High Concentrations Of Mn Research Articles

Dietary and drinking water intake of essential trace elements in a typical Kashin-Beck disease endemic area of Tibet, China

BackgroundEssential trace elements (ETEs), such as copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se), zinc (Zn), are very important elements for human health.MethodsIn this study, 89 drinking water samples and 85 highland barleys were collected from 48 villages in 11 townships, and the average daily dose (ADD) of ETEs were calculated, in addition, health effects of ETEs to rural residents in Luolong County, a typical Kashin-Beck disease (KBD) endemic area in Tibet, were assessed.ResultsThe mean concentrations of Cu, Fe, Mn, Mo, Se, Zn in drinking water were 0.278 ± 0.264 μg·kg−1, 0.766 ± 0.312 μg·kg−1, 0.411 ± 0.526 μg·kg−1, 0.119 ± 0.223 μg·kg−1, 0.155 ± 0.180 μg·kg−1, and 0.804 ± 1.112 μg·kg−1, respectively; and mean concentrations of Cu, Fe, Mn, Mo, Se and Zn in highland barley were 3.550 ± 0.680 mg·kg−1, 81.17 ± 38.14 mg·kg−1, 14.03 ± 1.42 mg·kg−1, 0.350 ± 0.200 mg·kg−1, 0.0028 ± 0.0056 mg·kg−1, and 23.58 ± 3.10 mg·kg−1, respectively. The ADD of Cu in the study area was appropriate; the ADD of Fe and Mn in each township were higher than the maximum oral reference dose recommended by the National Health Commission of China, indicating that Fe and Mn had non-carcinogenic health risks; the ADD of Mo and Zn in 36.36% and 54.55% of the townships exceeded the maximum oral reference dose; and 72.73% of the townships had insufficient ADD of Se. The ADD of Mo, Cu and Se in different townships was significantly correlated with the prevalence of KBD.ConclusionsTherefore, in order to prevent and control the prevalence of KBD and ensure the health of local residents, it is necessary to reduce the intake of high concentrations of Fe, Mn and Zn in diet, as well as increase the intake of Mo, Cu, especially Se.Graphical abstract

Nature and evolution of diagenetic fluids in the deeply buried Cambrian Xiaoerbulake Formation, Tarim Basin, China

Significant amounts of petroleum are found in the deeply buried Cambrian Xiaoerbulake Formation in the Tarim Basin. However, limited understanding of origin of diagenetic fluids hampers petroleum exploration. In this study, petrological and high-resolution geochemical methods have been performed to understand the origin and evolution of diagenetic fluids, and their effects on the formation of dolostone reservoir. The Xiaoerbulake Formation is characterised by microbialites. The matrix is characterised by modern seawater-like rare earth element and yttrium (REY) patterns and δ18O values of −6.02 ± 2.11‰ Vienna Pee Dee Belemnite (VPDB). Fine-crystalline dolomite cements have similar δ13C values and heavy rare earth element enrichment patterns to that of matrix dolomite, yet with lower δ18O values of −7.47 ± 1.2‰ VPDB. In the deep-burial regimes, medium- to coarse-crystalline dolomite cements and saddle dolomites were precipitated at temperatures of 90–120 and 130–190 °C, respectively, lower δ18O values, distinct middle rare earth element enrichment, and high Fe and Mn contents compared with matrix and fine-crystalline dolomite cements. These imply thermochemical reduction of Fe- or Mn-rich oxides and/or hydrothermal fluids. Compared with other types of dolomite cements, calcite cements are characterised by low δ13C values (as low as −6‰ VPDB), light rare earth elements enrichment and significantly elevated Y/Ho ratios (86 ± 59.3), likely related to the oxidation of organic matter during thermochemical sulfate reduction (TSR). Consequently, diagenetic fluid may have evolved from: Cambrian seawater, meteoric water, shallow-buried seawater-dominated pore water, medium-deep-buried ferrous-rich pore water, lately high-salinity hydrothermal fluid-dominated pore water and finally to acidic fluids related to TSR dissolution. Reservoir quality is enhanced by hydrothermal pulses and TSR in deep-burial settings. This study is significant for those concerned with the formation of deep-buried carbonate reservoirs.

Ore genesis of the Narenwula quartz-vein type W polymetallic deposit in the southern Great Xing’an Range W belt, NE China: Constraints from wolframite geochronology and individual fluid inclusion analysis

The Narenwula deposit, situated in the southern Great Xing’an Range W belt, is a large-scale quartz-vein type W polymetallic deposit in NE China. The mineralization is spatially associated with Late Jurassic monzogranite and granite porphyry. In this study, we present detailed description of the ore geology, wolframite in-situ U-Pb dating, and fluid inclusion analyses including microthermometry, laser Raman spectra, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) microanalyses to precisely constrain the timing of ore formation, origin and evolution of ore-forming fluids as well as metal precipitation mechanisms. In-situ U-Pb dating of hydrothermal wolframite yields a W mineralization age of 136.4 ± 2.0 Ma (1σ, MSWD = 1.3), which is ∼14 Ma younger than the zircon U-Pb ages of W-bearing granitoids, indicating the W-bearing granitoids are not genetically related to the W mineralization at Narenwula. The hydrothermal process can be divided into four stages: stage I is characterized by abundant wolframite (I), which is the dominant stage of W mineralization; stage II is featured with the development of wolframite (II) together with minor amounts of pyrite and chalcopyrite; stage III is the predominant stage of sulfide mineralization; and stage Ⅳ is characterized by lack of sulfide or wolframite and occurrence of quartz, carbonate, and fluorite. Cathodoluminescence analysis of quartz further revealed four generations of quartz, corresponding to the four hydrothermal stages. Four types of fluid inclusions were distinguished for quartz, including CO2-rich (C1-type), CO2-bearing (C2-type), liquid-rich (l-type), and brine (B-type) fluid inclusions. Fluid inclusion microthermometry shows a decrease in homogenization temperatures and salinities from the early to late stages. The ranges of the homogenization temperature for stages I to Ⅳ are 440–280, 320–240, 260–180, and 200–160 ℃, respectively, and the ranges of salinities for stages II to Ⅳ are 2.9–17.8, 1.4–10.2, and 0.4–6.7 wt% NaCl equiv., respectively. The salinities of fluid inclusions from stage I have a bimodal distribution in the ranges of 9.6–17.4 and 31.1–35.6 wt% NaCl equiv. Individual fluid inclusion LA-ICP-MS analyses suggest a magmatic source for the fluids of all stages, evidenced by the high Rb and Mn concentrations, high Rb/Na, K/Na, Cs/Na, Li/Na, and Zn/Na ratios, which are distinctly different from those of basinal brines. The Rb/Sr and K/Rb ratios of fluid inclusions are similar to those of Late Mesozoic highly fractionated W-mineralized granitoids in NE China, indicating that the metallogenic parent rocks at Narenwula are highly evolved. In combination with evidence of consistent Cs/Rb and Cs/(Na + K) ratios of fluid inclusions from all stages, we suggest that the mineralizing fluids originated from an underlying, geochemically uniform, and highly fractionated granitic magma. Fluid immiscibility and fluid-rock interaction (especially greisenization) are the main mechanisms for wolframite precipitation, whereas natural cooling of fluids may be subordinate. Fluid inclusion data provide evidence that the addition of meteoric water to the magmatic-hydrothermal fluid initiated at the sulfide mineralization stage, and the fluid dilution and cooling due to fluid mixing played an important role in the process of sulfide precipitation. This study highlights that W and base metals (e.g., Cu, Pb, Zn) in ore-forming fluids display different migration and precipitation progresses, the knowledge of which is important for elucidating multi-stage ore-forming processes of quartz-vein type W polymetallic deposits in NE China.

Effects of Pruning Mulch on Nutrient Concentration of Avocado (Persea americana Mill.) Fruit under Subtropical Conditions

In this study, avocados of the Hass variety cultivated in Almuñécar (Granada, Spain) are analyzed after soil mulching with pruning debris. The mulch treatment assay was composed of pruning wastes from subtropical crops (avocado, cherimoya, and mango) and garden wastes from the surrounding areas. The aim of this work is to analyze the nutrient content in avocado fruit and the effect of pruning-waste mulching on fruit development over four years. Avocado fruits collected in 2013, 2016, and 2017 were weighed, their volume and their sugar content were calculated, and macro- and micronutrients were analyzed in the peel, pulp, and stone (endocarp and seed). The pulp contained the highest concentration of nutrients, especially Cu, Zn, P, Na, and Ca. The peel presented high concentrations of Mn, K, and N, while the stone recorded the lowest values in nutrients, with the greatest decreases in years with the lowest precipitations registered. Over the study period, a decline was detected in the nutrient concentrations related to the alternation of high and low yields, typical of this crop, due to environmental factors. In the years 2016 and 2017, avocados accumulated higher amounts of micronutrients and P, presumably because of greater water availability in the soil. During the study period, the application of pruning wastes did not affect the nutrient concentration of fruits except for the garden pruning waste in certain elements in the pulp during the last study year.

Role of intracellular energy metabolism in Mn(Ⅱ) removal by the novel bacterium Stenotrophomonas sp. MNB17

Microorganism-mediated Mn(Ⅱ) removal has gained increasing attention as a valuble bioremediation approach. In this study, a novel strain Stenotrophomonas sp. MNB17 — obtained from marine sediments — was found to show Mn(Ⅱ) removal efficiencies of 98.51–99.38% within 7 days and 92.24% within 20 days at Mn(Ⅱ) concentrations of 10–40 mM and 50 mM, respectively. On day 7, 80.44% of 50 mM Mn(Ⅱ) was oxidized to Mn(Ⅲ/Ⅳ), whereas only 2.11–2.86% of 10–40 mM Mn(Ⅱ) was oxidized. This difference in the proportion of Mn-oxides suggested that the strain MNB17 could remove soluble Mn(Ⅱ) via distinct mechanisms under different Mn(Ⅱ) concentrations. At 10 mM Mn(Ⅱ), indirect mechanisms were employed by strain MNB17 to remove Mn(Ⅱ). The sufficient energy generated by increased cellular respiration led to enhanced ammonification, and MnCO3 was the main component of the Mn-precipitates (97.27%). Meanwhile, intracellular fatty acids were degraded and served as an important carbon source for respiration. At 50 mM Mn(Ⅱ), most of the soluble Mn(Ⅱ) was oxidized, and Mn-oxides dominated the Mn-precipitates (80.44%). Mn(Ⅱ) oxidation likely contributed to electrons for energy production, as the down-regulation of respiratory pathways resulted in a deficit of electron supply, which warrants futher study. The exogenous addition of tricarboxylic acid cycle substrates (malate, α-ketoglutarate, oxaloacetate, succinate, and fumarate) was found to accelerate Mn(Ⅱ) removal as MnCO3 at a concentration of 50 mM. Overall, this study reports a novel strain MNB17 with the biotechnological potential of Mn(Ⅱ) removal and elucidates the function of cellular energy metabolism during the Mn(Ⅱ) removal process. In addition, it demonstrates the potential of aerobic respiration-related substrates in accelerating the removal of high concentrations of Mn(Ⅱ) for the first time.

An alternative quenching and partitioning (Q&P) process via spheroidization

A hot-rolled Fe-CMnSiMo alloy was subjected to quenching followed by a spheroidization treatment, which resulted in a microstructure consisting of Mn enriched cementite particles dispersed in the ferrite matrix. The as hot-rolled and spheroidized material was subjected to short-duration intercritical annealing (IA) treatment followed by the full quenching and Q&P treatments. The IA treatment was such that the austenite formed as a result of dissolution of cementite particles retains its higher Mn content. The influence of this chemical inhomogeneity on martensite transformation and retained austenite stability was investigated using a dilatometer and interrupted compression experiments, respectively. The results were compared with the microstructure obtained in the absence of chemical heterogeneity by subjecting the hot-rolled material to similar heat treatment directly without the quenching and spheroidization treatment. After the IA treatment, the Ms temperature of the spheroidized material was 36 °C higher than the Ms temperature of the as hot-rolled material. Nevertheless, a higher fraction of retained austenite was stabilized in the spheroidized material after the IA treatment followed by full quenching. The SEM, TEM and DICTRA modelling results showed that cementite particles dissolve during the IA treatment of the spheroidized material and the product austenite retains its higher Mn content. Interrupted compression test results show that the retained austenite in the spheroidized material has greater stability because of its higher Mn content and small size.

Activation of persulfate via Mn doped Mg/Al layered double hydroxide for effective degradation of organics: Insights from chemical and structural variability of catalyst.

Considerable interest has been focusing on the activation of peroxydisulfate (PDS) by layered double hydroxide (LDH) for degradation of organic pollutants. However, understanding the structure and chemistry of LDH by which the activation of PDS could achieve a high degradation efficiency of organic compounds is an unsolved and fundamental question in advanced oxidation processes (AOPs), and one which, if harnessed, could enable the rational design of LDH with desired material properties. In this work, Mg/Al-LDH was synthesized with variable structures and compositions through doping different proportions of Mn2+. We advanced to understand this question of how LDH by these characteristics can affect the activation of PDS for degradation of organic pollutants. At a relatively low dosage of Mn (˂ 1%) in Mg/Al-LDH, the degradation rate of phenol by LDH activated PDS increased with the increase content of Mn, which was achieved by an increase of catalytic sites in Mg/Al-LDH interlayer. Rather, higher content of Mn (˃ 1%) significantly lowered the degradation performance of phenol as the decrease of interlayer space resulted in reduction of PDS intercalation in LDH and the formation of secondary Mn-related minerals (i.e., Mn3O4) led to meaningless consumption of PDS. Finally, the degradation of phenol by LDH activated PDS followed a non-radical (1O2) mechanism. Our ability to quantify how the chemical and structural variability of LDH influence the activation of PDS for organic degradation could mark an important step toward synthesis strategies for advanced catalysts.

Batch annealing enhances the yield strength of a high quenching temperature Q&P steel through accelerated bainitic transformation

Hot-dip galvanized quenching and partitioning (Q&P) steels exhibit excellent corrosion resistance and strength-ductility synergies. However, production using conventional continuous galvanizing lines (CGLs) is challenging because these lines cannot meet the required quenching and reheating capacity. The presence of ferrite and absence of sufficient primary martensite led to a substantial decrease in the yield strength of the material. To solve this problem, we propose a simple batch annealing (BA) treatment prior to continuous annealing and galvanization. The BA treatment resulted in spheroidization of cementite in the coiled samples and enrichment of Mn. During the intercritical annealing process, the higher Mn content in the cementite of the BA sample retards cementite dissolution. The retained cementite particles served as nucleation sites and significantly promoted bainite formation during quenching and partitioning. Consequently, the yield strength increased by approximately 90%, from 438 MPa to 821 MPa. The total elongation of the BA samples was not affected due to the simultaneous stabilization of the retained austenite. The effect of batch annealing time was also investigated, and the balance between Mn enrichment in cementite and the number density of spheroidized cementite before Q&P treatment was revealed.

A partial least squares-path model of environmental degradation in the Paraopeba River, for rainy seasons after the rupture of B1 tailings dam, Brumadinho, Brazil

The present study aimed to investigate the rupture of B1 tailings dam of Córrego do Feijão mine, which drastically affected the region of Brumadinho (Minas Gerais, Brazil). The contamination of water resources reached 155.3 km from the dam site. In the river channel, high concentrations of Mn, Al, As and Fe were detected and correlated to the spillage of the tailings in the river. The presence of the tailings also affected the chlorophyll-a content in the water, as well as the reflectance of riparian forests. With the increase of metal(oid) concentrations above permitted levels, water management authorities suspended the use of Paraopeba River as resource in the impacted areas, namely the drinking water supply to the Metropolitan region of Belo Horizonte. This study aimed to evaluate possible links between tailings distribution, river water quality, and environmental degradation, which worked as latent variables in partial least squares regression models. The latent variables were represented by numerous physical and chemical parameters of water and sediment, measured four times in 22 locations during the rainy season of 2019, in addition to stream flow and to NDVI evaluated in satellite images processed daily. The modeling results suggested a relationship between river flow turbulence and increased arsenic release from sand fractions, as well as desorption of Mn from metal oxides, both representing causes of water quality reduction. They also revealed increasing iron concentrations affecting the forest NDVI (greening), which was interpreted as environmental degradation. The increase of chlorophyll-a concentrations (related with turbidity decreases), as well as the increase of river flows (responsible for dilution effects), seemed to work out as attenuators of degradation. Although applied to a specific site, our modeling approach can be transposed to equivalent dam failures and climate contexts, helping water resource management authorities to decide upon appropriate recovery solutions.

Electrochemically Active Mn-Doped Iron Hexacyanoferrate as the Cathode Material in Sodium-Ion Batteries

In this work, for the performance enhancement of iron hexacyanoferrate, an electrochemically active Mn-doped iron hexacyanoferrate cathode is fabricated via a bottom-up approach. It is found that the pre-treatment of interstitial water and appropriate Mn doping are two keys to achieving higher capacity and higher stability. The interstitial water has a trade-off effect between the alleviation of volume expansion upon Na+ (de)intercalation and the retardation of Na-ion diffusion. The moisture-tailored iron hexacyanoferrate with appropriate Mn doping exhibits a high initial Coulombic efficiency of 94.8%, enhanced capacity and rate performance, and excellent cycling stability. These results benefit from the fact that the extraction/insertion of Na ions from/into the lattice via a solid-solution mechanism correspond to both the slight volume expansion and fast sodium diffusion rate; otherwise, the removal of interstitial water and a higher Mn content might lead to poor cycling stability due to excessive volume expansion resulting from rhombohedral to cubic phase transformation. Finally, the less demand on the control of air humidity for the fabrication of electrodes and the potential for the full cell coupled with hard carbon are also demonstrated, which shows great potential for practical applications.

New insights into the archives of redox conditions in seep carbonates from the northern South China Sea

Modern cold seeps are of fluctuant flux, which could result in variabilities of geochemical archives through intensively influencing the redox condition in pore fluids. However, the geochemical archives are not fully understood when the redox condition changes. Here, tubular carbonates from the Shenhu Sea Area were used to reconstruct the formation environment and redox conditions. The moderately negative δ13C values of the carbonates (−40.1‰ to −30.8‰, VPDB) indicate a mixed carbon source of thermogenic and biogenic methane. The low δ18O values (−2.7‰ to 1.0‰, VPDB) suggest a type of 18O-depleted pore fluid possibly influenced by gas hydrate formation. Co-variation of MoEF, WEF, CoEF, and CrEF suggests that high Fe contents in the rims of samples R1 and R2 are induced by Fe (oxyhydr)oxidation enrichment, while the positive correlation between MoEF and Mn/Al ratio indicates that high Mn contents in the rims of samples R3 and R4 are induced by Mn (oxyhydr)oxidation enrichment. The occurrence of Fe or Mn enrichment in the rims and the absence of Fe/Mn enrichment in the cores suggest Fe/Mn (oxyhydr)oxides forming in pore fluid rather than in bottom seawater. The carbonate phases of the rims enriched in Fe (oxyhydr)oxides are dominated by high magnesium calcite, while those of the rims enriched in Mn (oxyhydr)oxides are dominated by aragonite. The occurrence of Fe or Mn (oxyhydr)oxides corresponds to the previously proposed formation depth for the carbonate phase. The occurrence of dissolution textures in these rims indicates episodic oxic conditions, which would facilitate Fe2+/Mn2+ oxidation. We suppose that the Fe2+ and Mn2+ could be supplied through fluid seepage or diffusion from underlying sediments when the flux decreased. Similar archives may be applied to qualitatively reflect the changes of redox conditions in seep systems. Similar scenarios may help us understand the geochemical records in seeps of fluctuant flux.

Metamorphosis of the properties of the gas-phase fraction of ZnS:Mn obtained by the method of self-propagating high-temperature synthesis from the charge with a different Zn/S ratio

Performed in this work is a comparative analysis of photoluminescence, photoluminescence excitation and EPR spectra of gas-phase fraction of powdery ZnS:Mn obtained using the self-propagating high-temperature synthesis from the charge with a different Zn/S ratio. It was found that the size of particles in the synthesized materials was with in the range 10–300 nm. The size that is comparable with the Debye screening length (L). The luminescence and other characteristics of the studied material were found to differ significantly from the bulk ones. This finding has been explained by a unique energy structure of crystallites. Zn/S ratio has been shown to impact significantly on the crystallites sizes and the amount of incorporated Mn. The largest crystallite sizes and the high Mn content were observed in the powder synthesized with a stoichiometric Zn/S ratio, while the minimum particle sizes - in the powders synthesized with S excess. At sulfur excess, the size of particles is close to the Debye length, and carriers can freely migrate in the conduction band to the surface, where mainly nonradiative recombination occurs. The stoichiometric Zn/S ratio or Zn excess in the charge results in the increase of the particle sizes up to the values 2L ≤ d≤3L. Such materials are characterized by minimization of non-radiative losses. This finding opens new possibilities for ZnS application.

Metallogenic model of the Fengyan stratabound Zn-Pb deposit in Fujian of southeastern China: Constraints from fluid inclusions, C[sbnd]O[sbnd]S-Pb isotopes, and pyrite chemistry

The Fengyan stratabound Zn-Pb deposit (total resources: 24.7 Mt of ore @ 4.09 % Zn and 1.92 % Pb) is hosted by Neoproterozoic marble and metavolcanic rocks in the Meixian ore field of southeastern China. Hitherto, the genesis of this deposit has been a matter of debate, including a Neoproterozoic volcanogenic massive sulfide genesis (VMS) or an Early Cretaceous magmatic-hydrothermal origin. Based on fluid inclusion data from various hydrothermal stages, stable isotope data of hydrothermal minerals, and in-situ trace element analyses of poly-stage pyrite (Py1-3), the deposit can be classified as a distal skarn-type. A complex paragenesis reflects four hydrothermal stages: stage I (pyroxene + garnet + Py1), stage II (epidote + hematite + magnetite + Py2), stage III (quartz + sphalerite + galena + Py3a + Py3b), and stage IV (calcite). The prograde skarn comprises andradite-rich garnet (on average Ad57Gr34Py9) and pyroxene (on average Hd58Di10Jo32) with high Mn contents. Fluid inclusion data reveal salinity and temperature ranges for the prograde and retrograde skarn fluids as 11.5 to 14.6 wt% NaCl equiv. at 278 to 338℃ and 7.5 to 11.2 wt% NaCl equiv. at 235 to 275℃, respectively. The entrapment pressure is calculated as 130 bars. The sulfide ore minerals of stage III were precipitated at lower temperatures (186 to 259℃) from aqueous fluids with lower salinities (<6.6 wt% NaCl equiv.). Late-stage calcite was deposited from a more dilute (<2.2 wt% NaCl equiv.) and cooler (<200℃) fluid with extremely depleted δ18Ofluid values of −10.1 to −2.0 ‰ (V-SMOW), consistent with a meteoric origin. A mean δ34SV-CDT of 1.7 ± 0.9 ‰ of sulfide minerals points to a magmatic sulfur source. Lead isotopic compositions of sphalerite separates (206Pb/204Pb = 18.295–18.381, 207Pb/204Pb = 15.644–15.662, and 208Pb/204Pb = 38.494–38.724) are similar to those of the Yanshanian granitic bodies in the region but different from those of the ore-hosting marble and metavolcanic rocks. Calcite in the late stage has δ13CV-PDB values of −5.4 to −1.5 ‰, consistent with a predominant magmatic origin. Variations of Co, Ni, Se, and As in pyrite of different generations are interpreted to reflect changes in temperature during hydrothermal evolution. The Co/Ni ratios in all generations of pyrite, mainly between 1 and 10, indicate a magmatic-hydrothermal source. Overall, our new data indicate progressive mixing of a granite-derived magmatic fluid with meteoric waters, as is expected in a distal skarn deposit.

Geochemical behavior and fate of arsenic in middle Gangetic plain, Terai region of India, and its health risk quantification using Monte Carlo simulation and sensitivity analysis

The present study investigates the groundwater solute chemistry, hydrogeochemical behavior of arsenic (As) and the assessment of health risks through ingestion and dermal contact pathways to the adults and children of the Bahraich district, falling under the middle Gangetic plain, Ghaghara river sub-basin, Terai region of India. A Monte Carlo simulation and a sensitivity analysis were also performed to quantify the uncertainties and impact of various input variables in risk calculations, respectively. Concentrations major ions (Ca2+, Mg2+, Na+, K+, SO42−, PO43− NO3−, HCO3−, F− and Cl−), dissolved organic carbon (DOC), and trace metals (As, Fe, and Mn) as well as physical parameters (EC, pH, and Eh) were measured on the collected groundwater and river water samples. The concentration of As in the groundwater samples was found in range between 0.64 μg/L to 104 μg/L and ∼37% of the samples had As>10 μg/L (WHO and BIS acceptable limit of 10 μg/L for drinking water). River water samples also displayed high As concentrations (mean of 14 μg/L) with ∼73% of samples having As>10 μg/L, which could be attributed to infiltration from As-enriched sallow groundwater of the nearby regions. The groundwater of the study area was predominantly of Ca2+-Mg2+-HCO3- type. Bivariate weathering plots showed groundwater was influenced by silicate weathering and carbonate dissolution, along with the ion exchange and reverse ion exchange processes, with a minor contribution from evaporate dissolution. Most of the groundwater samples (n = 57) were anoxic and had low SO42− and NO3−, and high Mn, Fe and DOC concentrations. The observed values and correlations between various measured parameters, including groundwater As concentrations and saturation indices calculations, indicated the reductive dissolution of iron oxyhydroxide as the major process for As mobilization in the study area. The results of total non-carcinogenic risk (HI) estimated by the deterministic and probabilistic techniques were nearly identical for both adults and children, but an overestimation was observed in the case of carcinogenic risk calculated by the deterministic approach. Health risk results also showed that children were more susceptible to non-carcinogenic risk, whereas adults were at a higher risk of cancer in the study area. Sensitivity analysis indicated that the concentration of As in groundwater and exposure duration (ED) were the most effective variables for non-carcinogenic (HI) and carcinogenic (TILCR) risk estimation in both adults and children.

Polyphase hydrothermal sulfide mineralization in the minami–ensei hydrothermal field, middle okinawa trough: Implications from sulfide mineralogy and in situ geochemical composition of pyrite

The mineralogical and geochemical zonation of hydrothermal chimneys preserve important information on mineralization process and hydrothermal evolution. In this study, the sulfide mineralogy and in situ geochemical compositions of pyrite from a hydrothermal chimney in the Minami–Ensei (ME) hydrothermal field were analyzed systematically to determine the mineralization characteristics. Seven layers with different mineral compositions were observed in an individual chimney from ME, including four pyrite-dominant layers and three barite-rich layers. The barite-rich layers occur mainly as intercalations in the hydrothermal chimney, i.e., barite-rich layers and pyrite-dominant layers precipitate alternately, suggesting the occurrence of a polyphase mineralization process, which is highlighted by the in situ trace elements and sulfur isotope compositions of pyrite. The extremely low Co, Ni, Cu, and Se contents (<1 ppm) and high Pb, As, Tl, Mn, and Zn contents (up to several thousands of ppm) in pyrite indicate that the mineralization fluid temperature is unlikely to be higher than 200 °C, which allows the bacterial reduction of seawater sulfate, causing negative shifts in the δ34S values of ME pyrite (−5.00 ‰ to 4.01 ‰). The stable fluid pathway and aperiodic variations in magmatic intensity cause polyphase sulfide mineralization in an individual hydrothermal chimney in the ME hydrothermal field.

Petrochemical evaluation of gahnite from volcanogenic massive sulfide deposits in Betul belt, Central India: Insight from petrography and in‐situ trace element geochemistry

Gahnite occurs in diverse rock types and metamorphosed mineral deposits. The gahnite geochemistry is being used as an exploration tool for zinc sulfide deposits. In the present study, the geochemistry of gahnite and associated minerals viz. sphalerite, garnet, sillimanite, staurolite, anthophyllite, biotite, ilmenite, and chlorite, and their petrography have been used in studying the genesis, metamorphic evolution, deposit characterization, and exploration significance of seven Palaeoproterozoic volcanogenic massive sulfides (VMS) deposits in the Betul belt in the Central Indian Tectonic Zone, India. Different textural types of gahnites are recognized in the Betul belt. Field investigations of textural and geochemical characteristics suggest that the gahnites were formed by multiple geological processes: desulfidation of sphalerite, breakdown of almandine garnet, and zincian staurolite, and chloritization of zincian biotite corresponding with regional metamorphism. The temperature conditions of gahnite formation are estimated to be ~600–650°C using empirical Ti in biotite thermometry. The elemental concentrations in gahnites vary from Zn/Fe ratio 2–4; Co 1–30 ppm; Ga 14–573 ppm and Mn 126–3422 ppm, indicating that bimodal volcanics and volcano‐sedimentary rocks as protolith. High Mn content in gahnite suggests an influx of magmatic‐hydrothermal fluid in the protolith. Variations of trace elements (Mg vs. Al/V, Ti vs. Co/Mn, Co vs. V/Ga, Mn vs. Zn/Fe) and high‐temperature of gahnite formation attest to sensu stricto VMS type mineralization in Betul belt, which is entirely different from SEDEX, Broken Hill‐type, and non‐sulfide deposits. Principal component analysis of trace elements shows the geochemical variations at a few deposits and reveals that gahnites were formed as a result of the competing effect of fS2‐fO2 and governed by bulk rock composition.

Room temperature quenching and partitioning (RT-Q&P) processed steel with chemically heterogeneous initial microstructure

Microstructure heterogeneity has been regarded as being detrimental in obtaining reliable mechanical performance of steels. However, in the present study, we demonstrated that a proactive control of microstructure heterogeneity could deliver unprecedented tensile properties that was hardly achieved by using chemically homogeneous initial microstructure. The heterogeneity of Mn distribution generated by utilizing its solubility difference between ferrite, austenite and cementite at intercritical annealing, promoted the retention of austenite in the final microstructure subjected to the room quenching and partitioning process. The enhancement of fraction as well as the stability of austenite contributed to the simultaneous improvement of tensile strength and ductility which have been regarded as mutually exclusive properties. Furthermore, even in steel with lean Mn composition, the room temperature quenching and partitioning process combined with the chemically heterogeneous initial microstructure presented tensile properties comparable to those expected in steels with much higher Mn content, which exhibited the potential of heterogeneity-driven microstructure control for the development of advanced steel products.

Postglacial shelf erosion, riverine input and lake drainage in the eastern Kara Sea, Russia

Marine sediment core PS2719-1 represents a key sedimentary record for the reconstruction of the postglacial shelf evolution of the eastern Kara Sea west of the entrance to the Vilkitsky Strait. Sedimentological, chronological, geochemical, mineral magnetic and micropaleontological data were used to investigate the sedimentary evolution of the area in unprecedented detail. Four phases of sedimentation were identified, which are closely related to sea-level rise and input from the Yenisei and Taymyr Rivers. Sedimentation likely commenced directly after regional deglaciation prior to 13.6 cal ka BP. Basal sediments are coarse grained and rich in terrestrial organic matter, which points to shelf erosion as the dominating sedimentation process. Around 13.6 cal ka BP Yenisei River water masses reached the area, causing a shift in heavy mineral assemblages and a distinct peak in magnetic susceptibility. This phase was followed by increased sedimentation rates during the early Holocene, which were related to high sediment supply from Lake Taymyr, possibly due to the opening of an ice dam in the Lower Taymyra River area. These sediments are characterized by high terrestrial organic matter accumulation, a fine-grained composition, and a heavy mineral assemblage reflecting the sediment source on the Taymyr Peninsula. High burial rates are reflected by high Mn contents. The transition to modern conditions commenced already around 8.5 cal ka BP and were fully established at ca. 5 cal ka BP, being documented in mineral magnetic evidence and foraminiferal assemblages and are characterized by more marine conditions and a strong influence of the Yenisei River.

The Effect of Mn Substitution on Natural Sphalerites by Means of Raman Spectroscopy: A Case Study of the Săcărâmb Au–Ag–Te Ore Deposit, Apuseni Mountains, Romania

Natural samples of sphalerites containing Mn in the range 0 ≤ x ≤ 0.25 apfu from the Săcărâmb Au–Ag–Te ore deposit, found in the Apuseni Mountains, Romania, were investigated using Raman spectroscopy to determine its capability to provide estimates of Mn content. Raman data for the natural Mn-rich sphalerite have not been published so far, with the largest concentration of Mn in sphalerites being from Romanian territory (i.e., 14.1 wt.%). The results are in good agreement with SEM-EDS data. In this study, three genetic types of sphalerites were identified: from ferroan Zn0.87Fe0.16∑=1.03S0.97 to manganoferroan Zn0.77Mn0.14Fe0.06∑=0.97S1.03, as well as mangan-rich Zn0.8Mn0.25∑=1.05S0.95 compositions. Sphalerites with a high content of Mn (up to 14.1 wt.%) were strongly connected to the presence of alabandite in the mineralized assemblages. The formation of several types of sphalerites in the Săcărâmb Au–Ag–Te ore deposit was caused by the succession of different types of hydrothermal fluids and the interaction between the fluids and the host materials (host rocks and earlier mineralized stages).

Improving remineralization and manganese-removal of soft waters using a mixed CaCO3/MgO contactor

The aim of this study was to investigate the role of MgO on the long-term operation of a mixed media contactor. Specifically, the simultaneous removal of aqueous manganese and the remineralization of soft waters using pure calcite are limited by a remineralization breakthrough after 600 h of operation in the presence of high Mn concentrations (5 mg Mn/L). The introduction of as little as 5 % (m/m) MgO was able to improve the Mn removal kinetic, while maintaining remineralization objectives over 720 h of operation. After treating elevated concentrations of Mn, both media exhibited a Mn-coated layer which contributed to limiting the mass transfer from the media core to the liquid phase. X-ray photoelectron spectroscopy (XPS) identified this superficial layer as 10 % Mn oxides (MnOx) on MgO media compared to 1.4 % MnOx on calcite, suggesting the MgO acts as the preferred reaction surface during Mn removal. Therefore, it is postulated that in the presence of MgO, Mn removal is impacted by high pH conditions (pH = 10.5) which introduces a significant precipitation mechanism as Mn2+ is oxidized. For all the examined conditions, the formation of this coating improved Mn removal due to the autocatalytic nature of the adsorption/oxidation of dissolved manganese by MnOx. MgO is therefore thought to contribute to a complex sorption-coprecipitation process in the operation of a mixed media contactor.