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The level of metallic (Cd, Ni, Fe, Pb, Cu) contamination in the sampled sediments of five stations (S1, S2, S3, S4 and S5) from Woji creek bed between August and October 2019 was appraised using pollution load index (PLI), contamination factor (CF) and geoaccumulation index (Igeo). Results from the sediment analysis showed that Cd was not detected in stations 1, 3 and 5 in September, however, there was a high concentration of Cd in station 3 in October (43.590 ± 2.013 mg/kg). The concentration of Ni was highest in station 4 in August (247.682 ± 6.026 mg/kg). The mean spatial concentration of Pb ranged from 57.774 ± 75.647 mg/kg in October to 344.153 ± 112.184 mg/kg in August. Spatially, the highest concentration of Fe was measured in August (23.945 ± 17.828 mg/kg). Station 2 had the lowest concentration of Fe in the sediment temporally (5.667 ± 6.381 mg/kg) while station 3 had the highest concentration (19.496 ± 24.090 mg/kg); 37.188 ± 27.821 mg/kg (station 3) was the highest mean temporal concentration Cu, while station 2 had the lowest mean concentration of Cu (0.471 ± 0.358 mg/kg).The PLI values were in the trend: S3 (2.58 x 1015) >S4 (5.29 x 1014) > S1 (3.52 x 1014) > S5 (3.71 x 1013) > S2 (4.64 x 1012).These results indicated that the highest concentration of studied metals was found in S3 (except for Ni in S4), which emphasised the possible input of metallic matter into the sediment from the various operations along the creek connected with the disposal of metallic particulate wastes. All the metals present in the sampled sediments (except for Cu in S2) had concentrations between threshold effect level (TEL) and probable effect levels (PEL), which suggests the influence of unfavourable biological processes taking place from time to time. [ABSTRACT FROM AUTHOR]

As one of the most important margin seas around the west Pacific, the eastern China seas are important sink for terrigenous materials and forms multiple geology structures. So research the composition and spatial distribution of sediments could help us to understand the dynamics mechanism of the marine sedimentary environment, further to comprehend the land-sea interaction process. Based on high spatial resolution sediment survey in the eastern China seas, the distribution diagram of the sediment types was compiled to reveal the space regularities of sediment. In this study, the Principal Component Analysis (PCA) method was used to identify the controlling factors that are the main controls of the sediment distribution in the study area, which revealed three factors (F1, F2 and –F1) representing grain size categories of >5.75φ, 4.25–5.75φ and 1.50–3.00φ, respectively. F1 represents fine sediments (>5.75φ), -F1 represents coarse sediments (1.50–3.00φ), and F2 represents intermediate-sized sediments (4.25–5.75φ). The sediment transport patterns of the different grain size categories in the eastern China seas are discussed in the context of a comprehensive analysis of sediment grain size composition, material sources, flow patterns, and other factors. The results show that fine-grained sediments represent a "distant" sink of terrigenous material that formed in a stable and low-energy sedimentary environment. The coarse sediment deposits were formed in the late Pleistocene when the hydrodynamic conditions were relatively strong, and the intermediate-sized sediments were distributed in an area with a high concentration of suspension representative of mid-strength hydrodynamic conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

A new in situ radioactivity analysis method was developed to determine the fractional contributions of gamma-ray emitters in seawater and sediment from total measured counts. A semi-empirical formula to determine the fractional count contributions was derived using the variation characteristics of the gamma-ray attenuation rate and geometrical efficiency with the measurement points. The proposed method was employed to make in situ gamma-ray measurements using a CeBr3 detector for radioactivity analysis of seawater and sediment at a coastal area with a relatively high tidal range. The full energy peak efficiency of the detector at measurement site was obtained using the GEANT4 simulation code. The radioactivity concentration of 40K in seawater and sediment was determined using the proposed method and laboratory analysis with sampling. The MDA of the in situ measurement for 137Cs and 131I was also estimated assuming they were deposited on the sediment surface-layer. The validation of this method was demonstrated by comparing with the sampling analysis results. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the interactive effects of oil contamination and chemical dispersant application on bacterial composition and sediment remediation of an estuarine port environment. Methods and Results: A multifactorial controlled microcosm experiment was set up using sediment cores retrieved from an estuarine port area located at Ria de Aveiro lagoon (Aveiro, Portugal). An oil spill with and without chemical dispersant addition was simulated. Sediment oil hydrocarbon concentrations and benthic bacterial community structure were evaluated by GC‐MS and 16S rRNA high‐throughput sequencing respectively. Although initially (first 10 days) chemical dispersion of oil enhanced the concentrations of the heavier polycyclic aromatic hydrocarbons and of the C22‐C30 alkane group, with time (21 days), no significant differences in hydrocarbon concentrations were detected among treatments. Moreover, no significant changes were detected in the structure of sediment bacterial communities, which mainly consisted of operational taxonomic units related to hydrocarbon‐contaminated marine environments. We hypothesize that the environmental background of the sampling site preconditioned the communities' response to additional contamination. Conclusion: This experimental microcosm study showed that the chemical dispersion of oil did not influence sediment remediation or bacterial community composition. Significance and Impact of the Study: Our study showed that chemical dispersion of oil may not improve the remediation of port sediments. Further studies are needed to investigate the impact of chemical dispersants in combination with bioremediation strategies on the process of sediment remediation in port areas. [ABSTRACT FROM AUTHOR]

In order to study the effect of reed and cattail on the bacterial community structure of surface sediments of wetland in winter, high-throughput sequencing technology was used to analyze the bacterial composition. The results showed that 134 228 high-quality gene sequences were obtained by high-throughput sequencing in sediments of natural wetland in winter, and there were 13 866 OTUs, in which the number of OUT in sediments of reed wetland and cattail wetland was 6 677 and 7 189 respectively. The richness and diversity of bacterial communities in sediments of cattail wetland in winter were higher than those in sediments of reed wetland. Relative abundance of Proteobacteria in sediments of reed wetland and cattail wetland was 0.54 and 0.52, respectively. The dominant classes of bacteria were Betaproteobacteria, Deltaproteobacteria, Gammaproteobacteria and Epsilonproteobacteria, which belonged to gram-negative bacteria, indicating that the rhizosphere of wetland was easier to enrich gram-negative bacteria. Under the genus level, the dominant bacteria in the sediments were not obvious. [ABSTRACT FROM AUTHOR]

Sediments composed of oil-particle aggregates (OPAs) have unique physical characteristics. These in situ deposited sediments develop at locations where a continual or nearly continual discharge of non-aqueous phase liquids (NAPLs) have occurred, or are occurring through time. The NAPL discharged into the surface water body interacts with suspended particles in the water column. The particles adhere to the suspended NAPL, which generally is in the form of a bead, and produce a discrete aggregate. As the aggregate grows in response to additional particle adherence, the density of the unit increases and deposition occurs. The resulting sediment consists of a collection of discrete OPAs that form a network with small pores, where oil is tightly bound and/or contained. Porosity, water content, and dry bulk density measurements indicate the sediment formed by OPA deposition is physically unique. Although the sediment consists of a very open pore structure, the pore openings are relatively small, typically being less than 5 microns in diameter. These small pores inhibit fluid movement. Results of physical property testing suggest the OPA structure is retained upon deposition. Although the sediment contains NAPL, this original OPA structure inhibits the oil beads from coalescing, which would enable NAPL flow. [ABSTRACT FROM AUTHOR]

Heterocyclic aromatic compounds are organic contaminants present in low concentrations in sediments and include compounds containing N, S, and O atoms within a ring (NSO-HET). NSO-HETs have received increased scientific interest in the environmental pollution field because of their toxicity to ecosystems and towards humans. The lack of certified reference materials, the few authentic standards available, and the high number of potential isomers present challenges in the separation, identification, and quantitation these more polar polycyclic aromatic compounds analogue compounds. In this study, the sample preparation and instrumental methods to assess NSO-HET in sediments are reviewed, and the main advances and challenges are examined. The advantages and disadvantages of different analytical techniques, including classical and innovative approaches used to quantify and characterize NSO-HET in sediments, as well as the analytical quality control and availability of certified reference materials, are examined. Finally, future tendencies and challenges to be overcome are discussed. [Display omitted] • Properties and sources of major NSO-HET in sediment. • Extraction techniques for NSO-HET analysis in sediment. • Analytical methods for the determination of NSO-HET in sediment. • Future trends in the analysis of NSO-HET in sediment. [ABSTRACT FROM AUTHOR]

Atmospheric nuclear testing has occurred worldwide resulting in trace amounts of plutonium (Pu) isotopes in soils and sediments across the globe. Soils and sediments can vary greatly in both physical and chemical properties within close geographic regions presenting a major challenge for sample preparation in the analysis of fallout radionuclides. It is vital to have a rapid, agile method for the complete digestion of samples containing refractory Pu particles to address this challenge. A radioanalytical procedure for the analysis of Pu isotopes in soils/sediments has been developed improving sample preparation using fusion. This is done by eliminating the need for pre-dissolution combustion to remove organic material and providing greater application to a diverse range of samples including those of metal-bearing mineralogy. The integration of borate and peroxide flux materials creates a sample dissolution procedure that is greater than the sum of its parts. This method is applicable to the analysis of 239/240Pu in soil/sediment samples with a sample mass of 3 g, ranging from 0.05 to 5000 mBq/g achieving 242Pu tracer recoveries between 50 and 94%, with a trace-level detection limit of 0.04 mBq/g and measurement uncertainties down to 19%; adjustable to measurement priorities with variation in count time, background counts, chemical recovery and total activity of the sample. This sample preparation technique can be utilized with complementary analysis of alpha spectrometry or ICP-MS. Achieving these parameters provides a highly adaptable standard method for 239/240Pu in soil/sediment analysis applicable to samples from radioecological research at trace environmental levels to emergency response scenarios with 48-h turn-around producing highly repeatable, succinct and high-quality analysis. • An agile method for the analysis of refractory Pu particles in soils/sediments removing the need for pre-dissolution combustion. • Applicable to a diverse range of samples including metal-bearing mineralogy. • Validated for a range of 239/240Pu contamination (0.1–5000 mBq/g) achieving tracer recoveries between 50 and 94%, and a detection limit of 0.107 mBq/g using a combination of certified reference materials and real samples. • Highly adaptable method of analysis applicable to radioecological research at trace environmental levels and emergency response scenarios with 48-h turn-around producing highly repeatable, succinct and high-quality analysis. [ABSTRACT FROM AUTHOR]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.

• New seismic images off south-central Chile acquired with a 15-km-long receiver array. • The decollement is unusually shallow at the deformation front along S. central Chile. • Shallow sediment subduction along south-central Chile is among the world's thickest. • P-wave velocities imply S. central Chile trench sediments are well-drained and strong. • Thick, strong sediment subduction may enhance interplate coupling and earthquake size. The south-central Chile margin experienced the largest and sixth largest earthquakes ever recorded - the 1960 Mw 9.5 Valdivia and 2010 Mw 8.8 Maule megathrust earthquakes, respectively. In early 2017, we conducted a seismic survey along 1,000 km of south-central Chile to image these rupture zones using a 15.15-km-long multi-channel seismic streamer. We processed these data using pre-stack depth migration, which provides the best look at the shallow part of the south-central Chile margin to date. Relative to other sediment-dominated subduction zones, where sediment is typically accreted at the toe, an unusually large percentage of the thick trench sediments are consistently subducted beneath the slope with little thrust faulting or deformation. Analysis of the sediment P-wave velocities and structure in the trench and outer wedge leads us to conclude that most of south-central Chile contains well-drained, strong sediments. An exception in the vicinity of the subducting Mocha Fracture Zone (MFZ) has trench sediments that appear to experience localized delayed compaction, thus lowering their strength and allowing the development of protothrusts, similar to what is seen in other accretionary subduction zones. The very shallow décollement along the south-central Chile allows more sediment to pass beneath the lower slope than almost all other subduction zone, many of which have much thicker trench sections. We conclude that subduction of the strong, well-drained, thick sediment layer beneath the lower slope is typical for nearly all of the south-central Chile. Comparison to other thick-sedimented subduction zones worldwide reveals that the subduction of such a large fraction of the trench sediment is particularly unusual. This strong, thick, subducting sediment is likely a determining factor for developing a smooth plate interface located well above the subducted crust topography that ultimately becomes a broad megathrust with high, homogeneous frictional properties, and generates particularly large earthquakes along the south central Chile margin. [ABSTRACT FROM AUTHOR]

The exploration of the deep biosphere continues to reveal a great diversity of microorganisms, many of which remain poorly understood. This study provides a first look at the microbial community composition of the Costa Rica Margin sub-seafloor from two sites on the upper plate of the subduction zone, between the Cocos and Caribbean plates. Despite being in close geographical proximity, with similar lithologies, both sites show distinctions in the relative abundance of the archaeal domain and major microbial phyla, assessed using a pair of universal primers and supported by the sequencing of six metagenomes. Elusimicrobia, Chloroflexi, Aerophobetes, Actinobacteria, Lokiarchaeota, and Atribacteria were dominant phyla at Site 1378, and Bathyarchaeota, Chloroflexi, Hadesarchaeota, Aerophobetes, Elusimicrobia, and Lokiarchaeota were dominant at Site 1379. Correlations of microbial taxa with geochemistry were examined and notable relationships were seen with ammonia, sulfate, and depth. With deep sediments, there is always a concern that drilling technologies impact analyses due to contamination of the sediments via drilling fluid. Here, we use analysis of the drilling fluid in conjunction with the sediment analysis, to assess the level of contamination and remove any problematic sequences. In the majority of samples, we find the level of drilling fluid contamination, negligible. [ABSTRACT FROM AUTHOR]