Assessment of Rare Earth Elements, Actinides, and Radionuclides in Nearshore Sediments of Urban-Adjacent Coastal Zones in Athens (Greece) and Fujairah (UAE)

Assessment of Rare Earth Elements, Actinides, and Radionuclides in Nearshore Sediments of Urban-Adjacent Coastal Zones in Athens (Greece) and Fujairah (UAE) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Assessment of Rare Earth Elements, Actinides, and Radionuclides in Nearshore Sediments of Urban-Adjacent Coastal Zones in Athens (Greece) and Fujairah (UAE) Alexandros Santos, Christos Tsabaris, Janez Zavašnik, Ioannis Panagiotopoulos, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9077317/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study presents the first assessment of REEs, actinides (Th and U), and radionuclides in nearshore sediments from Athens, Greece (Kifissos River discharge into the Saronic Gulf) and Fujairah, UAE (harbor area), using XRD, ICP-MS, electron microscopy, and γ-ray spectrometry. REE concentrations were higher in Athens sediments, reflecting geological and anthropogenic influences as revealed by SEM- and TEM-EDS. Thorium in Athens is associated with minerals such as zircon, whereas U in both areas occurred at low crustal background levels. 40 K activity varied, while 137 Cs activity was higher in Athens and lower in Fujairah, consistent with historical Chernobyl atmospheric deposition. Marine urban sediments REE actinides radioactivity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Coastal zones adjacent to urban areas and harbors are often associated with significant environmental pressures caused by marine traffic, shipyards, fuel spills, sewage, and waste disposal. These pressures, along with broader environmental changes, also influence and interact with seafloor surface sediments. Such sediments are primarily composed of inorganic solid materials of various sizes—ranging from nanoparticles to larger grains—intermixed with organic compounds and diverse marine organisms. While most of these marine materials consist of well-known minerals (e.g., clays, Fe-oxides/oxyhydroxides), increasing attention is being paid to so-called "Anthropocene minerals", which have emerged in nature since the Industrial Revolution in the 19th century, as well as to radionuclides related to the Atomic Age in the 20th century.Rare earth elements (REE) and actinides (U and Th) are important constituents of nearshore sediments in urban-adjacent coastal zones. For example, Ashraf et al. [ 1 ] investigated REE in coastal East Malaysia, while El-Taher et al. [ 2 , 3 ] highlighted the significance and environmental implications of REE and natural radionuclides in marine sediments from harbors along the Egyptian Red Sea coast. The Kifissos River (also known as Kephissos or even Cephissus -Κηφισός-) traverses Athens (Greece) and discharges into the Saronic (Saronikos) Gulf in the western metropolitan area (~ 3.8 million inhabitants). It functions as a primary drainage conduit for a substantial portion of the city. Elevation across the basin ranges from 1350 m in upland areas to sea level at the estuary, with a mean elevation of 284.9 m. The catchment is subject to significant anthropogenic pressures, including industrial, agricultural and residential land use. The river has an approximate length of 22 km, with its upper reaches developing on alpine carbonate formations, while its lower course flows through Quaternary deposits within a highly urbanized environment. In the lower course, riverbed sediments exhibit a downstream fining trend, with coarse-grained gravelly sands in the upstream sections and fine-grained sediments (muds and sandy muds) in the estuarine zone near the Saronic Gulf. In an early study including sampling sites located very close to those of the present investigation, Panagiotopoulos et al. [ 4 ] analyzed surficial and sub-surficial sediments from the lower course of the Kifissos River and reported bulk enrichment in Cu and Zn. However, because XRF was used instead of ICP–MS, not all REEwere determined, and no micro- or nanoscale microscopic analyses were performed. Later, Argyraki et al. [ 5 ] investigated physicochemical parameters and selected metals (Cr, Ni, Mn, Cu, Zn, Pb; excluding REE and actinides) in water and sediment samples from three rivers/streams in the Athens metropolitan area (Kifissos, Podoniftis, and Pikrodafni) and reported Mn enrichment in Kifissos samples. Furthermore, Evrenoglou et al. [ 6 ], Partsinevelou and Evrenoglou [ 7 ], and Evrenoglou et al. [ 8 ] examined physicochemical parameters and selected metalloids and metals (As, Cr, Ni, Cu, Zn, Cd, Hg, Pb) in water samples from the northern Kifissos River catchment and compared these with concentrations in children’s scalp hair. More recently, Prifti et al. [ 9 ] analyzed selected metals in sediments of the Saronic Gulf, although their sampling sites were distant from the Kifissos River discharge area. Finally, Matiatos et al. [ 10 ] performed a preliminary assessment of nitrate sources pollution in the catchment of Kiffisos river. Thus, to the best of our knowledge, apart from the evident lack of studies addressing all REE in nearshore sediments influenced by the Kifissos River, there are also no published studies reporting radionuclide measurements in this system. The harbor of Fujairah, also known as Fujairah Port (Arabic: ميناء الفجيرة), is a deep-water port located in the Emirate of Fujairah, United Arab Emirates. It is the largest port on the eastern seaboard of the UAE and the world’s second-largest bunkering hub. The Port of Fujairah occupies a strategic location on the UAE’s only eastern seaboard and is connected to all other emirates within approximately 300 km.The bedrock geology is dominated by rocks of the Oman–UAE ophiolite complex, with a limited area in the central–northern sector underlain by medium- to high-grade metamorphic rocks. The bedrock is locally overlain by Miocene–Pliocene and Quaternary deposits.Regarding REE and radionuclides, in nearshore sediments from the urban-adjacent coastal zone of Fujairah, particularly within Fujairah Harbor, El Tokhi et al. [ 11 ] reported moderate to considerable enrichment of As, Ni, Cr, and Cd. However, their study did not include REE, actinides, or radionuclides. Thus, the present paper is the first in the literature to investigate rare earth elements (REEs) and radionuclides—both natural (including actinides) and anthropogenic—in nearshore sediments from urban-adjacent coastal zones in Athens, Greece (Kifissos urban river discharge into the Saronikos Gulf), and Fujairah, UAE (near the harbor). The analytical techniques employed include X-ray diffraction (XRD), inductively coupled plasma–mass spectrometry (ICP-MS), field-emission gun–focused ion beam scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (FEG-(FIB)-SEM-EDS), scanning/transmission electron microscopy with high-angle annular dark-field imaging and EDS analysis ((S)TEM-EDS/HAADF), and gamma-ray spectrometry.Rare earth elements (REEs) and actinides such as uranium (U) and thorium (Th) are commonly associated in natural geochemical systems due to their incompatible behavior during magmatic differentiation and their incorporation into similar accessory mineral phases, including zircon and monazite. In marine coastal sediments, REEs and Th are generally controlled by lithogenic inputs and tend to remain relatively immobile under oxic environmental conditions, whereas U may exhibit greater mobility because of its redox-sensitive geochemical behavior. This association is also of radiological significance because U and Th contribute to natural background radioactivity through their radioactive decay series. Consequently, the parallel determination of elemental concentrations and radionuclide activities—including both naturally occurring radionuclides ( 40 K and the 238 U and 232 Th decay series) and anthropogenic radionuclides such as 137 Cs—using γ-ray Spectrometry provides a comprehensive framework for evaluating sediment provenance, environmental radioactivity levels, and potential radiological implications in coastal marine systems. Experimental The samples studied in the present dissertation were collected from nearshore surface sediments in urban-adjacent coastal zones, specifically from the Kifissos River discharge area into the Saronikos Gulf, Athens, Greece, and from the coastal vicinity of the harbor in Fujairah, United Arab Emirates (Fig. 1 ). Throughout the study, the Kifissos samples are designated as “KIF,” whereas the Fujairah samples are designated as “FJR.” After appropriate field sampling using an inflatable boat and a Van Veen grab (KC Denmark A/S), the sediment samples were processed following a standardized protocol to ensure consistency and reproducibility. Initially, the marine sediments were wet-sieved with Retsch test sieves using deionized and distilled water to isolate the desired particle size fraction (< 2 mm) and remove pebbles, as well as fragments of rubbish and plastics. The sieved samples were then filtered through standard 0.45 µm membrane filters and subsequently air-dried or oven-dried at low, controlled temperatures to eliminate residual moisture without altering their mineralogical or chemical composition. For bulk compositional analyses, representative subsamples were pulverized to a fine powder using an agate mortar and pestle to prevent contamination and minimize particle-size effects. Additionally, density separation using Na-polytungstate heavy liquids (supplied by TC-Tungsten Compounds GmbH, Gruber Str. 15, 96271 Grub am Forst, Germany) was employed to selectively isolate specific mineral or particle fractions, which were subsequently subjected to microscopic and analytical investigations. Powder XRD patterns for all samples (< 2 mm, pulverized in agate mortar) were obtained using a Siemens (currently Bruker AXS) D-5005 X-ray diffractometer (Cu K α radiation at 40 kV and 40 mA), and evaluated using the EVA 10.0 program of the Bruker DIFFRACplus software package. Bulk chemical analyses for REE and actinides (U and Th) were performed using a Perkin Elmer ELAN® 9000 ICP-MS, following the LiBO 2 /LiB 4 O 7 fusion and HNO 3 digestion. Micro- and nanos-cale microscopic investigations of raw and heavy-liquid–separated sediment samples were conducted using a combination of optical microscopy, Scanning Electron Microscopy and Transmission Electron Microscopy, both equipped with energy-dispersive X-ray spectroscopy (EDS), enabling detailed characterization of particle morphology, size distribution, and solid-phase characteristics. Scanning Electron Microscopy study was mainly performed using a AURIGA 40 Zeiss FEG-(FIB)-SEM-EDS. Complementarily, a low-vacuum SEM (JEOL JSM-IT300LV), coupled with an EDS microanalytical system (Oxford Aztec STD X-act), was also employed. The system extends the vacuum pressure range up to 650 Pa, which, in low-vacuum mode, enhances SEM imaging versatility for samples that are wet, oily, prone to outgassing, or non-conductive, allowing observation without the need for conductive coating or other pretreatment.Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were conducted on a 200 kV field-emission microscope (JEM-2010F, JEOL Inc.) equipped with a slow-scan CCD camera (ORIUS SC1000A, Gatan Inc.) for high-quality imaging, and EDS with a Si(Li) detector (Oxford Instruments Link ISIS300, Oxford Instruments PLC) for elemental analysis. High-angle annular dark-field (HAADF) imaging in STEM mode enabled Z-contrast visualization, providing enhanced compositional and structural contrast at the nanoscale. Gamma(γ)-ray spectroscopy measurements of the pulverized samples were performed using a high-purity germanium (HPGe) detector (CANBERRA BE5030; diameter 101.6 mm, length 133.35 mm) coupled with the appropriate electronic equipment, including a digital signal analyzer (CANBERRA DSA-LX). Each sample was measured for 24 hours to achieve adequate counting statistics. To maximize detection efficiency, the samples were positioned in close contact with the detector endcap, thereby optimizing the sample-to-crystal solid angle. Spectral analysis was carried out using SPECTRW software [ 12 ]. For activity determination, the following photopeaks were used: 46 keV ( 210 Pb), 186 keV ( 226 Ra), 911 keV ( 228 Ac), 661 keV ( 137 Cs), and 609 keV ( 214 Bi). The energy (E), photopeak resolution (FWHM), and full energy photopeak efficiency (FEPE) calibrations of the detector were performed using a standard reference source (IAEA soil material from the ALMERA network). A separate reference source [ 13 ] was aslo used for the calibration of the system. Subsequently, correction factors accounting for True Coincidence Summing (TCS) of simultaneously emitted gamma-rays and for sample self-absorption (ET), due to differences in density and composition between the reference sources and the samples, were calculated for each energy peak using EFFTRAN 4.5 software and LabSOCS software [ 13 ]. The activity concentration A (Bq/kg) for each radionuclide was estimated by dividing the counting rate in the photpeak energy by the efficiency, the massand the intensity of the gamma-ray. The aforementioned corrections (TCS and ET) are also performed for impoving the accuracy of the mesurement. Results and discussion Powder X-ray diffraction (XRD) analysis identified, as dominant crystalline phases, mineral assemblages typical of coastal marine sedimentary environments in the Kifissos River discharge samples. These include quartz, calcite, and clay minerals such as illite and kaolinite. The mineralogical composition of the Fujairah harbor sediments is broadly similar; however, a distinct additional contribution from ophiolite-derived phyllosilicates was observed, particularly serpentine-group minerals and talc. The presence of these Mg-rich silicates is consistent with the regional geological framework of the Oman–UAE ophiolitic complex and confirms a strong mafic–ultramafic lithological influence on sediment composition in the Fujairah coastal zone.In the Kifissos discharge sediments, minor diffraction features suggest the possible presence of Fe–Mn–phosphate phases. These phases may partly reflect anthropogenic inputs, potentially associated with urban wastewater discharge and detergent-derived phosphates. Nevertheless, in both study areas, no crystalline phases containing detectable concentrations of rare earth elements (REEs), actinides (U, Th), or associated radionuclides were identified by bulk XRD analysis. This indicates that REEs and actinides are not hosted in discrete, well-crystallized mineral phases at concentrations above the XRD detection limit, but are instead incorporated within detrital minerals, adsorbed onto mineral surfaces, or present in micro- to nano-scale domains. The chemical analyses of rare earth elements (REEs) and natural actinides (U and Th), performed using ICP-MS, are presented in Table S1 . The Kifissos samples generally exhibit higher total REE concentrations compared to the Fujairah samples (ΣREE ranging from 24.51 ppm—which corresponds to a sample collected relatively far from the river discharge and considered representative of the local geological background—to 107.42 ppm) whereas Fujairah samples show a narrower concentration range (ΣREE: 20.08–22.89 ppm). These differences are primarily attributed to contrasting geological backgrounds and sediment source materials, with felsic sedimentary rocks dominating the Kifissos drainage basin and Ophiolitic lithologies being the principal source of detrital material in Fujairah. The observed difference between the Kifissos geological background sample and the remaining Kifissos sediments also suggests a possible anthropogenic contribution, potentially reflecting Anthropocene-era input of REEs associated with synthetic micro- and nano-particles transported into the coastal system. Similar regional differences were observed for Th concentrations, which ranged from 1.1 to 6.7 ppm in Greek samples and from 0.7 to 1.2 ppm in UAE samples. In contrast, U concentrations were relatively uniform between the two study areas, ranging from 1.2 to 2.3 ppm, suggesting limited localized anthropogenic uranium enrichment. Thorium and U distributions in both coastal environments are therefore interpreted as predominantly natural, particularly in the Kifissos sediments where abundant felsic detrital minerals, such as zircon, likely serve as primary host phases for these elements. Overall, REEs and actinides in both regions occur at relatively low geological background levels ( Figures S1 and S2 ) and generally exhibit negative geochemical anomalies relative to the Upper Continental Crust (UCC).The only notable exception is scandium (Sc) enrichment observed in Fujairah samples, which is attributed to the natural abundance of Sc in surrounding Ophiolitic rocks. When considering the combined group of REEs together with Y and Sc, the Kifissos samples show total concentrations (ΣREE + Y+Sc) ranging from 31.91 to 133.92 ppm, whereas Fujairah samples exhibit a relatively narrow and more uniform range of 41.70 to 47.73 ppm. The chondrite-normalized REE patterns of the studied sediments (Fig. 2 ) were generally characterized by relatively flat cerium (Ce) distributions, indicating limited redox-driven fractionation during sediment formation, transport, and post-depositional diagenetic modification. The near-flat Ce behaviour suggests that Ce predominantly remained in its trivalent state under oxic to mildly oxidizing environmental conditions, which are typical of well-aerated nearshore marine settings in the coastal zones of Athens and Fujairah. Such patterns imply that strong reducing microenvironments capable of promoting Ce(III) oxidation to insoluble Ce(IV) phases were not widely developed in the examined sediments. Consequently, Ce anomalies did not indicate significant redox-mediated scavenging or enrichment processes that could be associated with severe organic pollution or intense anthropogenic chemical forcing. In addition to Ce behaviour, the europium (Eu) anomalies observed in the samples provide further insight into sediment provenance and mineralogical control of REE distribution. The Eu anomaly values were comparable to those typically reported for Upper Continental Crust-derived materials, suggesting that REE signatures were largely governed by natural lithogenic inputs rather than anthropogenic chemical fractionation. Europium geochemical behavior is strongly influenced by feldspar-related mineral phases, where Eu²⁺ may substitute for Ca²⁺ during magmatic crystallization under reducing geological conditions. Therefore, the observed Eu anomaly patterns support the interpretation that sediment REE compositions were primarily controlled by detrital mineral inheritance and weathering processes. The NASC-normalized REE anomaly diagram, expressed as [Ce/Ce*] NASC vs. [Eu/Eu*] NASC , further elucidates the geochemical controls on sediment composition (Fig. 3 ). In the Kifissos River discharge zone, Ce/Ce* values ranging from 0.80 to 0.95 indicate weak negative Ce anomalies, suggesting partial oxidative removal of dissolved Ce³⁺ from the water column through adsorption and co-precipitation with Fe–Mn oxyhydroxide phases under nearshore oxic conditions. Similar behavior was observed in Fujairah sediments, where Ce/Ce* values ranged from 0.79 to 0.95, implying that marine redox processes, rather than provenance effects, primarily controlled Ce distribution in both study areas. Europium anomalies (Eu/Eu*) ranged from 0.96 to 1.10 in Kifissos sediments, close to the Upper Continental Crust (UCC) signature, whereas sediments from the Fujairah harbor zone exhibited pronounced positive Eu anomalies (1.11–1.48). This enrichment is consistent with detrital input derived from the Ophiolitic lithologies of the surrounding region -Oman–UAE ophiolite complex-, where Eu may occur in its divalent state (Eu²⁺) allowing substitution for Ca²⁺ in plagioclase minerals during magmatic crystallization. Weathering and mechanical erosion of Ophiolitic rocks therefore generate sediments retaining positive Eu anomalies, while the absence of REE-bearing anthropogenic particles in Fujairah sediments further supports a lithogenic origin. Overall, both coastal zones exhibit negative Ce/Ce* anomalies (0.79–0.95), indicating oxidative scavenging of Ce in the nearshore marine environment. The relatively narrow variation in [Ce/Ce*] NASC vs. [Eu/Eu*] NASC values suggests stable oxic depositional conditions in shallow wave-influenced coastal waters, despite differences in source lithology. Consequently, Eu anomalies are more effective for discriminating source lithological contributions, whereas Ce anomalies primarily reflect marine oxidative geochemical processes rather than provenance differences. Geochemical discrimination diagrams based on La/Th vs. Hf systematics provide additional support for provenance interpretation. The plotted data indicate that sediments in both coastal areas are compositionally “fresh,” meaning that they have undergone limited sedimentary recycling, chemical weathering, or prolonged transport (Fig. 4 ). Kifissos sediments plot closer to felsic source fields, whereas Fujairah sediments cluster toward basic to mafic compositional domains. These relationships are fully consistent with the known geological background of the two regions and independently corroborate the REE anomaly interpretations. High-resolution microscopic investigation using FEG-(FIB)-SEM-EDS and (S)TEM-EDS/HAADF provided further insight into the microstructural hosting of REE and actinide trace elements. Fujairah harbor sediments do not contain detectable REE- or actinide-bearing micro- or nano-particles. This absence of discrete REE-rich phases indicates that REE distribution in the harbor zone is primarily controlled by detrital mineral provenance rather than secondary adsorption onto anthropogenic particulates or nano-scale enrichment mechanisms. The positive Eu anomaly observed in Fujairah sediments therefore reflects intrinsic lithogenic control associated with mafic–ultramafic source rocks rather than industrial contamination or marine biogeochemical precipitation processes. In contrast, Kifissos discharge sediments contain abundant natural detrital minerals, particularly zircon (Fig. 5 ), which host measurable concentrations of REEs as well as U and Th. Zircon is a well-established geochemical carrier of high-field-strength elements and heavy REEs, and its presence confirms a strong felsic continental crustal contribution. In addition to natural mineral carriers, various clearly anthropogenic micro- and nano-particles were identified in the Kifissos sediments, indicating a notable association between Ce and Ti. These particles contain either Ce-enriched nano-domains or individual Ti–Ce and Ti–V–Ce nanoparticles, suggesting localized urban-derived particulate input into the coastal system (Fig. 6 ). The occurrence of REE(Ce)-rich nanostructures within a Si–O–Fe matrix, as well as Ti–(V)–Ce nanoparticles—phases that are not typical of natural marine sedimentary mineral assemblages—supports the presence of Anthropocene particulate signatures in this urban-adjacent coastal environment. These micro- and nanoscale observations demonstrate that REE partitioning in the Kifissos zone involves both natural detrital incorporation and particle-bound anthropogenic sequestration mechanisms. The combined mineralogical, microstructural, and bulk geochemical results indicate that REE distributions in the studied sediments are controlled by a hierarchical set of processes. Primary control is exerted by geological provenance, reflecting the relative contributions of felsic continental weathering products (Athens) and Ophiolitic mafic–ultramafic detrital material (Fujairah). Secondary controls are associated with micro- and nanoscale hosting mechanisms, including REE incorporation within zircon grains, which may simultaneously accommodate Th and U, and particulate associations involving anthropogenic Ti–Ce phases. Additionally, marine redox-mediated scavenging processes contribute to REE redistribution, particularly for Ce. Although bulk REE geochemical patterns predominantly reflect natural lithogenic signatures, electron microscopy analyses revealed localized anthropogenic particulate inputs in the urban-adjacent coastal sediments of Athens. These particles occur mainly as discrete micro- and nano-sized phases rather than as dissolved geochemical anomalies, suggesting that anthropogenic influence is spatially heterogeneous and primarily transported via particulate pathways. Potential sources include urban atmospheric deposition, maritime activities, and other local anthropogenic emissions. The observed divergence between microstructural evidence and bulk REE geochemistry emphasizes the complementary roles of high-resolution imaging and trace element analysis in environmental assessment. While REE systematics primarily record long-term provenance and sedimentary mixing processes, microscopic characterization enables detection of recent or localized anthropogenic particle inputs that may not significantly modify bulk sediment chemistry. Consequently, integrated mineralogical, microanalytical, and radiochemical approaches are essential for reliable evaluation of coastal sediment quality in urban marine environments. Gamma-ray spectrometric measurements ( Table S2 and Table S3 ) indicate that radioactivity in both areas is predominantly of natural origin, associated mainly with 40 K and the 238 U decay series. However, the presence of anthropogenic radionuclides, particularly 137 Cs, is evident in the Greek coastal sediments (Fig. 7 ). In Athens samples, activity concentrations range from 63 to 415 Bq kg⁻¹ for 40 K and from threshold to 6.01 Bq kg⁻¹ for 137 Cs. The detection of 137 Cs reflects mainly historical global atmospheric deposition following the Chernobyl nuclear disaster. In contrast, Fujairah sediments exhibit generally lower radionuclide activities and minimal detectable anthropogenic contribution ( 137 Cs up to 2.81 Bq kg⁻¹), consistent with regional fallout distribution patterns and the absence of significant local nuclear contamination sources. Conclusions The integrated mineralogical (XRD), geochemical (ICP-MS) and microscopic (FEG-(FIB)-SEM-EDS, (S)TEM-EDS/HAADF) evidence demonstrates that rare earth element (REE) and actinide (Th and U) behavior in nearshore sediments from the Kifissos River discharge zone in the Saronic (Saronikos) Gulf, Athens (Greece), and the coastal port area of Fujairah (UAE) is primarily controlled by lithogenic provenance, with secondary modification by coastal environmental and anthropogenic processes (Fig. 8 ). In the Kifissos discharge zone, REE distribution reflects mixed continental weathering inputs combined with urban particulate contributions, particularly microparticles hosting Ti-Ce-enriched nanophases, indicating localized anthropogenic particle input associated with urbanization and the evolving Anthropocene sedimentary signature. The near-unity Eu anomaly (0.96–1.10) is consistent with dominantly felsic crustal source material derived from weathered continental lithologies. In contrast, sediments from the Fujairah harbor zone exhibit pronounced positive Eu anomalies (1.11–1.48), which are attributed to detrital inputs from the mafic–ultramafic assemblages of the Oman–UAE Ophiolite complex. Negative Ce anomalies observed in both study areas (Ce/Ce* < 1) indicate deposition under generally oxic nearshore conditions, where Ce is preferentially removed from the dissolved phase through adsorption onto Fe–Mn oxyhydroxide surfaces. The absence of detectable REE- and actinide-bearing micro- or nanoparticles in Fujairah sediments suggests that REE, Th, and U distributions are primarily controlled by mineralogical provenance rather than secondary anthropogenic particle-associated enrichment processes. Thorium concentrations in Greek coastal sediments (1.1–6.7 ppm) were higher than those measured in the UAE samples (0.7–1.2 ppm), reflecting stronger continental crustal influence and possible accumulation of heavy mineral detritus in the Kifissos discharge environment. This is consistent with the presence of zircon crystal fragments, which are known to host both actinides and rare earth elements (REEs). Uranium concentrations were relatively uniform between the two regions (1.2–2.3 ppm), suggesting comparable marine background incorporation and limited evidence of localized anthropogenic U enrichment. Gamma spectrometric analysis revealed 40 K activity ranging from 63 to 415 Bq kg⁻¹ and 137 Cs activity ranging from thresholdto 6.01 Bq kg⁻¹ in Athens sediments. The presence of 137 Cs is attributed mainly to historical global atmospheric deposition associated with the Chernobyl nuclear disaster fallout, whereas generally lower radionuclide activities were recorded in Fujairah sediments. Overall, the integrated application of mineralogical characterization, micro- and nanoscale particle analysis, REE anomaly evaluation, trace actinide quantification, and γ-spectrometry provides a comprehensive multi-proxy framework for understanding sediment provenance, element-hosting mechanisms, and the environmental behavior of radioactive and trace elements in urban-adjacent coastal systems. Declarations Funding Declaration This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author Contribution A. Santos was the principal author and contributed to all stages of the research, data analysis, and manuscript writing. A. Godelitsas acted as supervisor and participated in all stages of the research, analysis, and writing. Chr. Tsabaris, J. Zavašnik, I. Panagiotopoulos, A. Gondikas, and A. Argyraki contributed to fieldwork, sample collection, and analytical measurements. All authors reviewed and approved the final manuscript. Acknowledgement We would like to thank Mr. Vasileios Stasinos, skipper of the HCMR high-speed vessel, who contributed to the sampling. Data Availability The datasets generated and analyzed during this study, including REE, actinide (Th and U), and radionuclide (40-K, 137-Cs) concentrations in nearshore sediments from Athens (Greece) and Fujairah (UAE), are included in this published article and its supplementary information files. Additional raw data and measurement details are available from the corresponding author upon reasonable request. 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Preliminary assessment of nitrate sources of pollution in the urbanized catchment of the Kifissos River. SEGH 2023 Conference, Book of Abstracts, 75 El Tokhi M, Amin BM, Alaabed SA (2017) Environmental Assessment of Heavy Metals Contamination of Bottom Sediments of Oman Gulf, United Arab Emirates. J Pollut Eff Cont 5:203 Kalfas CA, Axiotis M, Tsabaris (2016) C. SPECTRW: A software package for nuclear and atomic spectroscopy. NIM A 830/11:265 Eleftheriou G, Tsabaris C, Androulakaki EG, Pappa FK, Patiris DL (2024) High resolution gamma-ray spectrometry for routine measurements of environmental samples. Appl Radiat Isot 206:111234 Rudnick R, Gao S (2003) In: Treatise on Geochemistry, Holland H. D., Turekian, K. K. (eds) Composition of the continental crust, Elsevier-Pergamon, Oxford Additional Declarations No competing interests reported. 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Research","correspondingAuthor":false,"prefix":"","firstName":"Christos","middleName":"","lastName":"Tsabaris","suffix":""},{"id":607868410,"identity":"0a8c74ae-17cf-4814-98d9-320f24350424","order_by":2,"name":"Janez Zavašnik","email":"","orcid":"","institution":"“Jožef Stefan” Institute","correspondingAuthor":false,"prefix":"","firstName":"Janez","middleName":"","lastName":"Zavašnik","suffix":""},{"id":607868414,"identity":"80655dfe-2a4f-4a37-ad25-4fa8c3e06e63","order_by":3,"name":"Ioannis Panagiotopoulos","email":"","orcid":"","institution":"National and Kapodistrian University of Athens","correspondingAuthor":false,"prefix":"","firstName":"Ioannis","middleName":"","lastName":"Panagiotopoulos","suffix":""},{"id":607868417,"identity":"065262fd-a246-4417-a61d-efcd80a8c060","order_by":4,"name":"Andreas Gondikas","email":"","orcid":"","institution":"National and Kapodistrian University of Athens","correspondingAuthor":false,"prefix":"","firstName":"Andreas","middleName":"","lastName":"Gondikas","suffix":""},{"id":607868418,"identity":"c077d702-883a-4216-a3dd-d47150170f18","order_by":5,"name":"Ariadne Argyraki","email":"","orcid":"","institution":"National and Kapodistrian University of Athens","correspondingAuthor":false,"prefix":"","firstName":"Ariadne","middleName":"","lastName":"Argyraki","suffix":""},{"id":607868421,"identity":"06eaf913-d9e2-4867-b144-8ac932df9db6","order_by":6,"name":"Athanasios Godelitsas","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIiWNgGAWjYJACCYYCGyDF3ECKFoM0IMVImpbDJGjh71988MYHg/N2/eyNDcw8FXYM8tEHCNhw41my5QyD28kzew4CtZxJZjA8l0DAmhtnzKR5gFoMbiQ2MPO2MTMY9hDQIQ/S8sfgXLI9REs9YS0G53vMpBkMDtgZSIC1HGaQ5yGgxfAGW7Jlj0FygsSZgw0H55w5zmNASIvc+cMHb/yosLPnb28++OBNRbWcPCGHMUgkgKnEBiBxAIh5DA4Q0sIPUWEPF5BvIKRlFIyCUTAKRhoAANDaQpz1e6+iAAAAAElFTkSuQmCC","orcid":"","institution":"National and Kapodistrian University of Athens","correspondingAuthor":true,"prefix":"","firstName":"Athanasios","middleName":"","lastName":"Godelitsas","suffix":""}],"badges":[],"createdAt":"2026-03-09 23:23:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9077317/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9077317/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105084779,"identity":"437da893-7f45-4514-ae98-ac6bd6539e80","added_by":"auto","created_at":"2026-03-20 19:10:37","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":168646,"visible":true,"origin":"","legend":"\u003cp\u003eLocations of nearshore surface sediment sampling in urban-adjacent coastal zones: Kifissos River discharge into the Saronic (Saronikos) gulf, Athens, Greece; coastal area near the port of Fujairah, United Arab Emirates (UAE).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/41e8be62e657928225c7d08b.jpg"},{"id":105084778,"identity":"06306344-dac7-4554-b27c-1fd2f4dbd1fc","added_by":"auto","created_at":"2026-03-20 19:10:37","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":130077,"visible":true,"origin":"","legend":"\u003cp\u003eChondrite-normalized REE patterns of the studied nearshore sediments from urban-adjacent coastal zones in Athens (Greece) and Fujairah (UAE)\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/bbade610939f857e9b14bbf9.jpg"},{"id":105084781,"identity":"554e52d7-7944-4bd6-b712-e5d74fc83891","added_by":"auto","created_at":"2026-03-20 19:10:37","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":63089,"visible":true,"origin":"","legend":"\u003cp\u003eSediment discrimination diagram of NASC-normalized Ce and Eu anomalies in the studied nearshore sediments from Athens and Fujairah.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/d6908cfdeb308298c5f1b138.jpg"},{"id":105084786,"identity":"de13f3d3-34ca-42ed-910a-85850729a1d6","added_by":"auto","created_at":"2026-03-20 19:10:38","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":54533,"visible":true,"origin":"","legend":"\u003cp\u003eSediment provenance discrimination diagram based on La/Th and Hf systematics (Hf values adapted from Santos et al., 2026, submitted).\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/cf724319c668fab5a387eaff.jpg"},{"id":105084782,"identity":"47d5a1ac-47e4-451c-98f1-0ac53387cea4","added_by":"auto","created_at":"2026-03-20 19:10:37","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":152246,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of detrital natural zircon microcrystal fragments in nearshore sediments from the Kifissos River discharge zone.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/34c6ac3e3260d969aa0850f8.jpg"},{"id":105084785,"identity":"0dff4610-eb91-426a-8ba8-f5e0247a80d8","added_by":"auto","created_at":"2026-03-20 19:10:38","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":251552,"visible":true,"origin":"","legend":"\u003cp\u003e(S)TEM-EDS/HAADF evidence of anthropogenic Ti–Ce association in nano- and micro-particles in Kifissos river (Athens, Greece) nearshore sediments.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/7a068b59b8da7f40c4049f95.jpg"},{"id":105084776,"identity":"da00b770-e2f1-4644-a327-18000cff9f1b","added_by":"auto","created_at":"2026-03-20 19:10:37","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":77030,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative g-ray spectrum obtained from urban-adjacent nearshore sediment samples (KIF5).\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/134de5e50077dc6e4fdebffa.jpg"},{"id":105562952,"identity":"d920846a-5333-4340-9f83-a74c95414bae","added_by":"auto","created_at":"2026-03-27 12:45:23","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":208988,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic illustration depicting the conclusions of the study:\u003c/strong\u003e REE and actinide distributions reflect primarily lithogenic sources in Fujairah (UAE) and, in contrast, major anthropogenic input, including Chernobyl-derived radionuclides, in Kifissos (Greece).\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/a0fc314fe6e528e595627e35.jpg"},{"id":105569038,"identity":"77cbc911-f065-404f-b04b-25a01c070f96","added_by":"auto","created_at":"2026-03-27 13:11:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1608627,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/2f34cb6f-d374-453c-b093-da6583ee06e5.pdf"},{"id":105562764,"identity":"bfdbd22e-0013-4232-89c6-c2071845845b","added_by":"auto","created_at":"2026-03-27 12:44:35","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":133830,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-9077317/v1/ee35113c74d5b4b138cce699.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessment of Rare Earth Elements, Actinides, and Radionuclides in Nearshore Sediments of Urban-Adjacent Coastal Zones in Athens (Greece) and Fujairah (UAE)","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCoastal zones adjacent to urban areas and harbors are often associated with significant environmental pressures caused by marine traffic, shipyards, fuel spills, sewage, and waste disposal. These pressures, along with broader environmental changes, also influence and interact with seafloor surface sediments. Such sediments are primarily composed of inorganic solid materials of various sizes\u0026mdash;ranging from nanoparticles to larger grains\u0026mdash;intermixed with organic compounds and diverse marine organisms. While most of these marine materials consist of well-known minerals (e.g., clays, Fe-oxides/oxyhydroxides), increasing attention is being paid to so-called \"Anthropocene minerals\", which have emerged in nature since the Industrial Revolution in the 19th century, as well as to radionuclides related to the Atomic Age in the 20th century.Rare earth elements (REE) and actinides (U and Th) are important constituents of nearshore sediments in urban-adjacent coastal zones. For example, Ashraf et al. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] investigated REE in coastal East Malaysia, while El-Taher et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] highlighted the significance and environmental implications of REE and natural radionuclides in marine sediments from harbors along the Egyptian Red Sea coast.\u003c/p\u003e \u003cp\u003eThe Kifissos River (also known as Kephissos or even Cephissus -Κηφισός-) traverses Athens (Greece) and discharges into the Saronic (Saronikos) Gulf in the western metropolitan area (~\u0026thinsp;3.8\u0026nbsp;million inhabitants). It functions as a primary drainage conduit for a substantial portion of the city. Elevation across the basin ranges from 1350 m in upland areas to sea level at the estuary, with a mean elevation of 284.9 m. The catchment is subject to significant anthropogenic pressures, including industrial, agricultural and residential land use. The river has an approximate length of 22 km, with its upper reaches developing on alpine carbonate formations, while its lower course flows through Quaternary deposits within a highly urbanized environment. In the lower course, riverbed sediments exhibit a downstream fining trend, with coarse-grained gravelly sands in the upstream sections and fine-grained sediments (muds and sandy muds) in the estuarine zone near the Saronic Gulf. In an early study including sampling sites located very close to those of the present investigation, Panagiotopoulos et al. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] analyzed surficial and sub-surficial sediments from the lower course of the Kifissos River and reported bulk enrichment in Cu and Zn. However, because XRF was used instead of ICP\u0026ndash;MS, not all REEwere determined, and no micro- or nanoscale microscopic analyses were performed. Later, Argyraki et al. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] investigated physicochemical parameters and selected metals (Cr, Ni, Mn, Cu, Zn, Pb; excluding REE and actinides) in water and sediment samples from three rivers/streams in the Athens metropolitan area (Kifissos, Podoniftis, and Pikrodafni) and reported Mn enrichment in Kifissos samples. Furthermore, Evrenoglou et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], Partsinevelou and Evrenoglou [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], and Evrenoglou et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] examined physicochemical parameters and selected metalloids and metals (As, Cr, Ni, Cu, Zn, Cd, Hg, Pb) in water samples from the northern Kifissos River catchment and compared these with concentrations in children\u0026rsquo;s scalp hair. More recently, Prifti et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] analyzed selected metals in sediments of the Saronic Gulf, although their sampling sites were distant from the Kifissos River discharge area. Finally, Matiatos et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] performed a preliminary assessment of nitrate sources pollution in the catchment of Kiffisos river. Thus, to the best of our knowledge, apart from the evident lack of studies addressing all REE in nearshore sediments influenced by the Kifissos River, there are also no published studies reporting radionuclide measurements in this system.\u003c/p\u003e \u003cp\u003eThe harbor of Fujairah, also known as Fujairah Port (Arabic: ميناء الفجيرة), is a deep-water port located in the Emirate of Fujairah, United Arab Emirates. It is the largest port on the eastern seaboard of the UAE and the world\u0026rsquo;s second-largest bunkering hub. The Port of Fujairah occupies a strategic location on the UAE\u0026rsquo;s only eastern seaboard and is connected to all other emirates within approximately 300 km.The bedrock geology is dominated by rocks of the Oman\u0026ndash;UAE ophiolite complex, with a limited area in the central\u0026ndash;northern sector underlain by medium- to high-grade metamorphic rocks. The bedrock is locally overlain by Miocene\u0026ndash;Pliocene and Quaternary deposits.Regarding REE and radionuclides, in nearshore sediments from the urban-adjacent coastal zone of Fujairah, particularly within Fujairah Harbor, El Tokhi et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] reported moderate to considerable enrichment of As, Ni, Cr, and Cd. However, their study did not include REE, actinides, or radionuclides.\u003c/p\u003e \u003cp\u003eThus, the present paper is the first in the literature to investigate rare earth elements (REEs) and radionuclides\u0026mdash;both natural (including actinides) and anthropogenic\u0026mdash;in nearshore sediments from urban-adjacent coastal zones in Athens, Greece (Kifissos urban river discharge into the Saronikos Gulf), and Fujairah, UAE (near the harbor). The analytical techniques employed include X-ray diffraction (XRD), inductively coupled plasma\u0026ndash;mass spectrometry (ICP-MS), field-emission gun\u0026ndash;focused ion beam scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (FEG-(FIB)-SEM-EDS), scanning/transmission electron microscopy with high-angle annular dark-field imaging and EDS analysis ((S)TEM-EDS/HAADF), and gamma-ray spectrometry.Rare earth elements (REEs) and actinides such as uranium (U) and thorium (Th) are commonly associated in natural geochemical systems due to their incompatible behavior during magmatic differentiation and their incorporation into similar accessory mineral phases, including zircon and monazite. In marine coastal sediments, REEs and Th are generally controlled by lithogenic inputs and tend to remain relatively immobile under oxic environmental conditions, whereas U may exhibit greater mobility because of its redox-sensitive geochemical behavior. This association is also of radiological significance because U and Th contribute to natural background radioactivity through their radioactive decay series. Consequently, the parallel determination of elemental concentrations and radionuclide activities\u0026mdash;including both naturally occurring radionuclides (\u003csup\u003e40\u003c/sup\u003eK and the \u003csup\u003e238\u003c/sup\u003eU and \u003csup\u003e232\u003c/sup\u003eTh decay series) and anthropogenic radionuclides such as \u003csup\u003e137\u003c/sup\u003eCs\u0026mdash;using γ-ray Spectrometry provides a comprehensive framework for evaluating sediment provenance, environmental radioactivity levels, and potential radiological implications in coastal marine systems.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cp\u003eThe samples studied in the present dissertation were collected from nearshore surface sediments in urban-adjacent coastal zones, specifically from the Kifissos River discharge area into the Saronikos Gulf, Athens, Greece, and from the coastal vicinity of the harbor in Fujairah, United Arab Emirates (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Throughout the study, the Kifissos samples are designated as \u0026ldquo;KIF,\u0026rdquo; whereas the Fujairah samples are designated as \u0026ldquo;FJR.\u0026rdquo;\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAfter appropriate field sampling using an inflatable boat and a Van Veen grab (KC Denmark A/S), the sediment samples were processed following a standardized protocol to ensure consistency and reproducibility. Initially, the marine sediments were wet-sieved with Retsch test sieves using deionized and distilled water to isolate the desired particle size fraction (\u0026lt;\u0026thinsp;2 mm) and remove pebbles, as well as fragments of rubbish and plastics. The sieved samples were then filtered through standard 0.45 \u0026micro;m membrane filters and subsequently air-dried or oven-dried at low, controlled temperatures to eliminate residual moisture without altering their mineralogical or chemical composition. For bulk compositional analyses, representative subsamples were pulverized to a fine powder using an agate mortar and pestle to prevent contamination and minimize particle-size effects. Additionally, density separation using Na-polytungstate heavy liquids (supplied by TC-Tungsten Compounds GmbH, Gruber Str. 15, 96271 Grub am Forst, Germany) was employed to selectively isolate specific mineral or particle fractions, which were subsequently subjected to microscopic and analytical investigations.\u003c/p\u003e \u003cp\u003ePowder XRD patterns for all samples (\u0026lt;\u0026thinsp;2 mm, pulverized in agate mortar) were obtained using a Siemens (currently Bruker AXS) D-5005 X-ray diffractometer (Cu\u003cem\u003eK\u003c/em\u003e\u003csub\u003eα\u003c/sub\u003eradiation at 40 kV and 40 mA), and evaluated using the EVA 10.0 program of the Bruker DIFFRACplus software package.\u003c/p\u003e \u003cp\u003eBulk chemical analyses for REE and actinides (U and Th) were performed using a Perkin Elmer ELAN\u0026reg; 9000 ICP-MS, following the LiBO\u003csub\u003e2\u003c/sub\u003e/LiB\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e fusion and HNO\u003csub\u003e3\u003c/sub\u003e digestion.\u003c/p\u003e \u003cp\u003eMicro- and nanos-cale microscopic investigations of raw and heavy-liquid\u0026ndash;separated sediment samples were conducted using a combination of optical microscopy, Scanning Electron Microscopy and Transmission Electron Microscopy, both equipped with energy-dispersive X-ray spectroscopy (EDS), enabling detailed characterization of particle morphology, size distribution, and solid-phase characteristics. Scanning Electron Microscopy study was mainly performed using a AURIGA 40 Zeiss FEG-(FIB)-SEM-EDS. Complementarily, a low-vacuum SEM (JEOL JSM-IT300LV), coupled with an EDS microanalytical system (Oxford Aztec STD X-act), was also employed. The system extends the vacuum pressure range up to 650 Pa, which, in low-vacuum mode, enhances SEM imaging versatility for samples that are wet, oily, prone to outgassing, or non-conductive, allowing observation without the need for conductive coating or other pretreatment.Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were conducted on a 200 kV field-emission microscope (JEM-2010F, JEOL Inc.) equipped with a slow-scan CCD camera (ORIUS SC1000A, Gatan Inc.) for high-quality imaging, and EDS with a Si(Li) detector (Oxford Instruments Link ISIS300, Oxford Instruments PLC) for elemental analysis. High-angle annular dark-field (HAADF) imaging in STEM mode enabled Z-contrast visualization, providing enhanced compositional and structural contrast at the nanoscale.\u003c/p\u003e \u003cp\u003eGamma(γ)-ray spectroscopy measurements of the pulverized samples were performed using a high-purity germanium (HPGe) detector (CANBERRA BE5030; diameter 101.6 mm, length 133.35 mm) coupled with the appropriate electronic equipment, including a digital signal analyzer (CANBERRA DSA-LX). Each sample was measured for 24 hours to achieve adequate counting statistics. To maximize detection efficiency, the samples were positioned in close contact with the detector endcap, thereby optimizing the sample-to-crystal solid angle. Spectral analysis was carried out using SPECTRW software [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. For activity determination, the following photopeaks were used: 46 keV (\u003csup\u003e210\u003c/sup\u003ePb), 186 keV (\u003csup\u003e226\u003c/sup\u003eRa), 911 keV (\u003csup\u003e228\u003c/sup\u003eAc), 661 keV (\u003csup\u003e137\u003c/sup\u003eCs), and 609 keV (\u003csup\u003e214\u003c/sup\u003eBi). The energy (E), photopeak resolution (FWHM), and full energy photopeak efficiency (FEPE) calibrations of the detector were performed using a standard reference source (IAEA soil material from the ALMERA network). A separate reference source [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] was aslo used for the calibration of the system. Subsequently, correction factors accounting for True Coincidence Summing (TCS) of simultaneously emitted gamma-rays and for sample self-absorption (ET), due to differences in density and composition between the reference sources and the samples, were calculated for each energy peak using EFFTRAN 4.5 software and LabSOCS software [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The activity concentration A (Bq/kg) for each radionuclide was estimated by dividing the counting rate in the photpeak energy by the efficiency, the massand the intensity of the gamma-ray. The aforementioned corrections (TCS and ET) are also performed for impoving the accuracy of the mesurement.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003ePowder X-ray diffraction (XRD) analysis identified, as dominant crystalline phases, mineral assemblages typical of coastal marine sedimentary environments in the Kifissos River discharge samples. These include quartz, calcite, and clay minerals such as illite and kaolinite. The mineralogical composition of the Fujairah harbor sediments is broadly similar; however, a distinct additional contribution from ophiolite-derived phyllosilicates was observed, particularly serpentine-group minerals and talc. The presence of these Mg-rich silicates is consistent with the regional geological framework of the Oman\u0026ndash;UAE ophiolitic complex and confirms a strong mafic\u0026ndash;ultramafic lithological influence on sediment composition in the Fujairah coastal zone.In the Kifissos discharge sediments, minor diffraction features suggest the possible presence of Fe\u0026ndash;Mn\u0026ndash;phosphate phases. These phases may partly reflect anthropogenic inputs, potentially associated with urban wastewater discharge and detergent-derived phosphates. Nevertheless, in both study areas, no crystalline phases containing detectable concentrations of rare earth elements (REEs), actinides (U, Th), or associated radionuclides were identified by bulk XRD analysis. This indicates that REEs and actinides are not hosted in discrete, well-crystallized mineral phases at concentrations above the XRD detection limit, but are instead incorporated within detrital minerals, adsorbed onto mineral surfaces, or present in micro- to nano-scale domains.\u003c/p\u003e \u003cp\u003eThe chemical analyses of rare earth elements (REEs) and natural actinides (U and Th), performed using ICP-MS, are presented in \u003cb\u003eTable S1\u003c/b\u003e. The Kifissos samples generally exhibit higher total REE concentrations compared to the Fujairah samples (ΣREE ranging from 24.51 ppm\u0026mdash;which corresponds to a sample collected relatively far from the river discharge and considered representative of the local geological background\u0026mdash;to 107.42 ppm) whereas Fujairah samples show a narrower concentration range (ΣREE: 20.08\u0026ndash;22.89 ppm). These differences are primarily attributed to contrasting geological backgrounds and sediment source materials, with felsic sedimentary rocks dominating the Kifissos drainage basin and Ophiolitic lithologies being the principal source of detrital material in Fujairah. The observed difference between the Kifissos geological background sample and the remaining Kifissos sediments also suggests a possible anthropogenic contribution, potentially reflecting Anthropocene-era input of REEs associated with synthetic micro- and nano-particles transported into the coastal system. Similar regional differences were observed for Th concentrations, which ranged from 1.1 to 6.7 ppm in Greek samples and from 0.7 to 1.2 ppm in UAE samples. In contrast, U concentrations were relatively uniform between the two study areas, ranging from 1.2 to 2.3 ppm, suggesting limited localized anthropogenic uranium enrichment. Thorium and U distributions in both coastal environments are therefore interpreted as predominantly natural, particularly in the Kifissos sediments where abundant felsic detrital minerals, such as zircon, likely serve as primary host phases for these elements. Overall, REEs and actinides in both regions occur at relatively low geological background levels (\u003cb\u003eFigures S1 and S2\u003c/b\u003e) and generally exhibit negative geochemical anomalies relative to the Upper Continental Crust (UCC).The only notable exception is scandium (Sc) enrichment observed in Fujairah samples, which is attributed to the natural abundance of Sc in surrounding Ophiolitic rocks. When considering the combined group of REEs together with Y and Sc, the Kifissos samples show total concentrations (ΣREE\u0026thinsp;+\u0026thinsp;Y+Sc) ranging from 31.91 to 133.92 ppm, whereas Fujairah samples exhibit a relatively narrow and more uniform range of 41.70 to 47.73 ppm.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe chondrite-normalized REE patterns of the studied sediments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e) were generally characterized by relatively flat cerium (Ce) distributions, indicating limited redox-driven fractionation during sediment formation, transport, and post-depositional diagenetic modification. The near-flat Ce behaviour suggests that Ce predominantly remained in its trivalent state under oxic to mildly oxidizing environmental conditions, which are typical of well-aerated nearshore marine settings in the coastal zones of Athens and Fujairah. Such patterns imply that strong reducing microenvironments capable of promoting Ce(III) oxidation to insoluble Ce(IV) phases were not widely developed in the examined sediments. Consequently, Ce anomalies did not indicate significant redox-mediated scavenging or enrichment processes that could be associated with severe organic pollution or intense anthropogenic chemical forcing. In addition to Ce behaviour, the europium (Eu) anomalies observed in the samples provide further insight into sediment provenance and mineralogical control of REE distribution. The Eu anomaly values were comparable to those typically reported for Upper Continental Crust-derived materials, suggesting that REE signatures were largely governed by natural lithogenic inputs rather than anthropogenic chemical fractionation. Europium geochemical behavior is strongly influenced by feldspar-related mineral phases, where Eu\u0026sup2;⁺ may substitute for Ca\u0026sup2;⁺ during magmatic crystallization under reducing geological conditions. Therefore, the observed Eu anomaly patterns support the interpretation that sediment REE compositions were primarily controlled by detrital mineral inheritance and weathering processes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe NASC-normalized REE anomaly diagram, expressed as [Ce/Ce*]\u003csub\u003eNASC\u003c/sub\u003e vs. [Eu/Eu*]\u003csub\u003eNASC\u003c/sub\u003e, further elucidates the geochemical controls on sediment composition (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In the Kifissos River discharge zone, Ce/Ce* values ranging from 0.80 to 0.95 indicate weak negative Ce anomalies, suggesting partial oxidative removal of dissolved Ce\u0026sup3;⁺ from the water column through adsorption and co-precipitation with Fe\u0026ndash;Mn oxyhydroxide phases under nearshore oxic conditions. Similar behavior was observed in Fujairah sediments, where Ce/Ce* values ranged from 0.79 to 0.95, implying that marine redox processes, rather than provenance effects, primarily controlled Ce distribution in both study areas. Europium anomalies (Eu/Eu*) ranged from 0.96 to 1.10 in Kifissos sediments, close to the Upper Continental Crust (UCC) signature, whereas sediments from the Fujairah harbor zone exhibited pronounced positive Eu anomalies (1.11\u0026ndash;1.48). This enrichment is consistent with detrital input derived from the Ophiolitic lithologies of the surrounding region -Oman\u0026ndash;UAE ophiolite complex-, where Eu may occur in its divalent state (Eu\u0026sup2;⁺) allowing substitution for Ca\u0026sup2;⁺ in plagioclase minerals during magmatic crystallization. Weathering and mechanical erosion of Ophiolitic rocks therefore generate sediments retaining positive Eu anomalies, while the absence of REE-bearing anthropogenic particles in Fujairah sediments further supports a lithogenic origin. Overall, both coastal zones exhibit negative Ce/Ce* anomalies (0.79\u0026ndash;0.95), indicating oxidative scavenging of Ce in the nearshore marine environment. The relatively narrow variation in [Ce/Ce*]\u003csub\u003eNASC\u003c/sub\u003e vs. [Eu/Eu*]\u003csub\u003eNASC\u003c/sub\u003e values suggests stable oxic depositional conditions in shallow wave-influenced coastal waters, despite differences in source lithology. Consequently, Eu anomalies are more effective for discriminating source lithological contributions, whereas Ce anomalies primarily reflect marine oxidative geochemical processes rather than provenance differences.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGeochemical discrimination diagrams based on La/Th vs. Hf systematics provide additional support for provenance interpretation. The plotted data indicate that sediments in both coastal areas are compositionally \u0026ldquo;fresh,\u0026rdquo; meaning that they have undergone limited sedimentary recycling, chemical weathering, or prolonged transport (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Kifissos sediments plot closer to felsic source fields, whereas Fujairah sediments cluster toward basic to mafic compositional domains. These relationships are fully consistent with the known geological background of the two regions and independently corroborate the REE anomaly interpretations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHigh-resolution microscopic investigation using FEG-(FIB)-SEM-EDS and (S)TEM-EDS/HAADF provided further insight into the microstructural hosting of REE and actinide trace elements. Fujairah harbor sediments do not contain detectable REE- or actinide-bearing micro- or nano-particles. This absence of discrete REE-rich phases indicates that REE distribution in the harbor zone is primarily controlled by detrital mineral provenance rather than secondary adsorption onto anthropogenic particulates or nano-scale enrichment mechanisms. The positive Eu anomaly observed in Fujairah sediments therefore reflects intrinsic lithogenic control associated with mafic\u0026ndash;ultramafic source rocks rather than industrial contamination or marine biogeochemical precipitation processes. In contrast, Kifissos discharge sediments contain abundant natural detrital minerals, particularly zircon (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e5\u003c/span\u003e), which host measurable concentrations of REEs as well as U and Th. Zircon is a well-established geochemical carrier of high-field-strength elements and heavy REEs, and its presence confirms a strong felsic continental crustal contribution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition to natural mineral carriers, various clearly anthropogenic micro- and nano-particles were identified in the Kifissos sediments, indicating a notable association between Ce and Ti. These particles contain either Ce-enriched nano-domains or individual Ti\u0026ndash;Ce and Ti\u0026ndash;V\u0026ndash;Ce nanoparticles, suggesting localized urban-derived particulate input into the coastal system (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The occurrence of REE(Ce)-rich nanostructures within a Si\u0026ndash;O\u0026ndash;Fe matrix, as well as Ti\u0026ndash;(V)\u0026ndash;Ce nanoparticles\u0026mdash;phases that are not typical of natural marine sedimentary mineral assemblages\u0026mdash;supports the presence of Anthropocene particulate signatures in this urban-adjacent coastal environment. These micro- and nanoscale observations demonstrate that REE partitioning in the Kifissos zone involves both natural detrital incorporation and particle-bound anthropogenic sequestration mechanisms.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe combined mineralogical, microstructural, and bulk geochemical results indicate that REE distributions in the studied sediments are controlled by a hierarchical set of processes. Primary control is exerted by geological provenance, reflecting the relative contributions of felsic continental weathering products (Athens) and Ophiolitic mafic\u0026ndash;ultramafic detrital material (Fujairah). Secondary controls are associated with micro- and nanoscale hosting mechanisms, including REE incorporation within zircon grains, which may simultaneously accommodate Th and U, and particulate associations involving anthropogenic Ti\u0026ndash;Ce phases. Additionally, marine redox-mediated scavenging processes contribute to REE redistribution, particularly for Ce. Although bulk REE geochemical patterns predominantly reflect natural lithogenic signatures, electron microscopy analyses revealed localized anthropogenic particulate inputs in the urban-adjacent coastal sediments of Athens. These particles occur mainly as discrete micro- and nano-sized phases rather than as dissolved geochemical anomalies, suggesting that anthropogenic influence is spatially heterogeneous and primarily transported via particulate pathways. Potential sources include urban atmospheric deposition, maritime activities, and other local anthropogenic emissions. The observed divergence between microstructural evidence and bulk REE geochemistry emphasizes the complementary roles of high-resolution imaging and trace element analysis in environmental assessment. While REE systematics primarily record long-term provenance and sedimentary mixing processes, microscopic characterization enables detection of recent or localized anthropogenic particle inputs that may not significantly modify bulk sediment chemistry. Consequently, integrated mineralogical, microanalytical, and radiochemical approaches are essential for reliable evaluation of coastal sediment quality in urban marine environments.\u003c/p\u003e \u003cp\u003eGamma-ray spectrometric measurements (\u003cb\u003eTable S2\u003c/b\u003e and \u003cb\u003eTable S3\u003c/b\u003e) indicate that radioactivity in both areas is predominantly of natural origin, associated mainly with \u003csup\u003e40\u003c/sup\u003eK and the \u003csup\u003e238\u003c/sup\u003eU decay series. However, the presence of anthropogenic radionuclides, particularly \u003csup\u003e137\u003c/sup\u003eCs, is evident in the Greek coastal sediments (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e7\u003c/span\u003e). In Athens samples, activity concentrations range from 63 to 415 Bq kg⁻\u0026sup1; for \u003csup\u003e40\u003c/sup\u003eK and from threshold to 6.01 Bq kg⁻\u0026sup1; for \u003csup\u003e137\u003c/sup\u003eCs. The detection of \u003csup\u003e137\u003c/sup\u003eCs reflects mainly historical global atmospheric deposition following the Chernobyl nuclear disaster. In contrast, Fujairah sediments exhibit generally lower radionuclide activities and minimal detectable anthropogenic contribution (\u003csup\u003e137\u003c/sup\u003eCs up to 2.81 Bq kg⁻\u0026sup1;), consistent with regional fallout distribution patterns and the absence of significant local nuclear contamination sources.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe integrated mineralogical (XRD), geochemical (ICP-MS) and microscopic (FEG-(FIB)-SEM-EDS, (S)TEM-EDS/HAADF) evidence demonstrates that rare earth element (REE) and actinide (Th and U) behavior in nearshore sediments from the Kifissos River discharge zone in the Saronic (Saronikos) Gulf, Athens (Greece), and the coastal port area of Fujairah (UAE) is primarily controlled by lithogenic provenance, with secondary modification by coastal environmental and anthropogenic processes (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the Kifissos discharge zone, REE distribution reflects mixed continental weathering inputs combined with urban particulate contributions, particularly microparticles hosting Ti-Ce-enriched nanophases, indicating localized anthropogenic particle input associated with urbanization and the evolving Anthropocene sedimentary signature. The near-unity Eu anomaly (0.96\u0026ndash;1.10) is consistent with dominantly felsic crustal source material derived from weathered continental lithologies. In contrast, sediments from the Fujairah harbor zone exhibit pronounced positive Eu anomalies (1.11\u0026ndash;1.48), which are attributed to detrital inputs from the mafic\u0026ndash;ultramafic assemblages of the Oman\u0026ndash;UAE Ophiolite complex. Negative Ce anomalies observed in both study areas (Ce/Ce* \u0026lt; 1) indicate deposition under generally oxic nearshore conditions, where Ce is preferentially removed from the dissolved phase through adsorption onto Fe\u0026ndash;Mn oxyhydroxide surfaces. The absence of detectable REE- and actinide-bearing micro- or nanoparticles in Fujairah sediments suggests that REE, Th, and U distributions are primarily controlled by mineralogical provenance rather than secondary anthropogenic particle-associated enrichment processes. Thorium concentrations in Greek coastal sediments (1.1\u0026ndash;6.7 ppm) were higher than those measured in the UAE samples (0.7\u0026ndash;1.2 ppm), reflecting stronger continental crustal influence and possible accumulation of heavy mineral detritus in the Kifissos discharge environment. This is consistent with the presence of zircon crystal fragments, which are known to host both actinides and rare earth elements (REEs). Uranium concentrations were relatively uniform between the two regions (1.2\u0026ndash;2.3 ppm), suggesting comparable marine background incorporation and limited evidence of localized anthropogenic U enrichment. Gamma spectrometric analysis revealed \u003csup\u003e40\u003c/sup\u003eK activity ranging from 63 to 415 Bq kg⁻\u0026sup1; and \u003csup\u003e137\u003c/sup\u003eCs activity ranging from thresholdto 6.01 Bq kg⁻\u0026sup1; in Athens sediments. The presence of \u003csup\u003e137\u003c/sup\u003eCs is attributed mainly to historical global atmospheric deposition associated with the Chernobyl nuclear disaster fallout, whereas generally lower radionuclide activities were recorded in Fujairah sediments. Overall, the integrated application of mineralogical characterization, micro- and nanoscale particle analysis, REE anomaly evaluation, trace actinide quantification, and γ-spectrometry provides a comprehensive multi-proxy framework for understanding sediment provenance, element-hosting mechanisms, and the environmental behavior of radioactive and trace elements in urban-adjacent coastal systems.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eDeclaration\u003c/p\u003e \u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eA. Santos was the principal author and contributed to all stages of the research, data analysis, and manuscript writing. A. Godelitsas acted as supervisor and participated in all stages of the research, analysis, and writing. Chr. Tsabaris, J. Zavašnik, I. Panagiotopoulos, A. Gondikas, and A. Argyraki contributed to fieldwork, sample collection, and analytical measurements. All authors reviewed and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to thank Mr. Vasileios Stasinos, skipper of the HCMR high-speed vessel, who contributed to the sampling.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and analyzed during this study, including REE, actinide (Th and U), and radionuclide (40-K, 137-Cs) concentrations in nearshore sediments from Athens (Greece) and Fujairah (UAE), are included in this published article and its supplementary information files. Additional raw data and measurement details are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAshraf A, Saion E, Gharibshahi E, Kamari HM, Kong Y-C, Hamzah MS, Elias Md.S (2016) Rare earth elements in core marine sediments of coastal East Malaysia by instrumental neutron activation analysis. Appl Radiat Isot 107:17\u0026ndash;23\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEl-Taher A, Zakaly HMH, Elsaman R (2018) Environmental implications and spatial distribution of natural radionuclides and heavy metals in sediments from four harbours in the Egyptian Red Sea coast. Appl Radiat Isot 131:13\u0026ndash;22\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEl-Taher A, Badawy WM, Khater AEM, Madkour HA (2019) Distribution patterns of natural radionuclides and rare earth elements in marine sediments from the Red Sea, Egypt. Appl Radiat Isot 151:171\u0026ndash;181\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePanagiotopoulos I, Kapsimalis V, Hatzianestis I et al (2010) Environmental status of the metropolitan river (Kifissos) of Athens. Greece Environ Earth Sci 61:983\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArgyraki A, Paraskos F, Marmara M, Papadopoulou K, Maglaropoulou A (2013) Comparative geochemistry of three urban streams in Athens: Kifissos-Podoniftis-Pikrodafni. Bull Geol Soc Greece 47(2):910\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEvrenoglou L, Partsinevelou AS, Stamatis P, Lazaris A, Patsouris E, Kotampasi C, Nicolopoulou-Stamati P (2013) Children exposure to trace levels of heavy metals at the north zone of Kifissos River. Sci Total Env 443:650\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePartsinevelou Aik -S, Evrenoglou L (2016) Heavy metal contamination in surface water and impacts in public health. The case of Kifissos River, Athens, Greece. Int J Energy Env 10:213\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEvrenoglou L, Partsinevelou AS, Nicolopoulou-Stamati P (2017) Correlation between concentrations of heavy metals in children\u0026rsquo;s scalp hair and the environment. A case study from Kifissos River in Attica, Greece, Global NEST J. 19(X): XX-XX\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePrifti E, Kaberi H, Paraskevopoulou V, Michalopoulos P, Zeri C, Iliakis S, Dassenakis M, Scoullos M (2022) Vertical Distribution and Chemical Fractionation of Heavy Metals in Dated Sediment Cores from the Saronikos Gulf. Greece J Mar Sci Eng 10:376\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatiatos I, Amaxidis PC, Lazogiannis Y, Papadopoulos K, Dimitriou A (2023) E. Preliminary assessment of nitrate sources of pollution in the urbanized catchment of the Kifissos River. SEGH 2023 Conference, Book of Abstracts, 75\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEl Tokhi M, Amin BM, Alaabed SA (2017) Environmental Assessment of Heavy Metals Contamination of Bottom Sediments of Oman Gulf, United Arab Emirates. J Pollut Eff Cont 5:203\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKalfas CA, Axiotis M, Tsabaris (2016) C. SPECTRW: A software package for nuclear and atomic spectroscopy. NIM A 830/11:265\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEleftheriou G, Tsabaris C, Androulakaki EG, Pappa FK, Patiris DL (2024) High resolution gamma-ray spectrometry for routine measurements of environmental samples. Appl Radiat Isot 206:111234\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRudnick R, Gao S (2003) In: Treatise on Geochemistry, Holland H. D., Turekian, K. K. (eds) Composition of the continental crust, Elsevier-Pergamon, Oxford\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Marine, urban, sediments, REE, actinides, radioactivity","lastPublishedDoi":"10.21203/rs.3.rs-9077317/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9077317/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents the first assessment of REEs, actinides (Th and U), and radionuclides in nearshore sediments from Athens, Greece (Kifissos River discharge into the Saronic Gulf) and Fujairah, UAE (harbor area), using XRD, ICP-MS, electron microscopy, and γ-ray spectrometry. REE concentrations were higher in Athens sediments, reflecting geological and anthropogenic influences as revealed by SEM- and TEM-EDS. Thorium in Athens is associated with minerals such as zircon, whereas U in both areas occurred at low crustal background levels.\u003csup\u003e40\u003c/sup\u003eK activity varied, while\u003csup\u003e137\u003c/sup\u003eCs activity was higher in Athens and lower in Fujairah, consistent with historical Chernobyl atmospheric deposition.\u003c/p\u003e","manuscriptTitle":"Assessment of Rare Earth Elements, Actinides, and Radionuclides in Nearshore Sediments of Urban-Adjacent Coastal Zones in Athens (Greece) and Fujairah (UAE)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-20 19:10:32","doi":"10.21203/rs.3.rs-9077317/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6e66d69f-72a9-415a-b0c5-5422b1f0f7da","owner":[],"postedDate":"March 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-08T07:41:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-20 19:10:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9077317","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9077317","identity":"rs-9077317","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}