Spatial Distribution Of Elements Research Articles

Source Analysis and Contamination Assessment of Potentially Toxic Element in Soil of Small Watershed in Mountainous Area of Southern Henan, China.

In this study, the concentrations of potentially toxic elements in 283 topsoil samples were determined. Håkanson toxicity response coefficient modified matter element extension model was introduced to evaluate the soil elements contamination, and the results were compared with the pollution index method. The sources and spatial distribution of soil elements were analyzed by the combination of the PMF model and IDW interpolation. The results are as follows, 1: The concentration distribution of potentially toxic elements is different in space. Higher concentrations were found in the vicinity of the mining area and farmland. 2: The weight of all elements has changed significantly. The evaluation result of the matter-element extension model shows that 68.55% of the topsoil in the study area is clean soil, and Hg is the main contamination element. The evaluation result is roughly the same as that of the pollution index method, indicating that the evaluation result of the matter-element extension model with modified is accurate and reasonable. 3: Potentially toxic elements mainly come from the mixed sources of atmospheric sedimentation and agricultural activities (22.59%), the mixed sources of agricultural activities and mining (20.26%), the mixed sources of traffic activities, nature and mining (36.30%), the mixed sources of pesticide use and soil parent material (20.85%).

Spatial Distribution, Contamination Levels, and Health Risks of Trace Elements in Topsoil along an Urbanization Gradient in the City of Urumqi, China

For this study, we collected a total of 77 topsoil samples from urban, suburban, and rural gradients in the Urumqi city area in northwest China and analyzed their concentrations of seven trace elements: Arsenic (As), cadmium (Cd), nickel (Ni), lead (Pb), mercury (Hg), copper (Cu), and Zinc (Zn). To assess and compare the contamination levels and the potential health risk of trace elements in topsoil along an urbanization gradient, we employed the pollution index and the health risk assessment model introduced by the US Environmental Protection Agency; we also used geostatistical analysis to analyze the spatial distribution patterns. The results we obtained indicate that the contamination levels of trace elements in soil decreased in the order of urban > rural > suburban gradients. We found a similar spatial distribution pattern of contamination levels of Ni, Zn, Cd, and Pb elements, with a zonal distribution pattern, while the spatial distribution patterns of As, Cu, and Hg elements show high concentration patches in many of the areas investigated in this study. Furthermore, based on the identified concentrations, the topsoil is heavily contaminated by Hg and slightly contaminated by Pb, As, and Zn in the urban gradient, whereas it is heavily contaminated by Hg in suburban and rural gradients and slightly contaminated by As in the suburban gradient. The total non-carcinogenic risk index of the analyzed trace elements for adults and children decrease in the order of urban > suburban > rural gradients, whereas the total carcinogenic risk index of the analyzed elements for adults and children decreased in the order of suburban > urban > rural gradients. However, the contamination of topsoil in all gradients is more harmful to children’s health than to that of adults. Overall, urbanization has had obvious effects on the accumulation of trace elements in soil, and As is the main carcinogenic and non-carcinogenic risk factor among the investigated elements in topsoil in all urbanization gradients.

Characterization of geochemical elements in surface sediments from Chinese deserts

Northern China has 12 main deserts that range from extremely arid regions in the west to semi-arid or semi-humid regions in the east. Based on their geographical locations, we divided these deserts into western, central, and eastern deserts. We investigated the geochemical elements in their surface sediments and found that the concentration of the major element SiO2 gradually increased from west to east, whereas the other major elements tended to decrease; however, the CaO concentration was unusually high in the Taklimakan and Qaidam Basin deserts. The spatial distribution of geochemical elements was more homogeneous in the western and central deserts than in the eastern. Unlike the eastern deserts, the western and central deserts show greater physical than chemical weathering and lower mineral maturity due to the extremely low precipitation and a continuous supply of younger materials. Most major trace elements in the eastern deserts were more depleted relative to the upper continental crust than in the western deserts, but were moderately depleted in the central deserts. The potential source rocks of central and western deserts are composed of intermediate igneous source rocks, while the sediments in eastern deserts are derived from the mixing of felsic and intermediate igneous source rocks or the mixing of quartzose deposits and intermediate igneous source rocks. The spatial distribution of geochemical elements showed similar provenances of aeolian material in the Taklimakan Desert and Kumtag Desert, and similar provenances of aeolian material in the Badain Jaran, Tengger, Ulan Buh, and Hobq deserts. There were no obvious provenance relationships for the Otindag, Horqin, and Hulun Buir sandy lands in the central and western deserts.

Structural studies of the brass ingots from the Shcherbet historical complex of the Lower Kama region: neutron diffraction and tomography studies

The structural characteristics and phase composition of several ancient brass ingots obtained in the archeological Shcherbet complex has been studied using neutron diffraction and tomography methods. The XRF analysis and neutron diffraction provide high zinc content up to 30 wt.%. The neutron tomography yielded 3D data of the spatial distribution of chemical elements in the brass alloy of the studied ingots, as well as inner voids and cavities as a possible result of the gas output during casting process. The patina, as a cuprite phase, occupy volumes to 8 % of the volumes of the ingots.

Immunohistochemical characterization of stem cell, vascular, neural, and differentiation markers in the apical papilla and dental pulp of human teeth at various stages of root development

ABSTRACT This study aimed to evaluate the expression of several differentiation markers in the apical papilla (AP) and dental pulp (DP) of human permanent teeth. Twenty young human teeth were extracted and classified according to three Moorrees tooth development stages: initial root formation (Ri), root length ½ (R1/2), and root length complete (Rc). Immunohistochemical assays were performed using STRO-1, VEGF Receptor-2, Neurofilament heavy (NFH), and Nestin antibodies and analyzed under light microscopy. Decalcified, formalin fixed paraffin embedded tooth sections stained with hematoxylin and eosin showed an apical cell rich zone between the DP and AP. The AP revealed fewer vascular and cellular components than the DP. STRO-1 was expressed on vascular and neuronal elements beneath the odontoblast (OB) and in the sub-odontoblastic (SOB) zone, and VEGFR-2 positive cells were observed in the endothelium, arterioles, and blood vessels. Neuroepithelial stem cell protein (Nestin) was highly expressed in differentiated odontoblasts in the predentin odontotoblast and odontoblast cell processes. Neurofilament heavy (NFH) was expressed in mature axons throughout the DP. STRO-1 and VEGFR-2 microvascular expression was higher at the stages Ri and R1/2 while STRO-1 and NFH expression showed strong spatial distribution of Rc neuronal elements as compared to Ri and R1/2. Differentiated OB and SOB cells showed Nestin expression, indicating a reservoir of newly differentiated odontoblast-like cells.

Trace elements in public drinking water in Chinese cities: Insights from their health risks and mineral nutrition assessments.

The trace elements in the public drinking water have a duality: on the one hand, trace elements play an important role in maintaining human metabolism; on the other hand, high trace elements levels lead to significant health risks. To determine the impacts of trace elements in the public drinking water on physical health in China, water samples were collected from 314 Chinese cities to analyze the concentrations and spatial distributions of trace elements on a national scale. On this basis, the non-carcinogenic health risk assessments and the nutrient-based scores of trace elements (NSTEs) were applied to evaluate the public drinking water quality in terms of safety and nutrition. Most of the water samples were weakly alkaline: pH values fell in the range of 6.62-8.54, with a mean of 7.80. The results indicated that Sr and F- had the highest concentrations in public drinking water, with averages of 0.3604mg/L and 0.2351mg/L, respectively. Moreover, hazard index (HI) values in different regions followed the order: northwest China (NWC)>northern China (NC)>Qinghai-Tibetan Plateau (QT)>southern China (SC). The percentages of water samples with HI>1 in SC, NC, NWC, and QT were 5.49%, 16.82%, 25.81%, and 16.67%, respectively, indicating that the public drinking water in some cities had significant non-carcinogenic health risks. In addition, the intakes of Mn, Fe, Cu, and Rb through public drinking water made negligible contributions to their recommended nutrient intakes. In contrast, trace elements like Sr, F, B, Li, Mo, etc., contributed a lot. The NSTEs in NWC and most parts of NC were relatively high with averages of 8.0300 and 11.2082, respectively; however, the NSTEs in SC and the northeast part of NC were low with averages of 3.3284 and 5.2106, respectively. The results from this study provide a reference for establishing the public drinking water standards and improving drinking water quality.

Construction and Optimization Strategy of an Ecological Network in Mountainous Areas: A Case Study in Southwestern Hubei Province, China.

High-intensity urban development and economic exploitation have led to the fragmentation and isolation of regional habitat patches, and biodiversity is under serious threat. Scientific identification and effective optimization of ecological networks are essential for maintaining and restoring regional ecosystem connectivity and guiding sustainable socio-economic development. Taking the mountainous areas of southwest Hubei Province (MASHP) in central China as an example, this study first developed a new integrated approach to identify ecological sources based on a quantitative assessment of ecosystem services and the morphological spatial pattern analysis (MSPA) method; it then used the Linkage Mapper tool to extract ecological corridors, applied the principle of hydrological analysis to identify ecological nodes, evaluated each ecological element to quantify its importance, and finally constructed the ecological network and further proposed some optimization countermeasures. The results show that the ecological network in the MASHP is dominated by ecological resources composed of forestland. Connectivity in the central region is significantly better than in other regions, including 49 ecological sources with an area of 3837.92 km2, 125 ecological corridors with a total length of 2014.61 km, and 46 ecological nodes. According to the spatial distribution of crucial ecological landscape elements, a complete and systematic ecological framework of “two verticals, three belts, three groups, and multiple nodes” was proposed. The internal optimization of the ecological network in mountainous areas should focus on improving ecological flow, and strategies such as enhancing the internal connectivity of ecosystems, unblocking ecological corridors, and dividing ecological functional zones can be adopted. Based on the above analyses, this study also made recommendations for ecological protection and development and construction planning in mountainous areas. This study can provide realistic paths and scientific guidelines for ecological security and high-quality development in the MASHP, and it can also have implications for the construction of ecological networks and comprehensive ecological management in other mountainous areas.

Heavy metal levels and sources in suspended particulate matters of the glacier watersheds in Northeast Tibetan Plateau

This study collected summer meltwater runoff samples from several glacier watersheds of the northeast Tibetan Plateau during June-July 2017, and measured the concentrations of 17 trace elements (Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Mo, Cd, In, Sb, Cs, Ba) in meltwater suspended particulate matter (SPM), in order to reveal the elemental concentration, spatial distribution, and water quality in remote glacier watershed under regional anthropogenic activities. Results showed that, the concentration of heavy metal elements was relatively high in Yuzhufeng Glacier basin, ranging from 0.57 μg/L (In) to 1,551.6 μg/L (Ba), whereas in Qiyi Glacier basin it was the lowest, ranging from 0.02 to 85.05 μg/L; and relatively medium in other glacier watersheds, with total elemental concentration varying from 1,503.9 to 1726.2 μg/L. Moreover, enrichment factors (EFs) of SPM heavy metals showed significantly higher value in the downstream than that of upper glacier region of the watershed. Most heavy metals with low EFs mainly originated from crust dust, while others with higher EFs (e.g., Cd, Sb) probably originated from anthropogenic sources. Spatially, the EFs of heavy metals were higher in Yuzhufeng and Laohugou Glacier basins; while in other regions the EFs were relatively low, which may be caused by regional land-surface and atmospheric environmental differences surrounding the various glacier watersheds. Compared with other remote locations in global range, heavy metals level (e.g., Cu, Ni, and Zn) in this region is relatively higher. Meanwhile, we find that, though the water quality of the glacier basin in northeast Tibetan Plateau was relatively clean and pollution-free, it is still obviously affected by regional anthropogenic activities. Mining activities, transportation and natural weathering and erosion processes in the study areas have important effects on the content of heavy metal pollutants of river-water SPM in the glacier watershed. Moreover, backward air-mass trajectories demonstrated the potential atmospheric pollutants transport from the surrounding cities and suburbs, to deposit in the snowpack and glaciers, and then melted out and released into meltwater runoff. This study provides a new perspective on more complete view of heavy metals distribution in glacier watershed, and new understanding for the cryosphere water environment evaluation in the Tibetan Plateau region.

Qualitative imaging of elemental spatial distribution in stalagmites through laser ablation inductively coupled plasma mass spectrometry analysis

The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technique is considered versatile for multi-elemental analysis and imaging because it is easy to handle, compatible with different types of solid samples, requires minimal sample preparation, and provides high spatial resolution and sensitivity. One of the challenges of imaging analysis is to obtain accurate and precise spatial information of elements distribution in the sample, so the optimization of the laser ablation (LA) parameters is essential. In this context, this study aimed to optimize the LA parameters for direct analysis of speleothem samples. Laser intensity, frequency, and spot diameter were evaluated through multivariate experimental design and multi-response data, the influence of ablation scan speed and the use of 44Ca as an internal standard (IS) for the qualitative image of 66Zn, 137Ba, 55Mn, 57Fe, 88Sr, 60Ni, and 26Mg distribution in the sample were also evaluated. The multivariate optimization revealed positive interactions between the parameters evaluated, i.e., the greater the laser intensity, LA frequency, and spot diameter, the greater the analyte signal and, thus the sensitivity. Therefore, 90% laser ablation intensity, 20 Hz repetition rate, and 100 µm spot diameter were selected. In the scan speed evaluation, the images obtained with 40 and 20 µm s-1 were very similar for all isotopes. The use of 44Ca as IS did not impact the resolution of the images. The use of 44Ca can provide important information about the speleothem formation and paleoclimate changes.

Efficient and Chiral Electroluminescence from In‐Plane Heterostructure of Transition Metal Dichalcogenide Monolayers

AbstractAtomically thin transition metal dichalcogenides (TMDCs) are attractive materials for future optoelectronic applications because of their excellent electrical, optical, and quantum (spin‐valley) properties. In particular, in‐plane heterostructures based on TMDC monolayers provide opportunities to directly modulate band structures and lattice strains by the spatial distribution of constituent elements, leading to efficient control of their carrier transport and recombination. However, it is still challenging to create light‐emitting devices using such in‐plane heterostructures because of the technical difficulties associated with sample/device fabrication. This study demonstrated interfacial electroluminescence (EL) in diverse TMDC monolayer in‐plane heterostructures. Various combinations of large‐area, single‐crystalline in‐plane heterostructures with sharp interfaces are grown by chemical vapor deposition, followed by the adoption of electrolyte‐based light‐emitting devices to observe EL. The fine heterostructures enabled the capture of the linear‐shaped EL fixed along the junction interfaces. Significantly, the WS2/WSe2 in‐plane heterostructures exhibited circularly polarized EL with polarizability of 10% at room temperature. This can be explained by the interfacial strain‐mediated electronic structure evolution, in which the combination of electric fields and strain‐induced valley drifts realizes selective EL from the K/K’ valley. These findings pave the way for expanding the potential of monolayer in‐plane heterostructures for use in functional optoelectronic devices.

The second dimension of spatial association

• The concept of the second dimension of spatial associations (SDA) is proposed. • SDA can extract in-depth and multi-scale geoinformation outside sample locations. • SDA-based statistical, machine learning, and geostatistical models are developed. • Spatial prediction accuracy is critically improved by SDA models compared with FDA. • SDA models provide smooth, effective, and low-uncertainty spatial predictions. A reasonable and adequate understanding of spatial association between geographical variables is the basis of spatial statistical inference and geocomputation, such as spatial prediction. Most of the current models for exploring spatial association of variables are constructed using data at sample locations. In this study, approaches for exploring spatial association using observations at sample locations are defined as the first dimension of spatial association (FDA). However, geographical information outside sample locations is usually missing in current models. To address this issue, this study proposes the concept of the second dimension of spatial association (SDA), which is an approach that extracts geographical information at locations outside samples for exploring spatial association. Based on the concept of SDA, three SDA models, including SDA-based multivariate linear regression, machine learning (i.e., random forest), and geostatistical models (i.e., random forest kriging), are developed for examining spatial association and predicting spatial distributions of trace elements, including Cr and Cu, in a mining region in Western Australia. Model accuracy is evaluated by comparing with corresponding FDA models. A new R package “SecDim” is developed to conduct SDA models. Results show that SDA models have a series of advantages in examining spatial association compared with FDA models. First, the accuracy of spatial prediction can be critically improved by SDA compared with the FDA, although identical explanatory variables and models are used for the modeling and prediction. Second, SDA can effectively indicate the multi-scale effects and diverse information within explanatory variables of the geographical environment at local ranges using the second dimension variables. Third, SDA can avoid underestimating high values and overestimating low values in the general FDA-based statistical models, machine learning, and geostatistical models. Finally, SDA models provide more smooth spatial predictions across space than that predicted by FDA models and avoid massive fluctuations at local ranges. The concept of SDA provides new insight into geographical information-based spatial association. SDA and multiple types of SDA models have great potential for more accurate and effective spatial statistical inference and geocomputation in diverse fields.

LA-ICP-MS analysis of trace and rare-earth element distribution in calcite fracture fillings from Forsmark, Simpevarp and Laxemar (Sweden)

Concentrations and spatial distribution of trace elements in secondary minerals provide valuable information about mobility controlling processes in natural fractures. Important examples include rare-earth element contents that act as analogues for the retention of trivalent actinides such as Am/Cm or Pu(III). The secondary phases (carbonates) investigated in this study originate from exploration drilling bore cores of the Swedish Nuclear Fuel and Waste Management Company SKB (Forsmark, Simpevarp and Laxemar, Sweden).Here, high-resolution element analysis (Micro-X-ray Fluorescence-Spectrometry (µXRF) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)) is applied to scan for Na and the trace elements Mn, Fe, Sr, Pb, Th and U as well as the rare-earth elements Y, La, Ce and Yb associated with carbonate fracture fillings. High resolution element maps highlight growth zones and microstructures within the samples, which are not detected by the usual point and line measurements. Evidence of phase-dependent partitioning is observed.The partition coefficients, D, determined from formation water and carbonate data were compared to experimentally generated coefficients and values derived from a 17-year precipitation experiment carried out at the Äspö Hard Rock Laboratory (HRL).Distribution coefficients of the light rare-earth elements La and Ce have been found to be relatively high in the studied samples, whereas the coefficients of distribution of Sr and U are remarkably low.Overall, the results of this work show that the secondary calcite formed in deep granitic fractures coprecipitated periodically with significant amounts of radionuclide analogues (i.e., rare-earth elements).

DISTRIBUTION AND MIGRATION OF CHEMICAL ELEMENTS IN THE MINOR RIVER BASINS IN THE WEST OF THE SMOLENSK-MOSCOW UPLAND AS AN INDICATOR FOR ASSESSING LANDSCAPE STABILITY

Hydrological objects link the landscape into connected basins of the paragenetic system through energy and matter migration. It determines the relevance of geochemical monitoring of minor river basins as a condition for designing an effective ecological framework for the territory. We tried to identify regularities of the spatial distribution and migration of chemical elements in the basins of minor rivers in the west of the Smolensk-Moscow Upland. The method of cross-spectrum geochemical analysis helped us to study the river basins of the Vop-Dnieper hydrological region. We compiled 47 complex landscape descriptions. Thus, the maximum calcium and movable magnesium cations values are determined in the super-aqual landscapes of the river basins under study. In the minor river valleys, we find outwash of organic compounds from the outer layers of the geochemical landscape. The research determines the maximum values of the studied elements in the soils of super-aqual landscapes through migration with subsurface and surface run-off. The minimum values are in the eluvial landscape, where there is a partial loss of geochemically movable forms of metals, which increases due to acid and weak-acid reactions of the environment. Partial outwash of metals, in particular copper and zinc, happens to organic compounds of soils. Trans-eluvial landscape loses trace elements. However, some of them are retained due to falling out of solutions and suspensions. Calculations have shown that copper (conjugation coefficient is 2–3) and zinc (conjugation coefficient is approximately 2) are most actively involved in the migration. In contrast, manganese is less active. The research results present an assessment of the features related to the landscape-geochemical differentiation of the territory of the west of the Smolensk-Moscow Upland from the upper areas of watersheds to the lower elements of landscape-geochemical catenae, including simple drainage basins of minor rivers. The research shows that the active migration of chemical elements characterizes the minor river basins. They are indicators of the geochemical state of the landscape. One can use the research results to assess a landscape-ecological condition, improve an environmental management system, and optimize the natural environment.

Application of the fine-grained soil prospecting method in a loess-covered area of central China

Loess-covered landscapes occupy a large area of the globe and have substantially high potential for mineral exploration; however, as mineral information is obscured by loess cover, suitable prospecting techniques need to be applied. The fine-grained soil prospecting method—a deep-penetrating geochemical technology that can be used to identify concealed deposits—has been proven effective in some cases. In this study, we applied this method for mineral exploration in the loess-covered Luoning Basin in Central China. Our results revealed strong geochemical anomalies (e.g., Au, Ag, Pb, Zn, and Cu) over related and concealed ore deposits. Furthermore, a regional geochemical survey in the Luoning Basin revealed the spatial distribution and suites of elements that were consistent with the mineralization type. Moreover, higher geochemical anomalies of Au, Ag, Pb, and Zn were spatially related to an Au ore deposit and Ag–Pb–Zn polymetallic deposit, respectively. The results of a detailed geochemical survey in the Zhonghedi Ag–Pb–Zn polymetallic deposit further revealed that the distribution of surface element anomalies was associated with tectonic fractures throughout the exploration region, which are closely related to the distribution of orebodies. These results imply that the fine-grained soil prospecting method is suitable for anomaly delineation during detailed geochemical surveys as well as regional-scale surveys. Based on our results, we suggest that geochemical anomalies in the loess-covered surface in our study area are presumably the result of geogas dispersion processes; we provide a schematic model explaining how ore-forming and associated materials are brought to the surface by geogas flowing upwards along faults and fractures and, ultimately, accumulating in fine-grained loess soils. Overall, our research demonstrates that fine-grained soil prospecting can effectively aid the search for concealed mineral deposits in loess-covered landscapes.

Spatial Distribution and Eco-stoichiometric Characteristics of Soil Nutrient Elements Under Different Vegetation Types in the Yellow River Delta Wetland

To clarify the distribution characteristics and the ecological stoichiometric characteristics of nutrient elements in soils under different vegetation types, four typical natural wetlands, i.e., Phragmites australis wetland, Tamarix chinensis wetland, Suaeda salsa wetland, and Tidal flat wetland, as well as Gossypium spp. fields that were reclaimed from natural wetlands, were selected as study sites in the Yellow River Delta, and comparisons between the agricultural reclamation land and natural wetlands were conducted. The results showed that the soil total organic carbon (TOC) and total nitrogen (TN) contents in the natural wetlands were as follows:P. australis wetland and T. chinensis wetland>S. salsa wetland>Tidal flat, and the contents of TOC and TN were significantly negatively related to electrical conductivity (EC) and pH values (P<0.05). The contents of TOC, TN, and total phosphorus (TP) in Gossypium spp. fields were significantly higher than those in natural wetlands (P<0.05), especially the contents of nitrate nitrogen (NO3--N) in Gossypium spp. fields, which were 9.4-11.4 times that of natural wetlands. However, no significant correlations between TOC, TN, and TP and EC and pH values (P>0.05) were observed in Gossypium spp. fields. The results of correlation analysis showed that the C/N of natural wetlands were mainly controlled by the contents of TN (P<0.05), and the C/N of the Gossypium spp. fields were significantly lower than those of natural wetlands (P<0.05). The soil C/P and N/P of natural wetlands and Gossypium spp. fields in the Yellow River Delta were low, and the variation trends were consistent with those of soil TOC and TN. Comparative analysis revealed, on the whole, that there were significantly different soil nutrient element contents, C/N, C/P, and N/P in Gossypium spp. fields compared to those of natural wetlands (P<0.05). The process of reclamation could significantly change the spatial distribution of nutrient elements in wetlands. Our results should be of importance in revealing the biogeochemical process of soil nutrient elements in coastal wetland and the influence of agricultural reclamation activities on the differentiation of soil nutrient elements.

Understanding the surface segregation behavior of bimetallic CoCu toward HMF oxidation reaction

Surface segregation is ubiquitous in multi-component materials and is of great important for catalysis but little is known on the surface structure under graphene encapsulation. Here, we show that the graphene encapsulated CoCu performs well for the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) with the onset potential before 1.23 VRHE and a nearly 100% selectivity of FDCA under 1.4 VRHE. From the experimental results, the unprecedented catalytic performance was attributed to local structural distortion and sub-nanometer lattice composition of the CoCu surface. We accurately show the dispersed Cu doped Co3O4 nano-islands with a lot of edge sites on the bimetallic Co-Cu surface. While, the gradient components effectively facilitate the establishment of built-in electric field and accelerate the charge transfer. Theoretical and experimental results reveal that the surface Co and neighbouring Cu atoms in sub-nanometer lattice synergistically promote the catalysis of HMF. This work offers new insights into surface segregation in tuning the element spatial distribution for catalysis.

Novel insights on the near atomic scale spatial distributions of substitutional alloying and interstitial impurity elements in Ti-6Al-4V alloy

The present study explores the near atomic scale spatial distributions of substitutional alloying elements (aluminium and vanadium) and interstitial impurities (oxygen and carbon) in the microstructures of Ti-6Al-4V and its boron modified counterpart (Ti-6Al-4V-0.1B) alloys using transmission electron microscopy (TEM) and atom probe tomography (APT) techniques. The latter alloy possesses zero solubility of boron in α-Ti and high oxygen concentration around TiB particles. The results suggest that aluminium and vanadium atoms enrich α and β phases, respectively due to strong elemental partitioning between these phases, to an extent that the atomic scale concentrations of various elements considerably differ from the bulk compositions of the two alloys. Furthermore, oxygen atoms are preferentially distributed within the α phase where other interstitial impurities (carbon) also segregate. Substitutional aluminium atoms share an inverse interrelation with interstitial oxygen atoms while vanadium atoms reside besides the impurity-rich regions for both the alloys. The size differences for these elements (substitutional vs. interstitial) with host titanium atoms and related lattice distortion is (partially) held responsible for the atomic scale elemental distributions and the observed interrelations within the α phase. These arguments are further substantiated from DFT results previously obtained for Ti-6Al-4V alloy.

Мониторинг следовых элементов на территории Удмуртской Республики методом нейтронного активационного анализа

The results of the assessment of the degree of atmospheric pollution in the territory of the Udmurt republic by the method of moss biomonitors in combination with instrumental neutron activation analysis are presented. Concentrations of 37 macro-, micro- and trace elements were determined in moss samples. The factors of accumulation of individual elements are calculated using background values of their concentrations. The background concentration is determined by finding three minimum values and finding the average using descriptive statistics methods. Based on the analytical results, maps of the spatial distribution of heavy metals and other toxic elements in the study area were constructed using GIS technologies. Factor analysis was used as a method of multidimensional statistical analysis to identify the main sources of pollution — large industrial facilities located on the territory of the Udmurt Republic. This study is a continuation of work for other regions of Russia using multi-element instrumental neutron activation analysis and modern GIS technologies.

Effect of temperature on the neutron irradiation-induced cavities in tungsten

ABSTRACT To study the effect of temperature on the evolution of irradiation-induced cavities in tungsten, ITER Grade Product tungsten was characterised using transmission electron microscopy (TEM) after neutron irradiation to ∼1 dpa at 600°C, 800°C, and 1000°C. The results showcase irradiation temperature-dependent cavity formation and growth, which is majorly governed by the spatial distribution of transmutation elements in the matrix. Suppression of thermal neutrons fluence by applying stainless steel capsules resulted in a lower density of secondary phases as well as cavities than those reported in the literature for similar irradiation conditions. To further assess temperature effects on the cavity evolution and their stability, dedicated in situ TEM post-irradiation annealing (PIA) experiments were carried out. PIA of 600°C irradiated samples at 600°C for about 1 h revealed no noticeable change on the cavities size distribution. However, upon increasing annealing temperature and time, cavities became coarsened. Vacancy migration and absorption is found to be the dominant mechanism that governs cavity annealing kinetics in the present thin-foil PIA investigations. Furthermore, the cavity coarsening is dictated by the simultaneous evolution of the irradiation-induced dislocation loops, thin-foil free surfaces image forces, and the presence of the transmuted elements and their clusters in the matrix.

Assessment of the Spatial Distribution and Chemical Speciation of Potential Toxic Elements in Ikeja Wetland Sediments, Lagos, Southwest, Nigeria

Assessment of the Spatial Distribution and Chemical Speciation of Potential Toxic Elements in Ikeja Wetland Sediments, Lagos, Southwest, Nigeria