Mn Content Research Articles

Geochemistry of magnetite from Fe-skarn deposits along the central Loei Fold Belt, Thailand

Abstract Fe-deposits in Thailand are mostly located along the Loei Fold Belt in Central Thailand. The study areas, Khao Lek (KL) and Khao Thab Kwai (KTK), have Fe-deposits hosted in contact metamorphized Permian limestone and Permo-Triassic volcanic rocks. Magnetite forms over a wide range of geological conditions and incorporates various trace elements into its cubic spinel structure. The KL and KTK Fe-skarn deposits are mainly composed of massive magnetite. The main discriminator elements for magnetite are characterized by the distribution of Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, and Cu. Thus, this study focused on the chemical characteristics of magnetite to identify the origins of the iron ore deposits. This study investigated the trace element chemistry of the magnetite using laser ablation inductively coupled plasma mass spectrometry. The high Ca + Al + Mn and low Ti + V and Ni/Cr + Mn contents of hydrothermal magnetite in the KL and KTK deposits support a typical skarn origin, and the textural and trace element features of the KL and KTK magnetite are analogous to those of typical calcic-Fe skarn deposits worldwide.

Concentrations of Bioelements (Zn, Cu, Fe, Cr, Mg, Mn) in Serum and Bone Tissue of Aging Men Undergoing Hip Arthroplasty: Implications for Erectile Dysfunction

Background: Erectile dysfunction (ED) stands out as one of the most prevalent sexual disorders in men, with its incidence progressively escalating with age. As delineated by the International Consultation Committee for Sexual Medicine on Definitions/Epidemiology/Risk Factors for Sexual Dysfunction, the prevalence of ED among men under 40 years is estimated to be within the range of 1–10%. The aim of this study was to determine the relationship between the concentration of bioelements (Zn, Cu, Fe, Cr, Mg, and Mn) in the serum and bone tissue and the concentration of selected hormones in men with and without erectile dysfunction. Materials and methods: The retrospective cohort study included 152 men who underwent total hip arthroplasty for hip osteoarthritis at the Department of Orthopaedic Traumatology and Musculoskeletal Oncology at the Pomeranian Medical University in Szczecin. Certain exclusion criteria were applied to ensure the integrity of the study. These included individuals with diabetes, a history of cancer, alcohol abuse, liver or kidney failure, New York Heart Association (NYHA) class III or IV heart failure, and those taking medications that affect bone metabolism, such as mineral supplements, neuroleptics, chemotherapeutic agents, immunosuppressants, corticosteroids, or antidepressants. Patients with hypogonadism or infertility were excluded from the study. Results: The study showed an association between bioT concentrations and Cu concentrations in both patients with and without erectile dysfunction. A correlation between bioactive testosterone and Cr concentrations was also observed in both groups. Patients with erectile dysfunction showed a relationship between bioT concentration and Zn concentration, TT concentration and Mn concentration, FT concentration and Zn concentration, and E2 concentration and Cr concentration. An analysis of elemental concentrations in bone tissue showed an association between FT and Mg and Mn concentrations, but only in patients with erectile dysfunction. In patients without erectile dysfunction, a correlation was observed between FT and Cu concentrations. A correlation was also observed between bioT concentrations and Mg, Mn, and Zn concentrations, but only in patients with erectile dysfunction. In patients without erectile dysfunction, a correlation was observed between bioT and Cu concentrations. Conclusions: Studying the relationship between the concentration of bioelements (Zn, Cu, Fe, Cr, Mg, and Mn) in the serum and bone tissue and the concentration of selected hormones in men may be important in explaining the etiology of the problem. The study of the concentration of Zn and Cu in bone tissue and serum showed that these two elements, regardless of the place of accumulation, may be related to the concentration of androgens in men.

A method for studying the influence of Mn oxyhydroxides on the trace element content of aquatic bryophytes

The main objective of this study was to develop and test a method of separating externally deposited Mn oxyhydroxides and co-precipitated elements from samples of aquatic moss (the moss Fontinalis antipyretica). The method, which uses 0.1 M hydroxylamine to dissolve the oxyhydroxides, was tested with samples collected in rivers with slightly acidic, well‑oxygenated waters, where high rates of Mn precipitation occur. The method was effective (it extracted up to 84 % of the Mn) and selective (Fe oxyhydroxides were not extracted). The elements Ba, Cd, Zn and Ni were associated with the Mn oxyhydroxides, while Al, As, Cr, Cu, Fe, Hg and Pb were not. Deposition of Mn therefore increased the concentration of some elements in the moss samples. However, as Mn precipitation depends on Eh and pH, which are independent of the concentrations of the elements in water, the relationship between water and moss element concentrations is not clear (i.e. the data are noisy). This is a problem in biomonitoring studies, which assume a close relationship between element concentrations in moss and water. The value of the proposed extraction method is that it can be used to correct the effect of Mn deposition. We present an example of this correction applied to the Cd concentrations in the test data. We found that the noise introduced by the Mn, including age-related effects (observed by comparing concentrations in 0–2.5 and 2.2–5.0 cm sections from the shoot apex), can be reduced. Additionally, the correction revealed recent increases in Cd concentrations in one site that were not observed in the uncorrected data. Another finding of interest was the low content of total Mn and different extractability (of most elements) observed in moss samples collected in alkaline waters. Finally, we discuss how future studies designed for different environmental scenarios can benefit from application of the proposed method.

The influence of foliar macronutrient on growth and yield of sweet corn grown in Rengam and Rasau soil series under greenhouse conditions

The purpose of this study was to determine the effects of different rates of macronutrients as a foliar applications on growth and yield performance of sweet corn cultivated in Rengam and Rasau soil series of Malaysia under greenhouse condition. The study comprised five treatments of macronutrient fertilization as a foliar application (0, 25, 50, 75 and 100 % NPK). The plant height, stem width, leaf number, leaf area and cob height of sweet corn grown in Rengam soil series were significantly influenced by foliar macronutrient application. Notably, a rise in cob weight of sweet corns cultivated in Rasau soil series was observed at the 75 % rate, reaching 75 g, compared to 68 g for sweet corn grown in Rengam soil series. The foliar application of 100 % NPK resulted in the highest total leaf area at 252.92 cm2 compared to all other treatments. Regarding the cob fresh weight and dry matter content of sweet corn cultivated in the Rasau soil series, significant improvement noted with the 75 % NPK treatment, however plants grown in the Rengam soil series and treated with 75 % NPK as a foliar application did not exhibit significant effects. The concentrations of Fe and Mn in the corn stem from both soil series significantly increased with macronutrients foliar application. In the corn leaves grown in Rengam soil series, the concentration of nutrients was significantly influenced by the rate of NPK used as a foliar application in this study. Notably, the increased of Ca content in the treated leaves was significantly higher compared to control plants. Additionally, the contents of P, K, Cu and Zn in the corn flower of the plants in the Rengam soil series were significantly elevated in treated plants compared to untreated ones. Conclusively, based on this greenhouse study, it can be inferred that two foliar sprays of macronutrient solution at rates of 75 % and 100 % NPK greatly enhanced the growth, yield and nutrient contents of sweet corn cultivated in the Rengam and Rasau soil series.

Evaluation of heavy metal concentration in black tea and coffee marketed in Erbil, Iraq: a consumer health risk assessment

ABSTRACT Black tea and coffee are popular and widely consumed beverages worldwide. However, the potential accumulation of heavy metals in food products raises concerns regarding their toxicity. In this study, we investigated the concentrations of arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), manganese (Mn), zinc (Zn), and iron (Fe) in 102 samples of black tea and coffee purchased from Erbil city market in Iraq. Additionally, we determined the Hazard Quotient (HQ) and Hazard Index (HI) levels of heavy metal intake to evaluate the non-carcinogenic health risks for adult consumers. The mean concentrations of As, Cd, Cu, Cr, Pb, Mn, Zn, and Fe in black tea and coffee were found to be 0.023, 0.11, 10.29, 0.60, 1.69, 294.99, 25.59, and 39.80 mg/kg, respectively. In the case of black tea, the highest mean concentration observed was 607.28 mg/kg for Mn, while the lowest was 0.035 mg/kg for Cd in coffee. Arsenic was below the detection limit in coffee. Our results revealed that, except for Cd content in some tea samples, the concentrations of the studied metals were within the standard levels. The HQ and HI values for all elements were found to be less than one, indicating no adverse health effects associated with consuming these beverages. However, continuous monitoring is essential to ensure the ongoing safety of black tea and coffee.

Comparative Analysis of Laboratory-Made and Industrial-Made Sewage Sludge Ash: Implications for Effective Management Strategy Development

In the pursuit of environmentally and economically sustainable sewage sludge ash (SSA) management methods, researchers often employ laboratory-made SSA (L-SSA) as a substitute for industrial-made SSA (I-SSA) produced in fluidized bed furnaces. To check whether L-SSA is a material that imitates I-SSA well, the fractionation of metals whose presence is a significant problem during SSA management was performed. In addition, the grain distribution, specific surface area, and textural properties of the tested materials were examined. Differences in total Pb and Hg content and mobility of Cu, Ni, Mn, and Zn were observed between I-SSA and L-SSA. Larger particle sizes of L-SSA compared to I-SSA were confirmed, while comparable textural properties and specific surface area of both types of materials were maintained. Based on the results, it was concluded that L-SSA is chemically different compared to I-SSA, and that L-SSA should not be used as a reference in research focused on the design of SSA management methods. Moreover, fractionation of metals was performed in disposed fluidized beds (FBs), which are diverted to non-hazardous waste landfills without prior analysis. It has been proven that studied metals are present in FBs as abundantly as in SSA, while Cu, Mn, and Ni may show higher mobility than in I-SSA.

Assessment of macro, trace and toxic element intake from rice: differences between cultivars, pigmented and non-pigmented rice

Pigmented and non-pigmented rice varieties (grown in different areas) were collected in China, Yunnan, to investigate the content of macro-, trace elements and potentially toxic elements (PTEs), and to assess the health risk associated with dietary intake. The order of elemental concentrations in rice was Mn > Zn > Fe > Cu > Se for trace elements, P > K > Mg > Ca > Na for macro elements, and Cr > As > Cd for PTEs. Rice with a high concentration of essential elements also associated with a high content of PTEs. In addition, higher content of Cr, Mn and Na were found in pigmented rice. The health risk assessment showed that the daily intake of all elements was below the tolerable limit (UL). Moreover the intake of Fe, Zn and Se was far from sufficient for the nutrient requirement. The PTEs in rice dominated the health risk. Of concern is that this rice consumption is likely to contribute to carcinogenic risks in the long term and that adults are at higher health risk from pigmented rice compared to non-pigmented rice. This study confirms that the lack of essential micronutrients in rice and the health risk associated with rice diets should remain a concern.

Influence of Different Substrates on Nutrient Composition of Vermicompost and Vermiwash

Influence of Different Substrates on Nutrient Composition of Vermicompost and Vermiwash

Potentially toxic elements in urban soils of the coastal city of the Sea of Azov: Levels, sources, pollution and risk assessment

Coastal cities are major centers of economic activity, which at the same time has negative consequences for the environment. The present study aimed to determine the concentrations and sources of PTEs in the urban soils of Taganrog, as well as to assess the ecological and human health risks. A total of 47 urban and 5 background topsoils samples were analyzed by ICP-MS and ICP-AES. A significant excess of Cu, Zn, and Sb was noted in urban soils compared to the upper continental crust and average world-soil (1.7–2.9 times). Statistical analysis showed that the elements in soils were of geogenic, mixed and anthropogenic origin. According to the single pollution index (PI), the greatest danger of soil pollution was represented by anthropogenic elements, namely Cu, W, Pb, Zn, Cd, and Sn, the levels of which were increased in residential and industrial areas. The median contents of As, Mn, Cr, Sr, Mo, Sb, Cu, W, Pb, and Zn were 1.1–2.1 times higher, while Cd and Sn were 2.5 folds higher in the urban soils compared to the background ones. The total pollution index (ZC) showed that only 15% of the soils had high level of pollution, which is typical for the industrial areas. Overall ecological risks were negligible or low in 92% of soils, and were mainly due to elevated levels of Cu, Zn, As, and Pb. Non-carcinogenic risks to humans were mainly related to exposure to La and Pb. The hazard index (HI) values for all PTEs were less than ten, indicating that overall non-carcinogenic risk for adults and children was low-to-moderate and, moderate, respectively. The total carcinogenic risk (TCR) exceeded threshold and corresponded to low risk, with Pb, As, and Co being the most important contributors. Thus, the industrial activities of Taganrog is the main source of priority pollutants.

Altered spinels act as a mirror of multi-episodic fluid metasomatism in the forearc mantle: An example from the Minhe ophiolite in Qilian Orogen, NW China

Forearc mantle peridotites commonly undergo complex melt/fluid metasomatism, which inevitably has a considerable influence on their geochemical compositions at the whole-rock scale. Serpentinites predominantly comprise the Minhe ophiolite, which is a fragment of the Proto-Tethys Ocean that outcrops in the Qilian Orogen in NW China. These serpentinites contain zoned spinels that vary compositionally from the centers to the margins, with a spinel core overgrown by ferritchromite layer and magnetite at the outermost rim. The mineral chemistry of the spinel cores (i.e., Cr#, Mg#, Cr2O3, and Al2O3) suggests that the protolith of the serpentinites was an oceanic mantle remnant in a forearc setting. Moreover, the ferritchromite exhibited increases in Fe, Mn, Sc, and Ni contents and decreases in Mg, Cr, Al, V, Zn, and Ga contents. Considering the linear correlation among elements (e.g., Co, Ni, and Zn) and the absence of mineral inclusions, the ferritchromite likely formed through ionic substitutions induced by slab fluids. The magnetite was enriched in Cr, Ni, V, Zn, Co, and Cu, but did not have a magmatic origin owing to low V concentrations. All evidence indicates that the peridotites underwent at least two episodes of fluidic metasomatism in the subduction zone. During early slab subduction, aqueous fluids released from the dehydration of the subducted slab directly serpentinized the forearc mantle peridotites, thereby altering the olivine and orthopyroxene to lizardite/chrysotile. During this process, certain mobile elements (e.g., Fe, Ni, and Mn) in the fluids and/or olivine serpentinization were incorporated into existing spinels, favoring ferritchromite growth. The second fluidic episode was dependent on prograde metamorphism at greater depths in the subduction channel, which not only produced antigorite via the recrystallization of lizardite and chrysotile, but also drove the fluids towards a more oxidizing state, thereby facilitating the growth of Cr-magnetites. Subsolidus re-equilibration controlled by fluid infiltration further promoted the inter-diffusion of elements (e.g., Cr, V, Co, Ni, Cu, and Zn) in the zoned spinels.

Investigation of the effects and mechanisms of manganese-based NMs on rice growth.

Manganese-based (Mn-based) nanomaterials (NMs) have great potential as alternatives to conventional Mn fertilizers. Yet, its environmental risks and effects on plant growth are not completely well understood. This study investigated the physiological effects of manganese dioxide (MnO2) and manganese tetroxide (Mn3O4) NMs on inter-root exposure (0-500 mg/L) of hydroponically grown rice. The results showed that on inter-root exposure, 50 mg/L Mn-based NMs promoted the uptake of mineral elements and enhanced the enzymatic activities of antioxidant systems (CAT and SOD) in rice, whereas 500 mg/L Mn3O4 NMs disrupted the mineral element homeostasis and led to phytotoxicity. The promotion effect of MnO2 NMs was better, firstly because MnO2 NMs treatment had lower Mn content in the plant than Mn3O4 NMs. In addition, MnO2 NMs are more transported and absorbed in the plant in ionic form, while Mn3O4 NMs exist in granular form. MnO2 NMs and Mn3O4 NMs both can be used as nano-fertilizers to improve the growth of rice by inter-root application, but the doses should be carefully selected.

Crystal chemistry and formation of authigenic chlorite: Influence on tight sandstone reservoir in the Yanchang formation, Ordos Basin, China

Authigenic chlorite is a crucial diagenetic cement that significant impacts tight sandstone reservoirs. The occurrence, crystal chemistry, formation and influences on reservoirs of different authigenic chlorite types were studied in the Yanchang Formation tight sandstones from the Ordos Basin. This study identified two primary types of chlorites: alteration chlorite and autochthonous authigenic chlorite. The alteration chlorite, characterizing by high Fe, Mg, Ti and AlIV contents and low Si and AlVI contents, originated from biotite during diagenesis. The autochthonous authigenic chlorite can be further classified into grain-coating, pore-lining, and pore-filling chlorite. The grain-coating chlorite features thin layers and limited crystal form. During the syndiagenetic stage, Fe2+ and Mg2+ carried by water adsorbed onto the particle surfaces. Additionally, the grain-coating chlorite contains relatively high K content due to the hydrolysis of biotite during the eodiagenetic A stage. The pore-lining chlorite formed during the prolonged eodiagenetic B stage. The biotite and abundant intermediate-basic magmatic fragments released Fe2+ and Mg2+, contributing to the widespread development of euhedral pore-lining chlorite. Notably, the pore-lining chlorite displayed elemental composition variations from the grain edge to the pore center, with increased Fe, Mg and AlIV, and decreased K and AlVI. The pore-filling chlorite formed locally resulted from Fe2+ and Mg2+ crystallization due to the hydrolysis of intermediate-basic magmatic rocks and the dissolution early formed chlorite. The pore-filling chlorite contains the most Fe, Mg and Mn contents and the least K content. Overall, authigenic chlorite acts as a "double-edged sword" in tight sandstone reservoir. The grain-coating and grain-lining chlorite enhance the mechanical strength, resist compaction, and inhibit quartz overgrowth, while pore-filling chlorite trends to obstruct pore throats and break reservoir quality. This study provides valuable insights into the detailed control factors influencing reservoir quality and can serve as a reference for further research.

Evaluation of the phytoremediation potential of selected hydrophytes grown in wastewater. A case study in Sheikhupura, Pakistan

Water pollution is a major environmental issue and human health risk worldwide. With rapid industrialization and economic growth, water bodies are contaminated at large scale. In the current study the concentration of four heavy metals (HMs) cadmium (Cd), copper (Cu), nickel (Ni), and manganese (Mn) was measured in water, sediment, and hydrophytes (Eichhornia Crassipes, Pistia stratiotes and Lemna minor) samples collected from wastewater stream in Sheikhupura, Punjab, Pakistan. The results revealed that the concentrations of Cd (0.23 mg L-1), Cu (5.00 mg L-1), Mn (6.00 mg L-1), and Ni (3.00 mg L-1) in water samples were above the permissible limits (APL) set by the World Health Organization (WHO). However, the concentration of Cd, Cu, Mn, and Ni in sediment samples was found to be below the maximum permissible limits (BMPL) set by WHO. The WHO permissible limits for Cd, Cu, Mn, and Ni in water is 0.01, 0.02, 0.20, and 1.40 mg L-1 respectively while in sediments is 3.00, 100, 2000, and 50 mg kg-1 respectively. In addition, Mn concentration was highest among all the tested hydrophytes, water, and sediment samples. HMs contents were higher in hydrophytes as compared to water and sediment samples. In addition, all three hydrophytes were found to absorb HMs from wastewater with bioaccumulation factor ranging from 2.52 to 216. Current data revealed that Pistia stratiotes have greater potential to absorb HMs from water as compared to Eichhornia Crassipes, and Lemna minor

Review of soil environment quality in India near coal mining regions: current and future predictions.

Production and utilization of coal are one of the primary routes of accumulation of Toxic Elements (TEs) in the soil. The exploration of trends in the accumulation of TEs is essential to establishing a soil pollution strategy, implementing cost-effective remediation, and early warnings of ecological risks. This study provides a comprehensive review of soil concentrations and future accumulation trends of various TEs (Cr, Ni, Pb, Co, Cu, Cd, Zn, Fe, Mn, and As) in Indian coal mines. The findings revealed that average concentrations of Cr, Mn, Ni, Cu, Zn, Pb, and Co surpass India's natural background soil levels by factors of 2, 4.05, 5.32, 1.77, 9.6, and 6.15, respectively. Geo-accumulation index values revealed that 27.3%, 14.3%, and 7.7% of coal mines are heavily polluted by Ni, Co, and Cu, respectively. Also, the Potential Ecological Risk Index indicates that Cd and Ni are primary contaminants in coal mines. Besides, the health risk assessment reveals oral ingestion as the main exposure route for soil TMs. Children exhibit a higher hazard index than adults, with Pb and Cr being major contributors to their non-carcinogenic risk. In addition, carcinogenic risks exist for females and children, with Cr and Cu as primary contributors. Multivariate statistical analysis revealed that TEs (except Cd) accumulated in the soil from anthropogenic sources. The assessment of future accumulation trends in soil TE concentrations reveals dynamic increases that significantly impact both the ecology and humans at elevated levels. This study signifies a substantial improvement in soil quality and risk management in mining regions.

Thermodynamic Prediction and Experimental Verification of Transformation‐Induced Plasticity/Twinning‐Induced Plasticity Effects in Advanced Low‐C High‐Mn Steel at Different Deformation Temperatures

The effectiveness of transformation‐induced plasticity (TRIP)/twinning‐induced plasticity (TWIP) effects in Fe–0.06C–26Mn–3Si–3Al advanced ferrous alloy is analyzed over a wide temperature range of −40 to 200 °C. The specific deformation mechanisms in the steel are experimentally investigated and predicted using thermodynamic calculations of stacking fault energy (SFE). These predictions were correlated with the microstructure of the steel and its mechanical behavior. The study finds that applied thermodynamic models effectively predict the occurrence of TRIP/TWIP effects at different deformation temperatures, aligning well with experimental observations in terms of ε/α′ martensite formation, indicative of the TRIP mechanism. Some discrepancies in SFE results are observed at Mn contents significantly higher or lower than the nominal composition of steel.

Manganese exposure from spring and well waters in the Shenandoah Valley: interplay of aquifer lithology, soil composition, and redox conditions

Manganese (Mn) is of particular concern in groundwater, as low-level chronic exposure to aqueous Mn concentrations in drinking water can result in a variety of health and neurodevelopmental effects. Much of the global population relies on drinking water sourced from karst aquifers. Thus, we seek to assess the relative risk of Mn contamination in karst by investigating the Shenandoah Valley, VA region, as it is underlain by both karst and non-karst aquifers and much of the population relies on water wells and spring water. Water and soil samples were collected throughout the Shenandoah Valley, to supplement pre-existing well water and spring data from the National Water Information System and the Virginia Household Water Quality Program, totaling 1815 wells and 119 springs. Soils were analyzed using X-ray fluorescence and Mn K-Edge X-ray absorption near-edge structure spectroscopy. Factors such as soil type, soil geochemistry, and aquifer lithology were linked with each location to determine if correlations exist with aqueous Mn concentrations. Analyzing the distribution of Mn in drinking water sources suggests that water wells and springs within karst aquifers are preferable with respect to chronic Mn exposure, with < 4.9% of wells and springs in dolostone and limestone aquifers exceeding 100 ppb Mn, while sandstone and shale aquifers have a heightened risk, with > 20% of wells exceeding 100 ppb Mn. The geochemistry of associated soils and spatial relationships to various hydrologic and geologic features indicates that water interactions with aquifer lithology and soils contribute to aqueous Mn concentrations. Relationships between aqueous Mn in spring waters and Mn in soils indicate that increasing aqueous Mn is correlated with decreasing soil Mn(IV). These results point to redox conditions exerting a dominant control on Mn in this region.

Modeling Mn(II) autocatalytic sorption on MnOx-coated filtration media

This study reports a newly developed kinetic model for predicting manganese (Mn) removal in Mn-coated filtration media. Manganese oxides (MnOx) adsorb and catalyze the oxidation of Mn in the liquid phase to regenerate sorption sites. The most common kinetic models (pseudo-first- and second-order models) do not consider the regeneration of reactive sites, thereby inadequately describing the long-term uptake of Mn(II) by MnOx. We propose a new kinetic model that considers both the rapid initial sorption of Mn(II) onto MnOx and its subsequent slow oxidation to Mn(Ox). This model was generalized to account for different pH, temperatures, and initial Mn concentrations. The enhanced model demonstrated a prediction error of +/−1 % on the Mn(II) concentration measured in the column effluent of two different MnOx media recovered from industrial filters. Although the contribution of oxidation was found to be 10 times smaller than that of adsorption, it is important to consider if for the prediction of Mn(II) uptake over a 4-h column experiment.

Identification of spatial clusters of potentially toxic elements in different soil types using unsupervised machine learning and compositional data analysis

Soil health is an important concept and the generation of soil chemical composition data, including potentially toxic elements (PTEs) is one of its conceptual components. This study aims to reveal the spatial distribution patterns of soil PTEs contents, identify their potential sources, and unveil their geochemical associations in Aragatsotn region (Armenia). For that purpose, the contents of Cr, V, Ti, As, Zn, Cu, Co, Fe, Mn, Ba, and Pb were determined using the X-ray fluorescence spectrometer (Innov X-5000). The results showed that mean contents of Cr and As exceeded their upper continental crust by 1.50 and 3.12 times and their maximum acceptable values by1.53, 1.50 times, respectively. The detailed analysis of the spatial distribution pattern of PTEs demonstrated the presence of sites where all these elements displayed comparatively higher values. The combined application of compositional data analysis and geospatial mapping allowed to reveal multivariate outliers which were located in structural-metallogenic zones with an active exploitation of ore deposits. The application of unsupervised machine learning algorithm unveiled three groups within the main dataset and the clr-biplot identified the source-specific elements. Particularly, Group I included Cu and displayed the highest mean value among the identified groups. The soil samples included in Group I were found in areas where Calcisols were developed and comparatively high Cu contents were attributed to agricultural activities (vineyards) and vehicle emissions. The Group II is represented by the geochemical association of Fe, Co, Cr, Mn, Zn, and As. The formation of this group is conditioned by volcanic rocks of the local geological origin. However, no spatial pattern was identified in Group II distribution aligned with the soil types. The Group III included Ti, V, Pb, and Ba. This group may have a mixed origin as it is spatially distributed in areas where regional highways pass through and where Group II elements also exhibit their higher values.

Hydrogeochemical characteristics of groundwater contamination in Guwahati city, Assam, India: Tracing the elemental Threads

Groundwater serves as an important resource for drinking and agriculture in many countries, including India. Assessing the quality of groundwater is essential for understanding its chemical characteristics and suitability for consumption. This study aims to explore the factors affecting the hydrogeochemical changes in groundwater within Guwahati City, Assam, India. Groundwater samples were collected and analyzed for major and trace elements, as well as anion concentrations. Concentrations of As, Al, Ba, Cu, F−, Fe, Mn, and Pb exceeded the permissible limits set by both World Health Organization (WHO) and Bureau of Indian Standards (BIS), indicating serious health concerns for the local inhabitants. The distribution pattern of trace elements exceeding the guideline values is intricate, suggesting widespread contamination of groundwater throughout the study area. The Heavy Metal Pollution Index (HPI) and Water Quality Index (WQI) revealed that, except for the central zone, groundwater across the entire study area requires intervention. Piper plot illustrated that the groundwater is predominantly of Ca–HCO3 type, indicating the dominance of alkaline earth and weak acids. Groundwater hydrogeochemistry is mainly controlled by rock-water interaction and evolves through silicate weathering, carbonate weathering, and cation exchange processes. Multivariate statistical analysis identified distinct groups of groundwater based on chemical characteristics, emphasizing the role of both natural processes and anthropogenic activities in influencing groundwater quality. Regular monitoring, management, and intervention of groundwater sources throughout the study area are crucial for long-term use. The findings of this study will assist stakeholders, regulators, and policymakers in formulating strategies for the sustainable use of groundwater.

Effect of V and Mn addition on the HAZ softening and tensile properties of friction stir welded martensitic steel

This study explores the suppression of heat-affected zone (HAZ) softening in friction stir welding (FSW) joints formed above the A3 temperature of martensitic steels by leveraging short-time secondary hardening induced by vanadium (V) addition. The HAZ microstructure was examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). Mechanical properties were evaluated through Vickers hardness (HV) measurements and tensile tests. Analysis of hardness distribution indicates effective HAZ softening suppression with V addition, attributed to the precipitation of fine and high-density V carbides within the HAZ. The inhibition of HAZ softening was correlated not only with V content but also with the A1 temperature of the steels, regulated by the manganese (Mn) content. However, at 1 mass% V content, intergranular brittle fracture occurred within the HAZ due to continuously distributed fine carbides and Mn segregation along the prior austenite boundary.