Thioclava arctica sp. nov. and Zhongshania arctica sp. nov., isolated from the surface sediment of the Arctic Ocean and reclassification of Marortus luteolus Yu et al. 2019 as a later heterotypic synonym of Zhongshania marina On et al. 2019.

Two Gram-stain-negative bacterial strains, 15-R06ZXC-3T and R06B22T, were isolated from the surface sediment of the Arctic Ocean. Phylogenetic analyses based on the 16S rRNA gene and genome sequences indicated that strain 15-R06ZXC-3T belongs to the genus Thioclava, while strain R06B22T belongs to the genus Zhongshania. Strain 15-R06ZXC-3T showed the closest relationship to Thioclava indica DT23-4T. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 15-R06ZXC-3T and all of the type strains of the genus Thioclava ranged from 20.8 to 30.4% and 79.1 to 85.7%, respectively. Strain R06B22T was most closely related to Zhongshania marina DSW25-10T. The dDDH and ANI values between strain R06B22T and all of the type strains of the genus Zhongshania ranged from 18.6 to 20.4% and 77.5 to 79.4%, respectively. These dDDH and ANI values were all below the standard cutoff criteria for the delineation of bacterial species, indicating that the two strains may represent novel species within their respective genera. Furthermore, their phenotypic and chemotaxonomic characteristics also differentiated them from closely related species. Based on the polyphasic analyses, strains 15-R06ZXC-3T and R06B22T separately represent novel species of the genera Thioclava and Zhongshania, for which the names Thioclava arctica sp. nov. (type strain 15-R06ZXC-3T = MCCC 1A07434T= KCTC 8342T) and Zhongshania arctica sp. nov. (type strain R06B22T = MCCC 1A08273T= KCTC 8343T) are proposed. Additionally, phylogenomic analyses showed that the strain Marortus luteolus ZX-21T was clustered with the strain Z. marina DSW25-10T and all other type strains of the genus Zhongshania. Furthermore, the ANI and dDDH values between strains ZX-21T and DSW25-10T were 97.6% and 78.8±2.5%, respectively, strongly indicating that they represented a single species. Therefore, it is proposed that M. luteolus Yu et al. 2019 be recognized as a later heterotypic synonym of Z. marina On et al. 2019.

Distribution characteristics, sources and risk assessment of heavy metals in the surface sediments from the largest tributary of the Lancang River in the Tibet Plateau, China.

Angqu, positioned in the eastern expanse of the Tibet Plateau, claims the title of the largest tributary to the Lancang River. In October and December of 2018, in the sediment of Angqu, a comprehensive investigation was conducted on nine heavy metals-arsenic (As), manganese (Mn), chromium (Cr), cadmium (Cd), lead (Pb), mercury (Hg), copper (Cu), zinc (Zn), and nickel (Ni). This investigation aimed to scrutinize the spatial and temporal distribution patterns of these metals, assess the pollution status and ecological risks associated with the sediments, and delve into the sources contributing to their presence. The research results indicate that the average concentrations of As, Hg, and Cd in Angqu sediments exceed the soil background values of Tibet, while the concentrations of other heavy metals are below the soil background values of Tibet. Notably, arsenic poses potential ecological risks. In Angqu sediments, the concentrations of Mn, Cu, Ni, and Pb are generally higher in the wet season, but the seasonal variations of heavy metals in Angqu sediments are not significant. The sediments in the Angqu Basin are predominantly affected by mercury Hg, Cd, and As, with varying degrees of pollution at different sampling points. In the main stream of Angqu (City section), Hg pollution has reached above a moderate level, whereas As pollution near the tributary is only slightly polluted. The analysis of heavy metal sources reveals that there are five primary contributors to heavy metals in surface sediments of Angqu: parent material, agricultural activities, groundwater, atmospheric deposition, and other unidentified sources. Mn, Cr, Pb, and Ni are mainly derived from soil parent material, accounting for more than 50%. About 60.82% of As comes primarily from groundwater. Zn and Cd are mainly sourced from agricultural activities, accounting for 41.25% and 34.33%, respectively. Additionally, 20.6% of Hg originates from atmospheric deposition.

Singapore's urbanised coral reefs: Changes in heavy metal pollution between 1994 and 2021.

The heavy metal load in coral reefs of Singapore has not been comprehensively assessed since 1994. Here, we repeated the surveys conducted 27 years ago to quantify the levels of Cd, Cu, Cr, Fe, Pb, Ti, Zn in sediment and the sea urchin Diadema setosum from seven reefs. Cu and Cd showed significant reductions, Pb and Cr remained stable, while Fe, Ti and Zn had increased significantly. Overall, based on the Pollution Load Index (PLI), Singapore's reefs would not be considered polluted. Nevertheless, elevated concentrations of Cu, Pb and Zn were detected in sediment, with Cu and Pb exceeding the Threshold Effect Level. The spatial distribution of metal loads between sediment and sea urchin tissues were decoupled, underscoring the complexity of metal uptake and bioavailability. We reveal a mixed temporal trend among the heavy metals examined, each presenting different toxicity potentials and hence risks to local marine assemblages.

One century of variations in organic matter inputs in marine Antarctic sediments: Insights from bulk and isotopic data.

The elemental composition and carbon and nitrogen stable isotopes of sedimentary organic matter (OM) are vital geochemical tools for understanding environments, physical and biogeochemical processes, and even paleoclimatic conditions on Earth. Given that the Antarctic Peninsula region is one of the few areas that remain relatively preserved compared to many other regions on Earth, sensitive to climate change, and yet remains the least explored continent, this study aimed to characterise the elemental (total organic carbon and total nitrogen) and isotopic (δ13C and δ15N) composition of marine sediments from various regions of Admiralty Bay, King George Island, Antarctica. This was done to assess potential sources of OM. The sampling included: (i) 17 surface sediment samples collected across the bay in January 2020; (ii) surface sediment samples collected during the 2009-2019 period at three specific inlets of Admiralty Bay; and (iii) three sediment cores collected from each inlet in 2007-2008. TOC and TN varied from 0.09 to 0.99 % and 0.02 to 0.18 %, respectively. The δ13C values ranged from -25.9 to -18.4 ‰, while the δ15N values varied from -12.4 to 22.7 ‰. The C/N ratio values were from 2.5 to 19.3. OM in sediments from Ezcurra Inlet primarily originates from terrestrial plants prevalent in Antarctica, such as mosses and lichens, alongside aquatic plants like algae and phyto- and zooplankton. Similarly, Mackelar Inlet is characterised by substantial contributions from these abovementioned sources. In contrast, Martel Inlet exhibits diverse sources, predominantly influenced by various marine mammals and seabirds and their excrements, in addition to the signals from mosses and lichens. Recent sediments sampled post-2008 in Martel Inlet show a decreased contribution from animal sources, with mosses and lichens emerging as the predominant contributors, corroborating patterns observed in the other inlets. Our findings suggest that climate change is expanding ice-free areas, promoting the growth of terrestrial vegetation, and altering the composition of sedimentary OM in Admiralty Bay, indicating changes over the studied time scale.

Manganese reduction and associated microbial communities in Antarctic surface sediments.

The polar regions are the fastest warming places on earth. Accelerated glacial melting causes increased supply of nutrients such as metal oxides (i.e., iron and manganese oxides) into the surrounding environment, such as the marine sediments of Potter Cove, King George Island/Isla 25 de Mayo (West Antarctic Peninsula). Microbial manganese oxide reduction and the associated microbial communities are poorly understood in Antarctic sediments. Here, we investigated this process by geochemical measurements of in situ sediment pore water and by slurry incubation experiments which were accompanied by 16S rRNA sequencing. Members of the genus Desulfuromusa were the main responder to manganese oxide and acetate amendment in the incubations. Other organisms identified in relation to manganese and/or acetate utilization included Desulfuromonas, Sva1033 (family of Desulfuromonadales) and unclassified Arcobacteraceae. Our data show that distinct members of Desulfuromonadales are most active in organotrophic manganese reduction, thus providing strong evidence of their relevance in manganese reduction in permanently cold Antarctic sediments.

Release of perfluoroalkyl acids from sediments under the effects of the discharge ratio and flow flux at a Y-shaped confluence.

The sediments in riverine environments contain notably high concentrations of perfluoroalkyl acids (PFAAs), which may be released into the water body under different hydrodynamic forces, such as those occurring at Y-shaped confluences. The release of PFAAs may pose a significant risk to the surrounding aquatic ecosystems. However, our understanding of the release and transport of PFAAs from sediments at Y-shaped confluences remains unclear. Thus, in this study, we performed a series of flume experiments to explore the effects of discharge ratio and total flow flux on the release and redistribution of PFAAs. The results indicated that these two parameters significantly affected the hydrodynamic features of confluences and the water physicochemical parameters. PFAA concentrations in the dissolved phase and suspended particulate matter (SPM) rose significantly as the discharge ratio and total flow flux increased. The dissolved phase was the predominant loading form of PFAAs, with short-chain PFAAs being the main kind, while long-chain PFAAs were dominant in the SPM. The spatial distribution pattern of PFAAs in sediments at the confluence exhibited a high degree of correspondence with hydrodynamic zones. The separation zone and maximum velocity zone were consistent with sediment regions with low and high capacities to release PFAAs, respectively. The patterns of variation in PFAA distribution were comparable to those observed in hydrodynamic zones as the discharge ratio and total flow flux varied. Furthermore, these two parameters altered the partitioning behaviors of PFAAs; specifically, the PFAAs in sediments tended to be released into the pore-water, while the liberated PFAAs tended to attach to SPM. Linear regression and correlation analyses suggested that the stream-wise and vertical flow velocity components near the sediment-water interface were the primary contributors to sediment suspension and PFAA exchange between the water column and pore-water. These findings will help us to understand the patterns of PFAA release in sediments at Y-shaped confluences and assist in the management of PFAA-contaminated sediments at these locations.

Spatio-temporal variations of methane fluxes in sediments of a deep stratified temperate lake.

Spatio-temporal variability of sediment-mediated methane (CH4) production in freshwater lakes causes large uncertainties in predicting global lake CH4 emissions under different climate change and eutrophication scenarios. We conducted extensive sediment incubation experiments to investigate CH4 fluxes in Lake Stechlin, a deep, stratified temperate lake. Our results show contrasting spatial patterns in CH4 fluxes between littoral and profundal sites. The littoral sediments, ∼33% of the total sediment surface area, contributed ∼86.9% of the annual CH4 flux at the sediment-water interface. Together with sediment organic carbon quality, seasonal stratification is responsible for the striking spatial difference in sediment CH4 production between littoral and profundal zones owing to more sensitive CH4 production than oxidation to warming. While profundal sediments produce a relatively small amount of CH4, its production increases markedly as anoxia spreads in late summer. Our measurements indicate that future lake CH4 emissions will increase due to climate warming and concomitant hypoxia/anoxia.

Preferential deposition of buoyant small microplastics in surface sediments of the Three Gorges Reservoir, China: Insights from biomineralization.

Sediments act as sinks of microplastics (MPs) derived from terrestrial ecosystems. However, the fate and transport of MPs at the zone of sediment-overlying water in reservoir environment are poorly understood. Here, the MPs distribution patterns in surface sediments of the Three Gorges Reservoir (TGR) and dominant mechanisms responsible for the sinking of MPs at the zone of sediment-overlying water were comprehensively investigated. The predominant occurrence of small microplastics (<300 µm, SMPs) in surface sediments of the TGR was found, with buoyant polyethene (PE) was dominant polymer types. Interestingly, the high abundance of SMPs in sediments correlated well with the Ca2+/Mg2+ in overlying water, suggesting that divalent cations in overlying water may enhance the preferential deposition of SMPs. Simulation sinking experiments under the presence of Microcystis aeruginosa and two divalent cations using different-sized PE MPs demonstrated that the greater deposition of SMPs was mainly the result of the formation of biogenic calcite on the surface of MPs rather than magnesium minerals, which provides stronger ballasting effects for SMPs than for large MPs. This study first highlights that the impact of biomineralization on preferential sinking of SMPs and enhances the understanding of the transport behaviour of MPs in aquatic environment.

Trace metals and pesticides in water-sediment and associated pollution load indicators of Netravathi-Gurupur estuary, India: Implications on coastal pollution.

Various environmental indicators were used to evaluate the water and sediment quality of the Netravathi-Gurupur estuary, India, for trace metals and pesticide pollution. The descended order of studied metal concentrations (µg/L) in the water was Fe (592.71) > Mn (98.35) > Zn (54.69) > Cu (6.64) > Cd (3.24) > Pb (2.38) > Cr (0.82) and in sediment (mg/kg) was Fe (11,396.53) > Mn (100.61) > Cr (75.41) > Zn (20.04) > Cu (12.77) > Pb (3.46) > Cd (0.02). However, pesticide residues were not detected in this estuarine environment. The various metal indexes categorised the water as uncontaminated, whereas contamination factor, enrichment factor, geo-accumulation index, degree of contamination and pollution load index indicated low to moderate sediment contamination. Multivariate statistics showed that the dominance of natural sources of trace metals with little anthropogenic impact. Improvement in water/sediment quality during the study period might be due to COVID-19 imposed lockdown.

Correlation between polycyclic aromatic hydrocarbons and total organic carbon in surface sediments of the Bohai Sea and the North Yellow Sea.

The correlation between polycyclic aromatic hydrocarbons (PAHs) and organic carbon is an important indicator of the marine environment. In this paper, twenty-six surface sediment samples were collected from the Bohai Sea and the North Yellow Sea as the study area, and the contents of sixteen PAHs ranged from 71.34 ng·g-1 to 240.78 ng·g-1 with an average of 143.26 ng·g-1 by gas chromatography. The source analysis indicated the source of PAHs in the surface sediments of the study area was more complex, and the percentage of combustion sources was higher than that of petroleum sources, which might cause less negative ecological risks. The average content of total organic carbon (TOC) was 5.25%, as determined by automatic potentiometric titration, and the content of TOC was higher in the Bohai Sea than in the North Yellow Sea. TOC was significantly correlated with HWM-PAHs but was not correlated with LWM-PAHs, which proved organic matter was more effective in controlling high-molecular-weight PAHs than low-molecular-weight PAHs in the surface sediments of the Bohai Sea and the North Yellow Sea.

Microplastic contamination in Thai vinegar crabs (Episesarma mederi), giant mudskippers (Periophthalmodon schlosseri), and their surrounding environment from the Bang Pu mangrove forests, Samut Prakan province, Thailand.

The mangrove ecosystem becomes the receptacle for both land- and marine-based plastic waste. This study examines MPs contamination in the Bang Pu mangrove forests (BPMFs) in the inner Gulf of Thailand. For this, Thai vinegar crabs (TVCs) (Episesarma mederi) and giant mudskippers (GMs) (Periophthalmodon schlosseri) were investigated with their surrounding environment in both rainy and dry seasons. Two-step digestion was employed for biota samples. MPs abundance ranged from 7.5 ± 3.8 to 15.9 ± 6.7 items/individual in TVCs and 6.2 ± 5.0 to 10.6 ± 2.6 items/individual in GMs. MPs in small-size ranges (<0.5 mm) were predominant. Fiber MPs were mostly detected in the rainy season. Most MPs were transparent with polyethylene and polypropylene as dominant polymers in all samples. Bioaccumulation was not observed in GMs. The results indicated the imperiled status of MPs contamination in TVCs and GMs with contaminated surrounding environments.

Surface sediment classification using a deep learning model and unmanned aerial vehicle data of tidal flats.

This study proposes a deep learning model, U-Net, to improve surface sediment classification using high-resolution unmanned aerial vehicle (UAV) images. We constructed training datasets with UAV images and corresponding labeling data acquired from three field surveys on the Hwangdo tidal flat. The labeling data indicated the distribution of surface sediment types. We compared the performance of the U-Net model trained in various implementation environments, such as surface sediment criteria, input datasets, and classification models. The U-Net trained with five class criteria-derived from previous classification criteria-yielded valid results (overall accuracy:65.6 %). The most accurate results were acquired from trained U-Net with all input datasets; in particular, the tidal channel density caused a significant increase in accuracy. The accuracy of the U-Net was approximately 20 % higher than that of other classification models. These results demonstrate that surface sediment classification using UAV images and the U-Net model is effective.

Spatial distribution, conversion, and ecological risk assessment of hexabromocyclododecanes in the sediments of black-odorous urban rivers nationwide in China.

Hexabromocyclododecanes (HBCDs) have become a global pollution problem, particularly in China-a major producer and user of HBCDs. However, little is known about the HBCD pollution status in urban rivers nationwide in China. In this study, we comprehensively investigated the pollution characteristics of HBCDs in 173 sediment samples from black-odorous urban rivers across China. Total HBCD concentrations ranged from not-detected to 848 ng/g dw, showing significant differences among the various sampling cities, but generally increasing from west to east China. This distribution pattern of HBCDs was strongly associated with the local industrial output, gross domestic product, and daily wastewater treatment capacity. α-HBCD was the predominant diastereoisomer in most sediments, with an average proportion of 63.8 ± 18.8 %, followed by γ-HBCD (23.8 ± 19.5 %) and ß-HBCD (12.4 ± 6.49 %), showing a significant increase of the α-HBCD proportions relative to those in HBCD commercial mixtures and an opposite trend for that of γ-HBCD. These results suggested that HBCDs might undergo isomerization from γ- to α-HBCD and biotic/abiotic degradation with preference for γ-HBCD. Of these conversions, the microbial degradation of HBCDs was further verified by the preferential transformation of (-)-α-, (+)-ß-, and (-)-γ-HBCDs and the detection of HBCD-degrading bacteria, including Dehalococcoides, Bacillus, Sphingobium, and Pseudomonas. A risk assessment indicated that HBCDs pose low to moderate risks to aquatic organisms in most black-odorous urban river sediments.

Distribution, contamination assessment, and sources of heavy metals in surface sediments from the south of the North Yellow Sea, China.

This paper reports the contents of six heavy metals and particle sizes in the surface sediments of 120 sampling stations in the southern North Yellow Sea to reveal heavy metal distribution characteristics, contamination assessment, and sources. Cu and Cr enrichments were mainly found in coastal areas with high mud content (silt and clay). However, Zn, Cd, Pb, and Hg were enriched in Weihai Bay and Dongpu Bay, which have denser populations, estuaries, and shipyards. The geoaccumulation index and principal component analysis showed that Cu and Cr contamination was low, and the sources were mainly natural processes. In addition, Zn and Cd pollution in the nearshore area was moderate, and its provenance was natural processes and human activity. However, most areas exhibited Pb and Hg contamination due to waterborne traffic and industries, including shipbuilding and gold mining.

Spatio-temporal distribution of microplastic pollution in surface sediments along the coastal areas of Istanbul, Turkey.

Microplastics (MPs) have become prevalent in various environmental compartments, including air, water, and soil, attracting attention as significant pollutant parameters. This study investigated the prevalence of MP pollution in surface sediments along Istanbul's Marmara Sea, encompassing the megacity and the Bosphorus. A comprehensive sampling approach was employed, covering 43 stations across four seasons and depths ranging from 5 to 70 m. The objective was to assess the impact of terrestrial, social, and industrial activities on MPs. The average concentrations varied per season, with fall, winter, spring, and summer values recorded as 2000 ± 4100, 1600 ± 3900, 4300 ± 12,000, and 9500 ± 20,300 particles/kg-DW. The study identified river stations in the Golden Horn and sea discharge locations as hotspots for high concentrations. Notably, the dominant shape shifted from fibers in fall, winter, and spring to fragments during summer, coinciding with mucilage occurrences. The study identified 11 different polymers, with polyethylene (44 %) and polypropylene (31 %) being the most common.

Magnetic susceptibility and heavy metal contents in sediments of Riam Kiwa, Riam Kanan and Martapura rivers, Kalimantan Selatan province, Indonesia.

Kalimantan Selatan is proud of the Martapura River's natural and cultural history. Martapura tributaries include Riam Kanan and Kiwa. The Martapura River is essential because it provides clean water and a livelihood for riverside residents. Human-caused river pollution grows with population density (also known as anthropogenic pollutants). This study characterizes surface sediment magnetic characteristics and heavy metal contents along the Riam Kanan, Riam Kiwa, and Martapura rivers. The purpose of this research is to evaluate the magnetic signal with respect to heavy metal contents found in surface sediments taken from rivers and to confirm the use of the rock magnetism method in environmental studies in the study area. Surface sediment samples were gathered and tested for magnetic, heavy metal, and mineralogical content. According to the findings, the pseudo-single domain (PSD) magnetite mineral predominates among the magnetic minerals that can be found in the surface sediments of the rivers Riam Kanan, Riam Kiwa, and Martapura. This substantially greater grain size may be due to magnetic particles produced by erosion along the river banks. The mass-specific magnetic susceptibility of surface sediments ranges from 103.11 to 1403.64 × 10-8 m3/kg, with an average value of 355.67 × 10-8 m3/kg due to the peatland environment. Magnetic susceptibility strongly negatively correlates with heavy contents like Cu, Zn, and Hg, according to Pearson correlation analysis. Due to this correlation, magnetic susceptibility may indicate heavy metal pollution in certain rivers. This current study demonstrates the novelty of the relationship between magnetic susceptibility and the contents of heavy metals in surface sediments from rivers in peatland and tropical environments by illustrating how the relationship affects the magnetic susceptibility of the sediments.

Influence of land cover, point source pollution, and granularity on the distribution of metals, metalloids, and organic matter in the river and stream sediments in the Republic of Korea.

With increasing anthropogenic activities, rivers and streams have become vulnerable to pollution; therefore, monitoring potential contaminants and the pollution status of surface sediments is essential. This study analyzed the concentrations of organic matter, metals, and metalloids; indices for organic, metal, and metalloid pollution; and ecological risk in river and stream sediments at 82 stations across Korea in 2017, 2018, and 2020. We performed bootstrapped analysis of variance, principal component analysis, and cluster analysis and used a structural equation model (SEM) to investigate spatiotemporal changes in the pollution status, main pollutant chemicals, and the exogenous factors affecting pollution status. The results suggest no significant differences in any of the twelve single chemical parameters and three pollution indices across the surveyed years. Metals, metalloids (Cu, Zn, Pb, and Hg), and organic matter with nutrients were identified as the main pollutants. The SEM demonstrated the significant influence of pollution sources-water used for industrial purposes, landfill wastewater discharge, and industrial wastewater discharge-on organic pollution, metal and metalloid pollution load, and environmental toxicity. This study identified consistently polluted areas, proposed additional management policies and stricter regulations on major point pollution sources rather than on broader land-use types, and suggested the combined consideration of metal toxicity risk with nutrient accumulation for future risk assessments.

Vibrio paucivorans sp. nov. and Vibrio qingdaonensis sp. nov., two marine bacteria.

Two Gram-stain-negative, facultatively anaerobic, motile, rod-shaped and flagellated marine bacteria, designated strains DBSS07T and ZSDZ65T, were isolated from the surface sediments of the Bohai sea and Qingdao coastal seawater, respectively. Phylogenetic analysis based on 16S rRNA genes, multilocus sequence analysis (MLSA), phylogenomic analysis of single-copy gene families and whole-genome data placed DBSS07T and ZSDZ65T within the genus Vibrio. DBSS07T was most closely related to Vibrio aestivus M22T, with 97.51 % sequence similarity, whereas ZSDZ65T was most closely related to Vibrio variabilis R-40492T with 97.58 % sequence similarity. DBSS07T grew with 1-7 % (w/v) NaCl (optimum 3 %), at 16-37 °C (optimum 28 °C) and at pH 6.0-9.0 (optimum pH 7.0); whereas ZSDZ65T grew with 1-5 % (w/v) NaCl (optimum 2 %), at 16-32 °C (optimum 28 °C) and at pH 6.0-9.0 (optimum pH 8.0). Both strains shared the same major fatty acid components (more than 10 % of total fatty acids) of summed feature 3 (C16 : 1ω7c or/and C16 : 1ω6c), with different proportions. The DNA G+C contents of DBSS07T and ZSDZ65T were 44.7 and 44.3 %, respectively. On the basis of the results of polyphasic analysis, DBSS07T and ZSDZ65T are considered to represent novel species within the genus Vibrio, for which the names V. paucivorans sp. nov. (type strain, DBSS07T = KCTC 82896T= MCCC 1K06284T) and V. qingdaonensis sp. nov. (type strain, ZSDZ65T = KCTC 82893T = MCCC 1K06289T) are proposed, respectively.

Insights about levels and source appointment of petroleum hydrocarbons in Brazilian semi-arid coastal: baseline status assessment for ocean decade targets.

The Ocean decade (2021-2030) for sustainable development proclaimed in 2017 by the UN, seeks to promote and conserve the sustainable use of oceans, seas, and marine resources. For this, the distribution of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and biomarkers, in sediments from the Fortaleza coastal zone (Mucuripe harbor (MH) and Inner Continental shelf (ICS)) were used to assess the impacts of anthropogenic activities in the area. The concentrations of total n-alkanes (Σ16 n-alkanes) in MH and ICS sediments varied from 35.9 to 94.9 and 17.9 to 197.3 µg g-1, respectively, while the isoprenoids phytane and pristane in MH and ICS sediments ranged from 0.1 to 1.69 ug g-1 and from 0.14 and 1.20 µg g-1, respectively. Most of the sediment samples presented carbon preference index (CPI) values close to unity, indicating that the area is submitted to petroleum-related sources. The concentrations of Σ16 PAHs in MH and ICS sediments varied from 87.0 to 562.0 and 98 to 288.0 ng g-1. This work presents the first investigation of the petroleum biomarkers hopanes and steranes in the Fortaleza coastal zone, in which ΣBiomarkers varied from 0.10 to 1.79 and 0.02 to 0.24 ug g-1 in MH and ICS sediments, respectively. The presence at stations of biomarkers also indicates petrogenic input. The diagnosis of the distribution of pollutants in the investigated zones of the Fortaleza coast suggests contamination from urban areas and oil spills and vessel traffic.

Seasonal variation and provenance of organic matter in the surface sediments of the three gorges reservoir: Stable isotope analysis and implications for agricultural management.

The construction of the Three Gorges Dam has altered the hydrology and increased the trapping of sediment in the reservoir. This has also changed the composition and export of particulate organic matter in the Yangtze River. To understand the seasonal variations and sources of organic matter in sediments, total organic carbon (TOC), total nitrogen (TN), δ13Corg and δ15N in surface sediment samples from the mainstream and tributaries of the Three Gorges Reservoir were measured in the summer (July) and winter (December) of 2017, respectively. The results showed that the concentrations of TOC and TN in the surface sediments of the Three Gorges Reservoir were 0.79 %-1.46 % and 0.07 %-0.13 %, respectively. The ranges of δ13Corg and δ15N were - 26.35 ‰ to-24.70 ‰ and 2.59 ‰ to 5.67 ‰, respectively. According to δ13Corg and the TOC/TN ratio, the source range of organic matter was determined, and the contributions of different organic matter sources were quantified using a Bayesian mixed model. The results showed that soil organic matter and river plankton were the main sources of surface sediment organic matter in summer, whereas soil organic matter and aquatic vascular plants were the main sources in winter. The source of organic matter is related to biological factors in summer, whereas it is mainly caused by hydrodynamic conditions in winter. The analysis of δ15N further reveals that there are obvious external pollutants in the Three Gorges Reservoir, mainly related to artificial nitrogen fertiliser and domestic sewage. This study highlights the influence that soil nitrogen loss may be an important reason for the impact of agricultural non-point source pollution in the reservoir area, showing seasonal differences which were mainly affected by rainfall in summer and controlled by impoundment in winter. Hence, fine nitrogen management is required to reduce pollution in the Three Gorges Reservoir.