Different Types Of Sediments Research Articles

Reduction of the toxin microcystin-LR with different types of sediments

Microcystis aeruginosa blooms in water bodies, evidencing a high risk of exposure to human health due to the release of toxins, which affects water quality. Implementing physical, chemical, and microbial control methods requires an integrated understanding of cyanotoxin dynamics, especially their relationship with sediments. Consequently, sediment obtained from three stations of the Riogrande II reservoir (Antioquia, Colombia) was analyzed to determine the adsorption and removal capacity of the microcystin-LR (MC-LR). For this purpose, the sediment was subjected to different treatments to select the one with the highest MC-LR removal capacity. Furthermore, the effectiveness and stability of adsorption removal process were evaluated by analyzing mechanical processes such as aeration, sonication, and agitation. The dried sediment showed the highest reduction in toxin concentration (93%) after 24 h, followed by washed sediment (91%) and sterilized sediment (81%).On the other hand, the sediment was fractionated into silts and clays; the latter was the least effective. Finally, the fine and half silts were better adsorbents of the toxin, acting similarly over time. Initially, the utilization of sediment that has been dried by sunlight could be a complementary alternative to reinforce MC-LR control methodologies in water bodies.On the one hand, MC-LR desorption assays showed that aeration of the sediment for 30 min caused a release of up to 96% of the adsorbed compound. At the same time, the effect of sonication and agitation was less intense. However, the absorption process must be fast to avoid efficiency losses due to desorption since a high percentage of the toxin was spontaneously desorbed from the sediment in two days.

Comparison of leaching behaviour of heavy metals from sediments sampled in sewer systems - environmental and public health aspect.

The article analyzes the content of heavy metals and standard physical as well as chemical pollution indicators in different types of sediments from stormwater, combined sewer and sanitary sewer systems. Nickel, lead, chromium, copper, zinc and cadmium, as well as standard physical and chemical pollution indicators, were determined in sewage sediments. Aqueous extracts of sediments samples, taken from storm water sewer inlet sediments traps, storm sewers, sanitary sewers and combined sewers, were prepared in accordance with PN-EN 12457-2:2006. After mineralization, the concentrations of the metals: nickel, lead, chromium, copper, zinc and cadmium in the extracts were determined using the inductively coupled plasma emission spectroscopy technique. The results were analyzed with a non-metric multidimensional scaling algorithm. The heavy metal content was variable depending on the sediments collection site. The heavy metals nickel, lead, chromium, copper, zinc and cadmium were found in the sediments from stormwater inlets, storm sewer and sanitary sewer channels, with variability in the concentration of individual metals. The sediments from the flushing of sanitary sewers and combined sewers did not contain cadmium. The content of heavy metals in sediments varied depending on the sampling location and type of sewer system, indicating the need for detailed monitoring to identify the sources of emissions. Sediments from stormwater sewers have higher concentrations of heavy metals, with those from sewer inlets showing zinc concentrations exceeding regulatory limits, highlighting the variability and potential environmental impact of different sewer systems.

Let’s play with fire! Preliminary results of new experiments on animal bone of thermo-alterations

ABSTRACT Thermo-alterations in skeletal remains result from circumstances that can be key to understanding the context in which these appear. Here, we present the results of a series of experiments based on the exposure of animal remains to a range of different conditions and temperatures (up to 900°C) to document a variety of contexts that provide valuable information in fossil sites and forensic cases. Meat-bearing and defleshed remains (i.e. meat manually removed before the experiment) were exposed to high-temperatures, both directly or buried in different types of sediments (silt, sand, gravel and mixed sediment), in order to document colour changes and survival of soft tissues. Thus, our main goal was to monitor colour alteration and superficial modifications on the bone surface (i.e. cracks, as well as disarticulation of small mammal carcasses caused by high temperatures).

Patters of reactive nitrogen removal at the waters in the semi-constructed wetland

Protection and rectification patters of urban wetlands have been considered in strategies to balance services to society and negative consequences of excess reactive nitrogen (Nr) loading. However, the knowledge about strategies of semi-constructed wetlands on nitrogen (N) cycling pathways and removal Nr from the overlying water is limited. This study aimed to reveal considerable differences among rectification patterns of the typical semi-constructed wetland (Xixi wetland), comprising rational exploitation area (REA), rehabilitation and reconstruction area (RRA), and conservation area (CA) by analyzing the N distribution and N protentional pathways among them. Results pointed out that both NH4+ and NO3− concentration were prominently higher in REA, as opposed to CA and RRA. Sediments in RRA had relatively higher NH4+ content, indicating the efficiency of dissimilatory nitrate reduction (DNRA) in RRA. Moreover, there was a significant shift in the microbial community structure across different sites and sediments. Metagenomic analysis distinguished the N cycling pathways, with nitrification (M00804), denitrification (M00529), and DNRA (M00530) being the crucial pathways in the semi-constructed wetland. The relative abundance of N metabolic pathways (ko00910) varied among different types of sediments, being more abundant in shore and rhizosphere areas and less abundant in bottom sediments. Methylobacter and Nitrospira were the predominant nitrifiers in shore sediments, while Methylocystis was enriched in the bottom sediments and rhizosphere soils. Furthermore, Anaeromyxobacter, Anaerolinea, Dechloromonas, Nocardioides, and Methylocystis were identified as the primary denitrifiers with N reductase genes (nirK, nirS, or nosZ). Among these, Anaeromyxobacter, Dechloromonas, and Methylocystis were the primary contributors containing the nosZ gene in semi-constructed wetlands, driving the conversion of N2O to N2. This study provides important insights into rectification-dependent Nr removal from the overlying water in terms of N distribution and N metabolic functional microbial communities in the semi-constructed wetlands.

A new method for long-term in situ monitoring of seabed interface evolution: A self-potential probe

The evolution of the seabed interface is associated with various issues such as sediment accumulation at ports, erosion of shorelines, scouring of soil around bridge piles, deep-sea mining, and deformation of the seafloor. In order to gain insight into the evolution of seabed elevation and the status of seabed engineering structures, in-situ monitoring of the seabed interface is necessary. This paper presents a long-term in-situ monitoring method of seabed interface changes based on self-potential measurements. A sensor-free self-potential in-situ monitoring probe was developed, which has a vertical measurement range of 1 m and a resolution of 2 cm. Laboratory and in-situ test results show that the self-potential probe can identify the seabed interface, the interface between seawater and atmosphere, and the interfaces of different types of sediments. Even when the seabed surface is covered with polymetallic nodules, the seabed interface can still be identified and the layers of polymetallic nodules can be distinguished. This study contributes to a deeper understanding of self-potential measurements and provides a new technology for in-situ monitoring of the seabed interface.

Studying the Composition and Genesis of Organic Matter in Bottom Sediments of Polluted Small Watercourses in Khabarovsk City Territory

The distribution of organic matter, hydrocarbons, phytopigments, and ecological-trophic groups of microorganisms was studied in the bottom sediments of ten small tributaries of the Amur R. near Khabarovsk. The water showed high concentrations of organic matter, varying from 44.47 to 279.3 mg/L. The concentration of Corg in bottom sediments varied from 1.9 to 23.1% in different types of sediments; the amount of hydrocarbons reached 5081 mg/kg, exceeding the background level by a factor of up to 50. Studies of the molecular composition of hydrocarbons in sediments revealed in some streams the predominance (up to 100% of the total) of light (C8–C13) n-alkanes, typical of oil products and the products of vegetation combustion. High-molecular compounds dominated in HC composition in most watercourses, including n-alkanes, genetically associated with terrestrial vegetation, and heavy fractions of oil products with various levels of microbial degradation. Volatile organic compounds were quantitatively dominated by the products of microbiological transformation (acetaldehyde and methanol). In terms of the concentration of sedimentary pigments (up to 400 µg/g), the sediments of the majority of watercourses belong to the hypereutrophic type. The total abundance of microorganisms in water varied from 2.7 to 488.0 thousand CFU/mL; in sediments, it was distributed symbatically, but ranged from 0.1 to 19.3 million CFU/g. The number of heterotrophic bacteria in bottom sediments correlated with the parameter of overload of the self-purification capacity (r = 0.718), and the number of oil-oxidizing bacteria correlated with hydrocarbon concentration (r = 0.967), thus confirming the indication properties of this bacterial group.

Precision of mangrove sediment blue carbon estimates and the role of coring and data analysis methods.

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

Interactions between microbial activity and bioturbation modes of benthic invertebrates determine nutrient releases from reservoir sediments

Abstract Bioturbating invertebrates play key roles in nutrient recycling from sediments to the water column in most lentic ecosystems. Nevertheless, the role of bioturbating fauna on nutrient cycling depends on complex interactions between their bioturbation modes and both the sedimentary conditions and the microbial activity occurring inside sediments. This study aims to evaluate the effect of different bioturbation modes by two invertebrate species (tubificid worm Tubifex tubifex and chironomid larvae of Chironomus plumosus), on the release of nutrients (NH4+, NO3−, and PO43−) from three different types of sediments characterised by distinct microbial activities and nutrient (N and P) contents. We expected that the influence of a bioturbation mode on nutrient fluxes was dependent on the microbial activity and organic matter processes occurring in sediments. Aquatic mesocosms were setup in the laboratory with three fauna treatments (i.e. without fauna, with tubificid worms, and with chironomid larvae) and three sediment types (collected in three reservoirs). The presence of bioturbating invertebrates increased PO43− concentrations into the water column (from 1.3‐ to 17‐fold higher concentrations) depending on the sediments tested. PO43− releases in the water column were positively linked to total P concentration and microbial activity in sediments. The influences of tubificid worms and chironomid larvae on PO43− releases into the water were not only due to their bioturbation modes but also depended on the interactions with P dynamics (e.g. adsorption of PO43− by iron oxides) at the water–sediment interface. The influence of fauna on the release of dissolved inorganic nitrogen (DIN) varied strongly among sediments due to the control of N cycling by microbial processes. In sediments characterised by the lowest microbial activity, DIN release from sediments to the water column was significantly stimulated by invertebrates (from 1.3‐ to 3.7‐fold higher). In contrast, no fauna effect was detected compared to controls in sediments characterised by the highest microbial activity. This study demonstrated that the influence of the bioturbation mode on nutrient (i.e. PO43− and DIN) dynamics at the water sediment interface was largely modulated by the intensity of microbial activity and biogeochemical processes occurring in sediments.

Archaeometric Surveys of the Artifacts from the Archaeological Site of Baro Zavelea, Comacchio (Ferrara, Italy)

This work is part of a project of the Superintendence of Archaeology, Fine Arts, and Landscape for the enhancement of the widespread archaeological heritage of the Po delta area. Excavation activities, carried out in 2015, allowed the sampling of the stratigraphic elements and artifacts of the archaeological site of the lighthouse tower of Baro Zavelea, municipality of Comacchio (Ferrara, northeast Italy). In this work, the geochemical characterization of sediments and building materials was conducted using granulometric analyses, X-ray fluorescence analysis, and calcimetry on different types of samples, including sands, clays, mortars, and bricks, with the scope to better characterize all of the different types of sediments collected. This multidisciplinary approach allowed the diagnostic and evaluation of the state of conservation of Baro Zavalea. Granulometric analyses highlighted the fact that depositional environments were of very different natures: fluvial environments and paleo–alveo environments. In addition, XRF analysis allowed the discrimination of different clay samples, some from basins poor in carbonates, while, for the construction of the bricks of the second wall structure, clays rich in carbonate were chosen to add lightness to the structure.

Biotic and abiotic controls on sediment carbon dioxide and methane fluxes under short-term experimental warming

Due to the differences in biotic and abiotic factors between soil and sediments, the predicted linkages between biotic and abiotic factors and soil carbon dioxide (CO2) and methane (CH4) fluxes under warming may not be suitable for sediments. Additionally, the combination of biotic and abiotic factors which determines sediment temperature-dependent CO2 and CH4 fluxes remains unresolved. To address this issue, different types of sediments (including lake, small river and pond sediments) collected from 30 sites across the Yangtze River Basin were incubated under short-term experimental warming. During the incubating phase, the sediment temperature-dependent CO2 and CH4 fluxes as well as the accompanying biotic factors (organic carbon and microbial community) and abiotic factors (pH and dissolved oxygen (DO)) were determined and analyzed synthetically. Our results indicated that sediment CO2 fluxes were more sensitive than CH4 fluxes to warming, which might lead to a relatively large CO2 contribution to total greenhouse gas emissions in a warming climate. Additionally, temperature-dependent CO2 fluxes in pond sediments were more sensitive than those in lake sediments. Random forest analysis indicated that DO greatly affected the variation in the sediment temperature-dependent CO2 fluxes, whereas Methanococcales primarily predicted the CH4 fluxes under warming. DO also highly affected the variation in the temperature sensitivity of CH4 fluxes, whereas pH mostly predicted the temperature sensitivity of CO2 fluxes. Our findings suggest that biotic and abiotic factors, especially DO, pH and the composition of methanogens, coregulate CO2 and CH4 emissions in response to climate warming. Therefore, biotic and abiotic factors should be considered in the models for predication and investigation of sediment organic carbon dynamics under climate change.

The effects of climate warming on microbe-mediated mechanisms of sediment carbon emission

Due to significant differences in biotic and abiotic properties of soils compared to those of sediments, the predicted underlying microbe-mediated mechanisms of soil carbon emissions in response to warming may not be applicable for estimating similar emissions from inland water sediments. We addressed this issue by incubating different types of sediments, (including lake, small river, and pond sediments) collected from 36 sites across the Yangtze River basin, under short-term experimental warming to explore the effects of climate warming on sediment carbon emission and the underlying microbe-mediated mechanisms. Our results indicated that under climate warming CO2 emissions were affected more than CH4 emissions, and that pond sediments may yield a greater relative contribution of CO2 to total carbon emissions than lake and river sediments. Warming-induced CO2 and CH4 increases involve different microbe-mediated mechanisms; Warming-induced sediment CO2 emissions were predicted to be directly positively driven by microbial community network modularity, which was significantly negatively affected by the quality and quantity of organic carbon and warming-induced variations in dissolved oxygen, Conversely, warming-induced sediment CH4 emissions were predicted to be directly positively driven by microbial community network complexity, which was significantly negatively affected by warming-induced variations in pH. Our findings suggest that biotic and abiotic drivers for sediment CO2 and CH4 emissions in response to climate warming should be considered separately when predicting sediment organic carbon decomposition dynamics resulting from climate change.

High-Frequency Dependence of Acoustic Properties of Three Typical Sediments in the South China Sea

The acoustic characteristics of three fine-grained sediments (silty sand, silt, silty clay) in the South China Sea (SCS) were measured and analyzed at high frequency range of 27–247 kHz. The measurement results show that the sound speed dispersion is a positive linear relation at the measured frequency range, and the attenuation follows nonlinear frequency dependence, α = kfn, where n ranges from 0.59 to 0.85 for the three different sediments in the SCS. The frequency dependence of sound speed and attenuation were compared with the published literature. It was found that for silty clay, clayey silt, silt, and silty sand, the dispersion characteristics of these four sediments are basically consistent; in general, the dispersion of coarse particles is significant, and that of fine particles is weak, and permeability is the key parameter that determines the inflection point of high frequency to low frequency. By modeling these sediments with the Biot–Stoll model, it was found that the Biot–Stoll model can better predict the frequency-dependent characteristics of sound attenuation in a high-frequency band under the matching constraints of sound speed dispersion characteristics, indicating that the Biot–Stoll model has good applicability to different types of sediments in a high-frequency band.

Toxicity of Tire Rubber Microplastics to Freshwater Sediment Organisms

High emission of tire rubber particles to the surrounding environment is an inevitable consequence of the current habits of transportation. Although most of the emissions stay within a close range of the sources, it has been proven that the smallest particles can be transported to remote locations through the atmosphere, including inland water bodies. It has been estimated that a relevant portion of the global emissions of tire rubber particles reach surface waters, but effects on aquatic life in the receiving water bodies are not completely understood. In the present study, we used the freshwater sediment dwellers Lumbriculus variegatus and Chironomus riparius to examine the toxicity of tire rubber particles at environmentally relevant concentrations, using different types of sediment and two particle sizes of tire rubber. Overall, the experiments were unable to discern any effects on the growth, survival or reproduction of the two animals tested. Significant differences were found among the animals dwelling on different sediments, but the effects were not attributable to the presence of tire rubber particles. This study provides important information regarding the lack of effect of tire rubber particles in laboratory experiments with model sediment dwellers and opens more questions about the potential effects of tire rubber particles in the real environment with longer durations and varying environmental factors. The influence of other factors such as the leaching of additives in the overall toxicity of tire rubber particles should be also considered.

The paleo-lacustrine diatomaceous deposits of Monte Amiata volcano (Tuscany, Italy) and the Ezio Tongiorgi paleontological collection in the Museum of Natural History of the University of Pisa

At the foothillof Monte Amiata volcano (southern Tuscany, Italy), small extinct lake basins of late Pleistocene age are documented. These lake basins were characterized by the deposition of two very different types of sediment: a) derived from the authigenic precipitation of iron oxides (goethite) and exploited as earth pigments; b) biogenic siliceous sediment composed of fossil diatoms and named diatomaceous earth or diatomite. The lacustrine sediments of Mount Amiata volcano were widely exploited for various applications since ancient times. Literary documents begin in the 16th century, with the descriptions of Cesalpino, Gesner, Agricola, and Imperato. Specific references to the diatomites of Monte Amiata are quoted in the 17th century by Boccone and Bonanno. The quarrying activity was described by Micheli in 1733. During the 18th and 19th centuries, the diatomaceous earths of Monte Amiata are part of the important geological collections of Micheli, Targioni Tozzetti, Baldassarri, Campani, and Tommi. A particular significance has the collection of botanic and ichthyologic fossils collected by Ezio Tongiorgi, and now preserved in the Museum of Natural History of the University of Pisa sited at the Charterhouse of Pisa in the Calci village. These paleontological samples preserve the biological and physical testimonies of the environmental and climatic changes of the late Pleistocene and are now particularly valuable because they are the only remaining evidence of the diatomaceous lacustrine deposits of the paleo-lakes of Monte Amiata. For these reasons, they represent geological materials with a fundamental cultural value.

LITHOLOGY AND HYDRODYNAMICS OF THE BLACK SEA ODESSA COAST UNDERWATER PART

Problem Statement and Purpose. The results of lithological studies, including granulometric analysis, are needed to identify the conditions of sedimentation and distribution of rock fragments by size. They are an indicator of the sedimentation processes dynamic structure peculiarities. The study of the sediment regime is important for the development of measures related to the protection of shores from erosion. The aim of the work is to identify the lithological features of the bottom sediment types distribution on the protected section of the Odessa coast near Cape Maly Fontan. Data & Methods. The materials for this work were obtained in the field research in the summer 2019 in the coastal zone between the hydrobiological station of Odessa I. I. Mechnikov National University, and Cape Malyj Fountain. Three measuring profiles were made perpendicular to the shoreline at 1200 m towards the sea to a depth of 18 m. 35 samples were taken from the upper layer of bottom sediments. Field samples processing was performed in the Problem Research Laboratory of Engineering Geology of the Sea Coast, Reservoirs and Mountain Slopes of Odessa I. I. Mechnikov National University. Granulometric classification was performed. Excel, Statistica, Golden Software Surfer programs were used to process the results. Results. Underwater relief analysis showed that the coastal part is an abrasive terrace, on which ancient landslides relics are widespread. There are 7 main lithological types of bottom sediments detected. The largest areas covered by fine-grained loamy sands and shell detritus with gravel, pebbles and sand. Analysis of distribution curves and cumulative curves of granulometric distribution showed that coarse sediments are characterized by multi-vertex distribution curves and stepwise stretched cumulative curves, which indicates the heterogeneity of sediments in granulometric distribution. For fine-grained material, which is well sorted, the distribution curves are almost single-vertex, and the cumulative curves have a large steepness and a simple, non-stepped shape. There are three hydrodynamic detected in bottom sediments lithology according on statistical parameters of grain size. Outer marine part with depth more than 15 meters characterized by low hydrodynamic processes and presented by good-sorted sands and silt. The central part of polygon in 4–15 meters depth covered by shell detritus with gravel and pebble of carbonate rocks and connected with rocky extrusions after coastal landslides. The feature of this part is active hydrodynamic processes. The rocky extrusions presented like natural breakwater and due to waves braking and collection of different types of sediments. The coastal part in 2–4 m depth in front of constructed breakwater leads to decreasing of wave energy and sedimentation of good-sorted sands.

Determination and Quantification of Heavy Metals in Sediments through Laser-Induced Breakdown Spectroscopy and Partial Least Squares Regression

Conventional analysis techniques and sample preprocessing methods for identifying trace metals in soil and sediment samples are costly and time-consuming. This study investigated the determination and quantification of heavy metals in sediments by using a Laser-Induced Breakdown Spectroscopy (LIBS) system and multivariate chemometric analysis. Principle Component Analysis (PCA) was conducted on the LIBS spectra at the emission lines of 11 selected elements (Al, Ca, Cd, Cr, Fe, K, Mg, Na, Ni, Pb, and Si). The results showed apparent clustering of four types of sediment samples, suggesting the possibility of application of the LIBS technique for distinguishing different types of sediments. Mainly, the Cd, Cr, and Pb concentrations in the sediments were analyzed. A data-smoothing method—namely, the Savitzky–Golay (SG) derivative—was used to enhance the performance of the Partial Least Squares Regression (PLSR) model. The performance of the PLSR model was evaluated in terms of the coefficient of determination (R2), Root Mean Square Error of Calibration (RMSEC), and Root Mean Square Error of Cross Validation (RMSECV). The results obtained using the PLSR with the SG derivative were improved in terms of the R2 and RMSECV, except for Cr. In particular, the results for Cd obtained with the SG derivative showed a decrease of 25% in the RMSECV value. This demonstrated that the PLSR model with the SG derivative is suitable for the quantitative analysis of metal components in sediment samples and can play a significant role in controlling and managing the water quality of rivers.

An Integrated Horizon Picking Method for Obtaining the Main and Detailed Reflectors on Sub-Bottom Profiler Sonar Image

A sub-bottom profiler (SBP) can capture the sediment interfaces and properties of different types of sediment. Horizon picking from SBP images is one of the most crucial steps in marine sub-bottom sediment interpretation. However, traditional horizon picking methods are good at obtaining the main horizons representing the main reflectors while ignoring the detailed horizons. While detailed horizons are the prime objective, many tiny structures caused by interference echoes will also be picked. To overcome this limitation, an integrated horizon picking method for obtaining the main and detailed horizons simultaneously is proposed in this paper. A total of three main process steps: the diffusion filtering method, the enhancement filtering method as well as the local phase calculation method, are used to help obtain the main and detailed horizons. The diffusion filtering method smooths the SBP images and preserves reflectors. Enhancement filtering can eliminate outliers and enhance reflectors. The local phase can be used to highlight all of the reflections and help in the choosing of detailed horizons. A series of experiments were then performed to validate the effectiveness of the proposed method, and good performances were achieved.

Airborne geophysical investigations for landslide risk investigation along the Ångerman River, central Sweden

A study of landslide risks along the Ångerman River in Sweden is currently being performed by the Swedish Geotechnical Institute (SGI) with assistance from the Geological Survey of Sweden (SGU). In this work, knowledge of the distribution of different types of sediment is crucial. The area shows large variations in both sediment stratigraphy and sediment thickness (depth to bedrock) which makes it difficult to describe geotechnical properties for larger areas based on sparse geotechnical field investigations (soundings and sampling). Within the study area, the Ångerman River valley contains numerous fluvial terraces at various elevations separated from the river by steep erosional scarps. Although fluvial sand caps the terraces, their heights are often derived from the underlying silt and clay, which in turn overlies till or glaciofluvial sediment. The thickness of these general stratigraphic units is difficult to determine from existing data. Thus, in 2018, an airborne transient electromagnetic (ATEM) survey was performed along the river and the surrounding river banks with the objective of mapping and characterizing the sediments down to bedrock. The surveyed area is 2 km wide and covers 80 km along the river with a flight line distance of 75 m. From the ATEM data, the 3D resistivity distribution of the ground down to about 100 m below the surface can be determined. The silt and clay show very low resistivity compared to the overlaying sand layers. Therefore, they can be easily distinguished in the resistivity models from the ATEM data. Furthermore, the depth to the more resistive underlaying till and bedrock can be delimited in most areas. The 3D resistivity model derived from the ATEM data was integrated with other geoscientific data such as; geotechnical drillings, information from water wells and surficial deposits maps using 3D modeling software (Geoscene 3D from I-GIS). Based on the modelling results, the area was divided into six different classes based on the soil stratigraphy. The current method of analysis uses detailed geotechnical investigations performed in one location to ground truth the interpretation of geophysical data over a broad area. With the new results based on the ATEM data, the planning of new geotechnical drillings can be better focused on more poorly-understood areas. Furthermore, the number of geotechnical field investigations can be reduced.

Sound velocity characteristics of unconsolidated sediment based on high-resolution sub-bottom profiles in Jinzhou Bay, Bohai Sea of China

Accurate inversion of sound velocity in a Holocene stratum and a Quaternary stratum was achieved based on rich high-resolution sub-bottom profiles and boreholes in the Jinzhou Bay, Bohai Sea of China. The average value of the sound velocity is 1540.2 m/s in the Holocene stratum and 1764.7 m/s in the Quaternary stratum. The fitting analysis shows that there is an obvious positive linear correlation between the sound velocity and the burial depth of the stratum, with a gradient of 4.5 s−1. The method involving the solution of over-determined equations was innovatively put forward to explore the sound velocity characteristics of different types of sediments. The eigenvalues of the sound velocities of seven types of sediments and weathered rock in the study area are solved: the sound velocities of mud, muddy sand, muddy silty clay, muddy clay, silty clay, clay, silty sand, and strongly weathered rock are 1513.7 m/s, 1484.3 m/s, 1532.0 m/s, 1511.3 m/s, 1693.9 m/s, 1602.7 m/s, 1599.4 m/s, and 2137.7 m/s, respectively. And statistical analysis shows that the sound velocity of the sediment in the study area has obvious quadratic correlations with the void ratio and compressibility.

Modelling the transport of sediment discharged by Colombian rivers to the southern Caribbean Sea

The three-dimensional transport of sediments released by the main rivers in the Colombian Caribbean basin is investigated using numerical model simulations. Different types of sediments (fine sands, very fine sands and coarse silts) were tracked by implementing SedimentDrift software, a subclass of the OpenDrift open-source trajectory framework. The simulations were forced with climatological winds from ERA-5 and currents from the Copernicus Marine Environment Monitoring Service (CMEMS). In situ measurements from the area were utilised in the evaluation of the forcing fields. The diagnostic analysis of ERA-5 and CMEMS at the evaluated stations in the Colombian basin led to the conclusion that these datasets are reliable; hence, they can be used for several oceanographic and coastal engineering studies. The sediment transport of non-cohesive particles at each river mouth is subject to the variability of local hydrodynamics, morphological features and the grain size, which determines the settling velocities. These factors were considered and evaluated in detail. Given the lack of available in situ information, the performance of the Lagrangian model is evaluated by comparing the resulting simulations with previous studies reported in the area for river plume dynamics. However, this study presents an initial analysis of the pathways that sediments of different sizes follow, from the river mouth to the seafloor. This approach is convenient given that the Colombian rivers deliver large amounts of sediment of various grain sizes, there are insufficient in situ data to assess the seasonal cycle of sediment transport and many aspects of the sediment dynamics are not fully resolved. The resulting simulations provide evidence of the importance of high-resolution ocean current data, given that this is the main factor determining the trajectories and dispersion patterns at seasonal scales.