Bottom Sediment Samples Research Articles

Bottom Sediment Characteristics of a Tropical Lake: Lake Tana, Ethiopia

Sediment concentration of rivers in developing countries has been increasing greatly over the last 50 years due to the conversion of forest to continuously cultivated land with the increasing population. Few studies have addressed its effect on sedimentation and water quality of the lakes by analyzing bottom sediment characteristics. In this study, the objective was to investigate the spatial distribution (and their interrelationships) of the bottom sediment characteristics in the largest lake in Ethiopia, Lake Tana where water hyacinths have been spreading rapidly during the last decade. Sediment samples were collected from the lake bottom at 60 locations and analyzed for texture, organic matter, total nitrogen, and available phosphorus. Bottom sediment samples had a median of 75% clay, 13% silt, and 9% sand. Clay was greatest in the northwestern part and smallest in the areas near the major rivers entering or exiting the lake. Clay percentage and lake depth were strongly correlated. The mean organic matter content of bottom sediment was 16 g kg−1, total nitrogen 0.8 g kg−1, and Olsen available phosphorus 19 mg kg−1. Phosphorus concentrations peaked where water hyacinths were found in the northeastern part of the lake. This study will serve as a baseline for future water quality and sedimentation changes in Lake Tana. In particular, it might aid in explaining the spread of the water hyacinths.

Distribution and metal contamination in core sediments from the North Al-Wajh area, Red Sea, Saudi Arabia

Forty-one bottom sediment samples were collected from three cores at the mouth of Wadi Haramel, Wadi Antar, Wadi Dumaygh, north of Al-Wajh, Red Sea, Saudi Arabia, to evaluate the levels of heavy metal contamination, using the enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (Cf), soil pollution index (SPI), and multivariate statistical analysis (hierarchical cluster analysis and principal component analysis). Fe, Al, Pb, Mn, Cu, Ni, Co, Cd, Sr, V, Hg, and Total Organic Matter (TOM%) were quantified by Atomic Absorption Spectrophotometer. The vertical distribution of the heavy metals concentrations increased upwards indicating high heavy metals input. The results of enrichment factor and soil pollution index calculations indicate a strong anthropogenic supply of Cd and Sr (SPI = 1.10, 2.70, EF = 18.25, 17.99 respectively) while Cu and Ni show moderate anthropogenic input from urban, industrial activities and some new projects in the northern coast of Saudi Arabia.

Development and Efficiency Assessment of New Methods on Rapid Assessment of Toxicity in Environmental Monitoring

The transformation of hazardous pollutants in the environment usually results in formation of hard-to-identify compounds that may have a significant impact on ecosystems. They are difficult to identify by conventional methods of quantitative chemical analysis, but their detrimental effects can be detected by biological methods. The goal of this study was to develop novel methodological approaches to the express assessment of the state of the environment as well as toxicity of its components in the process of biological monitoring at hazardous industrial facilities. The article presents the results of comprehensive toxicity assessment of environmental objects using originally developed system of express methods. The objects of research were water fleas (Daphnia magna Straus and Ceriodaphnia affinis Lilljeborg), infusoria (Paramecium caudatum), preparation of lyophilized fluorescent bacteria based on recombinant Escherichia coli strain M-17 (Ecolum), algae (Chlorella vulgaris Beijer, Scenedesmus quadricauda (Turp.) Breb.), and mammalian gonads. The original methods for determining toxicity by changing the motor activity of water fleas at elevated temperatures of the studied environment are described. The description of the following original utility models is presented: “Method of bioassay for water samples and device for its implementation”, “Device for express assessment of natural environment quality” and “Device for comprehensive assessment of natural environment quality”, confirmed by the patents of the Russian Federation. Their use may significantly reduce the cost of ecotoxicological studies in terms of time and money expenditures. The effectiveness of the system of express methods was established during a biological monitoring of a sanitary protection zone of the Balakovo NPP. Toxicity of the samples of bottom sediments, soil, as well as water samples from the cooler pond and the adjacent water area of the Saratov reservoir were identified. The bioassay results were matched by both conventional methods’ results and originally developed system of express methods.

Transformation of metals migration and biogeochemical cycling under the influence of copper mining production (the Southern Urals)

This study aims to estimate the migration and accumulation of metals (Cu, Zn, Fe, Mn, Ni, Pb, Cd, Co, Cr, Zr, Ba, and Sc) in terrestrial and aquatic landscapes. The research is based on the results of a long-term study (1998–2018) in one of the copper mining centers in Russia in the vicinity of Sibay City in the Southern Urals. The metal contents in samples of water, bottom sediments, soils, plant shoots (total aboveground phytomass samples, agrobotanical group samples, and shoots of indicator terrestrial and aquatic species), and fish muscles are measured. It is found that within natural geochemical anomalies, the migration ability of chemical elements in the soil–plant system and general biogeochemical cycle is low because of the high soil buffer capacity (determined by the high humus content, high percentage of fine fractions in granulometric composition, and neutral pH) and the adaptation of local plants to ore mineralization. The ecosystems affected by low pollution maintain natural homeostasis, stabilize the flow of chemical elements, and preserve the natural features of geographic components. Metal pollution and the replacement of natural steppe vegetation with secondary herbaceous-ruderal communities in critical areas near copper–zinc mining objects can stimulate the mobilization and inclusion of chemical elements in biogeochemical cycling, as well as the disruption of bonds among landscape components. The water systems in catenae function as stabilizers through a system of geochemical barriers and low uptake of metals by hydrophytes, such as the common reed (Phragmites australis).

Development and Application of a Novel QuEChERS Method for Monitoring of Tributyltin and Triphenyltin in Bottom Sediments of the Odra River Estuary, North Westernmost Part of Poland.

A Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction method combined with Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) for determination of organotin compounds (OTC) has been newly developed. The novel analytical method was validated and the quality of the results was tested by the use of certificate reference material of freshwater sediment BCR 646. The method was applied in determination of OTC concentration in real samples of bottom sediments collected from the Polish part of Odra River Estuary. The samples came from locations with different anthropogenic impact. Additionally, the extraction recovery of OTC and matrix effect on MS signal response was investigated based on those real environmental samples. It was found that organic compounds and anthropogenic contaminations present in bottom sediments may affect extraction efficiency of the organotin compounds (OTC) and change the matrix effect on MS signal response. The highest concentrations of tributyltin were found in bottom sediments collected from locations in vicinity of the Szczecin harbor and shipyards. The presence of triphenyltin above limit of detection (5 ng TPhT/g of sediment) was observed only in two samples and its concentration was several times lower compared to concentration of tributyltin (from 58 ng/g to 5263 ng/g). In spite of the fact that, the application of TBT-based paints on hull of vessel entering EU ports has been banned by European Commission regulation No. 782/2003 since 2008, the OTC compounds are still present in bottom sediment and pose significant threat to the environment. This threat should be taken into account during dredging of waterways and other hydrotechnical works.

Spatial and temporal variability of metal(loid)s concentration as well as simultaneous determination of five arsenic and antimony species using HPLC-ICP-MS technique in the study of water and bottom sediments of the shallow, lowland, dam reservoir in Poland

The optimization of new methodology for simultaneous determination of arsenic [As(III), As(V)] and antimony [Sb(III), Sb(V), SbMe3] species using high-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) in water and bottom sediment samples collected from the dam Kozłowa Góra Reservoir (Poland) was studied. Samples were collected monthly from May to September 2018 in four-point (water) and fifth-point (sediment) transects. The contents of Mn, Co, Ni, Cu, Zn, As, Cr, Rb, Sr, Cd, Sb, Ba, Tl, Pb, and Sb were studied in water and bottom sediments using ICP-MS techniques. Additionally, arsenic and antimony fractions were determined in sediments with the BCR method. Pollution Load Index (PLI), Geoaccumulation Index (Igeo), LAWA classification, and Sb/As ratio indicated the presence of extreme sediment pollution for Zn, Cd, Pb, and Cr from anthropogenic sources. Research has shown that the easy-leached bottom sediment fraction contained in most cases more As(V) and Sb(V). But often Sb(V) concentration was equal as Sb(III), which can be released into the pelagic zone under favorable conditions. Even though As(V) and Sb(V) prevail in the reservoir bottom sediments, they can be transformed into As(III) and Sb(III) as a result of drastic changes in pH or redox potential. The Kozłowa Góra sediments are heavily polluted with Pb, Zn, Cd, and As, Cu, and Ni. The highest concentrations of the heavy metals were recorded in the middle of the tank and there was a small spatial variability. The migration of metals along the reservoir transect was closely related to its morphometry.

Study of Bottom Sediments of the Chiryurt Reservoir, Dagestan, Russia with a View to their Utilisation in Land Reclamation following Anthropogenic Interference

Aim. To study the physicomechanical and physicochemical properties of bottom sediments of the Chiryurt Reservoir, Kizilyurtovskiy District, Republic of Dagestan, Russia with a view to their possible utilisation as building materials for the production of certain grades of concrete and road asphalt-concrete, as well as for the preparation of soil substrate and as additives to potassium and phosphate mineral fertilizers. Material and Methods . The bottom sediments of the Chiryurt Reservoir, taken from different depths and different reservoir locations, were studied by spectrophoto-metric and granulometric methods. Results. The study identified: particle size distribution of samples of bottom sediments; humus content; soil fertility elements: potassium, nitrogen, phosphorus as well as heavy metal content. Conclusions: 1. Analysis of the bottom sediment samples indicates that the soil fertility elements potassium, nitrogen, phosphorus are not sufficient for them to be used as an independent fertilizer, although they might perhaps be used as an auxiliary additive to a principal fertilizer. The levels of toxicity of heavy metals were found to be very low - much lower than the Maximum Allowable Concentrations. 2. The sediments could be used as soils for the reclamation of land after anthropogenic interference (e.g. after a quarry has been excavated for brick production, after excavations during road construction of roads), for the modification of vertical terrain in settled areas, for landscaping, etc. 3. According to the granulometric analysis of the material composition of the samples, the bottom sediments are 85-90% composed of clay particles (thus there is no need to undertake procedures to separate out the sand fraction). 4. Since peat deposits are present in the bottom sediments of the reservoir, it makes sense to separately assess their volumes for independent development for use as fertilizer for the re-cultivation of floodplain lands.

Concentration of heavy metals and metalloids in the bottom sediments of the Vilkitsky Island’s lakes (the Kara Sea)

We performed this study in order to obtain relevant data about the actual ecological status of the lakes in remote areas of the Russian Arctic. The objective was to determine the level of technogenic pollution of bottom sediments in the lakes on the Vilkitsky island in the Kara Sea. To this end, we examined 8 of the island’s small lakes. The content of heavy metals and metalloids (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Y, Nb) in the samples of bottom sediments was determined using the method of Energy Dispersive X-ray Fluorescence (EDXRF). The total pollution value in the examined bottom sediments varied from Zc = 9.5 to Zc = 15.3. The maximum level of pollution was found in Lake 4 located in an anthropogenically disturbed area due to the levels of Cr, Co, Ni, As, Y, Nb.

Rare and Trace Elements in the Modern Bottom Sediments of the Barents Sea

The article presents a brief lithological description of modern bottom sediments collected in the Barents Sea during Cruise 67 of the R/V Akademik Mstislav Keldysh at test sites: (1) “Pechora Sea”; (2) “Western slope of the Kanin Shoal”; (3) “Central Barents Sea (Shtokman area)”; (4) “Russkaya Gavan Fjord”; (5) “Medvezhinsky Trough”; (6) area south of Spitsbergen; (7) “Kola Meridian”; (8) “Spitsbergen–Franz Josef Land Archipelago”; (9) “Cambridge Strait.” Distribution of Cr, Ni, Cu, Zn, Cd, and Pb in samples of modern bottom sediments (pelitic, aleuritic–pelitic and sandy–aleuritic–pelitic ooze) is compared with background concentrations and contents of these elements in the Post-Archean Australian Shale (PAAS). The data obtained are consistent with the notion that the distribution of heavy metals and other elements in bottom sediments is controlled primarily by the global geochemical background. Relationship of Sc, V, Cr, Ni, Y, Zr, Nb, Mo, Hf, Th, U, and REE concentrations with contents of the fine pelite (<0.001 mm) fraction and organic carbon (Corg) is considered. It was found that most of these elements are characterized by a moderate positive correlation with the fine pelite fraction in samples. Based on the coefficient of their correlation with the Corg content, the above elements can be assigned to three groups with: (1) moderate positive correlation, (2) low positive correlation, and (3) virtual absence of correlation. Distribution of element-indicators of the source rock composition (Sc, Th, Co, Cr, La, and Sm) and REE in modern bottom sediments of the Barents Sea indicates that the majority of them are geochemically mature, and they were sourced from the Kola Peninsula and Spitsbergen (?).Bottom sediments of the Cambridge Strait are represented by geochemically less mature material, which, apparently, entered the sea as a result of erosion of rocks of the Franz Josef Land Archipelago.

Heavy metals in the bottom sediments of the Tendrivska bay

The article describes several research results of geoecological direction, which included field sampling of bottom sediments, soils, coastal sediments at different sites within the territory of the Black Sea Biosphere Reserve NAS of Ukraine, in particular, the Tendrivska and Yahorlitska bays. The complex of the laboratory works included determination of chemical, microelement, particle size distribution composition of samples and study of their material characteristics on a scanning electron microscope. The study of the ecological state of the Reserve’s bottom sediments, as well as comparison of pollutant content in sediments of various parts of the protected water area was based, in particular, on determining the concentrations a few heavy metals (copper, nickel, zinc, lead, tin). The choice of research objects was determined by the peculiarities of the organization of agricultural activities within the arable lands bordering the boundaries of this reserve. The results obtained showed a significant impact of the geomorphological structure of the area and hydrodynamic characteristics of certain areas of the water area within it on the distribution of the material component of bottom sediments. The mineral and particle-size composition of bottom sediments should be considered the main factor in the uneven distribution of microelement concentrations, which in turn is determined by the location of zones of coastal erosion and sediment accumulation. Insignificant relative excesses of the copper content in the surface layer of the bottom sediments of the water area, fixed in the northern part of the Tendrivska Bay, can be connected with the discharge of fresh water from the network of canals, which is part of the agro complexes for rice cultivation, as well as “tailings” of water from the water supply systems of the Krasnoznam’yanska irrigation system. Studies have also shown that the content of most heavy metals in the upper layer of bottom sediments in the Black Sea Biosphere Reserve is lower than the average figures for modern Black Sea bottom sediments presented in literature sources.

Diatoms as biomarker in changes of the Lake Zapovednoye state (Evenkia, Russia)

As part of a multidisciplinary study aimed at paleoclimatic reconstruction in March 2015 and June 2018 cores of bottom sediments of Lake Zapovednoye (Evenkia, Russia) were obtained. Analysis of samples of bottom sediments by the diatoms composition - one of the main biomarkers or proxy of changes in a state of the lake, showed that, in addition to short-term changes, long-term changes in the species composition of diatoms at least twice occurred. It may be associated with changes in water inflow and level of Lake Zapovednoye. It is most likely these events could occur due to climate change.

Geochemical studies of surface bottom sediments and soils of small watercourses

Analytical data on samples of bottom sediments of the Novaya river watercourse made it possible to identify areas of pollution, sources of pollution and determine the nature of the influence of the anthropogenic factor on the state of the river. It was found that bottom sediments are divided into slightly polluted, moderately polluted, and dangerously polluted. Soils on the total indicator of pollution belong to the permissible category. The list of defined indicators includes: hydrogen index (pH), total metal content (cadmium, copper, lead, mercury, nickel, zinc), arsenic, petroleum products, benz(a)pyrene, ammonium nitrogen, phosphate ion, organic matter. Based on the results of the interpretation of the laboratory data, it was found that in accordance with the Regional standard, the precipitation the majority of samples are slightly polluted; at some samples, are moderately polluted; at a quarter of samples are dangerously polluted.

Experience of Application of Hydro/acustic Profilograph for Estimation of Bottom Sediments of Large Reservoirs (the Argazin Reservoir as a Study Case)

The work considers application of the method of sub-bottom profiling of bottom sediments of a large reservoir with the use of modern instruments. Such studies are effective in assessing the volume of bottom sediments and the nature of their occurrence. The use of acoustic profilographers in combination with control sampling of bottom sediments without disruption of their vertical structure (column) enables to obtain at minimum costs the necessary set of initial information for planning of further measures.

“Sea Diamond” Wreckage—12 Years after the Fatal Maritime Accident, the Vessel Remains an Environmental Concern

The present study was accomplished to fulfill the requisition of the Appeal Court of the city of Piraeus. According to the Court’s Decision, an environmental impact assessment should be made for the ongoing condition of the wreckage along with a study of the corrosion evolution process and a provision of the hull’s endurance should be estimated. The wreckage was sounded out, surveyed thoroughly by means of an ROV device immersed ad hoc. Extended videos and photo shots were taken and the exact position of the vessel depicted analytically on a sea contour depth chart. Hull corrosion, sea column & sea bottom sediment sampling carried out for the analysis of hazardous compounds PAHs, TPHs, PCBs and heavy metals in June and July of 2019. Fish and oyster tissues were analyzed in the lab for heavy metals’ detection. A great concern was given for (Cd) & (Pb) concentration in sea column nearby wreck. Α report of about 1000 pages of the methodology & results was handed over to the Appeal Court of which merely partial significant segments are presented herein. The technical report denotes that PCBs, PAHs, TPHs sea bed & sea column measurements nearby the wreck were, in general, low or below detectable level. As regards heavy metals concentration level in aquatic sea column, the results indicate that only in certain locations heavy metals i.e. (Pb) and (Ni) were measured above the detection limit and classified according to contamination factors from moderate to high contamination level and might attribute to the presence of the wreck in the close area. Contamination factor indices consolidate the approach that the hull presence in the bottom contributes to the environmental degradation of the “caldera” ecosystem. The vessel’s hull is expected to be wiped out in almost four hundred years period according to the applied corrosion model.

Літологічна та мікропалеонтологічна характеристика донних відкладів Stella Creek (західний шельф Антарктичного півострова)

Main objective of the study – comprehensive research of material, particle size, mineral, chemical and micropaleontological composition, together with analysis of depositional environment of the Stella Creek bottom sediments. Material – bottom sediments samples of the Stella Creek, a small inter-island section, which is the terminal drainage basin of the Galindez and Winter islands from the water area adjacent to the Ukrainian Antarctic Akademik Vernadsky station were studied. Methods: particle size, mineral and chemical composition analyses were carried out using a scanning electron microscope with microprobe analysis; ultrasonic disintegration of rocks was used to remove paleontological remains; photographing and determining the taxonomic composition of microalgae were performed with light and electron microscopes. Results. The mineral composition of the bottom sediments is represented by quartz, plagioclase, chlorite (iron-containing clinochlore), illite, opal (biogenic), amphibole (hornblende), siderite. Among terrigenous minerals of heavy fraction, ilmenite (with manganese), zircon, and monazite are determined. Authigenic minerals are represented by bacteriomorphic framboidal clusters of iron sulfide microcrystals, calcium sulfate, and barite. Among the organic residues in sediments, diatom frustules predominate. Diatoms have three intervals, which coincide with the layers defined by particles size distribution analysis. Conclusions. Bottom sediments were formed in Late Quaternary time in cold-sea conditions and low hydrodynamic activity with local conditions favorable for early diagenetic biogenic sulfate reduction.

РАСПРЕДЕЛЕНИЕ МЕТАЛЛОВ (Cu, Zn, Ni, Co, Cr, Pb, Fe И Mn) В ПОВЕРХНОСТНОМ СЛОЕ ДОННЫХ ОСАДКОВ СРЕДНЕГО И ЮЖНОГО КАСПИЯ

Atomic absorption determinations of a group of heavy metals (Cu, Zn, Ni, Co, Cr, Pb, Fe, Mn) in 190 samples of surface bottom sediments of the Middle and Southern Caspian Sea that were sampled by crab in middle of XX century (the collection of G.N. Baturin) and in 30 samples of recent sampling by grab also (2012–2015) were carried out. The aim of the investigations was to construct the schematic maps of heavy metal distribution in bottom sediments of both parts of the Caspian Sea on the materials of a half of century prescription that may serve as a base for comparison with the data of recent researches in frameworks of the program “The Caspian Sea System” under leadership of academic A.P.Lisitzin from 2012 till present time. The comparison between chemical composition of old and new sediment samples was realized, their similarities and divergences were revealed and probable reasons of divergences were presented. The maps of distribution of several metals (Fe, Mn, Co, Cr) are submitted together with necessary for interpretation maps of CaCO3, Corg and some other. It was shown that the structure of maps for all metals investigated was very similar because all these metals had concern to the group of iron.

Bacterial benthic community composition in the Baltic Sea in selected chemical and conventional weapons dump sites affected by munition corrosion

Microflora of marine waters and sediments play a significant role not only in the course of natural changes and circulation of elements in this environment, but can also be a decisive factor during erosion processes of various submerged objects or structures such as wrecks, sunken objects, pipelines, etc. The bacteria which have a significant influence on corrosion processes include aerobic and anaerobic sulfur bacteria as well as iron bacteria. Particular importance is attributed to sulfide reducing bacteria (SRB) which occur in waters, bottom sediments, creating biofilms on metal surface, and may start a process known as microbial induced corrosion (MIC). The occurrence of these bacteria and their populations indicates potential and intensification of corrosion processes.The aim of the study was to determine the number of microorganisms from various groups in the Baltic Sea sediments, especially those that are active in biological corrosion processes. This data can be used for a study comprehensive of corrosive processes in the marine environment, and as a result, to carry out a real assessment of the risks arising from the release of toxic substances into the environment from conventional and chemical weapons lying on the bottom caused by progressing corrosive processes, including biological corrosion.The article presents the results of research on the presence and accounts of microorganisms in bottom sediment samples taken from the dump sites of chemical and conventional ammunition in the Baltic Sea. Particular attention was paid to halophilic and halotolerant bacteria due to their significant contribution to both corrosion and decomposition processes of CWA and explosives, particularly in the saltwater environment.There were high and quite similar numbers of mesophilic, psychrophilic and halophilic bacteria in the studied samples, while significantly smaller numbers of anaerobic bacteria. The amount of mesophilic bacteria ranges from 6.42*103 to 2.85*107, on average 4.5*106 in 1 g DM, psychrophilic from 5.73*103 in1g DM to 4.11*107 in 1 g DM, on average 6.44*106 in 1 g DM, whereas for halophylic from 4.09*102 to 5.60*107, on average 5.83*106 in1g DM. The numbers of fungi were at a much lower level and ranged from 4.65*101 to 8.08*102, on average 2.63*102 in 1 g DM. mesophilic fungi and from 0 to 1.60*103, on average 3.58*102 in 1 g DM for psychrophilic fungi. The presence of sulfide reducing bacteria (SRB) was also detected in large populations, especially when they were isolated by means of the medium prepared with seawater (from 9.72 to 5.36*102, on average 2.52*102 in 1 g DM), which indicates their adaptation to the saline environment and promotes of biological anaerobic processes, including corrosive processes. No significant amounts of iron bacteria were found, probably due to the small amount of oxygen in the sampling area. The small number of iron bacteria indicates that primarily anaerobic sulfide reducing bacteria (SRB) have the major part in the microbial corrosion phenomena.

On the determination of transportation, range and distribution characteristics of Uranium-238, Thorium-232 and Potassium-40: a critical review

This research presents the theoretical and experimental results in real time and suggests spatial models after reviewing the spatial modelling method, which has an important place in earth sciences. It also reveals the geological and geophysical descriptions of mathematical models, calculations and the ease with which one can interpret the results. U-238, Th-232 and K-40 concentrations are determined in water and bottom sediment samples taken from Keban Lake as a sample study area. The point cumulative semi-variogram (PCSV) method application helps to identify the range, distribution and transport of radionuclide at each sampling station. The well-known semi-variogram (SV) is used in many scientific studies. In this study, the SV methodologies are reviewed leading to the application of the PCSV method for the real-time data. The radionuclide distributions in the lake are revealed by means of ten regional models. In addition, iso-radioactivity maps are obtained to provide an overview of the medium radioactivity with characterizations of the transport, range and distribution of the three radionuclides in the lake.

Microplastics in Cultured Oyster, Crassostrea madrasensis for Human Consumption

Microplastics (MP) are widely distributed in the marine environment, and are generally defined as plastic particles lesser than 5 mm in size. These MPs can be ingested by various aquatic organisms, including oysters and subsequently transferred to the higher trophic levels. The primary objective of this study was to determine the quantity and types of MPs in cultured oyster (Crassostrea madrasensis) and, in surface-water and sediment samples from three culture sites located in Kalpitiya lagoon. This study extensively paid attention to the effect of depuration process on removing microplastics from oysters. Six out of twelveoyster samples from each site were subjected to a sixteen-hour depuration period. Both depurated and non-depurated oysters were acid digested and filtered to extract MP particles. Sediment samples from the culture sites were density separated by air venting through a super saturated calcium chloride solution. Water samples were filtered over a 63 μm mesh and treated with 30% H2O2. Extracted MP particles from oysters, sediment and surface-water were observed under a stereo microscope and size eligible MP particles were confirmed using FT-IR spectrometer. Microplastic concentration of non-depurated oysters was 4.0±2.4 particles per individual oyster. In depurated oysters average MP concentration was 1.1±0.6 MP particles per individual oyster. Bottom sediment samples from oyster culture sites had the highest concentrations of microplastics, which was an average of 24.5±4.2 MP particles per 1 kg of sediment dry weight and water samples with an average concentration of 7.4±1.3 MP particles per 1 L of lagoon water. Among observed MP types, fibers (74.3%) were the most common typeof MPs. Depuration of oysters successfully removed 72.5%. of MPs. This study reveals that, an average portion of non-depurated oysters (250 g wet weight or 12 oysters) contains approximately 50 MP particles to which the consumer will be exposed. Continuation of investigations on microplastics in different edible aquatic speciesare required to have a comprehensive understanding of this potential human health risk.Keywords: Microplastics, Crassostrea madrasensis, Oysters, Depuration, Kalpitiya lagoon

Characteristics of Sediments in a Changing Environmental Conditions in Vistula Lagoon (Poland)

The Vistula Lagoon has been evolving since its formation in the late Atlantic period. At the beginning, the changes were mainly driven by the stabilization of the Baltic Sea level, and the development of hydrographic network. Later on, anthropogenic activities have become an important factor. Hydrotechnical works conducted at the turn of the 20th century, aimed at regulating the outflow of the Vistula River waters, have significantly limited the riverine input into the lagoon. In the past, the Vistula Lagoon contained freshwater and was constantly filing with sediments that made the basin shallow. With time, the lagoon has filled with brackish water, while its area became subjected to strong interactions between the driving forces of marine and terrestrial origin. As a result, the regime of sedimentation processes in the lagoon have been changed. The interpretation of sedimentation conditions for clastic sediments was based on the analysis of grain-size parameters that had been determined on the samples of bottom sediments and suspension collected in November 2016. The obtained results were compared to the pertinent data on bottom sediments collected by the Polish Geological Institute National Research Institute in 1994. Significant contrasts in particle size distributions were found. Also, the conducted study allowed the determination of underlying causes of these changes. Due to the shallow depth of the Vistula Lagoon, the sedimentation processes in this basin are significantly influenced by resuspension phenomenon. Resuspension is responsible for the differentiation and redistribution of sediment that originates from various sources, on the bottom of the basin. The process takes place in shallower areas, but this study indicates that its effectiveness increases in the deeper areas of the lagoon, which manifests itself in the replacement of clayey silt with silt. In connection with the plans of the Polish side of the cross-cutting of the Vistula Spit, the sedimentation conditions of Vistula Lagoon will be changed.