Beach Sediments Research Articles

Influence of windward versus leeward settings on microplastic distribution in beach sediments of Kish Island, Gulf region

Two beaches from Kish Island were compared with respect to their microplastics (MPs) load, by combining well established sedimentological methods with microplastic (MP) extraction by an oxidative procedure and subsequent density separation using ZnCl 2 solution. One beach (Site A) is located upwind experiencing low tourist pressure, while the other one (Site B) is a highly frequented tourist beach which is located downwind. Generally, the concentrations vary from 530.00 ± 14.14 to 580.00 ± 84.85 particles/kg, and thus are in the range of values reported from elsewhere, but on the higher side. The quantity of MPs was not substantially different between the two areas; particle sizes are larger upwind. Overall the extracted MPs are secondary particles (65.5%), dominated by fragments, followed in abundance by fibers (23.5%). Granules (6%) and films (5%) were less commonly observed. This distribution is in contrary to reports of beaches elsewhere where fibers are by far dominant. The present study points to dominant sources of MPs outside the island, being transported to Kish Island by marine pathways, where further wind-driven transport leads to an absence of small synthetic fibers in the windward setting (Site A). The present study provides an initial evaluation of MP pollution in beach sediments of Kish Island, and in the region of the eastern Gulf.

Temporal trends in anthropogenic marine macro-debris and micro-debris accumulation on the California Channel Islands

Accumulation of anthropogenic marine debris on shorelines is an issue of global concern, even impacting areas that are remote, uninhabited, or have protected area status. On islands in Southern California, USA, within the boundaries of a National Park and National Marine Sanctuary, we collected macro-debris on beaches and assessed micro-debris in beach sediment seasonally between 2016-2020. Macro-debris (>5mm) was collected from seven beaches on two California Channel Islands and two sites on the mainland. We assessed both the number of items collected and total mass of debris. Composition of macro-debris items was dominated by plastics, particularly fragmented hard and foamed plastics and food packaging. A substantial quantity of lost or discarded fishing gear was collected, with the most fishery-related debris found at sites with historically highest spiny lobster fishing effort. The initial density of debris items ranged from 0.01-0.13 items m-2 and the initial density of debris mass ranged from 0.01-0.02 kg m-2. Mean accumulation rates of debris were strongly site-dependent and ranged from 0.03-0.34 items m-2 yr-1 and 0.01-0.05 kg m-2 yr-1, and tended to be highest in the fall and winter months. Anthropogenic micro-debris (<5mm) was found in beach sediment at all sites. Micro-debris had no statistically significant relationship with accumulation rates of total macro-debris items, or plastic macro-debris items. There were, however, statistically significant relationships between accumulation rates of total macro-debris mass and plastic macro-debris mass. We compared the rate of accumulation of fishing debris items and mass during the lobster season (October-March) for the years 2017 to 2020. The accumulation of fishery-related debris differed significantly among sites, with apparent declines over time, likely reflecting declining effort in the fishery and trap-limit regulations implemented in the 2017-2018 season. Our assessment of marine debris accumulation on California Channel Island beaches has provided detailed information on the types of debris and patterns of accumulation. Unfortunately, remoteness from direct human impact and protected-area status does not protect these habitats against the onslaught of marine litter. Assessments of marine debris are critical to identify sources, to inform policy and to support efforts to reduce the impact of marine litter on vital coastal ecosystems.

Mineralogy and Geochemistry of beach sediments associated with the Precambrian crystalline rocks (Vijayan Complex) of Sri Lanka; perspective for heavy minerals

Southeastern landmass of Sri Lanka is laid on the Vijayan Complex (VC) rocks, a Precambrian basement characterized with specific geological features since the mineralized contact zone of the Highland–Vijayan boundary is nearby. However, the coastal sedimentation of such a basement is rarely interpreted. Hence, the mineralogy and geochemistry of surface sediments exposed along 45 km long southeast (SE) coast were studied to find the compositions and to interpret the terrestrial compart. Studied beach faces expose as sandy siliciclastic sediments with scatter depositions of black and red coloured heavy sediments, as 10–15 cm beds, within 1–3 km from deltaic environments. X-ray diffraction analysis of such heavy placers indicate the presence of predominant ilmenite, almandine garnet, zircon, monazite and ferrihydride. The sediments from other areas are rich in lighter minerals of quartz, albite and magnesium-calcite representing the average beach sediment mineralogy of SE coast. Upper continental crust normalized X-ray fluorescence data show an enriched tendency of Zr (9.8) > V > Nb > Th > TiO2 (6.2) > Cr (2.5) > MnO > Fe2O3 > As > Y > Zn and depleted tendency of Pb (0.8) > CaO >P2O5 > Sr > Sc > Cu (0.1) indicating the leachability of depleted elements and strong recycling processes of High Field Strength Elements (HFSE). Hierarchical cluster analysis and Pearson correlation matrixes indicate the presence of four geochemically related sample clusters. These analyses further showed that the cluster 1 relates to heavy sediments deposits with higher terrigenous influences while cluster 4 relates to siliciclastic sediments with higher marine influences. Hence, geochemical anomalies of cluster 1 to 4 show decreasing abundances for HFSE and opposite tendencies for CaO, Sr, I, Br, and F confirming the mineralogical results. Higher terrigenous influenced sediment samples evident for the presence of solid phases of titanium carriers (As–V–TiO2), phosphorus–HFSE carriers (Pb–Th–P2O5–Y–Cl–Nb–Zr), authigenic carbonates (Sr–Br–CaO) and Fe–Mn coatings (Zn–Cr–MnO–Fe2O3–Cu). Compatibility variable ratios of Th/Sc, Zr/Sc, TiO2/Zr, Cr/Th and V/Th respectively show 15.16, 364.38, 20.85, 2.95 and 9.73 values for these coastal sediments. Based on the published international and VC average lithological data, the present study concluded that the primary sources for the sedimentation have felsic signatures showing relations to granitic gneisses and granitic intrusive rocks of the VC. Apart from the terrestrial provenances, the coastal area has been affected by lower secondary influences of anthropogenic, marine inorganic and organic matters.

IChip-Inspired Isolation, Bioactivities and Dereplication of Actinomycetota from Portuguese Beach Sediments.

Oceans hold a stunning number of unique microorganisms, which remain unstudied by culture-dependent methods due to failures in establishing the right conditions for these organisms to grow. In this work, an isolation effort inspired by the iChip was performed using marine sediments from Memoria beach, Portugal. The isolates obtained were identified by 16S rRNA gene analysis, fingerprinted using BOX-PCR and ERIC-PCR, searched for the putative presence of secondary metabolism genes associated with polyketide synthase I (PKS-I) and non-ribosomal peptide synthetases (NRPS), screened for antimicrobial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, and had bioactive extracts dereplicated by LC/HRMS. Of the 158 isolated strains, 96 were affiliated with the phylum Actinomycetota, PKS-I and NRPS genes were detected in 53 actinomycetotal strains, and 11 proved to be bioactive (10 against E. coli, 1 against S. aureus and 1 against both pathogens). Further bioactivities were explored using an “one strain many compounds” approach, with six strains showing continued bioactivity and one showing a novel one. Extract dereplication showed the presence of several known bioactive molecules and potential novel ones in the bioactive extracts. These results indicate the use of the bacteria isolated here as sources of new bioactive natural products.

Development and testing of a SOSM approach to examine the natural attenuation of oil spillage on shorelines

Understanding the fate and behavior of spilled oil on the shoreline is crucial for helping decision-makers make trade-offs between natural attenuation and shoreline treatments. In this study, primary processes of oil attenuation and translocation on the shoreline, including penetration, washout, and biodegradation, have been considered to develop a numerical model, Shoreline Oil Spill Model (SOSM), for predicting the fate of spilled oil in various shoreline geological compartments. A holistic system design is employed to develop a user-friendly graphical interface system for SOSM. Global and local sensitivity analyses are used to examine the importance of the input factors on different outputs in SOSM. The results of the sensitivity analysis indicate that the input of oil spill mass correlates positively with the oil retention and surface and subsurface oil mass, while the oil concentration and penetration depth are sensitive to the grain size of the beach sediment. Subsequently, the SOSM is tested to hindcast the fate of stranded oil from the Exxon Valdez oil spill. Reasonable validation results have been obtained for the study site. It confirms the utility of the SOSM to examine and predict the level of shoreline oil contamination in the field following accidental spill events.

Ancylobacter gelatini sp. nov., isolated from beach sediment of Zhairuo Island, China.

A Gram-negative, aerobic, non-motile, oxidase-positive, catalase-positive, methyl red-positive, and lipase-negative bacterium, designated A5.8T, was isolated from beach sediment of Zhairuo Island located in the East China Sea. Growth occurred at 10-40°C (optimum, 30°C), pH 5.5-9.5 (optimum, 7.5), and 0-2% NaCl (optimum, 1.5%). Based on 16S rRNA gene sequence analysis, strain A5.8T belongs to the genus Ancylobacter, sharing the highest similarity with Ancylobacter aquaticus JCM 20518T (98.0%). Its polar lipids mainly consist of phosphatidylethanolamine (PE) and phosphatidylcholine (PC). The predominant fatty acids are summed feature 8 (C18:1ω7c and/or C18:1ω6c, 91.0%), and the major respiratory quinone is Q-10. The DNA G + C content is 67.2mol%. Based on above analysis, as well as digital DNA-DNA hybridization (22.5-22.9%) and average nucleotide identity (83.0-83.6%) of strain A5.8T with reference type strains of the genus Ancylobacter, strain A5.8T was suggested to represent a novel species of the genus Ancylobacter, for which the name Ancylobacter gelatini sp. nov. is proposed. The type strain is A5.8T (= MCCC 1K07167T = LMG 32566T).

Sand supplementation favors tropical seagrass Thalassia hemprichii in eutrophic bay: implications for seagrass restoration and management

BackgroundSediment is crucial for the unique marine angiosperm seagrass growth and successful restoration. Sediment modification induced by eutrophication also exacerbates seagrass decline and reduces plantation and transplantation survival rates. However, we lack information regarding the influence of sediment on seagrass photosynthesis and the metabolics, especially regarding the key secondary metabolic flavone. Meanwhile, sulfation of flavonoids in seagrass may mitigate sulfide intrusion, but limited evidence is available.ResultsWe cultured the seagrass Thalassia hemprichii under controlled laboratory conditions in three sediment types by combining different ratios of in-situ eutrophic sediment and coarse beach sand. We examined the effects of beach sand mixed with natural eutrophic sediments on seagrass using photobiology, metabolomics and isotope labelling approaches. Seagrasses grown in eutrophic sediments mixed with beach sand exhibited significantly higher photosynthetic activity, with a larger relative maximum electron transport rate and minimum saturating irradiance. Simultaneously, considerably greater belowground amino acid and flavonoid concentrations were observed to counteract anoxic stress in eutrophic sediments without mixed beach sand. This led to more positive belowground stable sulfur isotope ratios in eutrophic sediments with a lower Eh.ConclusionsThese results indicated that coarse beach sand indirectly enhanced photosynthesis in T. hemprichii by reducing sulfide intrusion with lower amino acid and flavonoid concentrations. This could explain why T. hemprichii often grows better on coarse sand substrates. Therefore, it is imperative to consider adding beach sand to sediments to improve the environmental conditions for seagrass and restore seagrass in eutrophic ecosystems.

Occurrence, distribution and sources of microplastics in beach sediments of Miri coast, NW Borneo

Microplastics (MPs) pollution has gained a lot of global interests due to its toxicity to the surrounding ecosystems. The aim of this study is to identify the abundances, physical characteristics, polymer type and elemental composition of MPs in beach sediments of Miri coast, located in Sarawak State, East Malaysia. A total of 1553 particles from 24 sediment samples, collected from eight different beaches along Miri coastline were identified. MPs from the sediments were extracted using density separation method and analyzed through stereoscopic microscope, ATR-FTIR and SEM-EDX. MPs were present most abundant in Lutong Beach, which is the hotspot for the recreational activities. Fragments were identified as the highest abundance type of MPs, followed by fiber, foam and pellet. MPs of size of <1 mm were predominantly present in the samples. Varieties of colors were distinguished in which transparent or no color MPs were the highest quantity studied in the samples. Polymers identified were mainly polyethylene (PE), polyester (PET), polystyrene (PS) and polypropylene (PP), derived from primary and secondary MPs. Carbon and oxygen were dominant and have the highest concentration identified with other elements such as Ca, Al, Ti and Cl. The primary use of these elements as additives are associated with the manufacturing process as they are used to enhance the quality during plastic production. The outcome of this study is to be the first report to identify and characterize the MPs in beach sediments of Miri coast. The occurrence of MPs in Miri beaches may negatively impact marine organisms as this affects their food chain. As consumers, humans are most likely to be affected by the presence of MPs due to their consumption of marine animals, particularly fish present in this region.

First evidence of plastic pollution in beach sediments of the Skikda coast (northeast of Algeria)

This study is the first attempt to provide original data on plastics debris occurrence in beach sediments of the Gulf of Skikda in Algeria (southwestern Mediterranean). Sediment samples from seven beaches were collected to extract, quantify and characterize mesoplastics and microplastics. Particles were classified by size into mesoplastics (5–25 mm) and large microplastics (1–5 mm). Overall, microplastics were the most abundant size fraction in terms of number of items. The average mass of mesoplastics was twice that of microplastics, revealing a notable reservoir of plastics that is scarcely ever reported in the literature. The predominant types were fragments and pellets, white/transparent in color. The average concentrations of total plastic were 1067.19 ± 625.62 items/m2, 106.98 ± 62.39 items/kg, and 50.65 ± 9.82 g/m2, showing variability between beaches and within sampling sites. Thus, the Skikda coast has high levels of pollution compared to other areas of the Mediterranean Sea.

A baseline study of meso and microplastic predominance in pristine beach sediment of the Indian tropical island ecosystem

The global presence and prevalence of microplastic have moved microplastic from an emerging pollutant to a persistent contaminant. Microplastic prevails in almost all spheres of the environment viz. terrestrial, marine and atmosphere the globe abundantly. The prevalence and toxic effects on marine organisms have been studied around the world but the studies are limited to the coastal regime of the Andaman and Nicobar Islands (ANI). This study aims to record microplastic prevalence on the tourist beaches of Port Blair, ANI. Three coastal stations namely Cove beach, Quarry beach and Wandoor beach were examined in detail in this regard. Microplastics in the form of lines, fragments, pellets, foams and fibres were found at the sampled sites. Wandoor beach recorded the highest microplastic particles ranging from 105–475 particles kg−1 of sediment with the mean value of 249.82 ± 105.78 particles kg−1. Quarry beach near the municipal waste dumpsite showed the lowest of 72.5–222.5 particles kg−1 with a mean value of 135.625 ± 62.83 particles kg−1. The polymeric forms found were High-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP) and polyethylene terephthalate (PET). This study revealed microplastic input from municipal dump waste near the beach. Fourier Transform Infrared spectroscopy (FTIR) revealed the presence of a new type of polymer namely plasta zinc in the beach sediment, which possibly could be a nanoplastic. Its presence reveals the biological enzymatic degradation of microplastic occurring in the marine environment. Further investigations are required to determine the factors influencing the prevalence of microplastic, its toxic effects on marine habitat and microplastic degradation mechanisms in the marine habitat.

Microplastic pollution at Qilianyu, the largest green sea turtle nesting grounds in the northern South China Sea.

Microplastics, new persistent pollutants, have recently attracted considerable attention. When present in beach sediments, microplastics may adversely affect the nesting and hatching of sea turtles on beaches. In this study, we investigate microplastic pollution at Qilianyu (northeastern Xisha Islands), the largest known nesting ground for green sea turtles (Chelonia mydas) in China. We found that the average abundance of microplastics in the beach surface sediments was 338.44 ± 315.69 thousand pieces·m−3 or 1,353.78 ± 853.68 pieces·m−2, with foam and fragments as the main microplastic type identified. The microplastic particles were categorised as small and were predominantly within the 0.05–1 mm size category. Most microplastic particles were white (71.31%). Polystyrene and polyethylene were found to be the most common forms of plastic present. Microplastic pollution was not only observed on the beach surface but also at the bottom of nests approximately 60 cm may be harmful to the incubation of sea turtle eggs. We suggest removing plastic litter, especially small pieces of plastic, on beaches to reduce the threat of microplastic pollution to marine life, including sea turtles. Furthermore, the foam used in aquaculture should be recovered and replaced before it becomes fragmented due to age. In addition, regional cooperation between stakeholders in the South China Sea should be strengthened to collectively promote the reduction and cleanup of marine litter.

Recent Transport and Deposition of Littoral Sand Across the Inner-Shelf of Central Oregon: Further Constraints on Estimating Depths of Closure (30–34 m) during Future Sea Level Rise in the Pacific Northwest Region, USA

In this article, geologically recent sedimentation rates across a high wave- and wind-energy inner-shelf are used to constrain depths of closure, which are needed to estimate potential offshore displacements of littoral (beach) sand that could result from future sea level rise (SLR). Seven shallow vibracores (1.0&amp;ndash;2.3 m subsurface depth) were analyzed from a single transect across the inner-shelf (19&amp;ndash;72 m water depth) at the South PacWave study site in the high-wave energy (peak wave Hs= 10&amp;ndash;15 m) coast of Central Oregon. The vibracores were 14C dated to establish 1) near-modern mixing depths and 2) net sedimentation rates that equaled or exceeded rates of coeval SLR (10 cm century-1) during very latest-Holocene time (&amp;le;1.0 ka). Sedimentation rates of 17 cm century-1 and 31 cm century-1 for vibracore P1-2A22 in 34 m water depth do exceed coeval SLR, even after accounting for apparent mixing depths of 60&amp;ndash;100 cm. But sedimentation rates in deeper core sites (47&amp;ndash;53 m water depth) do not approach coeval SLR rates. These results support a proposed near future (one century) 30 m depth of closure in the innermost-shelf of northern Oregon. Vibracore sand grain sizes (mean 0.20&amp;plusmn;0.03 mm 1&amp;sigma;, n=18) are similar across the inner-shelf, but heavy-mineral sand tracers confirmed that the latest-Holocene inner-shelf sand accumulations were supplied from seaward transport of littoral sand. The net loss of littoral sand to the inner-shelf sand sink accounts for the narrowing and thinning of beach deposits in northern Oregon during latest-Holocene time. A 1.0 m thickness of littoral sand displaced across the innermost-shelf (5&amp;ndash;30 m water depth) following a 1.0 m SLR, or equivalent increase in offshore accommodation space, would yield a cross-sectional area of 1.5x103 m2. That value is three times larger than the mean cross-sectional area of the modern adjacent beaches (mean 4.8x102 m2) in the South PacWave study area. Following a possible near future SLR of 1.0 m, the popular sandy beaches of northern Oregon could be converted to intertidal gravel/algae covered bedrock platforms.

Contamination of microplastics, surface morphology and risk assessment in beaches along the Thoothukudi coast, Gulf of Mannar region

Microplastics accumulation on beaches raises a serious concern worldwide. Hence, the present study was conducted with the focus of investigating the abundance, characteristics, risk assessment, surface morphology and elemental composition of microplastics (MPs) in the beach sediments of the Thoothukudi region, situated on the south-east coast of India, Gulf of Mannar region. The MPs abundance ranged between 19 ± 18.62 and 78.55 ± 95.17 items/kg with a mean abundance of 33.82 ± 26.11 items/kg and the spatial distribution of MPs showed insignificant variation. Fragments (59.48%), 0.5-1mm (43.66%) and blue-coloured MPs (45.61%) were highly predominant in the sediments. Attenuated total reflection - Fourier transform infrared (ATR-FTIR) spectroscopy showed the dominance of polyethylene polymers in sediments (52.26%) and their sources could be attributed to the direct inflow of sewage, recreational and fishing activities and accidental loss. The current study revealed that microplastics (< 5mm) are ubiquitous along the Thoothukudi coast, posing a serious threat to the marine environment and marine organisms. The ecological risk assessment of MPs in sediments was calculated by adopting 3 models: the polymer hazard index (PHI), pollution load index (PLI) and potential ecological risk assessment (RI). The overall PHIsediments = 698.96 exhibited a hazard level of IV, which was mainly due to the varying abundance of polymer composition in sediments. The value of PLIsediments is 2.51, which mainly depends on the MPs abundance in sediments and yields the hazard level of I. The ecological risk posed by MPs in beach sediments along the Thoothukudi coast (RIsediments = 241.06) falls into the medium category, indicating that steps must be taken to reduce the flow of plastics through management measures such as proper wastewater treatment practices, recycling of plastic waste and proper waste disposal. Field emission scanning electron microscopy (FESEM) images revealed that MPs surfaces were strongly weathered and energy dispersive X-ray (EDX) spectroscopy spectra showed that the presence of inorganic elements associated with the surface MPs might be derived from the surrounding environment or additives in plastics. Hence, further research has to be conducted in view of studying the combined effects of MPs pollution and organic pollutants, which will provide further understanding of the contamination of MPs in the marine environment.

What Are Lake Beaches Made of? An Assessment of Plastic Beach Litter on the Shores of Como Bay (Italy)

Plastic waste dispersion is a well-recognized environmental threat, despite continuous efforts towards improving waste disposal management over the last few decades. Plastic litter is known to strongly impact upon water bodies and shorelines, affecting the health of ecosystems and impacting upon the aesthetic value of sites. Moreover, plastic waste that is abandoned on beaches contributes towards different degradation processes that potentially lead to the formation of secondary microplastics (MPs), with likely cascade effects upon the whole ecosystem. In this view, this study aims to characterize the plastic beach litter found on the shores of the western basin of Como Lake (Italy) to better understand the origin of MPs in littoral sediments, including the recognition of object typologies and the chemical characterization of polymers using Fourier-transformed infrared analysis (FTIR). The results highlighted that the most abundant polymers on beaches are polypropylene (PP) and polyethylene (PE), representing 73% of the collected polymers. This confirms that floating, low-density polymers are more likely to accumulate on beaches. Moreover, almost 66% of litter is represented by commonly used manufactured items (disposable objects, packaging, and everyday items). This evidence, combined with the analysis of the main environmental features of the sampling sites (the main winds, distance to urban areas, and the presence of tributaries) indicate that abundance of beached litter is mainly linked to beach accessibility and the local winds. These results highlight that multiple factors affect the environmental fate of plastic litter and give insights into the assessment of secondary microplastics in beach sediments.

Mercury pollution on tourist beaches in Durban, South Africa: A chemometric analysis of exposure and human health

Mercury (Hg) is a global pollutant that is a major public health concern due to its mobility, stability and toxicity behavior in the environment. In this study Hg concentrations were determined in beach sediment samples (n = 43) collected from the South Durban Coast, South Africa. A human health risk assessment was also carried out to comprehend the potential health effects of incidental ingestion/direct contact with contaminated sediments in a recreational setting. Hg concentrations ranged between 0.62 and 4.88 mg kg−1 dw., exceeding all background and regulatory limits. Numerical values of calculated exposure pathways represented dermal contact with the sediments as one of the potential paths in both adults and children. Hazard Index (HI) values were found to be less than unity signifying no adverse health effects. This study validates the critical need for long-term monitoring of Hg in various scenarios in order to incorporate better public health management strategies.

Microplastics pollution in sediments of Moroccan urban beaches: The Taghazout coast as a case study

This work describes the spatiotemporal analysis of microplastics (MPs) pollution in sediments collected on a high urbanized beach located in Taghazout coast, central Atlantic part of Morocco. The study area is mainly composed of moderately well-sorted fine sands with an average density of MPs that ranged between 915 MPs/kg in 2018 and 1448 MPs/kg in 2019. The most polluted sites were in the south part of Taghazout coast, close to facilities of where beachgoers are often found. Microplastic Pollution Index (MPPI), Microplastic Impact Coefficient (CMPI), Agglomerative Hierarchical Clustering (AHC), and Multidimensional Scaling (MDS) revealed spatiotemporal variation of MPs pollution. Thus, the principal component analysis (PCA) showed a low correlation between the sediment characteristics (i.e., grain size, sorting, skewness) and MPs densities. Overall, the outputs of this baseline recommend implementing plastic management strategies to eliminate or at least minimize the collateral effects generated by MPs pollution in sediments of urbanized beaches.

Influence of air entrainment and gas kinetics on liquefaction triggering during tsunami loading

Tsunamis are a significant coastal hazard that pressurise sediment pore water, which can potentially induce liquefaction, enhance erosion and scour, and undermine the stability of beach sediments supporting natural and built infrastructure in the coastal nearshore environment. Tsunami-induced pressurisation of pore water is attributed to (a) mechanical pressurisation associated with the soil skeleton's tendency to contract or expand around the soil's pore fluid under the changing overlying water weight and (b) seepage of tsunami water into and out of the sand bed. The pore fluid compressibility, which is influenced by air entrainment due to water table fluctuations caused by the tides, can significantly influence development of stabilising and destabilising hydraulic gradients during tsunami runup and drawdown, respectively. Previous work has effectively assumed a constant air content in sand beds and neglected (a) the compression and dissolution of entrained air that influences the pore fluid compressibility and (b) the interaction between saturated sediment underlying sediment with entrained air. By considering the gas kinetics influencing the pore fluid compressibility in a seepage–deformation model, the effect of different pore fluid compressibility assumptions, thickness of sediment with entrained air, initial degree of saturation and tsunami wave properties (height and duration) were studied. The thickness of sediment containing entrained air, the assumed pore fluid compressibility assumption and subtle differences in the initial degree of saturation can significantly influence the predicted maximum depth and duration of tsunami-induced liquefaction.

Passive Seismic Surveys for Beach Thickness Evaluation at Different England (UK) Sites

In an era of environmental change leading to rising sea levels and increased storminess, there is a need to quantify the volume of beach sediment on the coast of Britain in order to assess the vulnerability to erosion using cheap, easy-to-deploy and non-invasive methods. Horizontal-to-vertical spectral ratio (HVSR) is a technique that uses the natural background seismic ‘noise’ in order to determine the depth of underlying geological interfaces that have contrasting physical properties. In this study, the HVSR technique was deployed at a number of settings on the coast of England that represented a range of different compositions, geomorphology, and underlying bedrock. We verified the results by comparison to other survey techniques, such as ground-penetrating RADAR, multichannel analysis of surface waves (MASW), and cone penetration tests. At locations where there was sufficient contrast in physical properties of the beach material compared to the underlying bedrock, the beach thickness (and therefore the volume of erodible material) was successfully determined, showing that HVSR is a useful tool to use in these settings.

Occurrence, spatial distribution, and risk assessment of microplastics in surface water and sediments of Saint Martin Island in the Bay of Bengal

Microplastics (MPs) are emerging contaminants in aquatic and terrestrial ecosystems and have caused substantial concern worldwide. This study surveyed the presence of MPs in surface water and sediments across the coastal area of Saint Martin Island in the Bay of Bengal. MPs were collected following the standard protocol and identified as various types like expanded polystyrene, foam, filaments, fragments, lines, fibres, and paint flakes. Total MPs pollution in beach sediment was 317 particles/kg across 14 sampling sites, varied from 11 to 10589 particles/m2 of dry sediment and 0.95 particles/m3, having ~2 to 19 particles/30 min trawl in coastal surface water samples. Most of the frequent MPs in beach sediments ranged from 1.0 to 2.0 mm, whereas the fragments were predominant in sediment and surface water samples. MPs distribution revealed that different shapes were dominant at different sites within the Island. The calculated pollution risk index due to the presence of MPs indicated that the sediment and surface water samples were under the low-risk category. However, polymeric risk assessment and contamination factors suggest that the coastline is significantly polluted, as high pollution load indices (PLI >1) were observed for sediments and coastal surface water samples. This work provides the detailed MPs data in the coastal environment of Saint Martin Island for the first time; hence it may be helpful to develop proper strategies to deal with environmental problems.

Multi-proxy approach to identify the origin of high energy coastal deposits from Laem Son National Park, Andaman Sea of Thailand

Understanding the frequency of high energy storm and tsunami events is crucial for apprehending the vulnerability of coastal communities. Identifying and dating sedimentary evidence deposited by such high energy events can assist in the planning and installation of suitable protection measurements. The Andaman Sea coast of Thailand is particularly vulnerable to such events as illustrated by the 2004 Indian Ocean Tsunami. Here, three shore-perpendicular transects and ten sediment cores along a beach ridge in the northern part of Lam Son National Park, Ranong Province, Andaman Sea coast are investigated with respect to high energy deposits. A multi-proxy analysis was conducted including stratigraphical correlations between cores, detailed description of physical characteristics, sedimentary structure, grain size, organic matter and carbonate content as well as identification of the remains of marine organisms. Optically stimulated luminescence (OSL) dating was applied for determining the age of the sediments on this beach ridge plain. The stratigraphy and sediment characteristics, in particular composition, of the sands in the study area clearly allow us to distinguish between high energy deposits and normal beach sediments. Two high energy deposits were identified and attributed to result from the 2004 Indian Ocean Tsunami as well as a past storm, which, based on OSL dating occurred more than 340 ± 20 years ago.