sites. Inundation frequency and accommodation space explain SAR variability within sites, while sediment availability predominantly determines spatial differences in vertical accumulation rates between sites. Organic carbon burial rates range from 75 to 345 gC m−2 yr−1, and show a strong correlation with SAR (r = 0.9, p < 0.001, n = 13) but no dependence on carbon content or density (r = 0.2, p > 0.05, n = 13). This highlights the role of sediment input in the accumulation and sequestration of carbon by minerogenic saltmarshes. Furthermore, isotopic analysis indicates a marine source dominance in organic carbon sediment. This research provides insights into how different environmental conditions affect saltmarsh morphological evolution and carbon sequestration rates, informing targeted coastal management strategies focused on enhancing ecosystem resilience and climate resilience.

Reduced magnitude of Early Pleistocene intensification of Northern Hemisphere Glaciation

Increased magnitude and expanding geographic distribution of ice-berg rafted debris in deep ocean sediment cores and increasing amplitude of variability in the benthic oxygen isotope (δ18O) proxy-global ice volume from ∼2.7 Ma marks the intensification of the Northern Hemisphere glaciation (iNHG). However, the location, extent and volume of Northern Hemisphere Ice Sheets (NHISs) is poorly constrained by proximal geologic evidence, and global sea-level records cannot determine individual polar ice sheet contributions alone.Quantitative relationships between sediment transport, water depth and grain size on a wave-graded continental shelf were previously applied to Pliocene shallow-marine sedimentary deposits in Whanganui Basin, New Zealand to provide an independent relative sea level record (PlioSeaNZ; 3.3–2.5 Ma). Here, we extend the duration of the sea-level record from 3.3 to 1.7 Ma (X-PlioSeaNZ) using a well-documented, shallow-marine sedimentary succession, that outcrops in the Rangitikei River Valley of the Whanganui Basin.The resulting glacial-interglacial, relative sea-level fluctuations are up to 45 ± 12.5 m paced by 41 kyr-obliquity frequency during the Early Pleistocene, but also contain modulation of 100 kyr-eccentricity cycle. These maximum sea-level amplitudes are more comparable to the mean of those previously reconstructed from calibrated benthic δ18O (e.g. Miller et al., 2020), and are significantly lower than estimates provided by albeit limited geological evidence proximal to the NHIS (Batchelor et al., 2019). Here we suggest that while NHISs acquired continental extent by 2.6 Ma, their collective volume may be overestimated in benthic δ18O calibrations and area-volume reconstructions, by as much as 50%.We propose that a reduced aspect ratio of ice sheets during iNHG was driven by 41-kyr changes in integrated summer insolation and enhanced by a subglacial regolith feedback reducing resistance to basal sliding. Regardless, the lower ice volume through the iNHG implies a lower ice sheet sensitivity (ice equivalent sea-level per degree Celsius change in temperature) under higher atmospheric CO2 of 4–6 m/°C compared to ∼20 m/°C for the period since the Last Glacial Maximum. This ice sheet sensitivity still has significant implications for society and sea-level will continue to rise under current emissions.

Tectonics and climate controlled sedimentary provenance in the teesta basin since mid-holocene

Erosion of the Himalaya Mountain and subsequent deposition of sediments in the flood plains, and distal fans are primarily regulated by tectonics, climates, lithology, and relief of the region. These eroded sediments preserve their chemical and isotopic compositions in their depositional archive, which can be used to trace the erosion processes, assess the relative role of controlling factors and their spatio-temporal variations. The present study have analysed the 87Sr/86Sr and ԐNd of in silicate phase of sediment recovered from a ~ 40 m long sedimentary core representing ~8 ky of sediment accumulation in the Teesta River mega fan. The lithostratigraphy of the core indicates rapid aggradational nature of the Teesta mega fan. The 87Sr/86Sr and ԐNd display large variability with depth, which ranges from 0.75700 to 0.89294 and − 15.1 to −25.0, respectively. The observed 87Sr/86Sr and ԐNd values in the core sediments have been interpreted in terms of differential sediment contribution from the Higher and the Lesser Himalayan lithology. The 87Sr/86Sr and ԐNd isotope profiles and estimated fractional sediment contributions identify the Lesser Himalaya as the major sediment contributor to the Teesta basin since the mid-Holocene, unlike the other Himalayan River basins, dominated by sediments from the Higher Himalaya after the Last Glacial Maximum. The rapid exhumation and erosion of the tectonically active Rangeet window with the focused precipitation and presence of rock types vulnerable to weathering in the Lesser Himalaya of the basin appear to be the major factors resulting the sedimentary budget of the Teesta River basin over at least last 8 ky. Our assessment suggests that tectonic activity and climate have a competitive effect for the observed sedimentary budget, with an additional role of lithology. The study infers a major control of active tectonics, precipitation, and lithology on the sedimentary budget of the Himalayan River basins.