Search Results (36)

Arsenic (As) contamination poses a critical threat to agricultural productivity, affecting rapeseed (Brassica napus L.), an agronomically important crop. A comparative assessment was performed to evaluate the efficacy of chemogenic and biogenic manganese nanoparticles (C-MnNPs and B-MnNPs) for mitigating As toxicity. B-MnNPs were biosynthesized using cell-free filtrate of Bacillus pumilus MAY4, while C-MnNPs were obtained from Cwnano Co., Ltd. (Shanghai, China). Greenhouse assays demonstrated that both C-MnNPs and B-MnNPs alleviated detrimental effects of As; however, B-MnNPs exhibited superior performance compared to their chemical counterparts. Compared to As-stressed plants, B-MnNPs enhanced leaf and root biomass (26.4% and 56.15%, respectively), net photosynthetic rate (64.8%), and stomatal conductance (50%). B-MnNPs more effectively reduced oxidative stress markers by activating antioxidant defense systems in both leaf and root tissues. Furthermore, B-MnNPs reduced in planta As accumulation while significantly improving uptake of essential nutrients, including potassium, phosphorous, magnesium, and manganese, etc., in rapeseed plants. Expression studies revealed that B-MnNPs upregulated antioxidant defense and redox homeostasis related stress-responsive genes under induced As stress. Biochemical assays further confirmed the enrichment of stress-responsive phytohormones, including salicylic acid, jasmonic acid, and abscisic acid, in B-MnNP-treated As-stressed rapeseed plants, indicating activation of multi-tier defense response by B-MnNPs to cope with As stress. These findings establish B-MnNPs as a highly effective nano-enabled strategy for managing As toxicity in the rapeseed cultivation system. This research provides critical insights into the molecular and physiological mechanisms underlying MnNP-mediated stress tolerance and offers a promising green nanotechnology approach for heavy metal-resilient crops. Full article

Background: There is growing interest in the potential role of manganese (Mn) in the development of Alzheimer’s Disease and related dementias (ADRD). Methods: In this nested pilot study of a ferroalloy worker cohort, we investigated the impact of chronic occupational Mn exposure on cognitive function through β-amyloid (Aβ) deposition and multi-omics profiling. We evaluated six male Mn-exposed workers (median age 63, exposure duration 31 years) and five historical controls (median age: 60 years), all of whom had undergone brain PET scans. Exposed individuals showed significantly higher Aβ deposition in exposed individuals (p < 0.05). The average annual cumulative respirable Mn was 329.23 ± 516.39 µg/m³ (geometric mean 118.59), and plasma Mn levels were significantly elevated in the exposed group (0.704 ± 0.2 ng/mL) compared to controls (0.397 ± 0.18 in controls). Results: LC-MS/MS-based pathway analyses revealed disruptions in olfactory signaling, mitochondrial fatty acid β-oxidation, biogenic amine synthesis, transmembrane transport, and choline metabolism. Simoa analysis showed notable alterations in ADRD-related plasma biomarkers. Protein microarray revealed significant differences (p < 0.05) in antibodies targeting neuronal and autoimmune proteins, including Aβ (25–35), GFAP, serotonin, NOVA1, and Siglec-1/CD169. Conclusion: These findings suggest Mn exposure is associated with neurodegenerative biomarker alterations and disrupted biological pathways relevant to cognitive decline. Full article

The rising demand for lithium-ion batteries (LIBs), driven by the growing consumption of electronic devices and the expansion of electric vehicles, is leading to a concerning depletion of primary metal resources and a significant accumulation of electronic waste. This urgent challenge highlights the need for sustainable recovery methods to extract valuable metals from spent LIBs, aligning with circular economy principles. In this study, the preparation of spent batteries for the bioleaching process was achieved with minimal manipulation. This included a preliminary discharge to ensure safety in subsequent processes and a brief crushing to facilitate the access of leaching agents to valuable metals. Unlike most studies that grind batteries to obtain powders between 70 and 200 microns, our approach works with particles sized around 5 mm. Additionally, our preparation process avoids any thermal or chemical treatments. This straightforward pre-treatment process marks a significant advancement by reducing the complexity and cost of processing. A systematic study was conducted on various fractions of the large particle sizes, using Fe (III) produced through bio-oxidation by A. ferrooxidans and biogenically obtained H2SO4 from A. thiooxidans. The highest metal extraction rates were achieved using the unsorted fraction, directly obtained from the black mass after the grinding process, without additional particle separation. When treated with bio-oxidized Fe (III), this fraction achieved a 95% recovery of Cu, Ni, and Al within 20 min, and over 90% recovery of Co, Mn, and Li within approximately 30 min. These recovery rates are attributed to the combined reducing power of Al and Cu already present in the black mass and the Fe (II) generated during the oxidation reactions of metallic Cu and Al. These elements actively facilitate the reduction of transition metal oxides into their more soluble, lower-valence states, enhancing the overall metal solubilization process. The extraction was carried out at room temperature in an acidic medium with a pH no lower than 1.5. These results demonstrate significant potential for efficient metal recovery from spent batteries with minimal pre-treatment, minimizing environmental impact. Additionally, the simplified residue preparation process can be easily integrated into existing waste management facilities without the need for additional equipment. Full article

Ferromanganese formations are widespread in the Earth’s aquatic environment. Of all the mechanisms of their formation, the biogenic one is the most debatable. Here, we studied the Fe-Mn crusts of hydrothermal fields near the underwater volcano Puy de Folles (rift valley of the Mid-Atlantic Ridge). The chemical and mineralogical composition (optical and electron microscopy with EDX, X-ray powder diffraction, X-ray fluorescence analysis, Raman and FTIR spectroscopy, gas chromatography—mass spectrometry (GC-MS)) and the magnetic properties (static and resonance methods, including at cryogenic temperatures) of the samples of Fe-Mn crusts were investigated. In the IR absorption spectra, based on hydrogen bond stretching vibrations, it was concluded that there were compounds with aliphatic (alkane) groups as well as compounds with double bonds (possibly with a benzene ring). The GC-MS analysis showed the presence of alkanes, alkenes, hopanes, and steranes. Magnetically, the material is highly coercive; the blocking temperatures are 3 and 13 K. The main carriers of magnetism are ultrafine particles and X-ray amorphous matter. The analysis of experimental data allows us to conclude that the studied ferromanganese crusts, namely in their ferruginous phase, were formed as a result of induced biomineralization with the participation of iron-oxidizing and iron-reducing bacteria. Full article

Posidonia oceanica significantly contributes to the health of oceans and coastal areas; however, its progressive decline is becoming an increasing source of concern. The present preliminary study aims to assess the chemical parameters that describe the state of preservation of the aforementioned plant meadows located in the Tremiti Islands archipelago. To better understand the plants’ response to external factors, the emission of biogenic volatile organic compounds (BVOCs) was investigated using Posidonia oceanica as a biological indicator. Subsequently, the heavy metal concentrations (Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sn, Ti, Tl, V, Zn) in sediments, leaves, and seawater were determined and pollution indicators were calculated to assess the deviation from the natural background levels of sediments. The dimethyl sulfoniopropionate (DMSP) to dimethyl sulfoxide (DMSO) ratio was calculated to evaluate the oxidative stress levels in the meadows because the DMSP naturally present in Posidonia oceanica is oxidized to DMSO and decreases the ratio of DMSP/DMSO. BVOC analysis revealed dimethyl sulphide (DMS) as the most abundant molecule. Morphological features led to variations in metal concentrations across sampling sites, with sheltered bays displaying a higher metal content. Degradation is indicated by a greater DMSO content in the outer leaves. In accordance with the metal content, the bioindicator ratio confirms greater degradation on the south side, which aligns with increased oxidative stress. Full article

A fungus, Acremonium strictum KR21-2, produces biogenic manganese oxides (BMOs) that can oxidize exogenous Mn²⁺ ions to form different BMO phases. When other guest ions are present during the BMO formation, it can strongly affect the mineralogical characteristics of the resultant BMO phase. The impact of coexisting Ni²⁺ ions on the mineralogy of BMO phases formed through enzymatic Mn(II) oxidation and its sequestration ability is not yet fully understood. To better understand it, repeated sequestration experiments were conducted using BMOs in Ni²⁺/Mn²⁺ binary, single Ni², and single Mn²⁺ solution systems with a pH range of 6.0 to 7.5. It was observed that simultaneous sequestration of Ni²⁺ and Mn²⁺ was efficient, with irreversible Ni²⁺ incorporation at pH values above 7.0. The resultant BMO phases showed that Ni²⁺-bearing Mn oxides resembling feitknechitite (β-MnOOH) were developed through enzymatic Mn(II) oxidation. At pH values below 6.5, the turbostratic birnessite structure was maintained even in Ni²⁺/Mn²⁺ binary solutions, and subsequently, the Ni²⁺ sequestration efficiency was low. The pseudo-first-order rate constants of enzymatically inactivated BMOs for Mn²⁺ sequestration were two orders of magnitude lower than those of active BMOs, indicating the crucial role of the enzymes in precipitating Ni²⁺-bearing Mn oxide phases. These findings provide new insights into the mechanism of Ni²⁺ interaction with Mn oxide through microbial activity under circumneutral pH conditions. Full article

Mn-oxidizing microorganisms oxidize environmental Mn(II), producing Mn(IV) oxides. Pseudomonas putida MnB1 is a widely studied organism for the oxidation of manganese(II) to manganese(IV) by a multi-copper oxidase. The biogenic manganese oxides (BMOs) produced by MnB1 and similar organisms have unique properties compared to non-biological manganese oxides. Along with an amorphous, poorly crystalline structure, previous studies have indicated that BMOs have high surface areas and high reactivities. It is also known that abiotic Mn oxides promote oxidation of organics and have been studied for their water oxidation catalytic function. MnB1 was grown and maintained and subsequently transferred to culturing media containing manganese(II) salts to observe the oxidation of manganese(II) to manganese(IV). The structures and compositions of these manganese(IV) oxides were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, inductively coupled plasma optical emission spectroscopy, and powder X-ray diffraction, and their properties were assessed regarding catalytic functionality towards water oxidation in comparison to abiotic acid birnessite. Water oxidation was accomplished through the whole-cell catalysis of MnB1, the results for which compare favorably to the water-oxidizing ability of abiotic Mn(IV) oxides. Full article

The compositions of metalliferous sediments associated with hydrothermal vents can provide key geochemical data for locating seafloor sulfides. In this study, we present the geochemistry of seabed sediments from the Xunmei hydrothermal field (HF) in the South Mid-Atlantic Ridge (SMAR). The results indicate that the sediments are mainly composed of pelagic material (biogenic calcium components), basaltic debris, iron-manganese oxides, and hydrothermal components. The sediments are significantly enriched in Cu, Zn, Fe, and Co deriving from hydrothermal fluids, as well as Mn, V, Mo, U, and P, which are primarily scavenged from seawater. The northeastern Xunmei has the highest concentrations of Cu and Zn, while the northeastern, northern, and southern regions are characterized by great inputs of Fe. Manganese and Mo are mainly enriched in the western and southern parts and show a strong positive correlation, indicating that Mo is mainly scavenged by Mn oxides. Uranium, P, and Fe exhibit strong positive correlations, suggesting that they coprecipitate with Fe from hydrothermal plumes. Vanadium and Co are introduced into sediments in different ways: V is scavenged and coprecipitated by hydrothermal plumes, and Co is derived from sulfide debris. Based on the contents of Cu and Zn and Cu/Fe (0.159), Zn/Fe (0.158), and Fe/Mn (1440) ratios, it can be inferred that a high-temperature hydrothermal vent existed in northeastern Xunmei. In combination with the distribution patterns of the above elements, the hydrothermal vents in the southern part ceased erupting after a short period of activity. In addition, the high Mn anomaly and the high U/Fe ratios at the boundaries of the investigated area indicate the presence of a relatively oxidized environment in southwestern Xunmei. Full article

Green synthesis offers a superior alternative to traditional methods for producing metal and metal oxide nanoparticles. This approach is not only benign and safe but also cost-effective, scalable, and straightforward, operating under ambient conditions. Notable metals and metal oxide nanoparticles, such as manganese oxides, iron oxides, silver, and gold, have been produced using various bio-reductants derived from plant extracts. These biological agents not only expedite the reduction process but also stabilize the nanoparticles, serving dual roles as reducing and capping agents. This review presents the green synthesis of nanoparticles (NPs) obtained from biogenic wastes and plant extracts. The green-synthesized nanostructured MnO₂ nanoparticles are evaluated as a potential photocatalyst for water treatment and as an electrode material in lithium-ion batteries and supercapacitors. The green-derived iron oxide nanoparticles are examined as promising antioxidant, anti-inflammatory, and anti-diabetic agents. Additionally, this review discusses the green synthesis of precious metal nanoparticles, specifically silver (Ag NPs) and gold (Au NPs), highlighting their potential medical applications in areas like antiviral treatments and cancer therapy. Full article

Many regions of the United States contain manganese deposits economically valuable in New England, Appalachian, and Piedmont regions in the Eastern United States, in Northern Arkansas, and, to a small extent, in Central–Western California. Mn oxide/hydroxide (commonly referred to as Mn oxide minerals) are found in a wide variety of geological settings and occur as fine-grained aggregates, veins, marine and freshwater nodules and concretions, crusts, dendrites, and coatings on rock surfaces (e.g., desert varnish). How manganese oxides form and what mechanisms determine which oxides are likely to form are limited and still debated. This paper focuses on Mn oxides collected at the southern bound of the abandoned open-pit site called Crimora Mine (Augusta County, Virginia). This study uses mineralogical and chemical features to shed light on the origin of manganese deposits in Crimora along the western foot of the Blue Ridge in South–West Virginia. We report the first detailed study on the genesis of the Crimora manganese deposit conducted since the mine was closed in the 1950s. Crimora Mine sample is dark black fine- to medium-grained round and oblong nodules coated with a fine-grained intermix of yellowish earthy limonite, clays, and quartz. Scanning electron microscopy (SEM) revealed that the Crimora Mn-oxides exhibit concentric layering, breccia-like matrices, and veins. X-ray powder diffraction (XRPD) identified the set of Mn minerals as hollandite and birnessite. The concentration and range of dissolved chemical species in freshwater, seawater, and hydrothermal depositional fluids impart a geochemical signature to the Mn-oxides, providing a diagnostic tool to shed light on their genetic origin. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis of the Crimora manganese oxides shows Mn, Fe, and Ti, as well as trace elements such as Co, Ba, Y, Zn, Cr, Ni, Tl, La, V, and Li. A bivariate analysis based on the geochemical correlation of Mn and other common substituting cations (e.g., Fe, Co, Ti) shows a mixed genesis in different environments with varying biological and sedimentary supergene (freshwater and marine) conditions. These data suggest that the Mn-rich deposit in Crimora, VA, was formed in a continental margin environment of surficial deposits and reprecipitated in mixed biogenic and supergene conditions. Full article

A black substance exuding from fractures was observed in 2012 in Ytterby mine, Sweden, and identified in 2017 as birnessite with the composition M_x[Mn(III,IV)]₂O₄∙(H₂O)_n. M is usually calcium and sodium, with x around 0.5. The Ytterby birnessite is unique, with M being calcium, magnesium, and also rare earth elements (REEs) constituting up to 2% of the total metal content. The biogenic origin of the birnessite was established in 2018. Analysis of the microbial processes leading to the birnessite formation and the REE enrichment has continued since then. The process is fast and dynamic, as indicated by the depletion of manganese and of REE and other metals in the fracture water during the passage over the precipitation zone in the mine tunnel. Studies of the exchangeability of metals in the structure are the main objective of the present program. Exposure to solutions of sodium, calcium, lanthanum, and iron led to exchanges and altered distribution of the metals in the birnessite, however, generating phases with almost identical structures after the exchanges, and no new mineral phases were detected. Exchangeability was more efficient for trivalent elements (REE) over divalent (calcium) and monovalent (sodium) elements of a similar size (ionic radii 90–100 pm). Full article

Peter the Great Bay and Lake Khanka are among the most important structural and industrial fishing parts of the Far East coastal ecosystem, which are used by a number of countries such as Russia, China, Korea, Japan, etc. At the same time, the active use of water resources, as well as industrial activities deployed on the coastal part of these reservoirs, are accompanied by a constant flow of pollutants into the water area. Among them, one can include heavy metals; their entry and migration are currently not fully controlled. There exists an important scientific and ecological task to study the features of heavy metal migration and transformation in natural objects. Bottom sediments act as a substrate for hydrobionts and, at the same time, serve as accumulators of pollutants, so that they can be used as the main component of the coastal-shelf ecosystem. The geochemical assessment of the behavior of heavy metals in the bottom sediments of Ussuri Bay and Amur Bay (Sea of Japan) and Lake Khanka (Xingkai) has been performed. Qualitative and quantitative elemental compositions of the bottom sediments have been established by means of the inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), and X-ray fluorescence analysis (XRF), whereas a correlation with the concentration of elements in seawater above sediments has been provided. The main phases of anthropogenic components as well as their relationship with an increased content of heavy metals have been established using X-ray diffraction analysis (XRD). Average values of the concentration of elements in the bottom sediments of Peter the Great Bay decrease in the following row: Fe > Cu > Cr > Zn ≥ Pb > Mn > Ni, and for Lake Khanka: Pb > Cu > Mn > Fe > Cr > Zn > Ni. Here, the excessive contents of Cr, Fe, Cu, Zn, and Pb in sea bottom sediments by 6, 32, 7, 3, and 4 times as compared with background values are the result of the formation of a large amount of carbonate and iron-oxide phases. At the same time, it was shown that, during the transition from the estuarine (coastal) area of river flow to the central (closer to the outlet to the ocean), the concentration of biogenic metals (Ni, Zn, Pb, Cu) generally decreased 2–4-fold along the profile, which was associated with the formation of their hydroxides and carbonates in the area of mixing of freshwater and seawater followed by that of complex compounds or absorption. A significant anthropogenic impact is observed in the lake sediments, which is demonstrated by the excess of Pb concentration by 6700 times, as compared with the Clarke number of the lithosphere. The non-uniform distribution of heavy metals along the core profile has been established, which is related to different contents of aluminosilicate and iron oxide phases in the form of hematite and magnetite. The sedimentation rate has been established by means of granulometric and radiometric analysis and equaled to 0.45 mm/year in Ussuri Bay, 1.6 mm/year in Amur Bay, and 0.43–0.50 mm/year in Lake Khanka. By calculating the distribution coefficients of heavy metals in the ‘water–deposits’ system, some features of migration and accumulation of individual elements have been established. To assess the potential pollution of the marine areas, the geoaccumulation index (Igeo) and the pollution factor (Kc) have been calculated. In comparison with the maximum permissible concentrations of the Russian Federation (MPC), the World Health Organization (WHO), the US Environmental Protection Agency (US EPA), and environmental protection agencies of China and Japan, Peter the Great Bay has an excess of Mn—2-fold, Fe—2-fold, Zn—3-fold, whereas in Lake Khanka, the situation is even less favorable, in particular, the excess of Mn is 79-fold, Fe—35-fold, Cu—2-fold, Zn—3–4-fold, which is clearly determined by the closeness of the water basin and the lack of water exchange. In comparison with the lithosphere Clarke number, the sediments of both water basins, as well as the coastal soil of the lake, are enriched with Pb and depleted with Cr, Ni, and Zn. The highest values of Igeo in both water basins have been observed for Pb, and equaled 12–16 in Peter the Great Bay and 6000 in Khanka Lake. Based on the data obtained, the areas with the greatest pollution caused by natural and anthropogenic factors have been identified. Full article

Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land–ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April–17 May 2021), a study about the possibility and efficiency of ²²⁶Ra and ²²⁸Ra recovery from seawater using various types of sorbents was conducted. The influence of seawater flow rate on the sorption of ²²⁶Ra and ²²⁸Ra isotopes was estimated. It was indicated that the Modix, DMM, PAN-MnO₂, and CRM-Sr sorbents show the best sorption efficiency at a flow rate of 4–8 column volumes per minute. Additionally, the distribution of biogenic elements (dissolved inorganic phosphorus (DIP), silicic acid, and the sum of nitrates and nitrites), salinity, and ²²⁶Ra and ²²⁸Ra isotopes was studied in the surface layer of the Black Sea in April–May 2021. Correlation dependencies between the concentration of long-lived radium isotopes and salinity are defined for various areas of the Black Sea. Two processes control the dependence of radium isotope concentration on salinity: conservative mixing of riverine and marine end members and desorption of long-lived radium isotopes when river particulate matter meets saline seawater. Despite the high long-lived radium isotope concentration in freshwater in comparison with that in seawater, their content near the Caucasus shore is lower mainly because riverine waters meet with a great open seawater body with a low content of these radionuclides, and radium desorption processes take place in an offshore area. The ²²⁸Ra/²²⁶Ra ratio derived from our data displays freshwater inflow spreading over not only the coastal region, but also the deep-sea region. The lowered concentration of the main biogenic elements corresponds to high-temperature fields because of their intensive uptake by phytoplankton. Therefore, nutrients coupled with long-lived radium isotopes trace the hydrological and biogeochemical peculiarities of the studied region. Full article

Groundwater serving as a drinking water resource usually contains manganese ions (Mn²⁺) that exceed drinking standards. Based on the Mn biogeochemical cycle at the hydrosphere scale, bioprocesses consisting of aeration, biofiltration, and disinfection are well known as a cost-effective and environmentally friendly ecotechnology for removing Mn²⁺. The design of aeration and biofiltration units, which are critical components, is significantly influenced by coexisting iron and ammonia in groundwater; however, there is no unified standard for optimizing bioprocess operation. In addition to the groundwater purification, it was also found that manganese-oxidizing bacteria (MnOB)-derived biogenic Mn oxides (bioMnO_x), a by-product, have a low crystallinity and a relatively high specific surface area; the MnOB supplied with Mn²⁺ can be developed for contaminated water remediation. As a result, according to previous studies, this paper summarized and provided operational suggestions for the removal of Mn²⁺ from groundwater. This review also anticipated challenges and future concerns, as well as opportunities for bioMnO_x applications. These could improve our understanding of the MnOB group and its practical applications. Full article