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The element geochemical behavior and provenance of marine sediments are of significance to understanding the oceanic material cycle. Here, we tested the grain size and major and trace elements of 35 surface sediments in the offshore area of Sierra Leone, analyzed the content characteristics and controlling factors of the elements, discussed the material source of the sediments, and made a comparative study with the sediments in the offshore area of China. The results show that sandy silt is the main sediment type in the research area, and the average sediment mean grain size (Mz) is 4.15Φ. The content of Ca in the samples is the highest among the major elements (except Si), with an average of 5.1%. The content of Sr is the highest among the trace elements (except Ti, P, and Mn), with an average of 378.2 μg/g. The results of correlation analysis and factor analysis show that there are three main sources of sediments in the research area, namely, terrigenous weathering products, ilmenite-dominated ore, and oceanic biochemical substances. Compared with the sediments in China offshore, the sediments in the study area are more affected by marine biochemistry and have special ore input characteristics. [ABSTRACT FROM AUTHOR]

Investigating the spatio-temporal variations of metal pollution in the sediment of an industrialized watershed, this study aims to identify ecological risks. Utilizing six risk assessment indices--enrichment factor (EF), geo-accumulation index (I-geo), potential ecological risk (RI), contamination factor (CF), ecological risk assessment (ER), and Pollution Load Index (PLI)--the research distinguishes between anthropogenic and geogenic sources. Surface sediment samples are collected from nine locations (comprising seven monitoring sites and two reference sites) across the watershed during both dry and wet seasons. Reference concentrations, tailored to accurately reflect local characteristics, are employed to compute the indices. Results indicate significantly elevated concentrations of Zn, Pb, Cr, Cd, and Ni throughout the basin, exceeding reference values by factors of 15, 20, 5, 10, and 5, respectively. Wet and dry season assessments reveal varying I-geo and EF values across monitoring stations. Cd emerges as the primary ecological risk, predominantly attributed to industrial discharges. Moreover, dry season contamination surpasses that of the wet season. Comparative analysis of the indices reveals PLI's efficacy for spatial assessments, while RI analysis better elucidates temporal variations. In conclusion, this study provides valuable insights for devising strategies to mitigate sediment contamination in industrial watersheds. [ABSTRACT FROM AUTHOR]

Under the steadily intensifying human activities in coastal areas, it is crucial to distinguish the sources of organic matter (OM) in sediments for better understanding of the environmental change. In this study, 25 surface sediments collected along the harbor and creeks areas off Karachi coast were used for total organic carbon (TOC), total nitrogen (TN), stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions, phytoplankton biomarkers (brassicasterol, dinosterol and cholesterol) and glycerol dialkyl glycerol tetraethers (GDGTs) analyses, to trace the distribution of OM and identify its sources. TOC, TN, δ13C, and δ15N are in the range of 0.04% to 5.28%, 0.01% to 0.57%, − 17.55‰ to − 26.31‰, and 2.83‰ to 6.04‰, respectively. C/N values range from 4.24 to 21.04. The δ13C, δ15N, C/N, BIT (Branched Isoprenoid Tetraether) index together with phytoplankton biomarkers show both marine and terrestrial OM input to the creeks and Harbor stations. In contrast, the stations from Western Coast indicate a marine source predominance. A clearly impact of human activities is seen from sediments near river mouths. [ABSTRACT FROM AUTHOR]

Taking the first-level tributary of Ningxia section of the Yellow River (Qingshui River) as the study area, surface sediment samples were collected during the seasons in 2018. The distribution characteristics, pollution levels, possible sources, influencing factors, and ecological risks of organochloride pesticides (OCPs) in the surface sediments were studied. The detected mean amounts were n.d. ~10.640 (1.474) ng·g−1, and the detection rate was 80.95%. The content (mean values) of Hexachlorocyclohexanes (HCHs), Endosulfan, Chlordane, and Dichlorodiphenyltrichloroethane (DDT) with higher detection amounts and detection rates were n.d. ~0.949 (0.153), n.d. ~1.973 (0.331), n.d. ~0.271 (0.052), and n.d. ~10.583 (0.819) ng·g−1, respectively. The total OCP amounts were detected in Changshantou and Liwang research sections, which have surrounding farmlands and low water flow. The total organic carbon plays a vital role in the residue and distribution of β-HCH and Dieldrin. In a high-salinity environment, the lower-layer sediments had higher adsorption efficiencies for DDT and γ-HCH and the HCH content decreased with the increase in pH. The total nitrogen and phosphorus in sediments were among the controlling factors affecting the distribution of Endosulfan II and p,p’-DDT, respectively, but their effects on Dieldrin only appeared in the spring flood season. Further, a functional model was established with respect to the adsorption amount of various OCPs and the influencing factors. The component analysis results showed that OCPs primarily originated from historical residues; however, only small amounts of Lindane, Dicofol, Endosulfan, and Chlordane compounds have been observed recently in the local environment. Using the low-effect interval and median method for potential ecological risk assessment, Endosulfan was noted to have potential ecological risks, mainly distributed in the middle and lower reaches of the river. The reasons for the potential harm require attention and further research. [ABSTRACT FROM AUTHOR]

AbstractSurface sediments from the intertidal area of Côte d’Ivoire were sampled to investigate trace metals (Hg, Cd, Cr, Cu, Pb, Zn, and As) concentrations to illustrate their spatial distribution and ecological risk of pollution. The average total organic carbon content was 2.04 ± 0.01%. Except for Cr and Zn, the spatial distribution exhibited a similar pattern for TOC, Hg, Cd, Cu, Pb, and As. The average concentrations of trace metals were less than their corresponding upper continental crust (UCC) values, except for Cd and Cr. The pollution indices indicated that sediment quality in the studied area has been impacted by Cd and the Assinie and Bleron sites were the most contaminated. A few ecological risks were posed by Hg, Cd, Cr, and Cu, based on sediment quality guidelines (SQGs). The Pearson correlation showed a significant (p < 0.05) correlation between As, Cd, Pb, Cr, and Hg, suggesting a common origin in sediments. The principal component analysis (PCA) identified As, Cr, Pb, Zn, and Hg might originate from natural source, Cd and Cu might be from natural and anthrogenic sources. Although this study presents the current status of littoral trace metals contamination level in sediments, further studies should integrate the statistical multivariate approach to determine the anthropogenic sources of the trace metals in the intertidal area of Côte d’Ivoire. [ABSTRACT FROM AUTHOR]

The quality of sediments in the mixing zone of river freshwater and marine saline water as an important geochemical barrier for potentially toxic elements (PTEs) remains poorly understood. This study aims to analyze the current pollution with PTEs and associated ecological risks in sediments of the Don River delta and the surrounding area of the Taganrog Bay of the Sea of Azov (Russia). The PTE content was determined in fifty-four collected samples using the WDXRF and assessed using geochemical and ecotoxicological indicators. The source of Cr, Mn, Ni and Pb is mainly river runoff, and Cu, Zn and Cd are from a variety of anthropogenic sources. As shown by the assessment of the geoaccumulation index (Igeo), single pollution index (PI) and contamination factor (CF), these elements are the priority pollutants. According to these estimates, high and very high contamination of sediments in the estuarine zone of the Don River with Cd and Pb was detected in 72–94% and 2–57% of samples, respectively. However, environmental risks are determined almost exclusively by the level of Cd. Total contamination as assessed by the Nemerow pollution index (NPI), modified degree of contamination (mCd) and metal pollution index (MPI) is of concern in 83–98% of the samples studied. The most heavily polluted sediments are in the vicinity of residential areas of the Taganrog Bay. Despite the lower average pollution levels of deltaic sediments, freshwater biota are exposed to higher potential toxic risks of adverse effects by PTE, particularly from Ni and Pb. Thus, the complex hydrological regime and uneven anthropogenic impact predetermine the geochemical state of the sediments of the estuarine zone of the Don River. [ABSTRACT FROM AUTHOR]

A Gram stain-positive, non-spore-forming, non-motile, short-rod actinomyces strain GXQ1321T was isolated from maritime surface sediments in Beihai (21° 41′ 21.65″ N, 109° 05′ 76.56″ E), Guangxi Zhuang Autonomous Region, and a number of categorization studies were performed. Following a period of 72 h of incubation at a temperature of 30 °C within a modified actinomycete culture medium, the colony was light-yellow, circular, smooth, central bulge, convex, opaque, with a 1.2–2.3 mm diameter. Strain GXQ1321T had the ability to degrade cellulose. Chemotaxonomic studies revealed that the major methylnaphthoquinones in strain GXQ1321T was MK-8(H2). The most prevalent cellular fatty acids were anteiso-C19:0, anteiso-C15:0, anteiso-C17:0, and iso-C16:0. The whole-cell sugars of the strain GXQ1321T were identified rhamnose, xylose and glucose. Meso-diaminopimelic acid was found in the peptidoglycan hydrolysate, and the polar lipids were identified as diphosphatidylglycerol, three phosphoglycolipid, phosphatidylglycerol and two unknown glycolipid. This strain had 69.6% DNA G+C content. Strain GXQ1321T is classified as Brevibacterium based on its 16S rRNA gene sequence. It is closely related to Brevibacterium samyangense SST-8 T (96.8%) and Brevibacterium rongguiense 5221 T (96.3%). The average nucleotide identity (ANI) values of GXQ1321T and the above two type strains were 73.9–77.1%, and the digital DNA-DNA hybridisation (dDDH) values were 15.3–21.1%. Based on the phylogenetic, chemotaxonomic and physiological data, strain GXQ1321T was considered to be a novel species of the genus Brevibacterium, named Brevibacterium litoralis sp. nov, with the type strain GXQ1321T (= MCCC 1K08964T = KCTC 59167 T). [ABSTRACT FROM AUTHOR]

Baiyangdian Lake, recognized as the largest freshwater body in northern China, plays a vital role in maintaining the regional eco-environment. Prior studies have pointed out the contamination of sediments with heavy metals, raising concerns about eco-environmental challenges. Therefore, it is imperative to evaluate the current pollution levels and ecological threats related to heavy metals found in the sediments of Baiyangdian Lake as well as in its inflow rivers. In May 2022, surface sediments with a depth of less than 20 cm were analyzed for Cu, Zn, Pb, Cr, Ni, As, Cd, and Hg to determine the pollution status, identify sources of pollution, and evaluate potential ecological risks. A range of evaluation methods used by predecessors such as geo-accumulation index (Igeo), enrichment factor (EF), ecological risk index (RI), sediment quality guidelines (SQGs), positive matrix factorization (PMF), absolute principal component score-multiple linear regression model (APCS-MLR), chemical mass balance (CMB), and UNMIX model were analyzed. After comparison, multi-methods including the geo-accumulation index (Igeo), absolute principal component score-multiple linear regression model (APCS-MLR), ecological risk index (RI), and sediment quality guidelines (SQGs) were utilized this time, leading to a better result. Findings reveal that pollution levels are generally low or non-existent, with only 1.64% of sampling sites showing close to moderate pollution levels for Cu, Pb, and Zn, and 4.92% and 1.64% of sites exhibiting close to moderate and moderate pollution levels for Cd, respectively. The main contributors to heavy metal presence are pinpointed as industrial wastewater discharge, particularly Cu, Zn, Pb, Cd, and Hg. The ecological risks are also relatively low, with 4.92%, 1.64%, and 1.64% of sampling sites demonstrating close to moderate, moderate, and strong risks in the inflow rivers, respectively. Additionally, only one site shows moderate potential biological toxicity, while the rest display non-toxicity. These findings will update our cognition and offer a scientific basis for pollution treatment and ecosystem enhancement for government management. [ABSTRACT FROM AUTHOR]

The Santiago-Guadalajara River (SGR) is one of the most polluted river systems in Mexico because there is still a significant amount of untreated industrial, agricultural and municipal wastewater discharged. A sediment monitoring campaign was carried out at 25 sampling points located in the Santiago and Zula rivers, as well as in their main tributaries. In this work, six indices and criteria were selected to assess the level of metal contamination in the main and tributary streams. The following sequence of metals of concern were identified (mean values in mg kg-1 dry basis): Zn (71.92)> Cu (35.22)> Cr (23.82) > Ni (14.95)> Pb (10.82) > As (2.82) > Cd (2.40) > Sb (2.06). Previous studies in the region agree that Al, Fe, Mn, and Ba are part of the natural lithologic composition of the basin, and what is found in the sediments is likely the result of the natural rock weathering processes rather than an anthropogenic contamination process. According to the proposed assess methods Cu, Cr, Ni, Pb, and Zn were found in low to moderate levels of contamination, and Sb and Cd were found in considerable to very high contamination levels in several of the monitored stations. [ABSTRACT FROM AUTHOR]

Lake Tanganyika, the second deepest lake in Africa, has a unique ecosystem that provides rich fish proteins for populations along the lake basin. With socioeconomic development and rapid population growth, Lake Tanganyika is threatened by environmental pollution. In this study, the concentrations of heavy metals, including Cr, Ni, Cu, Zn, Cd, Pb, Fe, and Mn, in the surface sediments of the inflow rivers in northeastern quadrant of Lake Tanganyika were characterized. The geoaccumulation index (Igeo) and enrichment factor (EF) were employed for heavy metal assessment. The results showed that heavy metal concentrations in the surface sediments of the inflow rivers in northeastern quadrant of Lake Tanganyika exhibited significant spatial variations. The concentration of heavy metals was the highest near urban areas, followed by the estuarine wetland and forest grassland. This indicated that heavy metal content was closely related to human activities. The concentrations of Zn, Cd, and Pb were defined as unpolluted, and the concentrations of Pb, and Fe were only slightly enriched. Principal component analysis and cluster analysis demonstrated that the heavy metals Cr, Zn, Cd, and Pb may originate from a mixture of natural sources and anthropogenic inputs, including agricultural and industrial inputs. Ni, Fe, and Mn were principally from natural sources, and Cu primarily originated from anthropogenic inputs such as vanadium iron ore mining and iron and steel smelting. These results are important for understanding the nonpoint sources of heavy metal pollution in the Lake Tanganyika Basin. [ABSTRACT FROM AUTHOR]

The Pearl River Estuary, a vital ecological and economic zone in Southern China, has been heavily impacted by industrial discharges, leading to significant heavy metal contamination. To address the ecological implications of different chemical forms of heavy metals, this study systematically evaluated the total concentrations and chemical speciation of Cu, Zn, Cd, and Pb in surface sediments (0–2 cm) collected from 17 sites. Chemical speciation was determined using a modified BCR sequential extraction procedure, and pollution and ecological risks were assessed via the geo-accumulation index (Igeo), potential ecological risk index (RI), and risk assessment code (RAC). The results showed that all four metals exceeded background values, with Cd presenting the highest enrichment (39 times) and contributing 97% of the ecological risk. Speciation analysis revealed that Cd predominantly exists in bioavailable forms, posing severe ecological threats. This study highlights the urgent need for targeted remediation strategies to mitigate Cd contamination and its ecological impact on the estuary.

A total of 21 surface sediment samples collected from Arasalar River are subjected to sediment texture (sand-silt-clay ratio), trace elements, organic matter, and CaCO3 studies to understand the accumulation dynamics of sediments. To assess the impact of metal pollution in estuarine sediments, the essential parameters should be done by checking the sediment characteristics, spatial distribution of heavy metal sources, sediment dynamics, and geochemical analysis. To evaluate the contamination level of metal pollution, a basic standard reference is required to decipher the values ranging from natural to anthropogenic contribution. From this research analysis, it is observed that the study area predominantly comprises silty sand and sand silty nature. The calcium carbonate content in the sediment is found to be proportional to the presence of shell fragments, whereas the organic matter (OM) is derived from riverine and coastal input which acts as a primary source. The obtained results confessed the average contents (mg/g) for the following selected eight elements in the order of Fe (35249–49068) > Mn (286–519) > Ni (107–279) > Cu (78.30–155.70) > Cr (50–99) > Zn (38.70–91.90) > Pb (39.90–62.40), and Co (12.6–29.1) by using an atomic absorption spectrophotometer (AAS) are utilized for this analysis. Multivariate analysis of heavy metals affirms geogenic sources (weathering of parent rocks) for Fe, Mn, Cr, Co, and Zn, whereas Cu, Ni, and Pb originated from anthropogenic activities (urban and industrial activities). The pollution load index, sediment pollution index, Igeo index, and PERI are categorized as under polluted, low to moderate polluted, and low potential environmental risk variety. Constant inspection and guidance are needed to prevent effluences from various agriculture and industrial activities in the nearby regions. The findings from this research may support and help the government to follow the suitable remediation on the better management of river and coastal areas. [ABSTRACT FROM AUTHOR]

The wetlands, with their delicate ecosystems, play a crucial role in regulating water regimes and supporting diverse plant and animal communities, particularly those associated with water habitats. Mogan Lake, located within the Gölbaşı Special Environmental Protection Area, stands out as a unique habitat, hosting over 200 bird species. This study aimed to assess the current water quality of Mogan Lake by analysing various water quality variables. Three sampling sites, representing the northern, middle, and southern parts of the lake, were selected to examine both surface water and bottom sludge characteristics through the analysis of 29 pollutant variables. Water samples were collected from 30 cm beneath the water surface and 50 cm above the bottom of the lake. Sediment samples were collected from the sludge at the lake basin. Additionally, to understand their impact on the lake's water quality, 26 pollutants were also measured in water samples taken from the five main streams that feed the lake. The results reveal a significant level of organic pollution in the lake, along with elevated nitrogen levels indicating hypertrophic conditions. Although organic pollutants were detected in the lake bottom sediment through analysis, they are considered non-hazardous in terms of heavy metals and other inorganic variables. [ABSTRACT FROM AUTHOR]

This study addresses the sources of aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the northwestern Persian Gulf and the muscle tissues of Jinga shrimp (Metapenaeus affinis), a commercially important aquatic species. In November 2018, 28 Jinga shrimp samples were systematically collected from four key fishing areas in Behrgan and Khormusi: Imam Khomeini Port (S1), Mahshahr Port (S2), Sejafi (S3), and Behrgan Wharf (S4). Additionally, sediment samples were collected from these locations, and AHs and PAHs concentrations were analyzed using gas chromatography-mass spectrometry (GC–MS). The average aliphatic concentration in Jinga shrimp was 4800.32 (μg g−1 DW), exceeding the sediment samples' 2496.69 (μg g−1 DW) estimate. Hydrocarbon component analysis revealed EPA priority list (PAH-16) and measured PAHs (PAH-29) concentrations in Jinga shrimp ranging from 1095.8 to 2698.3 (ng g−1 DW) and in sediments from 653.6 to 1019.5 (ng g−1 DW). Elevated AHs and PAHs in Jinga shrimp, compared to sediments, suggest a petrogenic source, notably at station S4 near Behrgansar and Nowruz oil fields. Low molecular weight (LMW) compounds dominated in both shrimp and sediment PAHs. Aliphatic composition profiles in shrimps closely mirrored sediment profiles, illustrating an even-to-odd carbon dominance gradient. Diagnostic ratio examinations of hydrocarbons indicated pervasive petroleum derivatives in the environment. This study establishes a direct correlation between hydrocarbon concentrations in shrimp and sediment samples and the corresponding aliphatic groups, PAH-16, and PAH-29. The findings underscore the potential of Jinga shrimp as a reliable indicator of hydrocarbon pollution in the northwestern Persian Gulf. [ABSTRACT FROM AUTHOR]

Recently developed temperature proxies based on hydroxylated isoprenoid Glycerol Dialkyl Glycerol Tetraethers (OH-isoGDGTs), such as % O H , R I - O H , R I - O H ′ and O H C , have shown potential for reconstructing past temperature changes. However, progress has been limited by the lack of a global core-top calibration with ample geographical coverage. Here, we compile an extensive global surface sediment dataset of OH-isoGDGTs as well as regular isoprenoid GDGTs (isoGDGTs), with both data generated at NIOZ (n = 575) and previously published data from other laboratories (n = 297). We find interlaboratory differences for proxy indices that incorporate both OH-isoGDGTs and regular isoGDGTs, indicating that care must be taken in compiling large GDGT datasets from multiple laboratories. Our results confirm a strong temperature signal in the isoGDGT distribution, especially for OH-isoGDGT-0 and non-hydroxylated isoGDGTs, but also reveal that water depth might have an impact on the distribution of OH-isoGDGTs with 1 and 2 cyclopentane moieties. This will affect the R I - O H and R I - O H ′ indices, particularly in tropical regions, where OH-isoGDGT-0 occurs at low abundance. We explore new proxy indices that combine the temperature dependence of both isoGDGT and OH-isoGDGT distributions and propose the use of T E X 86 O H , which includes OH-isoGDGT-0 in the denominator of the T E X 86 index. This modification leads to a much higher temperature sensitivity of the index, especially in regions with annual mean sea surface temperatures between 5 and 15 °C. Application of this novel paleothermometer to a polar sediment core suggests that this proxy is likely to result in more reliable temperature reconstructions in polar regions where OH-isoGDGTs are abundant. [ABSTRACT FROM AUTHOR]

This study assessed the accumulation levels and ecological risks associated with seven heavy metals (As, Pb, Cd, Hg, Cu, Cr, Zn) in the surface sediments of the Bong Mieu River in Quang Nam Province, Vietnam. The sampling encompassed 10 locations (S1–S10), considering areas both impacted and less impacted by gold mining activities. The findings revealed elevated levels of heavy metal pollution and associated ecological risks attributable to gold mining. Heavy metal content varied within specific ranges: As (70.6–341.2 mg/kg), Pb (216.3–504.1 mg/kg), Hg (0.138–0.252 mg/kg), Cd (0.91–1.51mg/kg), Cu (18.3–45.5 mg/kg), Cr (10.5–19.1 mg/kg), and Zn (49.3–84.1 mg/kg). Among these elements, Hg, Cu, Cr, Zn, and Cd adhered to the acceptable limits of VNTR 43:2017/MONRE (VNTR 43:2017/MONRE: National Technical Regulation/Ministry of Natural Resources and Environment of Vietnam). However, As and Pb content at all locations exceeded these limits significantly, with As being 4.1–20 times higher and Pb 2.3–5.5 times higher. The pollution of Pb and As was attributed to waste discharge from gold mining activities, which carry substantial amounts of these metals in various forms. The Igeo indicated heavy pollution of As and Pb in the sediments. Ecological risk factors were ranked as follows: E r i (As) > E r i (Pb) > E r i (Hg) > E r i (Cd) > E r i (Cu) > E r i (Cr) > E r i (Zn). The potential ecological risk (RI) due to combined heavy metal impact varied across locations, with S2 > S8 > S9 > S6 > S7 > S10 > S1 > S3 > S4 > S5, exhibiting low to moderate risk (RI values ranging from 73.4 to 252.8). The study area demonstrated high contamination levels for As and Pb, coupled with low to moderate potential ecological risks. [ABSTRACT FROM AUTHOR]

Detailed sedimentary study of a section of the Syrian coast (Umm al-Tuyour, Latakia) was carried out in order to determine the grain size analysis and characterization of sedimentary environment. Twenty-two samples of surface sediments were collected along the coastal area during the summer period of 2022. This research used an integrated methodology of analysis and software to determine the dynamic beach environment in the study area. The observation from this study shows that the sediments are coarse to very coarse grain size, moderately sorted, near symmetrical, and finally mesokurtic. These data confirm that the deposition occurred under high-energy conditions with continuous mixing of sediments by waves and ocean currents, where erosion processes are active. The results of the linear discriminant function analysis performed on the samples indicate beach, shallow marine deposition environment and the influence of fluvial processes. Analysis of sediments using CM diagram suggests that sediment deposition is mainly by rolling under tractive current conditions. [ABSTRACT FROM AUTHOR]

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Nutrients, organic matter (OM), and heavy metals (HMs) in lake sediments are critical elements contributing to water pollution. In April 2019, surface sediments from Wanghu Lake were collected, and the nutrient, organic matter, and heavy metal content of the sediments were determined. We mainly evaluated the sediment pollutants through four evaluation methods to assess pollution and provide a reference for pollution control in Wanghu Lake. The results indicated that the averages of total phosphorus (TP) and total nitrogen (TN) were (1045.74 ± 190.17) mg/kg, (945.27 ± 203.56) mg/kg; most of them showed serious pollution and moderate pollution, respectively. OM was (32.31 ± 5.11) g/kg. Among them, TP and OM in the northwestern Wanghu Lake were significantly higher than those in the eastern lake (p < 0.05). It shows that nutrients are greatly affected by historical aquaculture and urban human activities. TP was the most serious in the center of the lake, and the source of pollution was mainly the historical deposition. The average of Cd, Cr, Cu, Ni, Pb, Zn, Hg, and As in the sediments were 2.15, 1.09, 1.93, 1.37, 1.28, 1.49, 2.60, 1.77 times that of the soil background values of Hubei Province, respectively. Hg and Cd were the main factors contributing to the surface sediments, with levels at considerable and moderate risks, respectively. [ABSTRACT FROM AUTHOR]

Surface sediment samples from Al-Qahma lagoon in the southern part and Al-Wajh lagoon in the northern part of the Red Sea coast of Saudi Arabia were collected by a Van Veen grab sampler to determine the characteristics, distribution, and sources of aliphatic and cyclic hydrocarbons. The total extractable organic matter (TEOM) was extracted with a dichloromethane/methanol mixture after drying and sieving the sediments and identified by gas chromatography–mass spectrometry. The TEOM comprised n-alkanes (302.6 ± 446.7 ng·g−1 and 64 ± 50 ng·g−1), hopanes (29.8 ± 132.3 ng·g−1 and 1.0 ± 2.5 ng·g−1), steranes (0.0 and traces), n-alkanoic acids (745.8 ± 799.6 ng·g−1 and 120.7 ± 92.0 ng·g−1), n-alkanols (457.4 ± 1085.6 ng·g−1 and 49.7 ± 32.3 ng·g−1), polycyclic aromatic hydrocarbons (PAHs) (54.5 ± 96.8 ng·g−1 and 7.8 ± 8.5 ng·g−1), and phthalates (185.3 ± 169.9 ng·g−1 and 67.4 ± 70.4 ng·g−1) in the Al-Qahma and Al-Wajh lagoon sediments, respectively. The percentages of the various sources relative to total aliphatic and cyclic hydrocarbon concentrations were 6.9 ± 6% for terrestrial plants, 53.7 ± 19% for algae, 10 ± 2% for microbial, 16 ± 12% for petroleum, and 13.4 ± 7 for plasticizer inputs in Al-Qahma lagoon. In Al-Wajh lagoon, they were 9.7 ± 4% for terrestrial plants, 30.8 ± 14% for algae, 25.2 ± 5% for bacteria, 11.2 ± 3% for petroleum, and 23.1 ± 11% for plasticizers. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTEs) in the surface sediments of the Pasur river estuary was investigated to assess its distribution, potential sources, and current dangers to ecological and public health. The Pasur River is a tidal, meandering, perennial river in south-western Bangladesh with a considerable number of fisheries and industrial activities. Sediment samples were collected from seven sampling points from January to December 2022 to assess the contamination level of six potentially toxic elements (Pb, Cr, Cd, As, Cu and Zn). Flame Atomic Absorption Spectrophotometer was utilized to detect the concentration of PTEs by following some sequential analytical procedure. Concentration of PTEs followed the reducing trend of Zn > Cr > Pb > As > Cu > Cd with the mean value of 61.04 > 49.15 > 26.58 > 10.28 > 6.28 > 1.59 mg/kg, respectively. The principle component and cluster analyses justified the anthropogenic source of the studied PTEs. The mean values of contamination factor (CF), geo-accumulation index (Igeo) and enrichment factor (EFc) showed that Pb and Cd were highly responsible for sediment (uncontaminated to moderate) contamination. Pollution load index (PLI) indicated higher pollution of sediments near the port areas. Potential ecological risk index (PERI) indicated low to moderate risks due to the contaminated sediment. However, the contamination of sediment was not associated with the non-carcinogenic (HQderm and HI

The Inner Ambon Bay (IAB) is an important area for the economic development of the city of Ambon, one of only a few urban areas in eastern Indonesia. This study is intended to monitor the anthropogenic impact on IAB by employing combined rock magnetic and geochemical analyses on 20 samples collected from IAB and the surrounding rivers. Magnetic susceptibility values of samples in the IAB averaged 26.37× 10−8 m3/kg, which is relatively high and comparable to that of contaminated coastal environments. Magnetic susceptibility correlated positively with certain metals such as Cr, Co, Ni, and Mn but negatively with Hg. Geochemical analyses showed that Hg and Ag contents were relatively high but pose only moderate risk to the environment based on the geo-accumulation index. Furthermore, the potential ecological risk index (PERI) showed that there were two points that showed moderate ecological risk. Multivariate statistical analysis (principal component analysis (PCA), Pearson's correlation coefficient (PCC), and hierarchical cluster analysis (HCA)) outlined that the metallic accumulation in the sediments of IAB was related to lithological, geological, and anthropogenic impacts. Therefore, oil spills and household waste are likely major reasons for anthropogenic pollution in the sediments of the IAB.

This study aims to assess the pollution levels and sources of heavy metals (Al, Mn, Co, Ni, Sc and V) and radionuclides (Th and U) in sediments of Lékié Watershed in Cameroon. Surface sediment samples were collected from 14 stations across different areas of the Lékié Watershed. The heavy metal and radionuclide analysis on sediments were carried out and pollution indices such as enrichment factor (EF), contamination factor (CF), degree of contamination (DC), pollution load index (PLI), potential ecological risk assessment and multivariate statistical methods were utilized to evaluate the degree of contamination and estimate the source of metals in the sediments of Lékié Watershed. The results show that the mean concentrations are lower than those of the upper continental crust (UCC) reference values except those of Mn, Co, Ni, and V. The values of EF varied from moderate to severe enrichments (from 4 to 44). The contamination factor (1 < CF < 3), potential ecological risk ( 1, indicating pollution. The application of multivariate analysis to these metallic elements reveals contaminations attributed to anthropogenic activities, including the release of domestic, artisanal mining, and industrial effluents, as well as natural sources originating from the leaching of local surrounding soils and geological factors. To mitigate more pollution in this watershed which is closed from urbanization, it is crucial for local authorities to implement wastewater treatment measures.

Cold seeps are highly productive chemosynthetic ecosystems in the deep-sea environment. Although microbial communities affected by methane seepage have been extensively studied in sediments and seawater, there is a lack of investigation of prokaryotic communities at the surface sediments and bottom seawater. We revealed the effect of methane seepage on co-occurrence networks and ecological niches of prokaryotic communities at the surface sediments and bottom seawater in the Haima cold seep. The results showed that methane seepage could cause the migration of Mn and Ba from the surface sediments to the overlying seawater, altering the elemental distribution at seepage sites (IS) compared with non-seepage sites (NS). Principal component analysis (PCA) showed that methane seepage led to closer distances of bacterial communities between surface sediments and bottom seawater. Co-occurrence networks indicated that methane seepage led to more complex interconnections at the surface sediments and bottom seawater. In summary, methane seepage caused bacterial communities in the surface sediments and bottom seawater to become more abundant and structurally complex. This study provides a comprehensive comparison of microbial profiles at the surface sediments and bottom seawater of cold seeps in the South China Sea (SCS), illustrating the impact of seepage on bacterial community dynamics. [ABSTRACT FROM AUTHOR]

Clay minerals have great potentials in pinpointing sediment provenance for large depositional systems. However, source identification using clay minerals for small floodplain lakes is not well known. Situated in the North China Plain, the Dongping Lake receives sediments from both the Yellow River and the Dawen River, thereby representing an ideal site for testing the utility of this method. Here we use clay minerals in conjunction with the Bayesian end-member modeling analysis (BEMMA) to quantify the riverine contribution to modern sediments in the Dongping Lake. Results showed that modern sediments of the Dongping Lake are characterized by four primary clay minerals: illite, smectite, kaolinite, and chlorite, with average contents of 60.53%, 11.37%, 12.70%, and 15.40%, respectively. Clay minerals in modern sediments of the Dongping Lake are mainly delivered by the Yellow River, accounting for approximately 58.99–72.33%; whereas those originating from the Dawen River only account for 27.67–41.01%. It is also found that clay mineral from these rivers have a marked spatial variability. For example, source materials from the Yellow River are widely distributed across the lake, while those from the Dawen River only occur at the estuary of the river and slightly spread out in all directions under the action of water flow. [ABSTRACT FROM AUTHOR]

This study aimed to understand the occurrence of mercury in the water environment of typical cold and arid lakes and the regulating environmental factors. Water and surface sediment samples were collected from July to August, 2022 in the Wuliangsuhai Lake region for the analysis of total mercury (THg) and total methylmercury (TMeHg). Lake water THg and TMeHg ranged between 19.20 ~ 668.10 and 0.10 ~ 11.40 ng/L, respectively, exceeding China's environmental quality standards and contents of other lakes and reservoirs in China and other areas. Surface sediments showed lower mean THg and TMeHg of 261.85 and 0.18 μg/kg, respectively, with the former significantly exceeding the background value of Inner Mongolia and unpolluted natural lakes but lower than those of lakes affected by human factors, such as aquaculture. Sediments showed relatively low methylation and TMeHg (0.01–0.21%) concentrations. Correlation analysis identified salinity, total dissolved solids, conductivity, and redox potential as important factors affecting mercury speciation in water, whereas those in surface sediments were organic matter, pH, and total iron content. This study conducted preliminary research on the different species of Hg in Wuliangsuhai Lake water environment, which can provide scientific evidence for the specific treatment of Hg pollution in agriculture, or industry and other related fields. Our results suggest that upstream and downstream regulatory agencies should strengthen the regulation of agricultural and industrial production, moderately reduce human activities, and reduce the use of mercury-rich substances such as pesticides. [ABSTRACT FROM AUTHOR]

The presence of heavy metals in rivers in the Niger Delta region has become a source of concern due to its associated health challenges. The present study was conducted to assess the risk of heavy metal accumulation in surface sediments obtained from creeks and dredged tributaries of the River Ethiope, Delta State, South-South, Nigeria. Heavy metals in the sediments were extracted using the three-step sequential extraction method of the European Commission Standard Measurement and Testing Program. The heavy metals; magnesium (Mn), iron (Fe), zinc (Zn), lead (Pb), copper (Cu), cobalt (Co), arsenic (As), chromium (Cr), cadmium (Cd) and barium (Ba) were quantified by employing inductively coupled plasma-mass spectrometry (ICP-MS). Assessment of the extent of sediment contamination was carried out by determining the contamination factor (CF), degree of contamination (Cd), modified degree of contamination (mCd), pollution load index (PLI), ecological risk factor (Er), potential ecological risk index (PI) and geo accumulation index (1 geo). Pearson's correlation coefficient and principal component analysis (PCA) were used to determine the sources and the relationship between pollutants across sediments. The values of heavy metals ranged from 12.5 mg kg-1-116 mg kg-1 and 21.6 mg kg-1-71.1 mg kg-1 in the wet and dry seasons, respectively. The trend of heavy metals for risk index (RI) in this study is Cd > Pb > Cr > Co > Zn > Cu > Mn (wet season) and Cu > Cd > Pb > Zn > Cr > Mn > Co = As (dry season). It showed that heavy metal pollution was a result of Cd for extreme contamination, while moderate to high contamination levels were due to Pb and Cu. The Pearson's correlation coefficient analysis and PCA displayed strong positive loadings for Mn, Fe, Zn, Pb, Cu and Cd across seasons as a result of high contamination levels in the study sites. The pollution load index revealed that the sediments were polluted by the metals, and the mean and median analyses revealed that the metals datasets were normally distributed, except for Cu with an irregular distribution. [ABSTRACT FROM AUTHOR]

Rivers in deserts present unique geographical features owing to aeolian-fluvial interactions. In this study, 510 surface sediment samples were gathered from eight watersheds to systematically examine the major element characteristics of riparian sand dunes in northern China deserts. The findings revealed that these dunes could be categorized into three primary zones: Type I, comprising Keriya, Tora, Heihe, and Langqu rivers in the west; Type II, featuring the Maquan River in the Tibetan Plateau; and Type III, including Mu Bulag, Kuye, and Xar Moron rivers in the east. Specifically, the Type III region is characterized by a limited fresh material supply, a relatively high Chemical Index of Alteration (CIA), and the influence of nearby rivers on the provenance of riparian dunes, leading to a higher degree of chemical weathering than that of Type I in the west. Notably, Type II is marked by weak-moderate chemical weathering degree and a comparatively higher CIA value. These classifications and their difference of degree of chemical weathering are possibly governed by the type of parent rock and the availability of material. This research offers new insights into the classification of riparian dunes impacted by aeolian-fluvial interactions in arid regions of the northern China deserts. Furthermore, it provides valuable implications for studies focusing on the provenance of sediments. [ABSTRACT FROM AUTHOR]

Dinoflagellate cysts are commonly used to reconstruct past climatic, oceanographic and environmental conditions. Such applications are based on the relationship between modern dinoflagellate cysts and environmental parameters. To evaluate cyst diversity and driving factors of their distributions in sediments of the China Seas for paleoenvironmental reconstruction, dinoflagellate cysts were analyzed in 18 surface sediment samples from the Bohai Sea, the Yellow Sea (YS), the East China Sea and the South China Sea (SCS). A total of 59 dinoflagellate cyst taxa were identified with the greatest diversity reported in the SCS. The highest cyst concentrations were found in the YS, where Spiniferites ramosus , Spiniferites spp., and cysts of Pentapharsodinium spp. were predominant in the assemblages. The Yellow Sea Warm Current is likely creating the environment favoring the high numbers of Spiniferites ramosus in the YS. The highest Brigantedinium spp. abundances were observed near the Pearl River mouth and are positively correlated with sea-surface temperature (SST) in August. Spiniferites hyperacanthus , S. mirabilis , S. pacificus , and Lingulodinium spp. were most abundant in the SCS. In contrast, cysts of Protoperidinium spp. and Selenopemphix quanta were more common at the sites directly influenced by coastal upwelling rather than by river discharges. Redundancy Analysis results show that SST, sea-surface salinity (SSS) and nitrate concentration in water are statistically significant parameters influencing the cyst assemblages. We also examined the morphological characteristics of Spiniferites ramosus and recommend grouping S. bulloideus with S. ramosus in the northwest Pacific dataset for quantitatively reconstructing paleoceanographic conditions. [ABSTRACT FROM AUTHOR]

The operation of cascade reservoir systems has altered river hydrology and sediment distribution patterns. In this study, 31 surface water and sediment samples were collected from the Heihe River from July to August in 2019 and 2020 to investigate the spatial distribution and sources of heavy metals and assess their ecological risks. The results revealed that the concentrations of heavy metals in surface water were much lower than the quality standards for surface water in China, and there were no significant differences in the natural reaches, center and tail of the reservoir. Cd in surface sediments was at a heavy contamination and high risk level, and the heavy metal pollution levels in the main streams and tributaries differed greatly, especially in the graded reservoirs with a gradual accumulation trend. This may be related to the fact that there were many fine-grained sediments in the reservoir center near the dam. Factor analysis-multiple linear regression (FA-MLR) revealed that heavy metals mainly come from natural factors and anthropogenic input, with anthropogenic inputs mainly coming from mining activities in the tributaries and industrial and agricultural activities in the main stream. HIGHLIGHTS The effects of cascade dam construction on the spatial distribution of heavy metals in surface water and sediments of Heihe River in China were systematically studied.; The operation of cascade dams has a significant effect on the spatial distribution of heavy metals in surface sediments.; Heavy metals pollution and ecological risk of surface sediments were mainly concentrated for natural river sections in tributaries.;

Assessment of 17 polyaromatic hydrocarbons (PAHs) was made to understand the sources, toxicity risk and biological impact in surface sediments of Malad and Versova creek of Mumbai. The concentration of ΣPAHs was found to vary in the range of 2915–4204 ng/g dw (mean 3367 ± 948 ng/gdw). The concentration of high molecular weight PAHs (HMW PAHs) in the range of 2378–3394 ng/g dw (mean 2723 ± 755 ng/g dw) was higher than that of low molecular PAHs (LMW PAHs) which was in the range of 528–810 ng/g dw (mean 644 ± 202 ng/g dw). The contribution of HMW PAHs to the ∑PAHs was 80.86% while that of LMW PAHs was 19.14%. The concentration of carcinogenic PAHs was 1452–1996 ng/g dw (mean 1631 ± 447 ng/g dw) having contribution of 48.43% to the ∑PAHs. The assessment of biological risk and toxicity was made based on toxic equivalent quantity (TEQ) and sediment quality guideline quotient (SQGQ). The PAH levels are feared to increase in coming times thereby creating probable threat to the biological life and health hazard to the nearby human population. [ABSTRACT FROM AUTHOR]

Nitrogen (N) in sediments was a key element of lake eutrophication. The spatial distribution characteristics of four parts N in surface sediments were investigated by sequential extraction method, including free nitrogen (FN), exchangeable nitrogen (EN), hydrolyzable nitrogen (HN), and residual nitrogen (RN). Modified models were utilized to describe the adsorption isotherms of ammonia nitrogen (NH4+-N) in sediments and thus predict the risk of N release. The correlation between environmental factors and N concentration was discussed, as well as the migration or transformation and release risk of N between different mediums. The results showed that spatial variations characteristics of N fractions were influenced by the lake topography and surrounding human activities. The content of total nitrogen (TN) in the sediments was 933.4 ~ 3006.8 mg/kg, with an average of 1835 mg/kg. The HN, RN, FN, and EN in sediments accounted for 66.85%, 21.35%, 6.82%, and 4.92% of TN, respectively. There was a significant correlation between each fraction of N and TN and also between different fractions of N (p < 0.01). Fitting by modified Langmuir model indicated that the adsorbed amounts of N in the sediments at maximum (Qmax) was, from greatest to least, southeast lake (2905.3 mg/kg) > southwest lake (1415.4 mg/kg) ≈ north lake (1424.6 mg/kg). Environmental parameters (pH, DO, C/N, etc.) affected the occurrence fraction of nitrogen, which could cause the persistent and increased risk of sustained release of high concentrations of endogenous N. N pollution in sediment and interstitial water is severe, and the risk of endogenous N release will gradually increase in the future. [ABSTRACT FROM AUTHOR]

The horizontal distributions of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the surface sediments where complex aquaculture is conducted in Shido Bay, Seto Inland Sea, Japan, were determined to investigate the impact of fish and oyster farming. We also determined five fractions of phosphorus in the surface sediments. Relatively high phosphorus contents (P/C ratios) were observed in fish farming areas, likely due to the waste feed and fecal matter. Moreover, relatively high abundances of the Ca-bound P (Ca-P) and detrital P (Ref-P) fractions were observed in fish farming areas, likely due to bones of small fish used as feed. Our results strongly suggest that the P/C ratio and the Ca-P and Ref-P fractions in the surface sediments are good indicators of the effects of fish farming and allow its characterization, and are particularly valuable in the area of complex aquaculture. [ABSTRACT FROM AUTHOR]

The study of diatoms in the surface sediments of Academy Bay (Sea of Okhotsk) revealed a rich diatom flora (187 species and intraspecific taxa), represented mostly by marine and brackish water species. The predominance of benthic-planktonic and benthic species indicates a significant role of microphytobenthos in Academy Bay. The diatom assemblages distinguished with the use of cluster analysis are homogeneous in their taxonomic composition, but differ in ecological structure, which is mainly determined by water salinity. The concentration of diatoms in the sediments in the open part of Academy Bay and in the apex of Ulban Bay depends on a high productivity of waters and the lithological composition of sediments. A relatively low content of diatoms in the sediments is associated with the severe climatic conditions of the region that is close to the Arctic. [ABSTRACT FROM AUTHOR]

Abstract: Aim The Aurá River, located in the second-largest Brazilian Amazon city, has been experiencing the effects of human activities from riverine communities and the Aurá landfill for many years. In this study, we assess the occurrence, sources, and distribution of selected sterol markers in surface sediments of Aurá River in order to evaluate the organic matter inputs in this water body. Methods Gas chromatography-tandem mass spectrometry (GC/MS/MS) was used to identify and quantify sterol compounds. Pearson correlation, principal component analysis (PCA) and sterol ratios were used to assess sewage pollution. Results The sterol markers identified, the related diagnostic ratios, and statistical analysis showed that Aurá River sediments presented two primary sterol sources: anthropogenic (domestic sewage and inputs from Aurá landfill) and biogenic sources (terrestrial higher plants). Station 1 (the closest site to the Aurá landfill) presented the highest level of coprostanol (219.8 ng g-1). This maximum level of coprostanol and the sterol ratios indicate moderate human fecal contamination in the upper reach of the Aurá River. Coprostanol levels were similar to the lower to midrange concentrations reported for surficial river sediments around the world. Conclusions This study demonstrated that domestic sewage pollution from riverine communities and organic matter inputs from Aurá landfill might be assumed as potential threats to environmental and human health.

This literature review focuses on the use of Mytilus galloprovincialis, a common Mediterranean bivalve, as a bio-indicator for the detection of trace metals in the Mediterranean coastal marine environment. By analyzing various studies, we examined the ability of Mytilus galloprovincialis to bioaccumulate trace metals and its effectiveness as an environmental monitoring tool. We explored the methodologies employed, the levels of contamination detected, and the ecological and health implications. This review highlights current trends, gaps in knowledge, and proposes recommendations for future research. It offers a global perspective on the importance of Mytilus galloprovincialis in assessing the quality of the Mediterranean coastal marine environment, and highlights its potential role in environmental management strategies.

Article highlights Five heavy metals concentrations displayed a wide seasonal and spatial variation. The mean concentration was Cr ˃ Zn ˃ Cu ˃ Pb ˃ Cd in winter and Zn ˃ Cu ˃ Cr ˃ Pb ˃ Cd in summer. The average CF value was Cd ˃ Cr ˃ Pb ˃ Cu ˃ Zn in winter and Cd ˃ Cu ˃ Zn ˃ Pb ˃ Cr in summer, respectively. The average EF value was Cd, followed by Cu, Pb, Cr, and Zn in winter and Cd, Zn, Cu, Pb, and Cr in summer, from highest to lowest, respectively. Contamination caused by Cd was more severe than for other heavy metals in both winter and summer. Cd was the major contributor to the potential ecological risk in the study region. Multivariate statistical analyses results showed Cd and Cr was more distinct from other element in winter and summer, indicate that Cd and Cr have a mixed source include both anthropogenic and lithogenic sources.

Article Highlights Base line of the PTEs pollution for the Lake Mariout drainage network. Pollution indices analysis of water and sediment of Lake Mariout. Ecotoxilogical and background concentrations of PTEs in sediments.

ABSTRACT Microplastics (MPs) are present in surface sediments deposited on city streets as a result of stormwater runoff. The objective of this study was to determine the abundance and characteristics of MPs in surface sediments deposited by stormwater runoff from the village of Madeán in the Peruvian Andes based on size, shape, and color. Surface sediment samples were collected in triplicate at each of the eight sample sites. The sediments were deposited in some parts of the streets of this village due to the effect of rainwater runoff. The separation of MPs from the sediment was carried out in the laboratory by the density separation method with NaCl solution. The eight sampling sites in Madeán presented 292.91 ± 149.32 (MP Items/Kg of sediment) of MPs, showing significant differences in the abundance of MPs among the different sampling sites. The predominant characteristics of the MPs were small size (SMP) (50.95%) and large size MPs (LMP) (49.05%), being fiber (60.66%) and fragmented (38.39%) in morphology, and blue (29.86%), black (25.59%), and red (23.22%) in color, respectively. The following investigation suggests that solid waste is not being adequately managed by finding the presence of MPs in the sediments that are in the street ditches.

Lake Sevan (Armenia) is one of the large freshwater high-mountain lakes of Eurasia. Detailed information about the extent and fate of trace elements on lake sediment and water quality has not been published yet. For this reason, surface sediment and water samples were collected from the southern and northern basins of Lake Sevan to determine trace element concentrations and assess the trace element behaviour. Geo-accumulation index, potential ecological risk index, and hazard index were calculated to estimate the environmental risk potential. In comparison to reference values, the investigated sediment samples contained elevated concentrations frequently for V, Cr, Co, Ni, Mo, Cd, Be, Ti, Rb, Sr, Se, Hf, and Th and occasionally for Cu, As, Li, B, Ag, Sb, Tl, Bi, U, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm. An overall potential ecological risk posed by all the investigated trace elements in the sediments was assessed to be moderate-considerable, however, Mo, Hg, and Cd were the elements with the highest ecological risk potential. The two basins of the lake showed significantly different behaviour according to the investigated trace element contents in the sediments to be higher in the bigger basin compared to the smaller basin. In comparison to reference concentrations in water samples according to the use of the adapted geo-accumulation index, elevated values for Ti, Cr, Cu, Cd, and Pb were observed. Elevated concentration was also observed in the case of B in nearly all water samples in comparison with literature values. Nevertheless, several water samples can be seen as not strongly anthropogenic influenced by Co, Ni, Sn, Sb, Ag, Hg, and Bi. The concentrations of trace elements in the lake water caused health risks to humans particularly children in the case of lake water used for drinking purposes, moreover, As was the main element posing health hazards. The results point out further attention to the sources of elevated trace elements in Lake Sevan, including anthropogenic influences and geological characteristics.

Urmia Lake, in the northwest of Iran, is the largest body of saline water in the Middle East, which has been desiccated in recent decades. To investigate the pollution status and ecological-health risks of heavy metals and metalloids in the surface sediments of this lake, 26 sediment samples were collected along the salt marshes of the lake and were analyzed for heavy metals and metalloid concentrations. The potential ecological risk assessment was carried out using enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), and potential ecological risk (Eri) standard indices. The average concentrations (mg kg−1) of heavy metals and metalloids were as follows: Fe (11,714) > Sr (320.8) > Mn (274.3) > V (28.5) > Cu (24.7) > Zn (21.2) > As (17.3) > Ni (14.8) > Cr (12.6) > Pb (11) > Co (4.0) > U (1.7), Hg (0.6) > Mo (0.36). The concentrations of As, Hg, and Sr in lake sediments were higher than geochemical background values. The non-carcinogenic risks caused by heavy metals and metalloids were insignificant regarding health risks. Levels of carcinogenic risk for metal(loid)s were in the acceptable ranges (10−6–10−4). The ecological risk was low, except for As, Sr, and Hg which showed moderate to significant EF, Igeo, and CF values. Arsenic and Sr were enriched in the surface sediments in desiccated parts of the lake due to complete lake water evaporation. It seems that further drying of the lake increases the potential ecological risk of heavy metals and metalloids in the surface sediments of Urmia Lake. [ABSTRACT FROM AUTHOR]

Sedimentary organic matter is an important component of the metabolism of a lake's ecosystem, and it is generally derived from both the watershed and the primary productivity of a lake. Understanding the sources of organic matter in lakes and lake trophic status is important when evaluating the quality of lake ecosystems. We summarize the spatial distribution of total nitrogen (TN), total organic carbon (TOC), TOC/TN (C/N) molar ratios, and organic carbon isotope (δ13Corg) of the surface sediments of Fuxian Lake, Yunnan–Guizhou Plateau, Southwest China, which is the second deepest freshwater oligotrophic lake in China. The results show that the distributions of TN, TOC, C/N, and δ13Corg of the surface sediments are spatially heterogeneous, which is also the case for the trophic conditions of the lake. Compared with the adjacent eutrophic lakes and typical lakes in other areas with strong human activities, the content of organic matter is at a low level. Meanwhile, the autochthonous organic carbon in the surface sediments was characterized by lower δ13Corg (−25.3~−28.5) and C/N (8.7~12.9), suggesting that the biological carbon pump effect plays a significant part in the stability of carbon sinks by coupling with carbonate weathering. Our results emphasize the importance of the carbon sink of coupled carbonate weathering and aquatic photosynthesis in the evolution of the carbon cycle in lakes. Although modern monitoring shows that Fuxian Lake is an oligotrophic lake, there are potential risks of organic nitrogen pollution with respect to surface sediments, especially in northern and southern shallow-water areas. The organic pollution of lakes can be reduced by controlling the discharge of wastewater and reducing the nutrient loading of agricultural runoff. [ABSTRACT FROM AUTHOR]

Beryllium-10 (10Be) has proven to be an essential tool for building chronology and understanding millennial-scale surface processes. Measurements in both the water column and authigenic fractions from various archives (such as surface sediments and Fe-Mn crusts) have provided valuable information on processes regulating Be isotopic distribution in the global oceans. Unlike the Pacific and the Atlantic Oceans, Be isotopic measurements in the Indian Ocean are sparse. Here, based on Be isotopic measurements on surface sediments from the central and northern Indian Ocean, an attempt is made to understand the processes controlling spatial Be isotopic distribution. Our data from the northern Indian Ocean suggests that terrestrial input is one of the primary contributors of 9Be. Owing to higher terrestrial flux, the sediment samples from the Bay of Bengal show higher 9Be concentrations and lower 10Be/9Be ratios. Our study suggests that scavenging by sediment particles plays a vital role in the distribution of Be isotopes in well-mixed open ocean water. Between carbonates and clay particles, carbonates are less efficient in scavenging Be from the water column. [ABSTRACT FROM AUTHOR]

Environmental magnetism parameters have become a useful tool in addressing environmental issues. Due to the rapid, sensitive, economical and non-destructive characteristics of environmental magnetism, the present contribution focuses on magnetism parameters as proxy for heavy metal pollution, especially from their relationship with contents of heavy metal. We evaluated heavy metals pollution and examined environmental magnetism in the Dexing section of the Le'an River. The pollution load index (PLI) of Cr, Pb, As, Cu and Zn, as well as the concentration of other heavy metals, were analyzed, and the magnetic indexes of various sediments were analyzed. The results showed that the concentrations of all heavy metals far exceeded the local background values, and that the average contamination factor of Cu was as high as 22.88, making it the element of most serious contamination. The problem of heavy metal pollution near the mine is very serious. The content of magnetic minerals in sediments of Le'an River is relatively high and the composition of magnetic minerals is relatively stable. The stable-single domin (SSD) content is high at S1 and S10, indicating that ferromagnetic mineral content is relatively rich here, which dominates the magnetic characteristics of the sample. In general, it was found that environmental magnetism indicators did not exist in the Dexing section of the Le'an River that could clearly indicate the concentration of heavy metal pollution. Only a few heavy metals can be effectively indicated by magnetic parameters. IRM-20mT and S-ratio can be used as indicators of Cr, Pb, As, Cu and Zn, but they are not accurate. The correlation between Sr and magnetic indexes IRM200mT, IRM300mT, SIRM, IRM-300mT and HIRM is significant, which can be used as an indicator of Sr concentration. IRM20mT can also be used as an indicator of Hg concentration. [ABSTRACT FROM AUTHOR]

The present study evaluated the potentials of phytoremediation and the biomonitoring of potentially toxic metals (PTMs) (Zn, Ni, Fe, Pb, and Cu) in the mangrove leaves of Rhizophora apiculata from the tropical mangrove ecosystem in the Sepang Besar River and Lukut River, Peninsular Malaysia. Overall, the present studies concluded that (a) the levels of essential Fe, Cu, and Zn in lamina are significantly (p < 0.05) higher than in MP, (b) the levels of Pb and Ni in MP are significantly (p < 0.05) higher than in lamina, (c) the lamina has better potential as a phytoremediator of Cu, Zn, and Fe, while MP is a better potential phytoremediator of Pb and Ni, (d) lamina is a potential biomonitoring agent of potentially toxic metals based on better correlation coefficients with the surface sedimentary geochemical fractions, and (e) metal uptake in the mangrove leaves and comparative levels of metals is low with reported studies. Specifically, based on bioconcentration factors (BCF), their most obtained values were considered low (<1), suggesting that R. apiculata can be considered as a low-efficiency plant for the bioaccumulation of PTM. However, the present findings also suggested that R. apiculata may be classified as a potential phytoremediator for Zn, Cu, Pb, and Ni in the leaves, as indicated by higher metal accumulation in the MP, with BCFEFLE values > 1.0; BCFAR > 1.0 for Cu, Pb, and Ni. The mangrove leaves are potential biomonitors of PTMs since positive correlations of PTMs were found between the leaves and their habitat surface sediments. Having been identified as a potential phytoremediator and biomonitor of PTMs, the present study emphasized the possibility of establishing a framework for managing the coastal aquatic ecosystems along the mangrove ecosystems of Sepang and Lukut. [ABSTRACT FROM AUTHOR]

It is of great significance to study the distribution characteristics and transport of heavy metals in complex sedimentary environments and areas with intensive human activities. This study analyzed sediment size, heavy metal contents (Cu, Zn, Cd, Cr, and Pb), organic carbon content, and sulfide content in surface sediments collected from 27 sites in Chengbei Sea. The main controlling factors of the distribution and transport of heavy metals were discussed from the perspective of sediment dynamics. The concentrations of Cu, Zn, Cd, Cr, and Pb in surface sediments were 7.9–20.5 mg/kg, 33.8–94.6 mg/kg, 0.08–0.26 mg/kg, 6.3–62.3 mg/kg, and 3–13.4 mg/kg, respectively. According to the geoaccumulation index, the study area was not polluted by the heavy metals, except for Cd, which did not pollute only areas with relatively coarse-grained sediments. Combining the results of correlation analysis, tidal residual current analysis, sediment transport trend analysis, and principal component analysis confirmed that Cu, Zn, and Cd originate from natural sources, and their distribution characteristics are mainly controlled by the grain size of surface sediments. Cr and Pb could be attributed to human activities, such as oil exploration, and their distribution characteristics were affected by sediment transport and tidal residual current. Zonation of the sedimentary dynamic environment also provided reference for the relationship between the distribution of heavy metals in surface sediments and sedimentary environments. [ABSTRACT FROM AUTHOR]

Interest in the study of microplanktonic organisms in the Arctic has increased owing to their direct participation in the process of sedimentation and sensitive response to changes in environmental and climatic factors. This study presents new data on the taxonomic diversity and content of radiolarian skeletons and agglutinated tintinnid ciliate loricae in the Upper Holocene sediments of the Laptev Sea, East Siberian Sea, and the adjacent part of the Arctic Ocean. We traced the spatial distribution of representative microfauna of these groups in surface sediments and sediment cores. Radiolarian skeletons were found in the surface sediments of the continental slope of the Laptev Sea and adjacent parts of the Arctic Ocean. These belong to the following six species: Stylatractus (?) sp., Actinomma leptoderma leptoderma, Actinomma leptoderma longispina, Streblacantha circumtexta, Spongotrochus glacialis, and Cycladophora davisiana. The radiolarian fauna detected was in deep sea and close to the fauna of the Nansen Basin (Central Arctic). Furthermore, we found tintinnid ciliate loricae belonging to the following seven species: Tintinnopsis ventricosoides, Tintinnopsis fimbriata, Tintinnopsis turbo, Tintinnopsis nitida, Tintinnopsis sp. cf. fusus (?), Tintinnopsis sp., and Stenosemella nivalis. In the study area, the tintinnid ciliate loricae of these species were discovered for the first time and traced mainly in the coastal shelf zone, which can be explained by their ecology. The only exception is that of T. nitida, which was found only on the continental slope of the Laptev Sea. Our findings advance knowledge on the biodiversity of Arctic seas and can be used to monitor ecological and paleoceanographic changes in the Arctic region. [ABSTRACT FROM AUTHOR]

Our research was motivated by significant warming in the Arctic in recent decades and the influence of this warming on diatoms, which are the main producers in the seas of the Eastern Arctic. For this purpose, we studied the qualitative concentrations and quantitative ratio of diatoms from the surface sediments of the Laptev Sea (LS), the East Siberian (ESS) and Chukchi seas (ChS), and the Arctic Ocean (AO), obtained by box corers in 2016 and 2018. The ecological structure of the diatom assemblages of these sediments, reflecting the current environmental conditions, was also analyzed. Compared with the end of the last century, there were significant changes in species composition and quantitative ratio of the diatom assemblages in the sediments from the AO and the LS and ESS. In contrast, the diatom assemblages in the sediments from the ChS had not significantly changed in terms of species composition or quantitative ratio over the same three decades. The observed transformations in the diatom assemblages of the surface sediments were associated with substantial changes in water temperature, current flow, salinity, ice melting, and prolonged ice-free periods associated with global warming in the Northern Hemisphere in recent decades. The foregoing processes have clearly had strong impacts on the environment and the biota of the Arctic region. [ABSTRACT FROM AUTHOR]

Residence time of an element in the ocean is a consequence of its chemical behaviour and the various biogeochemical processes governing its distribution, sources, and sinks. Precise estimation of the residence time of beryllium(Be) is necessary for its application as a tracer for understanding present and paleo-environmental processes. We utilise cosmogenic 10Be and terrestrially derived 9Be measurements from surface sediments to estimate the residence time of Be in the Indian Ocean. Significant variation in Be residence time is observed, which ranges between 370 and 620 years in the central Indian Ocean, 64–205 years in the Bay of Bengal, 41–117 years in the Andaman Sea, and 179–443 years in the Arabian Sea. Large heterogeneity in the residence time of Be can be attributed to its variable scavenging efficiency in different regions. Active scavenging of Be by sediment particles contributed through various major rivers draining into the northern Indian Ocean results in short residence time of Be. The results of this study have significant implications for the selection of sample sites and the use of Be as a tracer in paleo reconstructions. • Residence time of Be in the Indian Ocean was estimated. • Significant spatial variation in Be residence time was observed. • Scavenging of Be from the water column largely controls the residence time. [ABSTRACT FROM AUTHOR]