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Carbon accumulation in coastal wetlands is normally assessed by extracting a sediment core and estimating its carbon content and bulk density. Because carbon content and bulk density are functionally related, the latter can be estimated gravimetrically from a section of the core or, alternatively, from the carbon content in the sample using the mixing model equation from soil science. Using sediment samples from La Paz Bay, Mexico, we analyzed the effect that the choice of corer and the method used to estimate bulk density could have on the final estimates of carbon storage in the sediments. We validated the results using a larger dataset of tropical mangroves, and then by Monte Carlo simulation. The choice of corer did not have sizable influence on the final estimates of carbon density. The main factor in selecting a corer is the operational difficulties that each corer may have in different types of sediments. Because of the multiplication of errors in a product of two variables subject to random sampling error, when using gravimetric estimates of bulk density, the dispersion of the data points in the estimation of total carbon density rises rapidly as the amount of carbon in the sediment increases. In contrast, the estimation of total carbon density using only the carbon fraction as a predictor is very precise, especially in sediments rich in organic matter. This method, however, depends critically on the accurate estimation of the two parameters of the mixing model: the bulk density of pure peat and the bulk density of pure mineral sediment. The estimation of carbon densities in peaty sediments can be very imprecise when using gravimetric bulk densities. Estimating carbon density in peaty sediments using only the estimate of organic fraction can be much more precise, provided the model parameters are estimated with accuracy. These results open the door for simplified and precise estimates of carbon dynamics in mangroves and coastal wetlands.

Several long half-life natural and anthropogenic radionuclides, including 137Cs, 226Ra, 232Th, and 40K, in a 45 cm-long sediment core collected from the east continental shelf of Hainan Island, South China Sea, have been analyzed. The results showed that mean activity of 137Cs, 226Ra, 232Th, and 40K were 2.03 ± 1.2, 20.4 ± 1.8, 45.7 ± 3.0, and 520.0 ± 20.0 Bq/kg, respectively. Radium equivalent activity and External hazard index imply a low radiation, and the study area could serve as a background reference value for environmental radionuclides in east continental shelf of Hainan Island, South China Sea.

Dating recent sediment archives (

International audience; Sediments are complex heterogeneous matrices allowing to some extent the recording of past environmental conditions by integrating sediment characteristics, contamination and the microbial community assembly. In aquatic environments, abiotic environmental filtering is considered the primary deterministic mechanism shaping microbial communities in sediments. However, the number and relative contributions of geochemical and physical factors associated with biotic parameters (reservoir of microorganisms) complicate our understanding of community assembly dynamics. In this study, the sampling of a sedimentary archive in a site alternately subjected to contrasting inputs from the Eure and the Seine Rivers allowed us to study the response of microbial communities to changes in depositional environment over time. The coupling of the quantification and sequencing of the gene encoding the 16S rRNA with analyses of grain size, organic matter and major and trace metal contents demonstrated that microbial communities reflected contrasting sedimentary inputs over time. Total organic carbon (TOC) was the main factor influencing microbial biomass, while the quantity and quality of organic matter (R400, RC/TOC), major elements (i.e. Al, Fe, Ti) and trace metals (i.e. Zn, Pb, Cu, Cr, Ni, As, Co, Ag, Sb) shaped the structure of the microbial community. Besides the effect of geochemical factors, a specific microbial signature was associated with the contrasting sedimentary sources, highlighting the importance of the microbial reservoir in the assembly of microbial communities. Indeed, the main genera identified in the facies influenced by the Eure River were affiliated with the phyla Desulfobacterota (Syntrophus, Syntrophorhabdus, Smithella, Desulfatiglans), Firmicutes (Clostridium_sensu_stricto_1), Proteobacteria (Crenothrix), Verrucomicrobiota (Luteolibacter), while the contributions of the Seine River were characterised by some halophilic genera Salirhabdus (Firmicutes), Haliangium (Myxococcota) SCGC-AB-539-J10 (Chloroflexi). This study sheds light on the overall processes determining the assembly of microbial communities in sediments and the importance of associating geochemical factors with reservoirs of microorganisms inherited from sediment sources.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are microbial molecular fossils ubiquitous in natural environments. The correlation between the Methylation Index of brGDGTs (the M B T 5 M E ' paleothermometer) and temperature offers an important tool for reconstructing past terrestrial temperatures. However, factors other than temperature could also affect the distribution of brGDGTs in lacustrine systems, hampering the quantitative application of this paleothermometer. Here we investigated brGDGT distributions in contemporary sediments collected from 52 lakes in mid-latitude Asia. Combined with published brGDGT data from other lakes across the globe, we have found a strong salinity control on the relative abundance of 5-methyl brGDGTs versus their late-eluting isomers (including 6-methyl, 7-methyl, and unknown isomers). This allows the development of novel indices based on the isomerization of brGDGTs for tracing past lake water salinity. We also demonstrate that salinity-controlled isomerization of pentamethylated and hexamethylated brGDGTs can significantly impact the M B T 5 M E ' paleothermometer, potentially leading to an overestimation of past temperature, but the temperature signal can be extracted out of the M B T 5 M E ' index after correcting the salinity effect. As demonstrated in application to a Lake Qinghai (China) sediment core spanning the last 18 kyr, our finding could facilitate the simultaneous retrieval of reliable temperature and salinity records using brGDGTs in lacustrine settings, in particular for lakes that have experienced large salinity changes during the geological past.

Acoustic models are effective methods for inverting the geo-acoustic properties of seafloor sediments. To investigate the main sediment types in the northern South China Sea, 221 sediment core samp...

Radionuclides dating have been applied in the chronological series of sediment core recovered from Satopanth Tal to estimate the sedimentation rate and its age. Several models include CRS and slope method, and 137Cs peak methods have been adopted. The depth concentration of 210Pbexc in the core determines the various parameters like sedimentation rate, geochronology, inventory, and mass fluxes. The CRS model and slope method infer the sediments deposited at a rate of 0.79 ± 0.04 cm/year dated to 120 years. Distinct peaks on 1963 and 1986AD, the 137Cs record estimate the mean sedimentation rate is 0.745 ± 0.03 cm/year respectively and dated to 77 years.

The timing of the flooding of the Danish/German/Swedish straits and the first marine influence in the Baltic Basin after the Ancylus Lake stage has been much debated. Here we present 47 new radiocarbon ages from sediment cores retrieved from Danish waters, ages that record the marine transgression of the area. Most of the ages are based on shells of marine molluscs, hence the ages are uncertain because we do not know the precise reservoir age in the past.We use a reservoir age of 400 years, which is based on dating of museum specimens collected live before testing of nuclear bombs. It appears from the ages that the Great Belt (Storebælt) was inundated before The Sound (Øresund). The oldest ages on marine shells from the northern part of the Great Belt region are about 8.9 cal. ka BP.From the central part of the Great Belt, the oldest ages are about 8.2 cal. ka BP, in Mecklenburg Bay 8.1 cal. ka BP and in the Arkona Basin 7.1 cal. ka BP. Sediments deposited prior to the occurrence of marine molluscs contain brackish-water ostracods (Cyprideis torosa and Cytheromorpha fuscata); the sediments are usually laminated and non-bioturbated mud. The brackish-water phase may have lasted 500–1000 years. The youngest lake deposits without signs of marine influence are dated to c. 8.8 cal. ka BP(central Great Belt), 8.7 cal. ka BP(Little Belt)and8.5 cal. ka BP(Arkona Basin). We see no evidence for marine influence at c. 10 cal. ka BP as recorded by some studies from the Baltic Basin.

Urmia Lake is a large-scale hypersaline lake that experienced a drastic water-level fall due to natural and anthropogenic forces during the last two decades. Construction of a causeway in the central part of the lake after 1989 has divided the lake into northern and southern parts and caused an extreme change of the lake hydrochemical system. Precipitation of evaporite minerals as crust on the lake floor was caused by the combination of lake level fall and increasing water salinity. However, some parameters controlling rates of salt deposition and dissolution and temporal and spatial variation in salt thickness in Lake Urmia are poorly understood. This study reviews 90 sediment cores from various parts of the lake to put forward a better understanding of the salt depositional system and salt thickness variations in the basin for the last 40 years (1977–2017). Our results indicate that the sedimentary system of Urmia Lake changed rapidly during the last two decades from a permanent hypersaline lake with predominantly fast terrigenous–biochemical sedimentation to a seasonally changing playa sedimentary environment with predominance of evaporite minerals. These changes are responsible for rapid salt deposition that generated a salt-crust with a maximum thickness of 2.95 m overlying Holocene terrigenous sediments. The salt-crust thickness and the water depth have a positive correlation for water depth greater than 1 meter, which means that salt-crust thickness increases where water depth increases. While the thickness of shallow deposits are affected by fresh-water dissolution. In addition, the average salt precipitation rate in the northern and the southern parts of the lake is 466 and 266 times higher, respectively, than the average (0.3 mm/y) sedimentation rate before the lake shrinkage. Similar to other large hypersaline lakes such as the Great Salt Lake (USA) and the Aral Sea (Central Asia), the manmade intervention at Urmia Lake (damming of the catchment, extension of agricultural fields, and causeway construction in the middle part of the lake) threatens its further hydrologic existence.

This paper describes the pollution level in sediment core collected from Sunairi Point of Karachi coastal area Pakistan. The sediment was characterized in terms of particle size, pH, total organic carbon, calcium carbonate, metals and mineralogical composition of sediments. The metals were determined using proton induced X-ray emission. It appeared from the results of grain size that sediment of core was mainly sandy in nature and neutral pH was observed throughout the core. The calcium carbonate in the core sediment seemed to be dependent on the pH outline of the sediment. The results of heavy metals in the sediment core indicated a significant upward enrichment in heavy metals with the highest concentrations found in the upper most layer sediments, may be due to anthropogenic activities, which could be the cause of upward enrichment in heavy metals. The pollution load index values, although showed no pollution, but showing an increasing trend from bottom to top in core, may be due to the influence of anthropogenic sources. The average geo-accumulation index values for sediment core showed that sediments were moderately polluted with Co and Pb. The results of sediment quality guidelines of United States Environmental Protection Agency, indicated, sediment of core was moderately polluted with Ni and Zn. It was concluded from the guidelines that heavy metals in sediment may cause danger to aquatic life. It was also inferred from the study that Sunairi Point area of Karachi coast is facing moderately metals pollution which increased with time.

We present results of multiproxy analysis of a sediment core collected from Billy Slope Meadow, a spring-fed wet meadow in Range Creek Canyon, Utah. Range Creek Canyon was the home to Fremont maize farmers between roughly 1200 and 800 cal BP (AD 750–1150). Stable carbon isotope analysis of core sediments from Billy Slope Meadow indicate the Billy Slope Meadow site was used as a field for maize agriculture during that time. Some scholars have suggested the florescence of the Fremont culture may have been driven by increased summer precipitation, which improved the economic profitability of dry farming maize. But analysis of pollen, macroscopic charcoal and sediment geochemistry from Billy Slope Meadow, and a comparison with a local tree-ring chronology indicate the Fremont period in Range Creek Canyon was probably marked by reduced summer precipitation, and not an invigorated monsoon. The Fremont maize farmers of Range Creek Canyon therefore likely used winter snowpack-derived water from Range Creek for maize agriculture. This observation has significant implications, as using creek water rather than direct precipitation and runoff necessitates the construction of dams irrigation infrastructure, limited evidence for which has been reported by archaeologists working in the Fremont region.

We present the results of the tephrochronology study of a 14.49 m long marine sediment core (TR 17–08) collected in the Edisto Inlet, Ross Sea (Antarctica). The core contains four cryptotephra layers at 55–56, 512–513, 517–518, and 524–525 cm of depth, which have been characterised by a detailed description of the texture, mineral assemblage, and single glass shards major and trace element geochemistry. The age model of the investigated sedimentary sequence, based on radiocarbon dating, indicates that the topmost cryptotephra correlates with the widespread 1254 CE tephra erupted by a historical eruption (696 ± 2 cal yrs BP) of Mount Rittmann, in northern Victoria Land. Deeper cryptotephra layers were derived from previously unknown explosive eruptions of Mount Melbourne volcano and were emplaced between 1615 cal yrs BP and 1677 cal yrs BP, e.g. between the 3rd and 4th centuries CE. This discovery demonstrates that the Mount Melbourne volcanic complex has been highly active in historical times allowing significant progress in the current understanding of regional eruptive history. Moreover, from a tephrochronological point of view, the detected cryptotephra provide new regional isochron markers to facilitate high-precision correlations and help stratigraphically constrain changes in environmental and climatic conditions that are identified by multidisciplinary studies.

This paper presents new multi-proxy records of the Holocene environmental and climatic changes in the Western Caucasus revealed from a continuous sediment sequence from mountainous Lake Khuko (Caucasus State Natural Biospheric Reserve, 1744 m a.s.l.). Palaeoecological analyses of a sediment core for grain size, magnetic susceptibility, loss on ignition, and pollen allowed us to determine five principal climatic phases with several subphases since 10.5 ka BP. The age model is based on seven accelerator mass spectrometry 14C dates, supplemented by 210Pb data for the uppermost part of the sediment core. Warm periods (10.5–6.7, 6.7–5.5, 3.5–2.4, 0.8–0.5 ka BP) were characterized by high biological productivity in the lake as indicated by high organic matter content and expansion of forests, typical of modern low and middle mountain zones, as indicated by the increase in abundance of Quercus, Ulmus, Corylus, and Tilia in the pollen assemblages. Cold periods (5.5–3.5, 2.4–0.8, and 0.5 ka BP–present) are marked by a consistent decrease in organic matter content in lake deposits and possibly higher intensity of the catchment erosion. The changes in pollen assemblages (for instance peaks of Abies, Picea, and Pinus) suggested a potential elevational decline in the boundaries of vegetation belts and expansion of high-altitude woodlands. Abrupt changes in the lake ecosystem were identified between 4.2 and 3.5 ka cal BP marked by a short-term variation in sediment regime shown by variation in organic matter content, magnetic susceptibility values, and sediment grain size. This was probably caused by climatic fluctuations in the Western Caucasus region as a result of complex shifts in the ocean-atmosphere system during the 4.2 ka event. Overall, the first Holocene multi-proxy continuous lake sediment record provides new insights into the climate history in the Western Caucasus.

A 3300 year-long reconstruction of paleoenvironmental moisture conditions was constructed from a sediment core from North Gate Bog (NGB) in the northern section of Range Creek Canyon within the Colorado Plateau. The methods used to analyze the record include loss on ignition (LOI), magnetic susceptibility (MS), elemental analysis with X-ray fluorescence (XRF), charcoal influx, isotopic analysis, elemental ratios and pollen percentages, influx, and ratios. This study adds two new insights to the paleoenvironmental record of the northern section of the Colorado Plateau. First, four climatic zones were established. Zone 1 (3300–2750 cal yr BP) had 100-year wet to dry variations with droughts recorded from 3300–3200, 3000–2900, and 2800–2700 cal yr BP. Zone 2 (2750–1600 cal yr BP) had an overall dry period with an 800-year transition to increased warmth and winter moisture. Zone 3 (1600–850 cal yr BP) had an overall warm, wet, summer precipitation climate conducive to the establishment of Zea Mays and Pinus edulis, two staple foods of the Fremont culture. The Medieval Climate Anomaly (MCA) registered warm and wet in this part of the Colorado Plateau. Zone 4 (850–0 cal yr BP) had a sharp transition to a drier climate from 850 to 400 cal yr BP. During the Little Ice Age (LIA), wetter climate taxon increases such as Artemisia, Cyperaceae, and Pinus edulis. The second overall finding in this study was that NGB was a place of human activity including Fremont farming. The identification of a Zea mays pollen grain confirms the archeological presumptions that this higher elevation site was used to farm corn along with other sites in Range Creek Canyon (RCC). The post Fremont occupation period was marked by a sharp increase in organic material and a return of pinyon-juniper woodlands.

High-altitude lake sediment can be used as a natural archive to reconstruct the history of pollutants. In this work, the temporal distribution of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined using a high-resolution gas chromatography coupled with high-resolution mass spectrometer (HRGC/HRMS) in an alpine lake sediment core collected from the southern Tibetan Plateau (TP) to examine whether the expected decreasing trends due to the implementation of the international Conventions could be observed. The concentrations of PCBs and PBDEs in the sediment core were in the range of 11.8-142 pg/g dw and ND-457 pg/g dw, and their fluxes were in the range of 2.51-31.7 ng/(m2·yr) and ND-43.2 ng/(m2·yr), respectively. The prevalence of low-chlorinated (tri-CB) PCBs and low-brominated (tri- to tetra-) PBDEs in most sections of the sediment profiles was observed, suggesting that the light molecular weight PCBs and PBDEs have most likely reached lake sediments by long-range atmospheric transport from distant sources. Despite the restrictions on their applications, the sediment records for the concentrations and fluxes showed no corresponding decreasing trend with restrictions for PCBs, which suggested that these POPs (e.g., PCBs) were still emitted to the environment owing to the influence of primary or secondary emissions. To our knowledge, this is the first report on input history of atmospheric PCBs and PBDEs recorded in TP Lake sediment.

Sediment oxygen demand (SOD) measurement currently requires a long preparation time and bulky experimental equipment, which represent major obstacles to conducting SOD measurements. We developed a new SOD measurement method that can be easily conducted in a shorter time than the existing laboratory method. The undisturbed sediment core was transferred into the custom-made small glass vial (inner diameter 12.8 mm, length 125 mm). The SOD sample was incubated in the dark with or without stirring the overlying water inside the vial. The change in DO concentration was measured using a non-contact fluorescent oxygen sensor, and then the SOD was calculated. For comparison and verification of the new method, SOD was also measured using a large undisturbed sediment core (inner diameter 11 cm, length 50 cm). The SOD measurements using the new method were positively correlated with the SOD measurements using the large undisturbed sediment core, suggesting that the new method is a feasible alternative to the conventional method. In the new method, many SOD measurements can be taken from a single sediment core sample. This makes it possible to reduce the uncertainty associated with the highly heterogeneous structure of the sediments, and thus the new method has great advantages in obtaining reliable SOD data. A novel high-throughput method for SOD was developed that shortens sample preparation time and improves convenience of measurement. The new method is expected to contribute substantially to the accumulation of SOD monitoring data and to make great progress in elucidating the dynamics of dissolved oxygen in lakes.

Continental margin sediments are important sites of marine nitrogen cycling and potential contributors to atmospheric N2O emissions. We employed trace‐level N2O microsensors to measure vertical N2O profiles at submillimeter resolutions in intact cores from outer continental margin sediments underlying the NE Pacific oxygen minimum zone. We used mathematical modeling to estimate depth‐dependent rates of N2O production and fluxes to the overlying water along a transect of diminishing bottom water oxygen concentrations. Net sediment efflux was observed at all sites on the outer continental margin, with a mean value of 524 nmol m−2 d−1. N2O efflux increased with decreased oxygen penetration depth in sediments. Enhanced N2O production and efflux were obtained when outer continental shelf sediments were experimentally exposed to lower bottom‐water O2 concentrations, to simulate upwelling conditions. Our results underline the need for further investigation of the drivers of N2O production in continental margin sediments, and the relative importance of these environments to the global N2O budget.

Sediment cores retrieved from rivers, lakes, and coastal marine environment have been widely utilized to reconstruct historical variations of anthropogenic pollutants. A sediment core was collected in the Kizilirmak River, Turkey during 2014 and analyzed for a suite of metals (Cu, Pb, Zn, Ag, Ni, Co, Mn, As, Cd, Sb, V, Cr, Hg and Se) to reconstruct their temporal variations. Chronology was attempted using excess 210Pb (210Pbxs), 137Cs and 239,240Pu in the sediment cores. The vertical profile of excess 210Pb indicates that this core is not datable using excess 210Pb method. The 137Cs-based linear and mass apparent accumulation rates were estimated to be 0.84 cm year−1 and 0.93 g cm−2 year−1, respectively. These values are in agreement with the 239+240Pu peak-based linear (0.88 cm year−1) and mass apparent accumulation (0.97 g cm−2 year−1) rates. There is considerable broadening in the peaks of both 137Cs and 239,240Pu, likely due to post-depositional mixing processes. The measured sediment inventories of 210Pbxs, 137Cs and 239+240Pu were 38, 29, and 0.42 dpm cm−2, respectively, which were generally higher than the expected inventories based on local atmospheric depositional inventories. We attribute these enhanced inventories to potential sediment focusing and additional watershed erosional input. The Al-normalized enrichment factors (ANEF) were used to evaluate the contribution from natural versus anthropogenic sources. The ANEF of Ag, Ni, As, Cd and Se were > 1.5, which suggests a significant contribution of anthropogenic sources for these trace metals varied between 226% and 1163%. The geoaccumulation index (Igeo) values of the sediment column suggest that Cu, Pb, Zn, Co, Mn, Sb, V and Hg were in an unpolluted level and the others were in a polluted level. Besides, both the ANEF and Igeo values of Cu, Pb, Zn, Ag, As, Se, Cd and Hg showed a peak at 28–30 cm layer (corresponds to 1978–1981), which is attributed to maximum metal release during 1970s.

We collected a sediment core from the 6th (6J) Triglav Lake, a remote mountain lake in NW Slovenia, and analysed it for 25 elements, using k0-instrumental neutron activation analysis (k0-INAA). For Hg, we used cold vapour atomic absorption spectrometry (CVAAS). Data were analysed using Principal Component Analysis (PCA). PCA indicated several distinct groups of elements and sediment core samples. Ca distribution was entirely different from all other sediment components. Ba, Br, Hg, Sb and Zn were associated with organic matter (OM), with Hg showing the strongest affinity to OM. As, Cr, Fe and U formed a group of redox-sensitive elements. Two events that occurred ca. 1915 and in the 1940s/1950s, were identified in the core. They were associated with increased inputs of allochthonous material into the lake, and significantly affected the stratigraphic distributions of all elements. Some trace elements, such as As, Hg and Zn, are probably effectively retained in the catchment, whereas Cr tends to be readily exported from the catchment. Atmospheric deposition affected not only elements of anthropogenic origin (As, Ba, Br, Hg, Sb, Zn and Cr) that started to increase after the 1970s, but also those of terrestrial origin (Ca, Fe, Na). Introduction of fish into the lake in 1991 and the subsequent increase in primary production, affected the distribution of Ca and elements that are redox-sensitive and/or associated with OM (As, Ba, Fe, Sb, U, Zn). Fe minerals in uppermost 6J sediments have a strong influence on the distribution of several trace elements. As and Zn closely tracked Fe, whereas Sb was likely released after oxidation. Climate change could also have enhanced inputs of elements from the catchment, but such changes were likely overwhelmed by the effects of increased eutrophication.

We present new updates to the calendar and radiocarbon (14C) chronologies for the Cariaco Basin, Venezuela. Calendar ages were generated by tuning abrupt climate shifts in Cariaco Basin sediments to those in speleothems from Hulu Cave. After the original Cariaco-Hulu calendar age model was published, Hulu Cave δ18O records have been augmented with increased temporal resolution and a greater number of U/Th dates. These updated Hulu Cave records provide increased accuracy as well as precision in the final Cariaco calendar age model. The depth scale for the Ocean Drilling Program Site 1002D sediment core, the primary source of samples for14C dating, has been corrected to account for missing sediment from a core break, eliminating age-depth anomalies that afflicted the earlier calendar age models. Individual14C dates for the Cariaco Basin remain unchanged from previous papers, although detailed comparisons of the Cariaco calibration dataset to those from Hulu Cave and Lake Suigetsu suggest that the Cariaco marine reservoir age may have shifted systematically during the past. We describe these recent changes to the Cariaco datasets and provide the data in a comprehensive format that will facilitate use by the community.

Seismic hazards and risks around an individual fault can be assessed from complementary paleoseismic data. A high-resolution sediment core recovered from the Yileimu Lake revealed 11 potential paleoearthquakes around the Fuyun fault in northern Xinjiang. Among them, three events recorded by ductile deformation and turbidites or coseismic subsidence were possibly correlated with Ms ≥ 7.0 earthquakes, and the others characterized by turbidites or coarse deposits were likely related to Ms ≥ 5.8 or Ms ≥ 5.5 earthquakes. Shaking intensities of 8.60 and 5.51 MMI were required to cause extensive landslides and turbidites, respectively; while 6.89, 6.35 and 5.34 MMI were likely to be required to cause coseismic subsidence, ductile deformation and coarse deposits related to landscape shattering in the catchment area, respectively. Absolute radiocarbon dating and historical earthquake-event markers disclosed a recurrence interval of 20–60 years for Ms ≥ 5.5 earthquakes, and a potential interval of 100 years for Ms ≥ 7.0 earthquakes during the last 450 years. A seismic quiescence of 89 years since the 1931/08/11 Ms8.0 Fuyun earthquake might have significantly increased the potential of a strong earthquake related to the fault in the near future.

A mass balance modelling approach was used to help understand the movement and impacts of tritium discharged from Canada Deuterium Uranium (CANDU) reactor facilities into Lake Ontario. A concentration-time model, previously developed, is updated in this study. Historical and projected tritium concentrations for Lake Ontario waters are presented. A model calculated accident scenario (10 times highest accidental release) indicates the importance of dilution to the dispersion of tritium; a “modelled” release in 2016 has tritium levels declining by the year 2030 to “previous 2016 levels”. As part of the mass balance approach, lake-bottom sediments were considered as potential radionuclide “sinks”. Tritium porewater results were noted as perturbations at depth in both short (30–50 cm cores) and long sediment core profiles (to 300 cm). These change in tritium concentrations with depth may have been due to CANDU emissions (as the most likely source) over time, based on records of accidental releases of tritiated coolant water. However, the exact process (advection and/or diffusion) responsible for the penetration of tritium into the lake bottom requires additional physical and hydrogeological characterization of the lake bottom sediments.

An anomalous layer enriched with chemical elements indicating the presence of terrigenous matter was discovered in the sediment core of Zapovednoe Lake located 60 km from the epicenter of the Tunguska event (1908) using synchrotron radiation X-ray fluorescence spectroscopy (SR–XRF). Radioisotope measurements indicate that the age of the layer is consistent with the date of the catastrophe. Apparently, the anomalous layer was formed as a result of an intense terrigenous matter inflow from the water catchment area due to massive forest falls and subsequent wildfires caused by the Tunguska event. Thus, it is established that targeted searches for microparticles of extraterrestrial origin can be carried out in the discovered and dated anomalous bottom sediment layer.

Intensification of anthropogenic activities and related processes have altered the morphology of modern deltaic systems. As a result, mapping of geomorphic features, such as paleochannels, using recently acquired digital elevation data has become increasingly difficult. Using the Nile River and delta as a test site, we developed and applied procedures to map the distribution of paleochannels that existed throughout the Holocene. A high-resolution digital elevation model (DEM) derived from an early, detailed topographic sheet collection was used to minimize the impact of recent man-made topographic artifacts. The DEM-inferred paleochannel distribution was verified using direct and indirect subsurface data. Using our adopted methodology, we identified 76 main and subsidiary paleochannels with a total length exceeding (by >500 km) previously mapped paleochannels. The overwhelming majority (>80%) of the reported historical and archeological sites (29 sites) in the Nile Delta were found to be proximal (

Laophonte cornuta Philippi 1840 was first reported in rather temperate regions and later noted to extend their distribution to the warmer coasts. The earlier reports were based on specimen collected from bottom vegetation or sediment enriched in organic matter. The present study was carried out during the warm month phenomenon which struck coral areas in the South China Sea in 2016. Sediment core samples were collected by SCUBA divers in the coral areas at Pulau Tulai (2°54'24.84"N,104° 5'57.67"E) and Batu Malang (2°52'29.98"N,104° 8'47.92"E), in the northern part of Tioman Island. The bottom substrates were covered by mostly dead corals and coral rubbles. Taxonomic observation was carried out following the sorting and microscopic dissection process in the laboratory. The denticulate margin of somites along with blunt short spinules distributed on the surface as shown from the Scanning Electroscopic Microscopy (SEM) observation proves their morphological adaptation to survive between the coral rubbles and gravels in the study area. Other variation found is on the size of the caudal rami which is very much slender than those reported from colder regions. Except for the setae formula, it shared similar characters with L. paradduensis reported from Maldives and L. aeutirostris from Monterey Bay. The present specimen also shared some variation found in specimen reported from the Andaman Sea. L. cornuta reported from the Tioman Island might be able to endure the harsh environment due to their robust feature of the body surface.

The Holocene evolution of climate in easternmost Fennoscandia and adjoining regions is poorly known, compared with regions to the west. To address this, a 224-cm-long sediment core from Lake Medvedevskoe, situated on the Central Upland of the Karelian Isthmus, northwestern Russia, was examined to investigate variations in the Holocene climate. Analyses indicate that the dry and cold late Pleistocene climate was replaced by the warmer and more humid early Holocene climate after ca. 10.5 cal ka BP. During the early Holocene, the lake transitioned from an oligotrophic to a mesotrophic state, characterized by a “Corynocera ambigua/Microtendipes pedellus-type” phase, which has been found in other lakes across Fennoscandia. Taxonomic shifts in the chironomid and cladoceran communities associated with climatic amelioration were identified at ca. 10.6 and 9.17 cal ka BP using breakpoint analysis. Reconstructed July temperatures indicate climatic patterns comparable to those seen in eastern Fennoscandia. The warm period between ca. 9.5 and 5.5 cal ka BP (T July 14.5–15°C) was interrupted by a slight cooling between ca. 8.5 and 8.1 cal ka BP, possibly relating to the 8.2 event, with peak temperature reached at ca. 7.8 cal ka BP. Neoglacial cooling started after ca. 5.5 cal ka BP, the median reconstructed July temperature dropped to 2–3°C cooler than present (mean T July 13.5°C) before recovering in recent time.

Polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) were detected by gas chromatography–mass spectrometry in the sediment core form Poyang Lake. The concentrations of...

We report on pollen, plant macrofossils, and associated lithostratigraphy of a sediment core extracted from the base of Silver Lake, a kettle lake in northern Lower Michigan, USA, which reveal a complex deglacial scenario for ice block melting and lake formation, and subsequent plant colonization. Complementary multivariate statistical and squared chord distance analyses of the pollen data support these interpretations. The basal radiocarbon age from the core (17 540 cal years BP) is rejected as being anomalously old, based on biostratigraphic anomalies in the core and the date’s incongruity with respect to the accepted regional deglaciation chronology. We reason that this erroneous age estimate resulted from the redeposition of middle-Wisconsin-age fossils by the ice sheet, mixed with the remains of plants that existed as the kettle lake formed at ca. 10 940 cal years BP by ice block ablation. Thereafter, the kettle lake became a reliable repository of Holocene-age fossils, documenting a mature boreal forest that existed until 10 640 cal years BP, followed by a pine-dominated mixed forest, an early variant of the mixed conifer–hardwood forest that persists to the present day. Our study demonstrates that researchers investigating kettle lakes, a common depositional archive for plant fossils in deglaciated landscapes, should exercise caution in interpreting the basal (Late Pleistocene/early Holocene-age) part of lake sediment cores.

Recent studies have revealed that areas with sediments pre-dating the Last Glacial Maximum (LGM) are more common in southern Scandinavia than previously thought. To describe and date these sediments, four deep core drillings were made in the province of Smaland and one in the province of Skane, southern Sweden, and an existing sediment core drilled in the 1960s from western Skane was re-examined and re-dated, all resulting in a total of 22 AMS 14C ages and 19 OSL ages. With some variation, the Smaland cores revealed a stratigraphy consisting of two tills separated by proglacial glaciofluvial and glaciolacustrine sediments, dated to between 46 and 25 ka BP (Marine Isotope Stage (MIS) 3 to 2). We suggest that these sediments were deposited during the ice retreat of the MIS 3 Ristinge glaciation over southern Scandinavia and the subsequent re-advance over the area in late MIS 3 and the transition to MIS 2, when the Fennoscandian Ice Sheet advanced towards its LGM marginal positions. This contrasts with the glacial history of southernmost Skane, where an additional MIS 3 glacial advance through the Baltic Basin is suggested by the occurrence of a till named Allarp till. New ages from sediments under- and overlying this till suggest that it was deposited by the same Baltic ice advance that deposited the Klintholm till in Denmark (Klintholm Advance, c. 34-30 ka). (Less)

Fishery activities are an important source of microplastic pollution in coastal areas but have received little attention. The Beibu Gulf, a traditional fishing ground of China and the China-Indo Peninsula, was selected in this study, and the focus was on the impacts of fishery activities on the horizontal distribution of microplastics in sediment. The results showed that the dominant contaminants (polypropylene fibers and polyethylene fibers) might originate from the abrasion of fishing gear and contributed to 61.6% of the total abundance of microplastics in surface sediment. The abundance of polypropylene fibers and polyethylene fibers exhibited a strong correlation (R2 = 0.8586, p = 0.015) with values of fishery yields of different districts, which highlighted the effects of different fishery activities on microplastic contamination in marine sediment. Microplastics could be "hidden" in deep sediment to a depth of 60 cm. The estimated storage of microplastics in deep sediment (185 tons) was 5 times that in surface sediment. The assessment of microplastic storage worldwide might be underestimated because most previous studies only examined surface sediment. The abundance distribution and size distribution of microplastics in the sediment core suggested long-term burial of microplastics in deep sediment. Bioturbation might be responsible for the vertical transport of microplastics, leading to "fresh microplastics" preservation in "old sediment".

Organic proxies have been widely used to reconstruct temperature and terrestrial input variation at the interface between land and sea. However, the impact of human activities on these proxies has been little constrained, which might cause the misinterpretation of the sediment profile. In order to study the climatic and human impact on the environment, proxies in coastal regions, glycerol dialkyl glycerol tetraethers (GDGTs) in a sediment core spanning 115 years was analyzed from Beibu Gulf, China. The results indicate that isoprenoid GDGTs in the Beibu Gulf were mainly derived from Thaumarchaeota and the branched GDGTs originated mainly from terrestrial soil bacteria. The TEX86 index was applied to reconstruct the temporal SST variation. The results show that variation of TEX86-derived SST is controlled mainly by East Asian Monsoon system and partly by ENSO events. The methylation index of branched tetraethers or the cyclization index of branched tetraethers (MBT/CBT) derived mean annual air temperature (MAAT) agreed with MAAT record at the Qinzhou Station before 1982 AD. However, the population growth and economic development after 1982 AD caused the reduction of terrestrial organic matter input and increase of nutrient, leading to the thriving of Thaumarchaeota and increasing of in situ branched GDGTs proportion, which created the scatter of the MBT/CBT-reconstructed MAAT after 1982 AD. Therefore, human influence on GDGT proxies can be constrained in this way to avoid misinterpretation of paleoclimate and paleoenvironment records.

Plastic pollution affects all oceans and sequestration of plastics in sediments is considered its ultimate sink. We report evidence of macroplastic burial retrieved within a sediment core collected at 38 m depth at the mouth of the Mazzarrà River, a torrential river able to carry a large amount of sediment during seasonal flash-floods. Two macroplastic items were found at 68 and 255 cm below the core top (corresponding to the seafloor). Their association with terrestrial vegetal debris and their inclusion in decimetre-thick sandy/silty intervals showing coarsening- and fining-upward trends, suggest that they were deposited by hyperpycnal flows possibly triggered by flood events. These findings testify the potential of sedimentary flows in burying macroplastic at depth below the seafloor, especially in nearshore prodelta environments. Furthermore they raise the quest on the magnitude of macroplastic storage in the subsurface and on the lack of specific devices and strategies for their reckoning.

The lesson of the past is that when climate changes, species move. For instance, as the world emerged from the last ice age, temperatures rose dramatically across North America and Europe. Areas that had been frozen under solid ice—outside the niche of virtually any organism—suddenly thawed and supported rich assemblages of life. Less dramatic changes in the tropics led to different climates replacing one another in the space of a few 1000years. Many other climate shifts have occurred throughout the Earth’s history, changing the average climate of the planet and also the living conditions of every place on the planet.

We discovered subfossil remains of Phreatalona protzi (Hartwig, 1900) (Cladocera: Anomopoda: Chydoridae) in a short sediment core taken from a small tundra lake Pe-03 located in the Pechora River delta, North-East of European part of Russia. This species had been described previously only from Central and Northern Europe. The occurrence of P. protzi in the Russian Arctic suggests that this chydorid species must be much more widely distributed than previously reported, and in the near future we expect findings of this species in other regions of Russia.

The aim of this study is to analyze the recent sedimentation rate in the center of the Limoncocha lagoon, a Ramsar site in the Ecuadorian Amazon, using the 210Pb dating method and identifying the potentially toxic elements along a 50 cm sediment core. A strategy based on the application of three single and four integrated indices is used to evaluate trace element contamination with depth. Single indices show mainly As and Mo, and Cu, Ba, Cd, Ni, and Pb to a lesser extent, as responsible elements of a minor enrichment between −10 and −40 cm. The multielement slight pollution shows a mixture of potential contamination sources, probably due to agricultural, oil activities, and urban wastewater discharges. However, integrated indices applied, classify the complete core as without potential risk. The 210Pbexcess profile shows three differentiated sections. A surface section where new materials with lower concentrations have been found, probably due to the underground currents that connect the lagoon and the nearby Napo River; a central section where CF-CS model and mass accumulation rate calculations provide a sediment accumulation rate of 0.56 ± 0.03 cm y−1; finally, a deeper section with a constant 210Pbexces profile, showing sediment reworking probably due to local flooding’s.

A sedimentary record of the 16 polycyclic aromatic hydrocarbon (PAH) pollutants from Dongping Lake, north China, is presented in this study. The influence of regional energy structure changes for 2–6-ring PAHs was investigated, in order to assess their sources and the impact of socioeconomic developments on the observed changes in concentration over time. The concentration of the ΣPAH16 ranged from 77.6 to 628.0 ng/g. Prior to the 1970s, the relatively low concentration of ΣPAH16 and the average presence of 44.4% 2,3-ring PAHs indicated that pyrogenic combustion from grass, wood, and coal was the main source of PAHs. The rapid increase in the concentration of 2,3-ring PAHs between the 1970s and 2006 was attributed to the growth of the urban population and the coal consumption, following the implementation of the Reform and Open Policy in 1978. The source apportionment, which was assessed using a positive matrix factorization model, revealed that coal combustion was the most important regional source of PAHs pollution (&gt, 51.0%). The PAHs were mainly transported to the site from the surrounding regions by atmospheric deposition rather than direct discharge.

Assessment of microplastics (MPs) in sediment cores is necessary to unveil global plastic pollution since most of the plastic litter might have been stored in sediment columns. In the current study, MPs inventory was determined in a 105 cm sediment core, collected in the Golden Horn Estuary, Sea of Marmara. Radiodating of sediment profile by using naturally occurring 210Pb and fission product 137Cs allowed us to couple the retrospective of global MP production to sediment MPs inventory. More than 90% of total MPs inventory was found in the deep layer of the sediment column (below 15 cm). Small MPs (20–200 μm) were more abundant than large ones (200–4000 μm). Elevated concentrations of MPs were attributed to industrial and municipal effluent of Istanbul metropolitan. On a local scale, this study suggests that the Golden Horn Estuary was polluted with MPs before the 1950s, and the abundance of MPs reached a maximum in the 1980s. We also propose on a global scale that “the missing” plastics might have been buried in deep sediment and radiodating of sediment is useful to reveal their historical input records.

This study is focused on the metals’ pollution level in sediment core collected from Manora Picnic Point of Karachi coastal area Pakistan. The sediment was categorized in terms of pH, particle size, total organic carbon (TOC), calcium carbonate, and heavy metals, besides the determining the mineralogy composition of sediment. Metals were determined using proton-induced X-ray emission spectroscopy (PIXE) technique. The results of abundant and heavy metals in the sediment core indicated a significant upward enrichment, which could be the cause of discharge of industrial effluents and domestic wastewaters of Metropolitan Karachi into sea. The average geo-accumulation index values showed that sediments were moderately polluted with Co and Pb, and unpolluted for metals (Al, Ca Mg, Cr, Cu, Fe, K, Mn, Ni, Ti, V, and Zn). The pollution load index values indicate an increasing trend from bottom to top, which may be due to the influence of anthropogenic sources. According to the sediment quality guidelines of United States Environmental Protection Agency (USEPA), core sediment was heavily polluted with Ni and moderately polluted with Pb, Cu and Zn.

Surface sediment samples from Taihu Lake in China and its inflow rivers, along with two lake sediment core samples, were collected and analyzed for organophosphate esters (OPEs). The concentrations of total OPEs varied from 28.60 ng/g to 158.72 ng/g (median: 54.25 ng/g) in river surface sediment and from 62.57 ng/g to 326.84 ng/g (median: 86.37 ng/g) in lake sediment. Tributyl phosphate (TnBP) was the predominant compound in river surface sediment, and tris(2-butoxyethyl) phosphate was predominant in lake sediment. High contamination occurred in the north-west region, which was related to the high level of urbanization and high usage of OPEs. The sediment-water partition coefficients of OPEs (logKoc) were calculated, showing a significant correlation with logKow (p < 0.05). The concentration and composition of OPEs in two sediment cores varied due to the different sampling locations, with more OPE species found in the northern region than in the southern one. Principal component analysis and positive matrix factorization indicated that sewage discharges, vehicle emissions, and atmospheric deposition were the possible sources of OPEs in Taihu Lake sediments. Tris(1-chloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, and TnBP were the main OPEs causing ecological risks.

Radionuclide depth distribution in bottom sediments in deep-water zones of dam reservoirs, where no sediment mixing occurs, can be used to reconstruct time changes in particulate activity concentrations of radionuclides strongly bound to bottom sediments. This approach was used to analyze the 137Cs concentration profile in a bottom sediment core collected from Ogaki dam reservoir on the Ukedo River in the Fukushima Dai-ichi nuclear power plant contaminated zone in October 2019. The derived 137Cs particulate concentrations provided a basis for estimating the dissolved concentration and its temporal trend in the Ukedo River, using the mean value of the apparent 137Cs distribution coefficient. The reconstructed particulate and dissolved 137Cs concentrations and their temporal trends are consistent with monitoring data. The annual mean particulate and dissolved 137Cs wash-off ratios were also calculated for the period of eight years after the accident. Interestingly, the particulate 137Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved 137Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. Both the particulate and dissolved 137Cs wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.

Sediment core samples from high tide lines and in submerged zones as well as surface water samples from eight beaches of Tenerife were analysed. Sampling was conducted over a period of one year in intervals of 5 weeks. The majority of particles were found in the high tide sediment (66%), followed by water samples (23%) and finally in sediment from submerged zones (11%). Regarding the particle amount per volume (items/L), accumulation in sediment samples was statistically higher compared to water samples. Mean values of items/L were higher in high tide sediments. In high tide and water samples, mostly white and transparent particles >1 mm were found. More than 70% were represented by fragments. In sediments from submerged zones, yellow and blue microparticles (

Dust storm variations over the past ~230 years were reconstructed on the northeast Loess Plateau using a sediment core from Lake Gonghai. The coarse component of the lake sediments (17.38–109.65 μm) was extracted using the grain size standard deviations method and could be used as a dust storm proxy. The reconstructed results suggest five dust storm peaks: in the 1810s, the late 1850s to the late 1880s, the late 1890s to the early 1920s, ~1950s to the early 1990s, and the late 2000s to the early 2010s. The 1950s–1990s had the highest frequency of dust storms over the past ~230 years, as a result of the combined effects of increased human activities, droughts, and strong winds. Before ~1950, the frequency of dust storms was influenced mainly by natural factors, such as drought events and high intensities of the Siberian High and the East Asian Winter Monsoon. After the 1950s, intensive human activity had a significant impact on dust storms, resulting in a relatively high frequency. However, because of a weakening trend in wind strengths resulting from global warming and ecological rehabilitation projects in North China, the frequency of dust storms has significantly decreased in the past two decades. This study highlights the significant effect of human activities on dust storm generation in Inner Asia and the variations in dust storms under global warming scenarios.

To understand siltation processes within the North Port of Incheon, Korea, this study estimated the sedimentation rate and then determined the dominant mechanisms for the siltation. The sedimentation rate was estimated by comparing bathymetric surveys adjusted with the dredged volume, and verified by the penetration depth of 11 gravity cores to the previous dredging surface. The average sedimentation rate was 64 cm/year but varied from 10 cm/year in the interior to about 100 cm/year at the entrance. To determine the dominant mechanisms for siltation, two ADCPs were deployed at the entrance and the interior end of the harbor over a month to estimate sediment flux. Detailed sediment transport processes were examined by two 13-h CTD profiling surveys near the entrance and interior end of the harbor. High siltation at the entrance is attributable to the influx of high turbidity water, the decrease of current velocity, and the formation of an eddy. Low sedimentation inside the harbor was attained by the slow settling of microflocs of about 20–30 mg/l concentration that are maintained regardless of time and space.

Integrating multiproxy results (geochemistry, mineral magnetism, grain size, and C/N ratio variability supported by 14C AMS dating), obtained from a 1.4-m sediment core retrieved from high-altitude Anchar Lake, Kashmir Valley, NW Himalaya, we present a 6000-years record of paleoenvironmental and paleolimnological shifts. Phase 1 (6000–4700 cal. yr BP) revealed a wetter climate with a significant terrestrial input corresponding to the gradual strengthening of the westerlies. Phase 2 (4700–3900 cal. yr BP) reflects an overall improved westerly precipitation and autochthonous sources of organic matter (OM). Magnetic parameters also indicate higher lake levels and reducing conditions during this phase. Phase 2 was followed by a gradual diminishing pattern of the westerlies as also represented by phase 3 (3900–2500 cal. yr BP) and phase 4 (2500–1600 cal. yr BP) indicating moderate precipitation conditions, catchment stability, and temperate and/or cold-dry climatic conditions. Phase 5 (1600–500 cal. yr BP) revealed the prevalence of moderately cold/dry and further subdued westerly precipitation. Phase 6 (500 cal. yr BP to present) is represented by reduced westerly precipitation, shrinking lake margins, and significant terrestrial/anthropogenic controls over the lake basin. Mineral magnetic parameters indicate reducing lake bottom water conditions and eutrophication during this phase due to anthropogenic activities. These paleoenvironmental shifts reveal near synchronous changes (within dating uncertainties) with other regional paleoclimate records close to the present Anchar Lake location and reflect the gradual late-Holocene diminishment of the amount of winter/early summer moisture provided by the mid-latitude westerlies.