Search Results (68)

Land degradation from trace metal pollution in North Africa severely compromises soil fertility. This study investigates the synergistic remediation potential of Eucalyptus biochar (EuB) and Casuarina glauca in iron mine soil contaminated with Fe, Zn, Mn, Pb, Cd, and As. Seedlings were grown for six months in: non-mining soil (NMS), contaminated soil (CS), and CS amended with 5% EuB (CS + EuB). Comprehensive ecophysiological assessments evaluated growth, water relations, gas exchange, chlorophyll fluorescence, oxidative stress, and metal accumulation. EuB significantly enhanced C. glauca tolerance to multi-trace metal stress. Compared to CS, CS + EuB increased total dry biomass by 14% and net photosynthetic rate by 22%, while improving predawn water potential (from −1.8 to −1.3 MPa) and water-use efficiency (18%). Oxidative damage was mitigated. EuB reduced soluble Fe by 71% but increased Zn, Mn, Pb, and Cd mobility. C. glauca exhibited hyperaccumulation of Fe, Zn, As, Pb, and Cd across treatments, with pronounced Fe accumulation under CS + EuB. EuB enhanced nodule development and amplified trace metals sequestration within nodules (Zn: +1.4×, Mn: +2.4×, Pb: +1.5×, Cd: +2.0×). The EuB-C. glauca synergy enhances stress resilience, optimizes rhizosphere trace metals bioavailability, and leverages nodule-mediated accumulation, establishing a sustainable platform for restoring contaminated lands. Full article

The interactive effects between nano-silicon dioxide (n-SiO₂) and elevated CO₂ (eCO₂; 645 ppm) on soybean physiology, nitrogen fixation, and nutrient dynamics under climate stress remain underexplored. This study elucidates their combined effects under ambient (aCO₂; 410 ppm) and eCO₂ conditions. eCO₂ + n-SiO₂ synergistically enhanced shoot length (30%), total chlorophyll (112.15%), and photosynthetic rate (103.23%), alongside improved stomatal conductance and intercellular CO₂ (17.19%), optimizing carbon assimilation. Nodulation efficiency increased, with nodule number and biomass rising by 48.3% and 53.6%, respectively, under eCO₂ + n-SiO₂ versus aCO₂. N-assimilation enzymes (nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase) surged by 38.5–52.1%, enhancing nitrogen metabolism. Concurrently, phytohormones (16–21%) and antioxidant activities (15–22%) increased, reducing oxidative markers (18–22%), and bolstering stress resilience. Nutrient homeostasis improved, with P, K, Mg, Cu, Fe, Zn, and Mn elevating in roots (13–41%) and shoots (13–17%), except shoot Fe and Zn. These findings demonstrate that n-SiO₂ potentiates eCO₂-driven benefits, amplifying photosynthetic efficiency, nitrogen fixation, and stress adaptation through enhanced biochemical and nutrient regulation. This synergy underscores n-SiO₂ role in optimizing crop performance under future CO₂-rich climates, advocating nano-fertilizers as sustainable tools for climate-resilient agriculture. Full article

Deep-sea Fe-Mn polymetallic nodules formed nowadays at the deep-sea ocean floor were evaluated as promising critical raw materials (CRMs). Here, we report results of polymetallic nodules from the H22_NE block of the Interoceanmetal (IOM) exploration area in the eastern part of the Clarion–Clipperton Zone (CCZ), NE Pacific Ocean. The polymetallic nodules were studied with X-ray Diffraction, Raman spectroscopy, SEM-EDS, and LA-ICP-MS (bulk nodules and in situ nodule layers). Additionally, we combine geochemical data of polymetallic nodules with the previously reported data of pore waters and sediments from six stations. Our study aims to define the mineral composition and determine the content of CRMs in the polymetallic nodules and to assess the main factors controlling metal deposition and nodule enrichment in some CRMs. Mn content and the Mn/Fe ratio of the nodules classify them mostly as mixed hydrogenetic–diagenetic type. They are also enriched in Ni, Cu, Co, Zn, Mo, W, Li, Tl, and REE. The in situ REE patterns exhibit MREE and HREE enrichment and a variable Ce anomaly that argues for a changing oxic/suboxic environment and periodically changing of diagenetic and hydrogenetic nodule growth. The results of the joint study of the bottom sediments, pore waters, and polymetallic nodules show a complexity of processes that influence the formation of these deposits. The changing oxic and anoxic conditions are well documented in the chemistry of the nodule layers. Probably the most important controlling factors are sedimentation rate, bioturbation, adsorption, desorption, and oxidation. In addition, growth rates, water depth variations, electro-chemical speciation, phosphatization, and the structures of the Fe-Mn adsorbents are also considered. The polymetallic nodule deposits in the IOM contract area are estimated for future mining for Ni, Cu, Co, and Mn resources. They, however, contain additional metals of economic importance, such as REE and other trace elements (referred to as CRMs) that are potential by-products for metal mining. They can significantly increase the economic importance of exploited polymetallic nodules. Full article

The thyroid gland is an endocrine organ whose hormones enable the proper functioning of the organism. The normal function of this organ is influenced by internal and external factors. One of the external factors is trace elements. Trace elements in appropriate concentrations are necessary for the proper functioning of the thyroid. Fe, Cu, Mn, I, Zn, and Se are part of the enzymes involved in oxidative stress reduction, while Cd, Hg, and Pb can increase ROS production. Cu and Fe are necessary for the correct TPO synthesis. An imbalance in the concentration of trace elements such as Fe, Cu, Co, I, Mn, Zn, Ag, Cd, Hg, Pb, and Se in thyroid cells can lead to thyroid diseases such as Graves’ disease, Hashimoto’s thyroiditis, hypothyroidism, autoimmune thyroiditis, thyroid nodules, thyroid cancer, and postpartum thyroiditis. Lack of adequate Fe levels may lead to hypothyroidism and cancer development. The thyroid gland’s ability to absorb I is reversibly reduced by Co. Adequate levels of I are required for correct thyroid function; both deficiency and excess can predispose to the development of thyroid disorders. High concentrations of Mn may lead to hypothyroidism. Furthermore, Mn may cause cancer development and progression. Insufficient Zn supplementation causes hypothyroidism and thyroid nodule development. Cd affecting molecular mechanisms may also lead to thyroid disorders. Hg accumulating in the thyroid may interfere with hormone secretion and stimulate cancer cell proliferation. A higher risk of thyroid nodules, cancer, autoimmune thyroiditis, and hypothyroidism were linked to elevated Pb levels. Se deficiency disrupts thyroid cell function and may lead to several thyroid disorders. On the other hand, some of the trace elements may be useful in the treatment of thyroid diseases. Therefore, the effects of trace elements on the thyroid require further research. Full article

The study of the influence of microorganisms on the formation of deep- and shallow-water ore deposits is a promising topic in environmental science. This problem, along with the role of organic matter in the growth of Fe-Mn nodules, remains understudied. This study focuses on the analysis of the composition and content of fatty acids in fast-growing Fe-Mn deposits and underlying sediments from various regions of the Kara Sea. Fatty acids serve as important biomarkers of diagenetic processes and reflect the different origins of organic matter. This work is based on the results of lipid extract analysis using GC–MS. Various sources of fatty acids were identified, including plankton, bacteria, terrestrial plants, and detrital material. It was found that FA content depends on the size of the nodules. Compared to underlying sediments, Fe-Mn nodules are enriched in FAs of bacterial and detrital origin, with SAFAs > MUFAs and a negligible content of PUFAs. Full article

The vast seabed holds tremendous resource potential that can provide necessary materials for future human societal development. This study focuses on the mineralogy of seafloor manganese nodules off the coast of China in the Western Pacific and the primary techniques for extracting valuable metal elements from manganese nodules. The research indicates that the main valuable metal elements in the manganese nodules from this region include Cu, Co, Ni, Mn, Fe, etc. The key to extracting these valuable metals lies in reducing Mn(IV) to Mn(II) to disrupt the structure of the nodules, thereby releasing the valuable elements. The extraction processes for the main valuable metal elements of manganese nodules are mainly divided into two categories: pyrometallurgical–hydrometallurgical and solely hydrometallurgical. In order to cope with the challenges of environmental change and improve utilization efficiency, bioleaching, hydrogen metallurgy, and co-extraction are gaining increasing attention. For promoting commercialization, the future development of manganese nodule resources can refer to the technical route of efficient short-process extraction technology, the comprehensive recovery of associated resources, and tail-free utilization. Full article

Ferromanganese (Fe-Mn) deposits are widely used in paleoenvironmental reconstructions owing to their mineralogical and geochemical properties. We analyzed Fe-Mn deposits using micro-X-ray fluorescence and Raman spectroscopy to study the paleo-ocean environment. Samples were collected from the OSM-XX seamount in the western Pacific. The Fe-Mn crust was divided into three parts: phosphatized, massive non-phosphatized, and porous non-phosphatized. Vernadite was identified in all layers. Furthermore, in the nodule, high values of Mn, Ni, and Cu were observed near the nucleus, with vernadite and todorokite, and these values decreased outward. A high Mn/Fe ratio near the nucleus indicates early diagenetic processes. Formation of Fe-Mn nodules began around 19–16 Ma, and this period corresponded to a minor phosphatization event and persistent reducing conditions. From 11–10 Ma, the Mn/Fe and Co/Mn ratios decreased due to the formation of a western Pacific warm pool during this period. Subsequently, with the opening of the Indonesian seaway and global cooling, the Mn/Fe and Co/Mn ratios in the Fe-Mn deposits increased again. The comparative analysis of variations in Mn/Fe ratio and vernadite crystallinity in the Fe-Mn deposits confirmed that it is possible to reconstruct paleo-productivity and redox condition changes in the western Pacific Magellan Seamount. Full article

A new occurrence of the Mn-Ba ore mineral, romanechite, has been discovered in a small paleo-doline of the Apulian karst on Mesozoic carbonate rock successions, characterized by reddish incrustations and nodules made essentially by Fe-bearing calcite. The conditions under which Mn-Ba ore minerals form represent an intriguing area of research, as these minerals can act as scavengers for heavy elements, impacting soils, surface sediments, and even associated aquatic systems. The genesis of romanechite is linked to the progressive interaction of silicate aqueous solutions enriched in Al, Si, and Fe with the limestone substrate. The findings provide new insights into the genetic processes responsible for the formation of reddish Mn incrustations, supporting their polygenetic origin because of the chemical alteration of limestone and allochthonous siliciclastic muds. Full article

Crystals of karwowskiite, Ca₉Mg(Fe²⁺_0.5□_0.5)(PO₄)₇, a new mineral of the merrillite group, were found on an amygdule wall in the central part of an anorthite–tridymite–diopside paralava of the Hatrurim Complex, Daba-Siwaqa, Jordan. The amygdule was filled with a sulfide melt, which after crystallization gave a differentiated nodule, consisting of troilite and pentlandite parts and containing tetrataenite and nickelphosphide inclusions. Karwowskiite crystals are colorless, although sometimes a greenish tint is observed. The mineral has a vitreous luster. The microhardness VHN₂₅ is 365 (12), corresponding to 4 on the Mohs hardness scale. Cleavage is not observed, and fracture is conchoidal. The calculated density is 3.085 g/cm³. Karwowskiite is uniaxial (−): ω = 1.638 (3), ε = 1.622 (3) (λ = 589 nm), and pleochroism is not observed. The composition of karwowskiite is described by the empirical formula: Ca_9.00(□_0.54Fe²⁺_0.23Mg_0.12Na_0.04 Sr_0.03 Ni_0.03K_0.01) _Σ1.00Mg_1.00(PO₄)_7.02. Karwowskiite is distinct from the known minerals of the merrillite subgroup with the general formula A₉XM[TO₃(Ø)]₇, where A = Ca, Na, Sr, and Y; X = Na, Ca, and □; M = Mg, Fe²⁺, Fe³⁺, and Mn; T = P; and Ø = O, in that the X site in it is occupied by Fe²⁺_0.5□_0.5. Karwowskiite is trigonal, space group R-3c with a = 10.3375 (2) Å, c = 37.1443 (9) Å, and V = 3437.60 (17) ų. Karwowskiite crystallizes at temperatures lower than 1100 °C in a thin layer of secondary melt forming on the walls of amygdules and gaseous channels in paralava as a result of contact with heated gases which are by-products of the combustion process. Full article

Arsenic (As) is of widespread concern, as its elevated contents in soil and water have a serious impact on the ecological environment and human health. Soils in karst regions are characterized by a high geochemical background of As. However, the bioavailability of As in paddy soils and the potential risk of As transfer from the soil to rice remain unclear. In this study, 305 paired soil–rice samples were collected from karst regions in Guangxi, China, in order to examine the controlling variables and As bioavailability in the soil–rice system. According to this study, the karst region’s paddy soil had higher As concentrations than the non-karst region’s paddy soil. The As concentration in the rice grains was low, with only 0.62% of the rice samples exceeding the permissible value of inorganic As (0.2 mg/kg). Arsenic in the karstic paddy soils existed mainly in the residual fraction, while the water-soluble and exchangeable fractions, which are readily absorbed by rice, accounted for a relatively small proportion. The high content but low bioavailability of As in the karstic paddy soil was mostly attributed to the abundant Fe–Mn nodules, which contributed 64.45% of the As content in the soil. Within the Fe–Mn nodules, As was primarily bound to Fe-(oxyhydr)oxides, which could be released into the paddy soil under certain reduction conditions via the reductive dissolution of Fe-(oxyhydr)oxides. Under the natural pH conditions of the karstic paddy soil (pH 4.9–8.38), the leaching of As was almost negligible, and As could be steadily retained within the Fe–Mn nodules. However, extremely acidic or alkaline conditions promoted the release of As from the Fe–Mn nodules. Full article

Legumes, due to their symbiosis with papillary bacteria, can receive nitrogen from the air. The remaining nutrients must be supplied in fertilisers, either soil or foliar. In the pot experiment, we recorded the responses of two soybean cultivars (Annushka, Pompei) to the foliar application of micronutrients (control, Zn, Fe, Cu, Mn, B, or Mo). The physiological properties were expressed as net photosynthetic rate (P_N), intercellular CO₂ concentration (C_i), transpiration rate (E), stomatal conductance (g_s), maximum quantum yield of photosystem II (F_v/F_m), maximum quantum yield of primary photochemistry (F_v/F₀), photosynthetic performance index (PI), and the development of soil plant analyses (SPAD), which were analysed. The effects of individual micronutrients on nodulation, plant growth, and condition were also investigated. Micronutrient fertilisation had a positive effect on plant fresh weight and no negative effect on plant condition. It was shown that elements such as B, Fe, and Mo had the most beneficial effect on nodulation compared to the control, regardless of the cultivar analysed. The application of single-component foliar fertilisers improved the physiological parameters of the plants. The relative chlorophyll content was most favourably affected by the application of Mn, B, and Mo in the Annushka cultivar, and Fe, Mn, and Mo in the Pompei cultivar. Similarly, in the case of chlorophyll fluorescence, the most stimulating effect was found for Mn and B, regardless of the cultivar. In the case of gas exchange, the application of Fe, Mo, and B for the Annushka cultivar and Cu for the Pompei cultivar had the most favourable effect on physiological measurements. The results obtained indicate that the foliar application of the evaluated micronutrients is justified in soybean cultivation and does not disturb the nodulation process. Full article

Ferromanganese (Fe-Mn) polymetallic nodules are significant marine mineral resources containing various metal elements of substantial economic and scientific research value. Previous studies have primarily focused on the mineralogy and geochemistry of the nodules, while research on their nano-mineralogy is still lacking. In this study, we conducted scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) porous structure gas adsorption/desorption, and specific surface area analysis to examine the nano-mineralogy and mineralization of the polymetallic nodules from the interbasin of seamounts in the western Pacific Ocean (IBSWP). The results indicate that the growth profiles of the IBSWP polymetallic nodules exhibit microstructural features such as laminated, stromatolithic, columnar, and mottled structures. The mineral compositions are primarily composed of Fe-Mn minerals and detritus, including quartz; minerals from the feldspar group; and minerals from the clay group. The Fe-Mn phase minerals are relatively poorly crystallized. The Mn-phase minerals contain vernadite and small amounts of todorokite, buserite, and birnessite, while the Fe-phase minerals are mainly comprised of amorphous FeOOH. The main ore-forming minerals consist of nano-minerals, and the nanostructures of the polymetallic nodules endow them with unusually large specific surface areas and pore volumes, resulting in strong adsorption properties. The unique nano-properties and surface/interface adsorption effects of Fe-Mn minerals play a crucial role in controlling the enrichment of ore-forming elements. Full article

The geochemistry and mineralogy of Mn nodules offer crucial insights into the origins, environmental changes, and distribution of abyssal resources. However, the conventional laboratory X-ray diffractometer, usually employed for semi-quantitative analysis of mineral composition in Mn nodules, often fails to sufficiently detect minor phases due to beam flux limitations and high background signals. In this study, we investigated differences in manganate composition, even when comprising around 1% of the phase fraction, in two manganese nodules (KC-8 and KODOS-10) using high-resolution synchrotron X-ray diffraction. The Mn/Fe ratios of KC-8 and KODOS-10 were 1.32 and 6.24, respectively, indicating that KC-8 and KODOS-10 were predominantly formed in hydrogenetic and diagenetic environments. Both samples contained quartz, vernadite, buserite, and feldspar. Todorokite and illite were exclusively observed in KODOS-10. In KC-8, the phase fractions of vernadite and buserite among manganates ranged from 94(5)%–100(4)% and 6(1)%–0%, respectively. However, in KODOS-10, the fractions of vernadite, buserite, and todorokite ranged from 47(1)%–56(2)%, 33.6(4)%–40.1(3)%, and 10(3)%–16.3(8)%, respectively. Full article

Marine Co-rich ferromanganese crusts and polymetallic nodules, which are widely distributed in oceanic environments, are salient potential mineral resources that are enriched with many critical metals. Many investigations have achieved essential progress and findings regarding critical metal enrichment in Fe-Mn crusts and nodules. This study systematically reviews the research findings of previous investigations and elaborates in detail on the enrichment characteristics, enrichment processes and mechanisms and the influencing factors of the critical metals enriched in Fe-Mn crusts and nodules. The influencing factors of critical metal enrichments in Fe-Mn crusts and nodules mainly include the growth rate, water depth, post-depositional phosphatization and structural uptake of adsorbents. The major enrichment pathways of critical metals in marine Fe-Mn (oxy)hydroxides are primarily as follows: direct substitution on the surface of δ-MnO₂ for Ni, Cu, Zn and Li; oxidative substitution on the δ-MnO₂ surface for Co, Ce and Tl; partition between Mn and Fe phases through surface complexation according to electro-species attractiveness for REY (except for Ce), Cd, Mo, W and V; combined Mn-Fe phases enrichment for seawater anionic Te, Pt, As and Sb, whose low-valence species are mostly oxidatively enriched on δ-MnO₂, in addition to electro-chemical adsorption onto FeOOH, while high-valence species are likely structurally incorporated by amorphous FeOOH; and dominant sorption and incorporation by amorphous FeOOH for Ti and Se. The coordination preferences of critical metals in the layered and tunneled Mn oxides are primarily as follows: metal incorporations in the layer/tunnel-wall for Co, Ni and Cu; triple-corner-sharing configurations above the structural vacancy for Co, Ni, Cu, Zn and Tl; double-corner-sharing configurations for As, Sb, Mo, W, V and Te; edge-sharing configurations at the layer rims for corner-sharing metals when they are less competitive in taking up the corner-sharing position or under less oxidizing conditions when the metals are less feasible for reactions with layer vacancy; and hydrated interlayer or tunnel-center sorption for Ni, Cu, Zn, Cd, Tl and Li. The major ore-forming elements (e.g., Co, Ni, Cu and Zn), rare earth elements and yttrium, platinum-group elements, dispersed elements (e.g., Te, Tl, Se and Cd) and other enriched critical metals (e.g., Li, Ti and Mo) in polymetallic nodules and Co-rich Fe-Mn crusts of different geneses have unique and varied enrichment characteristics, metal occurrence states, enrichment processes and enrichment mechanisms. This review helps to deepen the understanding of the geochemical behaviors of critical metals in oceanic environments, and it also bears significance for understanding the extreme enrichment and mineralization of deep-sea critical metals. Full article

The MSL Curiosity rover investigated dark, Mn-P-enriched nodules in shallow lacustrine/fluvial sediments at the Groken site in Glen Torridon, Gale Crater, Mars. Applying all relevant information from the rover, the nodules are interpreted as pseudomorphs after original crystals of vivianite, (Fe²⁺,Mn²⁺)₃(PO₄)₂·8H₂O, that cemented the sediment soon after deposition. The nodules appear to have flat faces and linear boundaries and stand above the surrounding siltstone. ChemCam LIBS (laser-induced breakdown spectrometry) shows that the nodules have MnO abundances approximately twenty times those of the surrounding siltstone matrix, contain little CaO, and have SiO₂ and Al₂O₃ abundances similar to those of the siltstone. A deconvolution of APXS analyses of nodule-bearing targets, interpreted here as representing the nodules’ non-silicate components, shows high concentrations of MnO, P₂O₅, and FeO and a molar ratio P/Mn = 2. Visible to near-infrared reflectance of the nodules (by ChemCam passive and Mastcam multispectral) is dark and relatively flat, consistent with a mixture of host siltstone, hematite, and a dark spectrally bland material (like pyrolusite, MnO₂). A drill sample at the site is shown to contain minimal nodule material, implying that analyses by the CheMin and SAM instruments do not constrain the nodules’ mineralogy or composition. The fact that the nodules contain P and Mn in a small molar integer ratio, P/Mn = 2, suggests that the nodules contained a stoichiometric Mn-phosphate mineral, in which Fe did (i.e., could) not substitute for Mn. The most likely such minerals are laueite and strunzite, Mn²⁺Fe³⁺₂(PO₄)₂(OH)₂·8H₂O and –6H₂O, respectively, which occur on Earth as alteration products of other Mn-bearing phosphates including vivianite. Vivianite is a common primary and diagenetic precipitate from low-oxygen, P-enriched waters. Calculated phase equilibria show Mn-bearing vivianite could be replaced by laueite or strunzite and then by hematite plus pyrolusite as the system became more oxidizing and acidic. These data suggest that the nodules originated as vivianite, forming as euhedral crystals in the sediment, enclosing sediment grains as they grew. After formation, the nodules were oxidized—first to laueite/strunzite yielding the diagnostic P/Mn ratio, and then to hematite plus an undefined Mn oxy-hydroxide (like pyrolusite). The limited occurrence of these Mn-Fe-P nodules, both in space and time (i.e., stratigraphic position), suggests a local control on their origin. By terrestrial analogies, it is possible that the nodules precipitated near a spring or seep of Mn-rich water, generated during alteration of olivine in the underlying sediments. Full article