Deposition Samples Research Articles

Radioactive contamination transported to Western Europe with Saharan dust.

The Reggane region, where the first French atmospheric nuclear tests were conducted in the 1960s in Southern Algeria, is located in one of the most active dust source regions responsible for recurrent massive Saharan dust events reaching Western Europe and affecting air quality. After a major outbreak in March 2022, a citizen participative science campaign was launched to study the radioactivity born by the dust. One hundred ten deposit samples were collected from six countries in Western Europe with 53 demonstrated as scientifically representative. Geochemical and mineralogical sample analyses combined with satellite observations and back trajectory calculations confirmed an origin from South Algeria, including the Reggane site. Plutonium isotopic signatures, a unique nuclear bomb fingerprint, remained in the range of the global fallout signatures largely dominated by US and former USSR nuclear tests, significantly different from French fallout signatures. Radioactive contamination detected in all samples did not, however, present a risk to public health in terms of radioactivity exposure.

Microstructure modulation and property enhancement via an underwater induction heating treatment strategy for underwater laser-directed energy deposition of Ti-6Al-4V

ABSTRACT In this study, an underwater in-situ induction heating treatment (UIHT)was carried out to modulate microstructure and improve the performance of underwater laser-directed energy deposition (ULDED) samples. The results showed that the redistributive behaviour of alloying elements during the UIHT process promoted the α′→α + β transition. Furthermore, the high temperature enabled dislocation motion, and the heterogeneous dislocations cancelled each other out, causing a decrease in the dislocation density. Notably, the changes in mechanical properties were primarily attributed to the changes in α grain size and dislocation density. The decomposition of martensite α′, characterised by a high dislocation density, elevated the likelihood of intergranular slip. The homogeneously dispersed α + β microstructure promoted coordinated deformation during slip, enhancing the ductility of the specimen and reducing the anisotropy of its mechanical properties. This study offers valuable guidelines for microgroup tailoring and property modulation of ULDED-repaired titanium alloys.

Optimization of Operational Parameters of Power Sprayer for Spraying in Mango Plantation

Portable horizontal triplex pump (HTP) power sprayer is dominant in Konkan region especially for mango orchard spraying. A field experiment was carried out to optimize the performance of power sprayer in mango orchard. The selected mango orchard had 4.5 - 5.0 m height trees planted at 10 × 10 m spacing. Water sensitive papers of 44 × 44 mm size were stapled on up and down sides of tree leaves at different canopy positions to catch the spray deposition samples. The selected power sprayer was equipped with horizontal triplex plunger pump having power 3 kW and speed 1000 rpm. The experiment was conducted by varying the suction pressure from 980 to 1961 kPa, nozzle-to-target distance from 0.50 to 0.60 m, travel speed in range of 0.30 to 0.60 m s-1. The two nozzle types, viz., hollow and solid cone nozzle were used in the experiment. The statistical optimization was carried out using response surface methodology (RSM) with Box Behnken, randomized subtype design with total 34 experiments. The optimum parameters viz., pressure, nozzle distance and travel speed were 1471 kPa, 0.55 m and 0.45 m s-1, respectively for power sprayer with hollow cone type nozzle. At these optimized levels, the dependent variables viz., droplet size, droplet density, uniformity coefficient and spray deposition were observed as 291.4 µm, 120.12 droplets cm-2, 1.78 and 0.64 µl cm-2, respectively. These optimized parameters resulted in improved pesticide spraying efficacy with better coverage and improved safety during spraying operation in the mango orchard.

The effect of interval pulsed laser deposition on the microstructure and mechanical properties of Inconel 718 parts using laser directed energy deposition

ABSTRACT The solidification process of laser directed energy deposition (LDED) affects elemental separation, microstructure, and tensile properties. This work proposes an interval pulsed laser deposition (IPLD) process to improve the cooling rate. The IPLD and continuous laser deposition (CLD) samples are prepared at the same laser power for comparative analysis. Solution treatment and aging (STA) heat treatment processes are developed to compare the as-deposited and STA samples. Finite element simulation results showed that the IPLD process has a smaller molten pool and a higher cooling rate. In the microstructure analysis, the IPLD samples have stronger < 001 > texture and smaller grains in all samples. Smaller Laves phase distributions and Nb-rich areas are found in IPLD as-deposited samples. After the STA, the long-chain Laves phases completely dissolve into discrete areas and the Nb-rich areas almost disappear. More short rod and needle-like δ-phases are observed around small Laves phases, and the proportion of large-size Laves phases decreases significantly. The Nb mass fraction of Laves phases is 16.9 in IPLD samples, which is lower than 26.66 in CLD samples. For IPLD samples, the YS (1095 Mpa), UTS (1310 Mpa), and elongation (24.5%) reached the level of Inconel 718 wrought parts.

Comparative analysis of metal oxide nanoparticle accumulation in landfill gas engine combustion chambers: Insights from three sites

Combustion chamber deposits adversely affect the operating performance of gas engines. In this study, the elemental composition of deposit samples collected from the inner surface of combustion chambers in gas engines across three different facilities was examined using various methods. The proportional changes in metal oxides along the internal cross-sectional surfaces of the deposits were examined to depict the deposit formation process from beginning to end. Additionally, the study investigated the identification of metals accumulated in the engine oil, their contribution to deposit formation, and the accumulation mechanisms of metal oxide nanoparticles on the engine’s interior metal surfaces. The main elements identified in the deposits from the Odayeri and Kömürcüoda facilities were Si, S, and Ca, whereas deposits from the Dilovası facility contained Si and Sb. These major elements, identified by SEM-EDS, were confirmed through XRF analysis. XRD analysis further confirmed the presence of Ca and S as CaSO4 crystals in the deposits. Ca originates from additives used to increase the total base number of engine oil and control the corrosive effects of landfill gas. It has been determined that silicon accumulates in engine oil over time. An important finding is that metal oxides in the combustion chamber primarily accumulate through impaction, sticking, and thermophoresis mechanisms.

TiC reinforced Ti6Al4V fabricated by circular oscillating laser directed energy deposition: Microstructure and wear resistance

Gaussian laser is a common laser source in the field of laser directed energy deposition (L-DED). However, Gaussian laser sources have certain limitations, as they produce elevated temperature differentials and internal stresses during L-DED, which can result in significant distortion and fracturing. To address these restrictions, this research proposes using a circular oscillating laser as the energy source for L-DED. TC4 deposition samples and 5 wt% TiC/TC4 composite deposition samples were prepared using both Gaussian laser directed energy deposition (GL-DED) and circular oscillating laser directed energy deposition (COL-DED), and the deposition samples prepared under the two laser modes were compared and studied. The results indicate that, in the process of COL-DED, the laser oscillates periodically at a constant frequency in the high-temperature molten pool, which produces a more consistent temperature gradient and improved stirring effect in the molten pool. This inhibits grain growth and effectively refines the grains. Compared to the TiC/TC4 deposition samples prepared with Gaussian laser, the average grain size of COL TiC/TC4 deposition samples decreased by approximately 54.3 %. Due to the effects of the high-power laser beam, TiC particles partially melted and decomposed into Ti and C. As the laser advanced, the molten pool cooled swiftly, ultimately precipitating uniformly distributed gray-white TiC hard phases. Compared to the TC4 alloy prepared with the Gaussian laser, the TiC/TC4 composite material manufactured with a circular oscillating laser exhibited a 24.5 % increase in microhardness (430.76 HV0.2) and a reduction in wear rate of approximately 42.15 % (to 1.4 × 10−6 g/mm). Circular oscillating laser directed energy deposition can, to a certain extent, improve the hardness and wear resistance of materials compared to Gaussian laser directed energy deposition.

Black powder and mineral deposits in the LPG production and processing line: Analytical study and formation mechanisms

The accumulation of mineral deposits such as black powder causes severe impacts throughout the gas production and transport process. The phenomenon takes place from gas wells to LNG/LPG treatment plants and terminals. The complexity lies in understanding the mechanisms by which these materials are formed in random quantities, as well as their varied nature. The aim of this study is to monitor black powder and other mineral deposits formation in a chain of gas production and processing situated in the south of Algeria and unravel their root causes. To that extent, an analytical study was carried out on four samples of both mineral deposits and black powder taken from an LPG processing and production unit. The adopted analytical approach included an exploration of the textural and structural properties. It also involves a composition characterizations related to the content of metallic elements, moisture, organic and mineral matter. The particle distribution is also determined. The analytical study was conducted using gravimetric determination, XRD, XRF, SEM/EDX and Raman spectroscopy. Particle distribution was given by Laser granulometry technique. The results of the DRX/FRX and EDX characterization primarily revealed that the samples contain a variety of mineral components such as iron oxides; magnetite Fe3O4 and hematite Fe2O3, iron oxy-hydroxide FeO(OH), iron sulphide FeS2, calcite CaCO3, SiO2 and halite NaCl. The presence distribution of these components depends on the location of the sample in gas line. Granulometry study shows that black powder contamination can be spread over a wide spectrum of particle sizes ranging from 1.51 µm to 678.50 µm. This study has allowed to elucidate the nature and distribution of particles deposited at different positions in the LPG production chain and to propose probable mechanisms for their formation.

Geochemical Characteristics of Clay Deposits, Bussaya Area, Southern Iraq

This study concerned with the geochemical characteristics of clay deposits belong to Nfayilbeds (Middle Miocene) in Al Muthana Governorate southern Iraq, as a new resource of clayraw material. Twenty three samples of clay deposits were analyzed by using X-RayFluorescence technique (XRF) for the major oxides; (SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O,K2O, TiO2, and L.O.I), and trace elements; (V, Cr, Co, Ni, Cu, Zn, As, Sr, Pb, Ga, Rb, Ba, andZr). The chemical results demonstrated due to the relation between Sr and Cu, that thedepositional environment predominated by hot and arid paleoclimate conditions, while from therelation between Al2O3 with (Al2O3, CaO, Na2O, and K2O) reveals a low to relatively moderatechemical weathering. Whereas the ratio of Ni/Co reveals that the deposition was within hypoxicenvironment, while due to the ratio of Al2O3 / TiO2 in which advocated by Ti- Zr relation whichdemonstrates that the intermediate igneous rocks as a provenance of the studied clays.

Investigating the deposition of fibrous zeolite particles on leaf surfaces: A novel low-cost method for detecting the presence of airborne hazardous mineral fibers

Naturally occurring fibrous minerals, such as erionite, can pose a significant threat to human health when disturbed and subsequently respired. Understanding the spatial abundance and characteristics of these hazardous fibrous minerals in ambient air is crucial for minimizing human exposure and assessing risk. Conventional detection methods for airborne hazardous mineral fibers, such as those developed for asbestos, are of limited utility in environmental settings where fiber concentrations are low and different fiber types may be present and can be costly especially when monitoring large areas over long periods of time. This study presents an innovative methodology for detecting and identifying the presence of airborne naturally occurring fibrous zeolites, using leaf surface deposition sampling, SEM-EDX analysis for the detection and assessment of elemental composition, and TEM-SAED with continuous rotation diffraction (MicroED) to determine their crystallographic unit cell parameters. In total, 309 fibrous zeolite particles (FZPs) were identified on a range of tree leaf surfaces across 80 % of the sampling sites located close to both active and disused zeolite quarries in the Taupo Volcanic Region, New Zealand. The FZPs displayed various morphologies including aggregates, bundles, and fibril-like structures. Of the FZPs detected, 92.2 % were < 5 µm in length. Tetrahedral Si:(Si+Al) ratio results indicated that 40 % of the FZPs were in the reference range for zeolite mordenite. TEM-SAED plus MicroED analysis resulted in 61 % of tested FZPs indexed to unit cell parameters that matched with mordenite. This research demonstrates the potential of leaf sampling as a cost-effective method for detecting airborne FZPs while the MicroED data can be utilized for distinguishing between different types of airborne fibrous zeolites in ambient air.

An investigation of subaqueous failures triggered by the 1935 CE Mw 6.1 Témiscaming earthquake, Quebec, Canada, as an analogue for a paleoseismic study

Subaqueous mass transport deposits (MTDs) attributed to the Mw 6.1 1935 CE Témiscaming earthquake were mapped at 17 sub-bottom acoustic profile survey areas on 11 lakes near Témiscaming, Quebec. Distributed over about 1270 km2, MTDs are the product of shallow failures, up to several metres thick, that occurred along planar surfaces and involved primarily lacustrine sediments. Core samples of unfailed deposits indicate that the failure planes occurred within soft sediments at the top of a glaciolacustrine unit or at the base of overlying lacustrine deposits. Radioisotope dating of sediment samples from six coring sites on Tee and Kipawa lakes confirm that the MTDs are the product of failures triggered by the 1935 CE earthquake. To assess the application of such a mapping study to a paleoseismic investigation, the minimum magnitude of an earthquake that can generate an MTD distribution of 1270 km2 was extrapolated from a published empirical plot. The resulting magnitude of Mw/Ms 5.7–5.8 is less than the instrumental Mw 6.1 magnitude and deemed a reasonable estimation of minimum earthquake magnitude. The distribution of MTDs triggered by the 1935 CE earthquake forms the only such signature within the Témiscaming study area since roughly 8 ka cal B.P. The lack of an analogous, older signature(s) is consistent with the absence of equivalent shaking to the 1935 CE earthquake over this period, but the actual timespan may be shorter and begin when gyttja deposits on slopes became thick enough to be prone to failure from such an event.

Influence of the Mixture of Xanthates collectors on the Flottation of Difficult Copper Ici de Oré to Float-Case of Minerals Fill 18 Deposit Shangulowe

This paper presents the results of a study conducted to highlight the influence of the mixture of xanthate collectors on the flotation of copper oxide ores. The Shangolowe deposit sample assayed 3.22% copper and 0.08% cobalt, and by means of mineralogy and chemical analysis the gangue appears dolomitic. Test optimization ratio and the main sulfudizing collector were performed, testing after which the dosage rates of 4000g NaSH / dT ore and 400g KAX /dT ore were used as a reference for further testing. Xanthate collectors namely: KAX, KEX, SIBX and SNPX were tested alone and their specific behaviors were reported. The study showed that KAX increase the recovery and three other collectors improved concentrates quality. They were then taken two to two mixed in the proportions of 25% -75% 50% -50% 75% -25%. It appears from these tests that the mix-KAX/SIBX taken in ratios of 75 and 25%, stood out all tests because it offered good selectivity and improved metallurgical performance. Comparative testing of cleaning under standard conditions and the best test mixture, also confirmed an improvement in the selectivity of 7 points compared to the usual KAX. A comparison of the collector’s costs, helped highlight a desired gain per ton contained copper with the use of mixed collectors which was about 13% compared to the use of KAX alone. Operating conditions and flotation scheme on the test which offered the best metallurgical performance subsequently proposed to the operator, who was consolidating the results obtained previously with cyclic tests in laboratory and pilot plant.

Comparison of off-target pesticide drift in paddy fields from unmanned aerial vehicle spraying using cellulose deposition sampler

Off-target pesticide drift in paddy fields following unmanned aerial vehicle (UAV) spraying was evaluated using cellulose deposition samplers (CDSs). An analytical method for quantifying ferimzone Z and E isomers deposited on CDSs was developed using LC-MS/MS. The suitability of the CDS method was confirmed by comparing deposition patterns on CDSs with residue levels in rice plant samples. To assess pesticide deposition in paddy fields, CDSs were strategically placed at varying distances from target areas, followed by UAV spraying. The fungicide agrochemicals were applied with and without adjuvants, and wind direction affected the drift trajectory for all treatment groups. Adjuvants, particularly soy lecithin as the major component, significantly enhanced pesticide deposition within the spray pathway while reducing drift rates relatively by 47.9–68.0 %. Higher wind speeds were found to exacerbate drift, but adjuvant-treated sprays showed less variability in deposition patterns under these conditions. Pesticide residues in harvested brown rice were found to be below the maximum residue limits (MRLs), ensuring safety for consumption. These findings highlight the importance of selecting appropriate adjuvants in UAV-based pesticide applications to optimize deposition efficiency and minimize environmental contamination.

Lastarria volcano, a major emitter of boron and chalcophiles in northern Chile and the Central Volcanic Zone

This study examines the trace element chemistry of fumarolic deposits and fumarolic plumes at Lastarria volcano, located in northern Chile. Fumarolic deposits were manually collected, while fumarolic plumes were sampled using the filter pack technique; after sample preparation, both sample types were analyzed by ICP-MS. The research focuses on chalcophile elements (As, Cd, Sb, Te, Cu, Zn, Tl, Pb, and Bi) and B, with the findings revealing significant enrichment of As and Pb in fumarolic deposit samples, especially in medium- and high-temperature fumarolic vents, respectively. On the other hand, filter pack measurements in the fumarolic plume indicate a notable enrichment in Te, B, As, and Tl, with Sc-normalized enrichment factors within the range of 104–106. From these elements, B, Tl, and Te appear to be less scavenged at the vent, presenting more significant enrichments in fumarolic plumes than in fumarolic deposits. By comparing our results with subduction-related volcanoes such as Etna, Stromboli, Lascar, Masaya, or La Soufrière de Guadeloupe, Lastarria fumarolic plume can be regarded as the one with the highest concentrations of B and As ever recorded. Moreover, Lastarria has chalcophile enrichments comparable to those volcanoes with shallower magma chambers and high-temperature magmatic emissions such as Stromboli. The higher abundance of chalcophiles suggests a significant magmatic influence feeding Lastarria fumaroles and the presence of ligands, such as Cl, which can transport significant amounts of chalcophiles at shallower levels of the crust during late-stage magma crystallization. Large amounts of chalcophiles released by Lastarria and Lascar volcanoes could be responsible for the naturally elevated concentrations of these elements in the Altiplano-Puna area. Future studies should focus on the lifetime of chalcophiles in the Central Andean atmosphere, where these elements could reside for a longer time given the dominant hyperarid environment.

Effect of hydrogen flow rate on the plasma state and quality of diamond crystals grown by MPCVD

The electronic application of diamond is still immature because of the relatively high density of dislocation. Hydrogen flow rate is one of the key parameters that determine the crystalline quality of diamond, but most of the previous works focus on the growth of polycrystalline diamond. Herein, the effects of hydrogen flow rate on the growth rate and crystalline quality of single crystal diamond have been evaluated while keeping the CH4/H2 ratio. It demonstrates that a medium H2 flow rate can balance the C2 concentration and nitrogen leakage in the chamber, resulting in the maximum of growth rate. Similarly, the dislocation density decreases firstly and then increases with a minimum value of 4 × 104/cm2 under a medium H2 flow rate. The variation of growth rate and dislocation density versus hydrogen flow rate can be double-confirmed from both high pressure and high temperature and chemical vapor deposition samples. The incline angle of step riser relative to the terrace is smaller than 20°, which helps to switch the propagation direction of dislocation towards the raiser region. A relatively wider step width under a medium H2 flow rate means a lower density of step riser region to display the dislocation. Therefore, we conclude that a medium hydrogen flow rate can effectively balance the crystalline quality and growth rate of the single crystal diamond.

Mutational Features and Tumor Microenvironment Alterations in High-Grade Appendiceal Cancers Treated With Iterative Hyperthermic Intraperitoneal Chemotherapy.

High-grade appendiceal adenocarcinomas (HGAA) with peritoneal metastases (PMs) are associated with poor survival. Hyperthermic intraperitoneal chemotherapy (HIPEC) is a novel treatment approach for unresectable HGAA-PM. However, its influence on immunogenomic profiles has not yet been fully explored. We obtained 79 samples of metastatic peritoneal tumor deposits from patients diagnosed with HGAA and performed whole-exome sequencing, RNA sequencing, and immunoprofiling before and after HIPEC. Tumor biopsies were subjected to immunogenomic profiling to detect mutational signatures and immune populations associated with oncologic outcomes. Fifteen patients with HGAA-PMs were included in the study. The median progression-free survival (PFS) was 6.7 months (2.7-25.3) and the median overall survival was 11.4 months (4.7-42). Mucin-associated genes (MUC16, MUC3A, and MUC5AC) and titin (TTN) had the highest mutation frequencies. Mutational signatures such as single-base substitution 29 and doublet-base substitution 11 were present in >50% of single-base and double-base mutations. Higher PD-L1 coexpression on CD8+ T cells demonstrated a higher PFS both intratumorally (P = .019) and at the margin (P = .025). HIPEC-associated mutational signatures were identified in HGAA-PMs. Elevated PD-L1+ cytotoxic T-cell populations after HIPEC had better PFS, offering valuable insights for prognostication in the context of HIPEC treatment.

Analysis of carbon and nitrogen from atmospheric sources by bulk deposition sampling at various locations in Germany

Atmospheric deposition of particulate matter is an important indicator of air pollution and a significant factor in material surface fouling. The elemental composition of this nutrient-containing dust depends largely on the exposure region and time as well as on climate. Therefore, in this paper we report an analysis of atmospheric pollutions with a self-made low-cost bulk deposition sampler directed at sampling deposition via air transport and rainfall. We used the device in diverse environments - thus comparing an urban region, an area surrounded by forest and an area mainly dominated by agriculture. The total organic carbon (TOC) and total nitrogen (TN) amounts were selected as indicator parameters and analyzed in a biweekly rhythm for three and a half and two years, respectively. The TOC value responded to particulate matter in the urban area, especially significant were the influences of the New Year's firework in urban and pollen in the rural forest area. In contrast, the TN value was more under the influence of the nitrogen emissions in the agriculture-dominated area. However, the TN value did not correlate with the NOx values in the urban area because the atmospheric nitrogen emissions in the city might originate from various emission sources. Summarizing, the TOC and TN values of the self-made low-cost bulk deposition sampler were in good agreement with environmental events of their immediate surrounding. Moreover, the selected containers and sampling procedures are universally applicable to monitor and analyze organic as well as inorganic parameters (e.g. metal ions) of atmospheric deposition.

A novel ultrasonic rolling assisted direct energy deposition method with semi-solid thixo-forming characteristics for AA6061

In order to overcome the defects during the process of additive manufacturing for AA6061, a novel ultrasonic rolling assisted direct energy deposition method with semi-solid thixo-forming characteristics was proposed in this study, which used cold deformed AA6061 wire as raw material, and a corresponding process platform was established. The results showed that under the conditions of laser heating temperature of 750 ℃ and heating plate temperature of 200 ℃, the sample could achieve continuous multi-pass deposition while retaining some of the cold-drawn plastic deformation energy. When the vertical deformation rate was 0.153 and the ultrasonic amplitude was 20 μm, the microstructure of deposition sample after semi-solid heat-treat exhibited typical equiaxed grain characteristics, corresponding to average grain diameter of 95.6 μm and shape coefficient of 1.263. Thin-walled samples with different shapes were formed to verify the capability of process platform. The inference of the formation mechanism of semi-solid microstructure was revealed at last: the introduction of ultrasonic rolling supplemented the plastic deformation energy, and semi-solid heat-treat provided temperature and time for the incubation of equiaxed grains, both of which were crucial for the formation of the semi-solid microstructure.

Dry deposition fluxes, source, and potential ecological impact of amino acids in the Danjiangkou Reservoir of China's South-to-North water transfer project

As a nitrogen source for biological growth, amino compounds can participate in global nitrogen cycle processes and directly impact ecosystems. Dry deposition samples were collected from September 2020 to August 2021 from the Danjiangkou Reservoir of the South-to-North Water Transfer Project. The dry deposition characteristics of amino acids in the reservoir area were analyzed, their sources were resolved, and the potential ecological impacts were evaluated. The results showed that the dry deposition flux of dissolved free amino acids was 0.48 kg N ha−1 yr−1 and that of dissolved combined amino acids was 1.09 kg N ha−1 yr−1 in Danjiangkou Reservoir. The dominant amino acid fractions were glutamic acid and aspartic acid. Agricultural activities, coal combustion, and primary biogenic particles influenced the amino acid deposition in the reservoir area. The potential source areas for amino acid deposition mainly influenced the northeast, southwest, northwest, and south of the reservoir. The amounts of amino acids entering the water bodies via dry deposition was 85.72 t N yr−1, contributing 0.83 g C m−2 yr−1 of new production to the reservoir water bodies. To summarize, this research depicted that the potential ecological impact of dry deposition of amino acids on artificial freshwater lakes should not be overlooked.

Givetian megaspore assemblages of the Mikhailovksy mine (Kursk oblast)

Background. Disperse megaspores from the Givetian deposits of the Mikhailovsky mine, Kursk Oblast, were studied for the first time. Following chemical maceration of the samples, their selection and identification, 12 species belonging to 8 genera of disperse megaspores were identified. The conducted analysis of the layer-by-layer distribution of disperse megaspores in the studied outcrop, two megaspore assemblages were established, describing the lower (M1) and upper (M2) parts of the section. Both assemblages are dominated by small-sized azonate megaspores of the Hystricosporites McGregor genus, although belonging to different species. The upper assemblage (M2) is more diverse in terms of taxonomic composition. Along with the Givetian deposits of the Mikhailovsky mine, the identified disperse megaspores were previously found in coeval deposits of Canada and Libya.Aim. To study of disperse megaspores from the Givetian deposits of the Mikhailovsky mine (Kursk Oblast) and to establish megaspore assemblages for this section.Materials and methods. Samples of the clay deposits of the Givetian stage of the Middle Devonian from the Mikhailovsky mine (Kursk Oblast, Zheleznogorsk) were collected by employees of the Paleontological Institute of the Russian Academy of Sciences (PIN RAS) in the summer of 2017. The samples were macerated at the Department of Paleontology using concentrated (55%) hydrogen peroxide. The samples heavily contaminated with megaspores were additionally treated with hydrofluoric acid and further purified in hot drops of denaturated alcohol. Selection, counting, and determination of macerated samples of disperse megaspores were carried out using an Olympus CZ65 stereomicroscope at a 20x magnification or greater. Microphotographs were taken using a TESCAN Vega-3 scanning electron microscope (PIN RAS).Results. A total of 12 species belonging to 8 genera were identified. These included Hystricosporites McGregor, Verrucisporites Chi et Hills, Nikitinsporites Chaloner, Biharisporites Potonié, emend. Glasspool, Ancyrospora Richardson, Contagisporites Owens, Grandispora Hoffmeister, Staplin et Malloy, emend. McGregor, and Lagenicula (Bennie et Kidston) Dybova-Jachowicz et al. On the basis of disperse megaspore distribution along the section, two megaspore assemblages were established: M1 (lower, layers 7–12) and M2 (upper, layers 18–21).Conclusion. The disperse megaspores established in the Givetian deposits of the Mikhailovsky mine were early described in the Arctic Canada. The majority of the studied megaspores were most likely produced by lycopsids. This conclusion is based on their comparison with identical in-situ megaspores, as well as on the ultrathin structure of the sporoderm, previously established for some species. Consequently, the Givetian forests of the studied region were populated with numerous lycopsids, including tree-like ones, among heterosporous plants, with an insignificant role of archaeopteridalean tree-like species.

Distribution, sources, ecological and human health risks of organic ultraviolet filters in coastal waters and beach deposits in Hainan, China

Organic ultraviolet filters (OUVFs) are extensively incorporated into both cosmetic items and industrial products and have been commonly found in water ecosystems. This study aims to examine the environmental levels, sources, ecological and human health risks of 14 commonly used OUVFs both in coastal water and beach deposit samples collected from the nearshore regions of Hainan Island and the South China Sea. This is first study highlighting the contamination of OUVFs in Hainan Island and utilizing economic and tourism data to confirm the potential source of OUVF pollution in costal aquatic and coastal ecosystem. Along the coastal tourist regions of Hainan Island, the median concentrations in coastal waters and beach deposits of these OUVFs fall within the range from 1.2 to 53.2 ng/L and 0.2–17.0 ng/g dw, respectively. In coastal water and beach deposit, the concentration of BP-3 was the highest, with median concentrations of 53.2 ng/L and 17.0 ng/g dw, respectively. Regarding human health risks, the daily intake of all 14 OUVFs through swimming was found to be 40–48 ng/kg/day. Ecological risk assessment indicates that BP-3 presents a medium risk for marine microalgae with a concurrent low risk for corals. The correlation analysis underscores a substantial interrelation of OUVFs in both coastal waters and beach deposits with various economic indicators, including annual rainfall, overnight tourists, total hotel rooms (unit), room occupancy rate, and sewage treatment capacity.