Search

This study investigated the tolerance of resting eggs of Eurytemora pacifica to storage under low temperatures, which is of particular interest in light of the recent use of nauplii as living food in aquaculture, other than conditions experienced also in the wild during winter cold events in the Northern Hemisphere. Sediment samples collected in August 2020 were used to store the resting eggs at two different freezing temperatures (−5 and −20 °C) for five different durations (1, 3, 6, 9, and 12 months). The mean hatching success rates of the resting eggs after one month of storage were 85.3 ± 1.5% (−5 °C) and 85.0 ± 3.6% (−20 °C), with no significant difference between freezing temperatures. However, significant differences emerged over time, with the mean hatching success rate remaining at 85.0 ± 3.6% at −5 °C after three months, while it dropped sharply to 1.7 ± 2.1% at −20 °C. For the non-freezing conditions, the hatching success at 10 °C increased gradually over the one-month incubation period, ultimately reaching 71.0%. These findings demonstrate the remarkable cold tolerance of E. pacifica but also indicate a limit to this tolerance at longer durations. These results underscore the importance of considering the adoption of storage freezing for resting eggs to be used for aquaculture and also suggest the possibility of the species better surviving the extreme weather events in comparison with other species. [ABSTRACT FROM AUTHOR]

A modified gravity corer (MGC) for more efficient and high-quality sediment core sampling is considered. Such design elements as the core catcher, section muff joints, the weight, and loop have been modified; the crown and locking plate have been removed. As a result of comparative testing in the South Chukchi Basin of the Chukchi Sea, it is shown that the MGC sampled 30% longer cores than the standard gravity corer (SGC). Judging from the distribution of such a redox-sensitive element as iron in the cores, when the MGС is used, a surface oxidized film remains in sediments. Thus, the disturbance of properties and textures/structures of sediments under sampling is the lowest. [ABSTRACT FROM AUTHOR]

We present a multiproxy analysis of a sediment core from Freshwater Pond, Barbuda, one of just a few inland paleoenvironmental records from the Lesser Antilles. Our results shed light on the relative contributions of climate variability and Pre- and Post-Columbian human activities to vegetation and fire dynamics on Barbuda. The presence of macroscopic charcoal and pollen of ethnobotanically-useful and disturbance-indicator plant taxa in the sediment record suggests that Pre-Columbian subsistence activities occurred within a few kilometers of the pond between ~150 BCE and ~1250 CE. Our record extends anthropogenic fires back into the early Ceramic (500 BCE–1500 CE) and possibly late Archaic Ages (3000–500 BCE) adding evidence to the timing of arrival of the island's earliest inhabitants. The history of island-wide biomass burning inferred from microscopic charcoal fragments showed heightened fire activity between ~540 and ~1610 CE followed by a period of quiescence that reflected the transition from Pre- to Post-Columbian land-use practices associated with European colonization of the region. The British established a permanent settlement on Barbuda in the 1660s, but given Barbuda's unsuitability for large-scale agriculture, timber harvesting, small-scale farming, and livestock rearing, activities that left no detectable charcoal footprints likely dominated post-colonial land use. The lack of any clear correspondence between the reconstructed histories of fire and effective moisture at Freshwater Pond supports the idea that Late-Holocene fire activity on Barbuda was driven primarily by human activity. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are produced by incomplete combustion of biomass and fossil fuel, yet PAHs have been rarely analyzed in coastal sediment cores as a tracer for human activities before industrialization. The aim of this study was to assess if the historical trend of PAHs can be related to past human activities. To this end, we have determined the concentrations of PAHs in a 9 m-long sediment core from Osaka Bay, which records history of the last 2400 years. The concentration of PAHs before the beginning of the 17th century CE, the beginning of the peaceful Edo period, was consistently low (<100 ng g−1) and mainly comprised of smoke-derived PAHs reflecting the natural background. A relative higher abundance of 4−6 ring PAHs from the early 17th century CE and a higher PAH concentration from the early 18th century CE until approximately 1800 CE agreed with a population increase, Cu smelting activities and increasing combustion of charcoal. The constant PAH concentration until the late 19th century CE overlapped with a decline in the population in the Osaka area. An increasing PAH concentration from the late 19th century CE marked the beginning of industrialization in the Modern age. The peak in PAH concentration in 1945 CE was likely caused by burning of wooden structures due to air raids on Osaka City. A second peak around 1980 CE indicated the introduction of cleaner energies. We conclude that PAHs in coastal sediment cores can be used to reconstruct past human activities. [ABSTRACT FROM AUTHOR]

A new hydrothermal field (Tianshi) was discovered on the rift valley wall through plume anomaly surveys and geological work conducted in 2012 and 2018 between 2°35′N and 2°43′N of the slow-spreading Carlsberg Ridge (CR). Here, the results of two expeditions conducted to detect and characterize the new hydrothermal field are reported. Mineralogical and geochemical data, as well as 14C ages of a sediment core collected near the field are presented to reveal the hydrothermal history. Results show that the Tianshi field is a basalt-hosted hydrothermal system. Geochemical data of the sediments collected near the field indicate a strong hydrothermal contribution, and hydrothermal Fe and Cu fluxes range from 30 to 155 mg/(cm2.ka) and 0.59 to 11.49 mg/(cm2.ka), respectively. Temporal variations in the fluxes of hydrothermal Fe indicate that there have been at least three amplified hydrothermal venting events (H1, H2, and H3) in the Tianshi field over the last 35.2 ka, in 28.6–35.2 ka BP, 22.0–27.6 ka BP, and 1.2–11.4 ka BP, respectively. Hydrothermal event H2 was driven by an increased magmatic production associated with sea level fall during the Last Glacial Maximum, while event H3 was promoted by tectonic activity associated with a rapid sea level rise. This study further verified the role of sea level change in modulating hydrothermal activity on mid-ocean ridges. [ABSTRACT FROM AUTHOR]

The first systematic sediment survey by the icebreaker Shirase (AGB-5003) was conducted during the 61st Japanese Antarctic Research Expedition (JARE-61). Sediment samples were obtained from a total of 28 sites in 3 areas of the Totten Glacier front–Dalton polynya, Lützow-Holm Bay and Cape Darnley polynya using a large-bore gravity corer and GSJ-type K-grab sampler. In this paper, details of the survey operation are described as a reference for the future experience. In addition, preliminary results of the obtained sediments are reported as a fundamental information for future analysis using these samples.

The complex aquatic system of dam reservoirs is known to trap emerging pollutants as microplastics (MPs) in sediments and water column. Considering the knowledge gaps in this type of environment, we investigated the amount and distribution of MPs in the surface water layer, as well as in the surface and deep sediments of the Siriu Reservoir in the Buzău River system, which is located in the southern area of the Eastern Carpathians, Romania. There was a discrepancy between MP abundancy in both water and sediment samples collected near the reservoir (5.3 MPs/m3, 315.5 MPs/kg) and at several kilometers downstream of the dam (1.4 MPs/m3, 132.5 MPs/kg). The chronological accumulation of MPs in the lacustrine sediments was determined by analyzing 5 cm intervals of a 50 cm length core extracted from the reservoir bed. By comparing the concentration of MPs identified in each interval with the solid debit volumes registered in the last decade, we found that flood events could be traced easily due to abundant MP accumulation. Morphologically, the particles were observed mainly as fibers and fragments. Fourier transform infrared spectroscopy (FT-iR) investigations identified most of the MPs as polypropylene (28%), polyethylene (26%), and polyethylene terephthalate (19%). [ABSTRACT FROM AUTHOR]

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.

Evaluating the ecological risks of metals and identifying their sources is useful for preventing and controlling heavy metal pollution in water bodies. Four sediment cores (S1~-S4) were collected from the Changhu Reservoir of South China to determine lead (Pb) concentrations and geochemical fractions, as well as the isotopic compositions of core S1. The results show that Pb concentrations increased from the upstream site (S1:173.2 mg kg-1) to the downstream site (S4:313.5 mg kg-1), resulting in a moderate to significant enrichment in the sediments. Sediment Pb in the geochemical fractions followed a decreasing order of residual (F4:54.7%) > reducible (F2: 23.1%) > oxidizable (F3: 16.6%) > acid-soluble fraction (F1: 5.8%). The geoaccumulation index (Igeo) and risk assessment code (RAC) showed that sediments were moderately polluted by Pb in S1 and S2 core, while sediments were moderately to heavily polluted in S3 and S4 core. The ecological risk of Pb in all sediment samples is generally at a low risk level, except for the sediments at a depth of 30-40 cm in the S4 core. Significant correlation between Pb concentration and 206Pb/207Pb ratios suggested possible binary mixing of Pb. In the present study, mining activities, which was the major anthropogenic Pb source base on its isotopic composition, contributed significantly (means: 45.3-77.5%) to sediment Pb. The anthropogenic Pb in sediments is most likely to come from Sphalerite and Galena. [ABSTRACT FROM AUTHOR]

Methane (CH4) emissions from reservoir to the atmosphere depend on the balance of microbial CH4 production and oxidation, and temperature is an important factor to both processes by influencing directly the activity of microorganism. Six sediment cores of 30 cm were collected from the Meiziya Reservoir, China, a small water conservancy project with the maximum water depth of 9.7 m. The main input of reservoir was terrigenous organic matter, and the δ13C of organic matter in sediments ranged from − 27.5 to − 23.3‰. Using a self-made device for monitoring CH4 production rate, we measured the CH4 production and oxidation rates in sediment cores simultaneously at the range of 6–27 °C with an interval of 3 °C. The CH4 net production rates and oxidation rates in sediment cores varied in the range of (4.2–2489.0) × 10−3 µmol/L·h−1 and (16.0–1287.5) × 10−3 µmol/L·h−1, respectively. Increasing temperature enhanced the CH4 production and oxidation rates, and the former increased over temperature with an exponential trend. In the Meiziya Reservoir, a large proportion of CH4 (69.7–70.6%) that originated from sediments was depleted before escaping to the surface sediments. During the mineralization of organic matter in sediments, the release of CH4 accounted for 1.1–66.8% of gaseous carbon (calculated by the mass of C). [ABSTRACT FROM AUTHOR]

This study presents morphological descriptions and ecological information for 58 terrestrial pollen taxa and seven water-related pollen taxa from the Brazilian Cerrado, obtained from two sediment cores, Lake Feia (LFB1) and Getulio Swamp (VGE-17), encompassing the last 5000 and 15,000 cal yr BP, respectively. The relationships between the ecological and morphological traits (pollination syndrome, vegetation stratum and grain size) within each of the two depositional environments were investigated. In the LFB1 core, the pollen assemblages were dominated by arboreal pollen from closed physiognomies and lower storey trees (<10 m in height), while a combination of closed and open physiognomies was observed in the pollen assemblages from the VGE-17 core. The vast majority of the pollen taxa exhibited the entomophilous pollination syndrome, and a higher influx of entomophilous pollen was observed in both cores. Anemophilous and anemophilous/entomophilous syndromes were less well represented. Small and medium pollen grain classes were the most abundant, while the large pollen grain class was rare. The influx of small pollen grains was slightly more abundant in the lake record, while in the swamp record medium pollen grains were more abundant. Our results show that swamps and lakes differ in their representation of local versus regional pollen and in their sensitivity and responses to water-level changes. Landscape physiognomy also influences pollen dispersion: a closed physiognomy increases the local pollen signal, while a more open physiognomy results in better representation of local and regional signals. [ABSTRACT FROM AUTHOR]

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10–93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

Perfluoroalkyl substances (PFAS) are an emerging class of contaminants that have been produced since the 1950s. The first report on PFAS to raise global concerns was published in 2001. Since then, many countries have implemented policies to control PFAS. In this study, PFAS in the water, sediment, and biota in coastal areas were surveyed to review their use since their earliest production by using chronological methods combined with previous policy restrictions imposed on PFAS. In the meantime, reports of existing PFAS were evaluated to assess the ecological and health risks of seafood consumption by coastal populations. Following the restrictions on PFAS, the concentrations of PFAS have been decreasing steadily. With regard to the current occurrences of PFAS in water and sediment, there is almost no ecological risk. However, different gender and age groups are still at risk of exposure to perfluorooctane sulfonate and require constant monitoring. It is expected that the negative impacts of PFAS on the environment and human health will continue to decrease with the implementation of the emerging pollution control policy by the Chinese government in 2023.

This study investigated the tolerance of resting eggs of Eurytemora pacifica to storage under low temperatures, which is of particular interest in light of the recent use of nauplii as living food in aquaculture, other than conditions experienced also in the wild during winter cold events in the Northern Hemisphere. Sediment samples collected in August 2020 were used to store the resting eggs at two different freezing temperatures (−5 and −20 °C) for five different durations (1, 3, 6, 9, and 12 months). The mean hatching success rates of the resting eggs after one month of storage were 85.3 ± 1.5% (−5 °C) and 85.0 ± 3.6% (−20 °C), with no significant difference between freezing temperatures. However, significant differences emerged over time, with the mean hatching success rate remaining at 85.0 ± 3.6% at −5 °C after three months, while it dropped sharply to 1.7 ± 2.1% at −20 °C. For the non-freezing conditions, the hatching success at 10 °C increased gradually over the one-month incubation period, ultimately reaching 71.0%. These findings demonstrate the remarkable cold tolerance of E. pacifica but also indicate a limit to this tolerance at longer durations. These results underscore the importance of considering the adoption of storage freezing for resting eggs to be used for aquaculture and also suggest the possibility of the species better surviving the extreme weather events in comparison with other species.

Sediment is an important carrier of evidence about environmental evolution which receives huge volumes of organic material originated from both anthropogenic and natural sources. In this study, based on sedimentary chronology, the vertical trends of particle size distribution, total organic carbon (TOC), total nitrogen (TN), and their stable isotopes (δ13C, δ15N) in the sediment core of the nuclear power sea in southwest Daya Bay were analyzed, and the distribution characteristics and contribution ratios of different sources of organic matter in the sedimentary environment over the past 70 years were resolved using a Bayesian mixing model (MixSIAR). TOC, TN, δ13C, and δ15N ranged from 0.89 to 1.56%, 0.09 to 0.2%, − 22.3 to − 20.6‰, and 4.38 to 6.51‰, respectively. The organic matter in the sediment is controlled by a mixture of terrestrial input and marine autochthonous, the proportion of organic matter from terrestrial sources increases, while that from marine sources decreases in the sediment core, which persists from 1960 to 2000, yet organic matter from marine sources still dominates. The first signs of increased primary productivity occurred in 1960, and it was primarily due to agricultural activity. After the 1980s, the rapid increase in population around Daya Bay, the construction of nuclear power plants, the rise of aquaculture, and the quick expansion of industrial bases were all major factors that changed the ecological environment of Daya Bay. [ABSTRACT FROM AUTHOR]

A sedimentary record of the 19 organochlorine pesticides (OCPs) pollutants from Dongping Lake, north China, is presented in this study. According to the dating of core sediment and OCP content analysis in samples, from 1904 to 2016, the total concentration of OCPs varied from undetectable levels (n.d.) to 33.1 ng/g. The OCP concentration was first detected in the samples of 1938, and then gradually increased to a peak level in 2000 thereafter decreased until 2016. Among the detected OCPs, hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant and the most frequently detected contaminants in the core sediment, with concentrations ranging from n.d. to 16.9 ng/g and from n.d. to 8.8 ng/g, respectively. The distribution of OCPs in the sediments was affected by organic carbon concentration, showing a significant positive correlation (r = 0.93, p < 0.001), especially for HCHs (r = 0.98, p < 0.001). The source analysis showed that HCH contamination mainly derived from historical use of technical HCHs, while in recent years, it derived from lindane usage. DDT pollution was attributed to historical use of technical DDTs, as well as the microbial degradation of historic DDT residues. Finally, risk analysis was performed for OCPs in sediment cores based on sediment quality guidelines from the Canadian Council of Ministers of the Environment, showing that DDTs presented a high ecological toxicity risk during the period of 1959–2010. [ABSTRACT FROM AUTHOR]

Atribacteria play an important role in global carbon cycling. Little is known, however, about the Atribacteria communities found in alpine lakes. The presence and diversity of Atribacteria in the sediment core of alpine Sayram lake in China were investigated using Illumina MiSeq sequencing in this study. According to the findings, Atribacteria affiliated with JS1 were dominant in the sediment core of Sayram Lake, with a relative abundance of 0.19 to 10% (average 3.75%) of all bacterial sequences. Furthermore, the relative abundance of Atribacteria associated with JS1 increased with sediment depth. As a result, this study significantly contributes to our understanding of Atribacteria community habitat.

The Gulf of Guinea is known to be highly productive owing to its ecological and economical significance. Given its importance, detailed evaluation of the major elements (Fe, Mn, Ca, Mg, Na, Al, K and Si) and trace metals (Cu, Zn, Pb, Cr, Ni, As, Sc, V, Th and U) were analyzed from the sediment core within this basin for the first time. This study aims to determine their baseline composition, pollution level, and ecological risk. Analyses of these metals using inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) with Agilent SPS3 Autosampler showed the descending order of Na > Fe > Ca > Si > Mg > Al > K > Mn and Zn > U > V > Ni > Cr > Th > Pb > As > Cu > Sc for major and trace element respectively. The pollution indices and sediment qualities were assessed using the contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), potential ecological risk factor (Er), modified hazard quotient (mHQ), pollution load index (PLI), ecological risk index (RI), single metal toxic risk index (TRIi) and integrated Toxic risk index (TRI) at three stations (stations A, B, and C). Except for As and U, the mean concentrations of the metals were lower than their respective background values. Based on the pollution indices, the studied trace metals were found to have severe EF (>25) with respect to Zn and V, considerable CF (3 ≤ CF ≤ 6) for As, and high CF (> 6) for U. The Igeo values of all the trace metals indicated unpolluted to moderately polluted status (0 ≤ lgeo ≤ 1). The Er ranges (0.05–41.80) indicate low to moderate ecological risk, while mHQ (< 1) values indicate very low severity of contamination. There was no significant risk from the combined metals recovered from the sediment core of the study area to the marine ecosystems according to RI (

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France–Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition. [ABSTRACT FROM AUTHOR]

The suitability of lake sediment cores to reconstruct past inputs, regional pollution, and usage patterns of pesticides has been shown previously. Until now, no such data exist for lakes in eastern Germany. Therefore, 10 sediment cores (length 1 m) of 10 lakes in eastern Germany, the territory of the former German Democratic Republic (GDR), were collected and cut into 5–10-mm layers. In each layer, concentrations of trace elements (TEs) As, Cd, Cr, Cu, Ni, Pb, S, and Zn, as well as of organochlorine pesticides (OCPs), i.e., dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), were analyzed. A miniaturized solid–liquid extraction technique in conjunction with headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS) was used for the latter. The progression of TE concentrations over time is uniform. It follows a trans-regional pattern and is indicative of activity and policy making in West Germany before 1990 instead of those in the GDR. Of OCPs, only transformation products of DDT were found. Congener ratios indicate a mainly aerial input. In the lakes' profiles, several regional features and responses to national policies and measures are visible. Dichlorodiphenyldichloroethane (DDD) concentrations reflect the history of DDT use in the GDR. Lake sediments proved to be suitable to archive short- and long-range impacts of anthropogenic activity. Our data can be used to complement and validate other forms of environmental pollution long-term monitoring and to check for the efficiency of pollution countermeasures in the past. [ABSTRACT FROM AUTHOR]

The influence of anthropogenic activities on pollution of trace metals (TMs) during the last few decades in the lower reaches of the Yell ow River was reconstructed with sediment cores in the present study. The results showed that As, Cd, Cu, Pb, and Zn averaged 7.65, 0.10, 26.39, 45.83 and 48.33 mg/kg in Core C 1 located in Gaocun in Heze city, and 8.54, 0.135, 33.2, 39.1 and 58.5 mg/kg in Core C2 located in Luokou in Jinan city. Therefore, the levels of TMs in Core C2 were much higher than those in Core Cl. Zn and Pb exhibited the highest levels in two cores. The historical TM concentrations revealed obvious differences between two cores. In addition, TMs in the sediment of Core C2 had the high ecological risk and severe contamination status. The combined excessive concentrations of these five metals indicated a significant overall increase in the last two decades, implying the significant accumulation of TMs in the sediment of the Yellow River in recent years. The above results showed that the rapid development of urbanization, industrialization, and modern agriculture significantly accelerated the accumulations of TMs in the sediment of the Yellow River. The worsening trend of TM pollution in the sediment from the bottom to the top of two cores showed the deep influence of the intensified human activities on the TM pollution in sediment in recent years. [ABSTRACT FROM AUTHOR]

Ice scours are formed when the keels of floating icebergs or sea ice hummocks penetrate unlithified seabed sediments. Until now, ice scours have been divided into "relict" and "modern" according to the water depth that corresponds with the possible maximum vertical dimensions of the keels of modern floating icebergs. However, this approach does not consider climatic changes at the present sea level, which affect the maximum depth of ice keels. We present an application of 210Pb dating of the largest ice scour in the Baydaratskaya Bay area (Kara Sea), located at depths of about 28–32 m. Two sediment cores were studied; these were taken on 2 November 2021 from the R/V Akademik Nikolay Strakhov directly in the ice scour and on the "background" seabed surface, not processed via ice scouring. According to the results of 210Pb dating, the studied ice scour was formed no later than the end of the Little Ice Age. Based on the extrapolation of possible sedimentation rates prior to 1917 (0.22–0.38 cm/year), the age of the ice scour is estimated to be 1810 ± 30 AD. The mean rate of ice scour filling with 70 cm thick sediments from the moment of its formation is around 0.33 cm/year. [ABSTRACT FROM AUTHOR]

To understand the spatial distribution and vertical evolution of sediments in the Pearl River Estuary in recent decades, two sediment cores (80 cm long) from the western and eastern areas of the outer Lingdingyang Bay (LDB) were analyzed in terms of grain size (GZs) and organic matter content. The results showed that the sediment profiles of the two cores could be divided into two time sections with clear changes in grain size. The core in the western region showed a coarse-to-fine trend from the lower to the upper section, whereas that in the eastern region showed a fine-to-coarse trend. Parametric correlations of the cores suggest that different sediment sources and hydrodynamic environments resulted in opposite sediment trends in the two cores. Based on some reported sedimentation rates, the GZs of the western and eastern cores responded well to changes in the average annual fluvial sediment load and tidal range in the western and eastern areas of the LDB, respectively. The increase in grain size and decrease in sorting value in the upper section of the two cores can provide evidence of a strengthened tidal current in recent years. Our results can provide a baseline for future studies on the responses of marine environment to anthropogenic activities in the Guangdong-Hong Kong-Macao Greater Bay Area. [ABSTRACT FROM AUTHOR]

Coastal wetlands rely on sediment for exchange and development, and a study on the temporal trend of sedimentation can provide a tool for comprehensive interpretation of how the wetland will evolve. To reveal long-term sedimentation processes in the Xuan Thuy Natural Wetland Reserve in Vietnam, five sediment cores were taken for sediment chronology by 210Pb techniques. Results show that, from 1930s to 1965 period, the wetland experienced a low sediment accumulation rate (SAR) but from 1965, SAR started to increase gradually. Changes in the sedimentation process at different locations started in 1980. For the last 40 years, SAR at site A decreased from 1.70 ± 0.18 to 0.77 ± 0.11 cm year−1 while at sites B, C, D, and E, SARs kept increasing. For the last 40 years, SARs at these sites have elevated average values of 1.32 ± 0.29, 1.64 ± 0.37, 1.73 ± 0.46, and 1.74 ± 0.43 cm year−1, respectively. According to the recent temporal trend of sedimentation, it is predicted that in about 75 years, the Con Ngan tidal flat will be above the high tide water level. In about 80 years, swamps for mangrove forests in the Con Lu tidal flat will be displaced to the area along the Tra River tributary and the lagoons for shellfish farming at the end of Con Ngan and Con Lu. [ABSTRACT FROM AUTHOR]

Microplastics are widespread in coastal and marine environments, and sediments serve as a sink for microplastics. In this study, four sediment cores were collected from the Kuala Gula Mangrove area. The abundance of microplastics in mangrove sediments ranged from 25–130 items/kg dry weight. The highest abundance of microplastic was observed at the KG04 site near the mouth of the river. The number of microplastics by sampling site was significantly different (p < 0.01), with station KG04 having the highest fiber content. The dominant color of microplastics was blue, and the main shape was fiber. Rayon, cotton, Polyethylene terephthalate (PET), and azlon were observed from FT-IR, indicating that the potential sources of microplastic and fiber could come from household laundry wastewater. Microplastics tended to accumulate in deeper depths at KG01 (p < 0.01), whereas other stations showed no significant difference (p > 0.05). However, this study provides evidence that mangroves can be a trap for microplastics and can be used as baseline data for future studies. [ABSTRACT FROM AUTHOR]

With the development of urbanization and economic growth, the urban lake ecosystem faces many challenges derived from external factors. As pollutants in the aquatic environment, heavy metals and microplastics negatively influence the urban lake ecosystem due to their intrinsic properties. To understand the distribution patterns and multidecadal deposition characteristics of heavy metals and microplastics, six sediment cores were collected in March 2021 from a Chinese urban lake, Xinghu Lake, and the isotopic composition of cesium-137 and lead-210 was analyzed for the chronology of the sediment core. Here, the classifications of comprehensive ecological risk evaluation methods for heavy metals and microplastics were adjusted further. Meanwhile, the correlations among heavy metals, microplastics, sediment grains, and natural and social factors were further analyzed. The results showed that the sediments of Xinghu Lake were mainly fine silt (39%), and the average surface area of sediment was 1.82 ± 0.60 m2/g. The average concentrations of cadmium, chromium, copper, nickel, lead, vanadium, and zinc were 0.268 ± 0.077, 59.91 ± 16.98, 23.29 ± 6.48, 52.16 ± 13.11, 36.83 ± 11.78, 119.57 ± 26.91, and 88.44 ± 29.68 mg/kg, respectively. The average comprehensive potential ecological risk indexes of heavy metals and microplastics in sediment cores were 46.59 ± 9.98 and 105.78 ± 23.32 in Xinghu Lake, and their risks were projected to reach high and very high levels by 2030 and 2050. The annual average temperature was the key natural factor for the abundances of heavy metals and microplastics, and the small sediment grain had a significant correlation with these. Agricultural activities were major pollution sources of heavy metals and microplastics, while the chemical fibers and plastic products were closely related to the abundance of microplastics. [ABSTRACT FROM AUTHOR]

To clarify the impact of human activities on the natural environment, as well as the current ecological risks to the environment surrounding Zhushan Bay in Taihu Lake, the characteristics of deposited organic materials, including elements and 16 polycyclic aromatic hydrocarbons (∑16PAHs), in a sediment core from Taihu Lake were determined. The nitrogen (N), carbon (C), hydrogen (H), and sulfur (S) contents ranged from 0.08 to 0.3%, 0.83 to 3.6%, 0.63 to 1.12%, and 0.02 to 0.24%, respectively. The most abundant element in the core was C followed by H, S, and N, while elemental C and the C/H ratio displayed a decreasing trend with depth. The ∑16PAH concentration was in the range of 1807.48–4674.83 ng g−1, showing a downward trend with depth, with some fluctuations. Three-ring PAHs dominated in surface sediment, while 5-ring PAHs dominated at a depth of 55–93 cm. Six-ring PAHs appeared in the 1830s and gradually increased over time before slowly decreasing from 2005 onward due to the establishment of environmental protection measures. The ratio of PAH monomers indicated that PAHs in samples from a depth of 0 to 55 cm were mainly derived from the combustion of liquid fossil fuels, while the PAHs in the deeper samples mainly originated from petroleum. The results of a principal component analysis (PCA) showed that the PAHs in the sediment core of Taihu Lake were mainly derived from the combustion of fossil fuels, such as diesel, petroleum, gasoline, and coal. The contributions of biomass combustion, liquid fossil fuel combustion, coal combustion, and unknown source were 8.99%, 52.68%, 1.65%, and 36.68%, respectively. The results of a toxicity analysis indicated that most of the PAH monomers had little impact on the ecology, and the annual increase of a small number of monomers might have toxic effects on the biological community, resulting in a serious ecological risks, that requires the imposition of control measures. [ABSTRACT FROM AUTHOR]

Abstract Osaka Bay adjacent to the Kyoto–Osaka–Kobe metropolitan area was affected by severe metal pollution during the twentieth century; yet little is known about the trace metal sources and pre-industrial human activities. We have determined the elemental concentrations and zinc stable isotope ratios (δ66Zn) in bulk sediments and the trace metal concentrations in chemical fractions of a 9-m-long sediment core from Osaka Bay. Our goals were (1) to reconstruct the historical trace metal contamination, and (2) to identify anthropogenic Zn sources and the solid phases of anthropogenic trace metals. The core provided a continuous environmental record of the last 2300 years based on radiocarbon dating of molluscan shells. Copper, Zn, and Pb showed an initial enrichment from the 1670s AD, which could be caused by human activities due to an increasing population. In agreement with previous findings, the trace metal concentrations slightly increased from the 1870s, strongly increased from the beginning of the twentieth century, and peaked around 1960 before environmental pollution control laws were enacted. Increasing trace metal concentrations in the acid-labile and reducible fractions obtained by the Community Bureau of Reference (BCR) sequential extraction procedure toward the surface indicate carbonates and Mn oxyhydroxides were the primary fractions for anthropogenic trace metals. The δ66Zn values (1) were constant until the 1940s, suggesting that the average δ66Zn of industrial sources was indistinguishable from that value of the natural background, (2) showed a slight decrease from the 1950s and remained constant until the present, and (3) fell in a binary mixing process between a lithogenic (~ + 0.27‰) and an anthropogenic endmember (~ + 0.17‰), the latter likely representing a mixture of various Zn sources such as road dust, tire wear, industrial effluents, and effluents from wastewater treatment plants. We conclude the combination of Zn stable isotopes together with chemical fractions obtained by the BCR method represents a promising approach to assess the trace metal sources and their potential mobility in sediment cores from anthropogenically affected coastal areas.

BACKGROUND The contamination of arsenic and mercury in intertidal sediments will lead to excessive levels of arsenic and mercury in the flora and fauna of the region, which will seriously affect the ecological environment of local vegetation and further affect the survival and safety of human beings. Therefore, it is of great practical significance to study the changes in the contents and spatial distribution of arsenic and mercury in intertidal sediments. OBJECTIVES To investigate the contents of arsenic and mercury in sediments, so as to provide basic information on the pollution of arsenic and mercury in intertidal sediments. METHODS The contents of arsenic and mercury in the sediments of the study area were determined by atomic fluorescence spectrometry (AFS), and iron was selected as the normalized element to establish the environmental background values of arsenic and mercury elements in different intertidal sediments. The geoaccumulation index method and potential ecological hazard index method were used to evaluate the pollution status of arsenic and mercury in the study area. RESULTS Background value of arsenic content: Minjiang Estuary (2.90mg/kg) < Daliao Estuary (6.42mg/kg) < Yancheng Shoal in northern Jiangsu (11.02mg/kg) < Pearl River Estuary (19.19mg/kg). Background value of mercury content: maximum in Pearl River Estuary (0.08mg/kg), less in Daliao Estuary, Yancheng shoal and Minjiang Estuary (0.02mg/kg, 0.02mg/kg, 0.03mg/kg, respectively). The maximum values of background values of arsenic and mercury were both found in the Pearl River Estuary, and the minimum values were located in the Minjiang Estuary. The maximum values of arsenic and mercury of sediments were both found in the Pearl River Estuary, which were 42.90mg/kg and 0.287mg/kg, respectively, and were greater than the first class of Marine Sediment Quality Standard (arsenic: 20.0mg/kg; mercury: 0.2mg/kg). Arsenic belonged to no pollution and slight potential ecological hazards in the four intertidal sediments. Mercury was a medium potential ecological hazard in the Pearl River Estuary, and slight pollution or no pollution in the other three intertidal sediments. CONCLUSIONS The distribution of arsenic and mercury in the sediments of the four intertidal zones in the study area is characterized by "high in the south and low in the north". The arsenic and mercury contents in the intertidal sediments of Minjiang and Pearl River estuaries are more influenced by industrial and agricultural activities, thus causing the distribution features. The pollution of arsenic and mercury in the Pearl River Estuary is more serious than other intertidal areas, so it is urgent to strengthen the control of their pollution trends.

In this study, frequency and diversity of benthic foraminifera of 44 samples from a 14C dated sediment core were used to assess the effects of human activities on pollution and creating hypoxic conditions in coastal sediments of Bandar Abbas. The results showed that during the last century, the construction of coastal infrastructures and expansion of the city caused 5% elevation of sand input to the area. Variations of frequency and diversity of benthic foraminifera during the last decades also follows the above-mentioned changes. During the recent decades, the relative abundance of opportunistic hyaline taxa such as Cribroelphidium, Asterorotalia and Ammonia, and also conical species such as Bolivina and Bulimina which show higher ability to survive in polluted environments with lower oxygen content increased 100 to 200%. On the other hand, more than 150% reduction of species with thicker walls (Milliolids such as Massilina and Quinqueloculina) in this time show the intense environmental changes caused by human activities in coastal areas of Bandar Abbas. Altogether, significant increase in sewage runoff due to urban and industrial development of Bandar Abbas has had a great impact on the coastal ecosystem of the city, which should be mitigated by taking the right management decisions

Using geochemical and sedimentological properties of a sediment core IK2 from the 210 m deep Karamürsel Basin of the İzmit Gulf, temporal evolution of pollution and sources of trace elements (As, Co, Cr, Cu, Hg, Pb and Zn) were investigated. The core sequence extends back to AD865 and includes four mass-flow units (THU-1 to THU-4 from top to base) that were triggered by major earthquakes of AD 1999, 1509, 1206 and 865. The vertical profiles of elements and total organic carbon (TOC) in core IK2 display the highest enrichments in THU-1 that was triggered by the 1999 İzmit earthquake (Mw 7.4). The profiles also display massive erosion of sediments below THU-1, belonging to the industrial period. Principal component analysis (PCA) of geochemical data from core IK2 showed three clusters: (1) PC1 (Co, Cu, Zn, Hg, TOC); (2) PC2 (As, Cr); (3) PC3 (Al). Enrichment of PC1 elements in THU-1 indicates that the unit represents the contaminated surficial sediments remobilized mainly from the relatively steep slopes of the Karamürsel Basin by the earthquake shaking. Strong correlation between TOC and Cu, Zn, Hg, Co suggests additional contamination sources, such as the seepages from the disrupted industrial pipelines, oil refinery and storage tanks, following the earthquake. Moderate enrichment in Pb, and As severe enrichment in Zn and very severe enrichment in Hg in the THU-1 sediments occurred in the last century, but significantly magnified by the devastating 1999 İzmit earthquake and early diagenetic processes. [ABSTRACT FROM AUTHOR]

Copyright of Anuario do Instituto de Geociencias is the property of Universidade Federal do Rio de Janeiro, Instituto de Geociencias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Paleolimnological assessment of Ladik Lake (N Turkey) using diatoms was carried out along a 62 cm-long sediment core recovered from the southeastern part of the lake. The chronology of the sediments was established by 137Cs - 210Pb dating. Accordingly, three major chronostratigraphical diatom assemblage zones (DAZ) were defined by the CONISS (constrained cluster analysis) program. The oldest assemblage, DAZ C (AD 1925-1958), was dominated by Ulnaria ulna (Nitzsch) Compère, Cocconeis placentula Ehrenb. and Cocconeis pediculus Ehrenb. taxon. In DAZ B (AD 1958-1986), in addition to Ulnaria ulna species that dominated through the whole core, Epithemia spp. occasionally dominated the assemblage in this zone. Ulnaria ulna and Pantocsekiella ocellata (Pant.) K.T. Kiss & Ács predominated since the beginning of DAZ A (AD 1986-2006). After the first regime of the lake with dystrophic character, the diatom community underwent a significant shift, with decreased abundance of periphytic diatom samples. The improvement of the regulator in 1986 resulted in a larger water level increase that affected the lake ecology, causing a shift from a diverse periphytic diatom to planktonic diatom assemblage. Based on our monitoring it can be inferred that the limnological regime shifts in Ladik Lake during the 20th century are of anthropogenic origin, rather than being due to climatic changes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The historical trends and inventory of organophosphate esters (OPEs) were investigated based on depth profiles of OPEs in sediment core collected from the tidal flat of the Liao River estuary in northeastern China. The concentration of ∑13OPEs in sediment core has increased continuously since records began, reaching a peak of 10.8 ng g-1 dry weight (dw) in the 1960s, then began to decline and fall to a low of 3.91 ng g-1 dw in the 1980s, before rising again and increasing to 20.4 ng g-1 dw in the 2000s. After a brief decline, It started to increase again and reached a peak of 27.0 ng g-1 dw in 2018. Tributyl-n-phosphate was found in each layer of the sediment core, accounting for 31.9 - 100% of ∑13OPEs. The fluxes of OPEs ranged from 46.5 to 105 ng cm-2 y-1 in the sediment layers deposited between 2007 and 2018. The inventory of OPEs in the sediment core was estimated to be 1541 ng cm-2. This work reports for the first time the historical contamination trends of OPEs in Chinese sediments, which is important for assessing the environmental risk of OPEs.

Chemical analysis, grain size distribution and short-lived radionuclides (210Pb and 137Cs) were combined to investigate the sedimentary processes in the Oualidia lagoon. Grain size and major elements profiles indicate an unexpected change in the layers characterising 1978 and 1986. Sediment accumulation rates (SAR) depth profiles exhibited the same behaviour and revealed two different sediment deposition conditions or regimes, involving modification of this ecosystem equilibrium. The profiles of major elements behave vertically almost the same as SAR, and grain size distribution. The observed changes reflect modifications in sediments supply and ecosystem drivers due to the variation of hydrodynamics conditions, confinement phenomena located in the upstream zone of the lagoon and to the various anthropogenic activities around the Oualidia lagoon. [ABSTRACT FROM AUTHOR]

A growing body of work has demonstrated that the δ2H values of alkenones reflect the δ2H values (δ2H H2O) and / or salinity of the fluid in which they are produced. If so, δ2H alkenone values would act as a surface seawater isotope / salinity proxy, similar to foraminiferal δ18O values, but advantaged in locations with poor carbonate preservation and / or high organic content. Nevertheless, laboratory culture, sediment trap, and water column studies have failed to consistently characterize the effects of temperature, alkenone-producing species, and salinity itself on the δ2H alkenone -salinity and -seawater isotope relationships, and a robust sedimentary alkenone-based calibration remains elusive. Most δ2H alkenone datasets report δ2H C37 , i.e., combined δ2H C37:3 and δ2H C37:2 values, and differ in how they address inter-alkenone fractionation (i.e., α C37:3-C37:2). To constrain controls on alkenone hydrogen isotope systematics in the natural environment, we measured δ2H values of C 37 and C 38 alkenones from 20 open ocean core tops by gas chromatography-stable isotope ratio mass spectrometry after separation of di- and tri-unsaturated forms. Core-top δ2H alkenone data points are currently concentrated in extreme-salinity regions; in combination with our new values from a more moderate range of open ocean δ2H H2O / salinity values, for sedimentary alkenones, we show that 1) mean inter-alkenone hydrogen isotope fractionation is negligible (α C37:3-C37:2 = 1.002 ± 0.006), and therefore that δ2H C37:3 and δ2H C37:2 values can be measured in bulk; 2) temperature and salinity have little impact on alkenone-water fractionation (i.e., α C37-H2O) (mean 0.803 ± 0.010) relative to their expected variability in the ocean; and 3) δ2H C37 and δ2H H2O values are correlated such that statistically identical δ2H C37 -, δ2H C37:3 -, and δ2H C37:2 -δ2H H2O regressions yield a core-top-based calibration of δ2H C37 = 1.44 (± 0.13) * δ2H H2O – 191.62 (± 1.13) ‰. This is indistinguishable from water column calibrations, suggesting a consistent response of environmental δ2H C37 values to changes in δ2H H2O values. This calibration still contains a high amount of scatter (∼ 7 ‰), perhaps attributable to irradiance, growth rate, intra- or interspecies variability, or other factors difficult to constrain in sedimentary material. Nevertheless, when applied to the well-constrained Last Glacial Maximum-to-present mean ocean δ2H H2O change of ∼ 8.8 ‰, it (1.44 ‰ δ2H C37 per 1 ‰ δ2H H2O change) reproduces the mean δ2H C37 Modern – δ2H C37 LGM shift observed from the handful of extant down-core records, legitimizing the observed lack of temperature or salinity effects on α C37-H2O. This suggests that combined δ2H C37:3 + δ2H C37:2 values are a valid proxy for δ2H H2O values in open ocean settings where E. huxleyi and G. oceanica dominate, although additional efforts will be required to refine the core-top calibration for universal use. [ABSTRACT FROM AUTHOR]

The level and pollution status of Zn, Cd, Pb, Cu in sediment cores of Bagan Pasir estuary, Sungai Buloh estuary, and the coastline of Port Dickson was assessed. Based on the vertical profiles of metals concentrations, the order of metals' concentration in decreasing manner was Zn>Pb>Cu>Cd at Bagan Pasir and Sungai Buloh stations, while Zn>Cu>Pb>Cd at Port Dickson station. Most of the analyzed metals were below the Interim Sediment Quality Guidelines and the effect range-low (ERL) at all sampling stations. The results of geo-accumulation index, contamination factor and pollution load index classified the sediments quality as unpolluted with studied metals with the exception of the element Pb at certain depths of the sediment cores as well as historical pollution at bottom sediment at Sungai Buloh station. Therefore, metal concentrations in the sediments of these stations were not at an alarming stage, however, requires regular monitoring from the authorities to maintain sustainable management of these areas especially at Sungai Buloh due to anthropogenic activities. [ABSTRACT FROM AUTHOR]

• PCA-MLR, PMF, and Unmix receptor models were successfully identified PAHs sources in sediment core. • PAHs reached its peak around 2000 in a remote lake of Tibet Plateau. • Biomass and coal combustion are important soueces of PAHs in sediments. • Temporal trends of factor contributions were consistent with different ring number PAHs. Receptor models are a useful tool for identifying sources of polycyclic aromatic hydrocarbons (PAHs) in multiple environmental media. In this study, three different receptor models (including the principal component analysis-multiple linear regression (PCA-MLR), positive matrix factorization (PMF), and Unmix models) were used to apportion the sources of 16 priority PAHs in a sediment core of Lake Dagze Co. The ∑PAHs (sum of all 16 measured PAHs) concentrations ranged from 51.89 to 132.82 ng/g with an average of 80.39 ng/g. The ∑PAHs were dominated by 2-3 ring PAHs, accounting for 80.12% on average, thereby indicating that they mainly originated from biomass and coal combustion and/or from long-range atmospheric transportation. The three models produced consistent source apportionment results. The greatest contributor to ∑PAHs was biomass combustion, followed by coal combustion, vehicle emissions, and petrogenic sources. Moreover, the temporal variation of the common sources was well-correlated among models. The multi-method comparison and evaluation results showed that all three models were useful tools for source apportionment of PAHs, with the PMF model providing better results than the PCA-MLR and Unmix models. The temporal trends of factor contributions were verified by PAHs with different ring numbers. Significant correlations were found between the simulated concentrations of each source factor and the PAHs with different ring numbers (P <0.01), except for the petrogenic source identified by the Unmix model (P >0.05). This study can provide useful information for further investigation of source apportionment of PAHs in the sediment cores. [Display omitted] [ABSTRACT FROM AUTHOR]

This study's objective was to evaluate the depth profiles of rare earth elements (REEs) in two Pb-210 dated sediments cores retrieved from the Oualidia lagoon, reconstruct their anthropogenic history, and assess their potential ecological risk. The sediment cores analysis was carried out using instrumental neutron activation analysis. Other physical-chemical parameters (bulk, organic matter, grain size) were also measured. The results indicated that the highest values were recorded in the topmost layers of the sediment cores and depleted with depth. The historical records of REEs revealed an exponential increase in their concentrations from the 50s. The enrichment factor, geo-accumulation index, and contamination factor calculated for each sediment core layer have exhibited important concentrations of Gd, Sm, and Eu, suggesting an anthropogenic origin of detected elements. Based on ecological risk >40 and the risk index >220, Gd, Eu, and Sm pose a high risk on the study area, while the other elements present moderate and mild risk. The obtained results revealed an increasing tendency of REEs accumulation into the Oualidia lagoon and suggested that a new source is feeding the lagoon sediments by these elements. These findings provided a clear picture of REEs evolution between 1903 and 2014 and baseline information on the historical deposition of these elements in the Oualidia lagoon. [ABSTRACT FROM AUTHOR]

Osaka Bay adjacent to the Kyoto–Osaka–Kobe metropolitan area was affected by severe metal pollution during the twentieth century; yet little is known about the trace metal sources and pre-industrial human activities. We have determined the elemental concentrations and zinc stable isotope ratios (δ66Zn) in bulk sediments and the trace metal concentrations in chemical fractions of a 9-m-long sediment core from Osaka Bay. Our goals were (1) to reconstruct the historical trace metal contamination, and (2) to identify anthropogenic Zn sources and the solid phases of anthropogenic trace metals. The core provided a continuous environmental record of the last 2300 years based on radiocarbon dating of molluscan shells. Copper, Zn, and Pb showed an initial enrichment from the 1670s AD, which could be caused by human activities due to an increasing population. In agreement with previous findings, the trace metal concentrations slightly increased from the 1870s, strongly increased from the beginning of the twentieth century, and peaked around 1960 before environmental pollution control laws were enacted. Increasing trace metal concentrations in the acid-labile and reducible fractions obtained by the Community Bureau of Reference (BCR) sequential extraction procedure toward the surface indicate carbonates and Mn oxyhydroxides were the primary fractions for anthropogenic trace metals. The δ66Zn values (1) were constant until the 1940s, suggesting that the average δ66Zn of industrial sources was indistinguishable from that value of the natural background, (2) showed a slight decrease from the 1950s and remained constant until the present, and (3) fell in a binary mixing process between a lithogenic (~ + 0.27‰) and an anthropogenic endmember (~ + 0.17‰), the latter likely representing a mixture of various Zn sources such as road dust, tire wear, industrial effluents, and effluents from wastewater treatment plants. We conclude the combination of Zn stable isotopes together with chemical fractions obtained by the BCR method represents a promising approach to assess the trace metal sources and their potential mobility in sediment cores from anthropogenically affected coastal areas. [ABSTRACT FROM AUTHOR]

Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH 2 -NH 2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH 2 OH·HCl) and sodium bisulfite (Na 2 S 2 O 5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in solution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine-129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores. [ABSTRACT FROM AUTHOR]

Wetlands are one of the most important ecosystems on earth, which help sustain life, yet they are reported to be at the receiving end of the high rate of pollution. The state of Kerala on the southwest coast of India is bestowed with several wetlands including Ramsar sites. Although the larger wetlands have been extensively studied, smaller or local wetlands have often been neglected; however, the environmental problems will be first reflected in the small wetlands. In this study, the ecological risk assessment of core sediments of one such site, the Biyyam wetland, a wetland of national importance, is reported for the first time. Sediment core samples were collected from four different stations of Biyyam wetland, and concentrations of heavy metals such as Ni, Zn, Mn, Cu, Cd, and Pb were determined. Statistical analysis indicated that correlation among different metals differed with respect to stations, but the percentage of organic matter showed a positive correlation with the concentration of the metals. The mean concentrations of Ni, Pb, and Cd exceeded the global average shale value. The quality of the sediments was assessed based on numeric Sediment Quality Guidelines. The degree of Contamination, Pollution Load Index, Enrichment Factor, Geoaccumulation Index, Ecological Risk Index, Toxic Unit, and Toxic Risk Index were used to evaluate the ecotoxicity of the heavy metals in the sediment core samples. The results inferred serious anthropogenic pollution in the wetland, and Cd was reported as the prominent metal contributing to heavy metal toxicity and ecological risk in the study area, which may in long run be toxic to the aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Sub-annual-scale environmental and ecosystem changes since the mid-18th century were reconstructed in a semi-closed lagoon, Lake Hiruga, located along the Sea of Japan in central Japan. Lake Hiruga is one of the Mikata Five Lakes and is connected to Lake Suigetsu through an artificial tunnel, the Saga Tunnel. Analyses of siliceous phytoplankton (diatoms, silicoflagellates, and chrysophyte cysts) and elemental composition (carbon, nitrogen, sulfur) of laminated sediments were conducted to determine the impacts of irregular hazards and anthropogenic tunnel construction on the lagoon ecosystem. In this lagoon, sediment laminae were deposited after the first Saga Tunnel re-excavation in 1844–1848, and the dominant phytoplankton taxa have changed with each re-excavation. The behaviors of total nitrogen, total organic carbon, freshwater diatom taxa, and chrysophyte cysts in Lake Hiruga are strongly affected by tunnel excavation and water gate construction. In addition to anthropogenic effects, the deposits show extreme hazard impacts of the Lake Hiruga ecosystem. The peaks of marine diatom taxa, silicoflagellate abundance, and sulfur content of Lake Hiruga showed close relationships with the local earthquake event. A relatively high sea level in the coast of Sea of Japan by local subsidence induced active seawater exchange with Lake Hiruga around AD 1928–1930. Furthermore, the peaks of freshwater diatom taxa and chrysophyte cyst showed a freshening event of this lake caused by local extreme events, such as continuous flooding around AD 1900. [ABSTRACT FROM AUTHOR]

Ice scours are formed when the keels of floating icebergs or sea ice hummocks penetrate unlithified seabed sediments. Until now, ice scours have been divided into “relict” and “modern” according to the water depth that corresponds with the possible maximum vertical dimensions of the keels of modern floating icebergs. However, this approach does not consider climatic changes at the present sea level, which affect the maximum depth of ice keels. We present an application of 210Pb dating of the largest ice scour in the Baydaratskaya Bay area (Kara Sea), located at depths of about 28–32 m. Two sediment cores were studied; these were taken on 2 November 2021 from the R/V Akademik Nikolay Strakhov directly in the ice scour and on the “background” seabed surface, not processed via ice scouring. According to the results of 210Pb dating, the studied ice scour was formed no later than the end of the Little Ice Age. Based on the extrapolation of possible sedimentation rates prior to 1917 (0.22–0.38 cm/year), the age of the ice scour is estimated to be 1810 ± 30 AD. The mean rate of ice scour filling with 70 cm thick sediments from the moment of its formation is around 0.33 cm/year.

Abstract We investigated diatom assemblages for the last 19 ka in a piston core KY07-04 PC01 collected from the northern Okinawa Trough, East China Sea. Most of the diatom taxa in the Core KY07-04 PC01 were subtropical to temperate marine species throughout the core. Pronounced turnover of major diatom groups from periphytic to planktonic taxa occurred during deglaciation between 17 and 14 ka ago. During the Last Glacial Maximum (LGM) to early deglaciation, the representative taxa were Paralia spp., a periphytic diatom abundant in continental shelves of the modern East China Sea covering the Chinese Coastal Water. Relative abundances of Paralia spp. rapidly decreased during 15–14 ka ago, corresponding to sea-level rise, displaced by planktonic taxa such as Thalassionema. Thalassionema nitzschioides varieties living in subtropical water increased since 12 ka and have reached the present level at 8 ka ago, suggesting strengthening the influences of Kuroshio water in the northern East China Sea during the early to middle Holocene. Warm planktonic diatom taxa such as Nitzschia bicapitata also gradually increased from 12 to 8 ka ago. Near the core top, a sudden increase in N. bicapitata might relate to the intensifying Kuroshio during the latest Holocene.

In this study, the environmental fate of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in tropical lake sediments and their potential sources have been discussed. 15 PAHs (i.e. ΣPAH) have been investigated in two lakes, namely Songkhla Lake (SKL) and Nong Han Kumphawapi Lake (NHL), which are located at the southern and north-eastern parts of Thailand, respectively. Since these two lakes are registered as important wetlands under the Ramsar convention (United Nations Educational, Scientific and Cultural Organization: UNESCO), the quantitative identification of potential contributors of PAHs is an inevitable analytical tool for launching an evidence-based policy. The ΣPAH concentrations observed in SKL and NHL sediments (n = 135) were in the range of 19.4–1,218 ng g−1 and 94.5–1,112 ng g−1, respectively. While the exponential decline of ΣPAH contents were detected in SKL sediments, NHL showed a trend of enhancing PAH contents with depth. The averaged benzo [a]pyrene (B [a]P) contents of surface sediments in both lakes were much below the value stipulated by the United States Environmental Protection Agency (US-EPA) guidelines for carcinogen risk assessment. Based on numerous multivariate statistical techniques coupled with source apportionment analysis, “biomass burning” and “anthropogenic activities” are two potential contributors of the PAHs detected in the study areas. To achieve the long-term conservation of nature with related ecosystem services and cultural values, it is therefore important to promote decision-making based on ecotoxicological studies of carcinogenic substances.