Mn In Sediments Research Articles

Anatomy of the Major Baltic Inflow in 2014: Impact of manganese and iron shuttling on phosphorus and trace metals in the Gotland Basin, Baltic Sea

The deep basins of the Baltic Sea experienced dramatic climate- and eutrophication-induced redox changes between oxic and euxinic water column conditions. Irregularly appearing Major Baltic Inflows (MBI) carrying North Sea waters to the Baltic Sea are partly able to oxygenate euxinic bottom waters within several weeks. After an absence of ~10 years, an exceptional strong inflow event in December 2014 reached the Gotland Basin in early March 2015 providing the opportunity of detailed studies on the impact of fast redox shifts on elemental cycles. Here we report on P and trace metal (Co, Mo, U, V and W) dynamics in the water column, pore water, and sediment of the central Gotland Basin over a 4.5 year-long observation period. These time series record the entire redox development including the primary MBI-related oxygenation, the transitional development to anoxia before a second inflow pulse, and the final re-establishment of euxinia. Samples obtained in August 2012 represent the previous euxinic stagnation period not affected by MBI's since nearly a decade. Concentration measurements and a budget calculation suggest only a limited impact of the MBI on the water column P inventory and the corresponding eutrophication level of the Gotland Basin. This is due to insufficient Fe availability preventing efficient trapping of phosphate during water column oxygenation. In addition, the fast recovery of reducing conditions allowed only a short-term storage of deposited Mn–Fe–P mineral phases in the surface sediment. Due to pronounced scavenging by Mn oxides, substantial water column depletion occurred intermittently for V and W, but again, re-establishing reducing conditions favored Mn oxide dissolution and the release especially of W back into the water column. Mo and U were less affected by Mn and Fe shuttling and Mo even showed an increasing water column inventory due to replenishment by intruding North Sea waters. In contrast, the water column inventory of Co remained on an approx. 50% level about 4.5 years after the inflow suggesting a significant sedimentary burial of Co within the course of the inflow event. Although sedimentary Mn carbonate layers, which were commonly formed in concert with the frequent inflows between ~1960 and 1980, were missing or only weakly developed after the single inflow events in 1994, 2003, and 2014, dated short cores from the study area reveal clear Co and less pronounced V enrichments during the latter inflows. Because Mo, U and W are synchronously depleted compared with their normal sapropel levels, the combination of these trace metals and Co may help to identify past MBIs not reflected by Mn carbonate presence.

Separation of Fe from Mn in the Cryogenian Sedimentary Mn Deposit, South China: Insights from Ore Mineral Chemistry and S Isotopes from the Dawu Deposit

Manganese and Fe have similar geochemical properties in the supergene environment. Separation of Mn and Fe is an important process for the formation of high-grade sedimentary manganese deposits. Large-scale manganese carbonate deposits (total reserves of approximately 700 Mt) were formed during the interglacial of the Sturtian and Marinoan in South China. The orebodies are hosted in the black rock series at the basal Datangpo Formation of the Cryogenian period. The Fe contents in ores range from 1.15 to 7.18 wt.%, with an average of 2.80 wt.%, and the average Mn/Fe ratio is 8.9, indicating a complete separation of Mn and Fe during the formation of manganese ores. Here, we present element data of manganese carbonates and sulfur isotopes of pyrite from the Dawu deposit, Guizhou, China, aiming to investigate the separation mechanism of Mn and Fe and the ore genesis. The Fe in ores mainly occurs as carbonate (FeCO3) and pyrite (FeS2). The Mn, Ca, Mg and Fe exist in the form of isomorphic substitutions in manganese carbonate. The contents of FeCO3 in manganese carbonates are similar in different deposits, with averages of 2.6–2.8 wt.%. The whole-rock Fe and S contents have an obvious positive correlation (R = 0.69), indicating that the difference of whole-rock Fe content mainly comes from the pyrite content. The δ34SV-CDT of pyrite varies from 40.0 to 48.3‰, indicating that the pyrite formed in a restricted basin where sulfate supply was insufficient and the sulfate concentrations were extremely low. Additionally, the whole-rock Fe content is negatively correlated with the δ34S values of the whole-rock and pyrite, with correlation coefficients of −0.78 and −0.83, respectively. Two stages of separations of Mn and Fe might have occurred during the mineralization processes. The reduced seawater became oxidized gradually after the Sturtian glaciation, and Fe2+ was oxidized and precipitated before Mn2+, which resulted in the first-stage separation of Mn and Fe. The residual Mn-rich and Fe-poor seawater flowed into the restricted rift basin. Mn and Fe were then precipitated in sediments as oxyhydroxide as the seawater was oxidized. At the early stage of diagenesis, organic matter was oxidized, and manganese oxyhydroxide was reduced, forming the manganese carbonate. H2S was insufficient in the restricted basin due to the extremely low sulfate concentration. The Fe2+ was re-released due to the lack of H2S, resulting in the second-stage separation of Mn and Fe. Finally, the manganese carbonate deposit with low Fe and very high δ34S was formed in the restricted basin after the Sturtian glaciation.

Mineral Prospectivity Prediction via Convolutional Neural Networks Based on Geological Big Data

Today’s era of big data is witnessing a gradual increase in the amount of data, more correlations between data, as well as growth in their spatial dimension. Conventional linear statistical models applied to mineral prospectivity mapping (MPM) perform poorly because of the random and nonlinear nature of metallogenic processes. To overcome this performance degradation, deep learning models have been introduced in 3D MPM. In this study, taking the Huayuan sedimentary Mn deposit in Hunan Province as an example, we construct a 3D digital model of this deposit based on the prospectivity model of the study area. In this approach, 3D predictor layers are converted from the conceptual model and employed in a 3D convolutional neural network (3D CNN). The characteristics of the spatial distribution are extracted by the 3D CNN. Subsequently, we divide the 22 extracted ore-controlling variables into six groups for contrast experiments based on various combinations and further apply the 3D CNN model and weight of evidence (WofE) method on each group. The predictive model is trained on the basis of the coupling correlation between the spatial distributions of the variables and the underground occurrence space of the Mn orebodies, and the correlation between different ore-controlling factors. The analysis of 12 factors indicates that the 3D CNN model performs well in the 3D MPM, achieving a promising accuracy of up to 100% and a loss value below 0.001. A comparison shows that the 3D CNN model outperforms the WofE model in terms of predictive evaluation indexes, namely the success rate and ore-controlling rate. In particular, the 1–12 ore-controlling factors selected in experiment 5 provide a significantly better prediction effect than the other factors. Consequently, we conclude that the Mn deposit in the study area is not only related to the stratum and interlaminar anomalous bodies but also to the spatial distribution of the faults. The experimental results confirm that the proposed 3D CNN is promising for 3D MPM as it eliminates the interference factors.

Environmental Effects of Heavy Metals from the E-Waste Dismantling Site, South China

ABSTRACT E-waste dismantling activities have caused serious heavy metals pollution in some parts of China. In this study, the contents of 15 metals (Ag, As, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, Rb, Sb, Sn, Tl, and Zn) in soil, sediment, and water hyacinth derived from the e-waste dismantling activities were investigated. Based on these data, the Geo-accumulation index (Igeo) and the potential ecological risk index (RI) were used to assess potential ecological risk. The results showed that the concentration of As, Cd, Cu, Sb, Sn, and Zn in soil for 6.4–131, 0.09–11.2, 25.5–5900, 3.7–443, 5.7–272, and 39–2040 mg kg−1, which the average content exceeded the natural background levels for 5.6, 57, 87, 142.7, 16.7 and 12.7 times, respectively. The concentration of Cu, Sb, Sn, and Zn in sediment for 41.2–468.3, 2.59–33.83, 10.3–92.9, and 148–502.7 mg kg−1, respectively, which the average content exceeded the natural background levels for 14.7, 20.9, 7.1, and 5.7 times, respectively. The Igeo indicated that soil and sediment at sites where e-waste was still heavily contaminated with a variety of heavy metals (such as Cd, Cu, Pb, Sb, Sn, and Zn), which were obvious accumulation effects. The RI in the surface of sediment indicated the average ecological risk of As, Cd, Co, and Cu was high risk and the total risk reached a very high risk at each sampling site. Water hyacinth has strong ability to enrich heavy metals. We suggest that the heavy metals in soil and sediment should be periodically monitored, especially Cd, Cu, Pb, Sb, Sn, and Zn. Water hyacinth can be used to monitor these heavy metals contaminated in river. The cleaning up of the soil and sediment should be a priority for any future remediation program in the study area.

Distribution of heavy metals in sediments and their bioaccumulation on benthic macroinvertebrates in a tropical Brazilian watershed

The objectives of this study were (i) to evaluate the quality of the Ouro River, a tropical Brazilian river, assessing the concentration of the metals in surface waters, sediments, and benthic macroinvertebrates; (ii) to investigate the possible sources of pollution in Ouro River basin through field research and spatial analysis (G.I.S.); (iii) to evaluate the possible occurrence of metals bioaccumulation in the trophic chain, by comparing the concentration of the metals in water, sediments (total and bioavailable) and in benthic macroinvertebrates; and (iv), to assess the biological metrics of benthic macroinvertebrates that inhabit the Ouro River, and the possible relation regarding its distribution (richness, abundance, dominance) with the human occupancy. Water, sediment, and macroinvertebrates samples were assessed in five sample sites for 9 months. The macroinvertebrates were arranged, identified, and analyzed taxonomically. The concentrations of Cu, Zn, Fe, Mn, Cd, Pb, and Cr in waters and sediments (total and Mehlich-1) were determined, the obtained results were compared to Brazilian and international standards indexes (Igeo and E.F.). According to our findings, the quality of Ouro River is directly affected by the human activities carried out in the watershed, and despite that the vast majority of the assessed metals in water was found below the legislation maximum levels, these accumulate in sediments, with extremely high enrichment of Cd, and moderately to heavily contamination of Cd, Mn, and Cu. Also, Zn and Pb high bioaccumulation in macroinvertebrates was observed, in which concentrations were 172% and 92% higher than the mean total concentration in sediment. The fit's goodness indicates that Mehlich-1 could be used as an extractant solution for the correlation of Pb in sediments and B.M.I. On average, Pb levels in the benthic are 14.94× higher than the bioavailable fraction in sediments (Mehlich-1). Mainly for Decapoda, Bivalve, and Gastropoda, results indicate high adsorption rates of Pb and Zn. The probable metal contamination in the Ouro River basin is from diffuse sources such as agriculture erosion (fertilizers and fertilizers with heavy and toxic heavy metals).

Reproducibility of Coral Mn/Ca‐Based Wind Reconstructions at Kiritimati Island and Butaritari Atoll

AbstractGlobal surface temperatures during the twentieth century are characterized by multidecadal periods of accelerated or reduced warming, which are thought to be driven by Pacific decadal variability, specifically changes in trade‐wind strength. However, the relationship between trade‐wind strength and global surface warming remains poorly constrained due to the scarcity of instrumental wind observations. Previous work has shown that corals growing at Tarawa Atoll (1.3°N, 173°E) incorporate dissolved Mn flushed from lagoon sediments by El Niño‐related westerly wind events (WWEs), providing records of both westerly wind variability and trade‐wind strength (on decadal time scales). Here, we explore the utility of this novel coral Mn/Ca‐wind proxy at two nearby islands that also feature west‐facing lagoons. Short coral Mn/Ca records from Butaritari (3°N, 173°E) and Kiritimati (2°N, 157.5°W) track WWEs, albeit with some intercolony variability in the magnitude and timing of the signal. Variability in coral Mn/Ca signal intensity among records from Butaritari suggests that wind‐driven mixing of the sediment Mn reservoir may be finite and/or localized. At Kiritimati, a coral growing outside the lagoon shows higher Mn/Ca concentrations during the 1997/1998 El Niño event, suggesting that nearshore sediments may be an overlooked dissolved Mn reservoir. Taken together, these results highlight a need for additional studies of Mn reservoir variability within and across atolls that hold promise for recording WWEs. These results also suggest that Mn/Ca records from multiple coral colonies and sites are needed to generate robust coral‐based wind reconstructions, particularly from sites with unknown or complex Mn transport pathways.

Assessment of metals pollution and subsequent ecological risk in water, sediments and vegetation from a shallow lake: a case study from Ranipet industrial town, Tamil Nadu, India

ABSTRACT The present study investigated the distribution, sources, bioavailable fractions, and ecological risks of nine metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn) in water, sediment, and vegetation samples collected from a shallow lake within the industrial town of Ranipet, India. The lake water samples exceeded the concentrations of Al, Cd, Cr, Cu, Fe, Mn, and Pb beyond BIS (Bureau of Indian Standards) limits for drinking water with Cr to be highest as 6.73 mg/L. The Geo-accumulation index for lake bed sediment samples were in the order of Cr>Cu>Co>Mn>Zn>Pb. The bioavailability of the metals in sediment samples determined through Sequential Extraction Procedure (SEP) showed Cr>Co>Zn>Cu>Pb>Mn>Fe>Al. The sediment samples collected from the root zone of different plant species (Cynodon dactylon, Sida acuta, and Eclipta prostrata) exhibited varied bioavailable fractions than lake bed sediments, which indicated the influence of plants in mobilising and fixing the metals. The plant samples had metals concentration in the order of Root>Stem>Leaves and showed the possibility of phytoremediation. Principle Component Analysis (PCA) and Pearson Correlation Matrix (PCM) in the lake bed sediment samples identified the clustering of Al and Fe which indicated probable lithological origin. The lone clustering of Cr from Co, Mn, and Cu indicated separate anthropogenic sources. Further Al, Fe, and Mn showed strong correlations with TOC (Total Organic Carbon) substantiate their distribution under influence of TOC. The study indicated elevated metals pollution is water, sediment, and plants samples from lake area which require immediate attention from all the stakeholders. The assessment of pollution in small and shallow lakes amidst industrial belts need to be prioritised as they often become victims of industrial encroachment and cease to exist in long run.

Metal concentrations in marine sediments of the Rio de Janeiro Coast (Brazil): A proposal to establish new acceptable levels of contamination

This work aims to propose new standards to assess the degree of sediment contamination in saline and brackish environments, since the legislation currently used in Brazil is based on Canadian/American regulations, which do not comply with the conditions in Brazil. This study is based on geochemical analyses of 340 surface sediment samples collected in the Green Coast region (Rio de Janeiro, Brazil), including Mangaratiba, Angra dos Reis and Ribeira coves and Ilha Grande and Sepetiba bays. This region is influenced by industrial, harbor, urban and tourist activities and was affected by a dam rupture episode that released contaminated material. The results show heterogeneity in the distribution and range of metal concentrations in the study area depending on the supply of metals from natural and anthropogenic sources. Environmental characteristics such as coastal and tidal currents, water temperature and salinity, local depth, sediment grain size, sedimentary dynamics and biogeochemical processes influence the dispersion or retention of metals. The pollution load index (PLI) suggests that Sepetiba Bay is the region with the most environmental degradation due to anthropogenic contamination. In this context, we propose the establishment of new levels of contamination according to the Cd, Cr, Cu, Mn, Ni, Pb, V and Zn concentrations in sediments of salt and brackish waters, considering I) background level; II) level 1 - with anthropogenic influence; and III) level 2 - contaminated. The results of this work also suggest that, except for zinc, the range of metal concentrations admitted by Brazilian legislation are quite permissive and not adequate for Brazilian coastal environments.

Potentially toxic elements distribution in the contaminated bottom sediments by the industrial genesis within Lower Don river system

The work presents the results of studying the content of potentially toxic elements (Mn, Cu, Zn, Cr, Pb, Ni and Cd) in bottom sediments sampled at monitoring stations in the natural-anthropogenic systems of the Lower Don adjacent to the impact zone of the Novocherkassk Power Plant. The relationship between the content of metals in bottom sediments and their sorption properties is largely determined by the conditions of formation and the type of bottom sediments. Evaluation of the potentially toxic element content in sediments indicated that in particle size fractions (≤ 0.001 mm) could accumulate more than 15 times the levels of Cr and Zn and more than 6 times the levels of Cu, Cd and Ni in comparison to the particle size fractions that are 1.0 mm. Local zones of polyelemental pollution of bottom sediments with respect to Cu, Zn, Pb Cd and Cr were determined. These zones are confined to the geochemical sorption barriers of small watercourses of the power plant.

Assessment of Sediment Contamination by Heavy Metals in the Water of Mgoua Catchment in the Industrial Zone of Douala (Cameroon)

Aquatic ecosystems are increasingly affected by human activities, notably urban sewage and industrial effluent discharges, particularly in rivers. This study assesses heavy metals contamination of sediments of the Mgoua River in Douala, Cameroon. The Geoaccumulation Index (Igeo), the Contamination Factor (FC), the Sediment Pollution Index (SPI), the Enrichment Factor (EF) and the Pollution Load Index (PLI) were used to assess the contamination risk. The mean concentration of Ti, V, Cr, Co, Ni, Cu, As, Cd, Zn, Pb, U, Rb, Sr, Y, Zr, Mo, Mn, Fe, Cs and Ba in sediments was 12601.08, 111.96, 151.93, 9.47, 65.43, 161.81, 7.55, 2.27, 419.30, 248.30, 49.30, 12.65, 89.50, 39.69, 3017.52, 5.95, 313.26, 39667.32, 0.97 and 243.19 µg/l, respectively. Heavy metals concentrations in sediments creased in the following order: U < Cs < Cd < Mo < As < Co < Rb < Y < Ni < Sr < V < Cr < Cu < Ba < Pb < Mn < Zn < Ti < Fe. The Igeo, CF and EF indicate a polymetallic contamination dominated by Cu, Cd and Pb being the most important in all studied sites. The value of SPI varied between 10.95 and 37.84, suggesting that the sediments are moderately to highly polluted, with PLI higher than 1. These indices reveal that the sediments of Mgoua river catchment were polluted with most of the heavy metals. The high concentrations of some of the metals were due to anthropogenic sources particularly the discharge of untreated industrial wastes in to watercourses. This study can therefore be used as a reference to monitor the quality of sediments of the Mgoua river.

Carajás Mineral Province - Example of metallogeny of a rift above a cratonic lithospheric keel

The Carajás Mineral Province (CMP) is located on the southeastern margin of the Amazonian Craton, in northern Brazil. It is the largest producer of high-grade iron ore and a major world supplier of copper, nickel, manganese and gold. This article presents the CMP as a product of oblique rift evolution (2.76–2.06 Ga) controlled by the Canaã and Cinzento strike slip system. The Carajás rift is hosted in the tonalite-trondhjemite-granodiorite (TTG)-greenstone Rio Maria terrains (3.0–2.85 Ga). It overlies a subcratonic lithospheric mantle (SCLM) keel as indicated by seismic tomography and is filled by the Carajás plutonic-volcanic sedimentary sequences (CPVSS) that host the CMP. The rifting stage (Grão Pará Group) began with intense tholeiitic fissure volcanism with basalt and rhyolite flows, coeval intrusions of alkali granites and mafic-ultramafic bodies, BIFs, shales and restricted tuff beds. The Azul and Águas Claras Formations consist mainly of shales and sandstones deposited during the sag stage. The calc-alkaline signature of the Grão Pará metavolcanic rocks was demonstrated to reflect the composition of the melted TTG basement. The high magnesium and platinum-group elements (PGE) contents of Puma and Onça mafic-ultramafic complexes indicate extensive partial fusion, conditions that are indicative of a plume origin. We are proposing that CMP's IOCG deposits were formed from saline carbonate fluids exsolved from deep-seated metasomatic mantellic magmas (MMM), channelled and concentrated along jogs and step-overs in strike-slip fault systems in the Carajás rift.The CMP comprises three main ore-forming stages: (1) a plume stage, ca. 2.76–2.73 Ga, creating supergiant exhalative sedimentary biogenic Fe deposits (Serra Norte, Serra sul and Serra Leste), syngenetic exhalative Cu–Au–Zn (Pojuca deposit), exhalative Mn (Antonio Vicente), Ni-PGE-reef deposits in a magma mixing zone of layered intrusions (e.g. Luanga deposit), and Siqueirinho IOCG deposit; (2) a metasome stage including crustal extension and mantle flash melting (60–100 km depth), ca. 2.68–2.50 Ga, forming the most important IOCG deposits like Salobo, Alemão and Igarapé Bahia. and (3) a sag stage, ca. 2.68–2.06 Ga, with sedimentary Mn deposited in a redox-controlled stratified oceanic environment. The deposits related to granitic intrusion, ca. 1.88 Ga, with Cu-(Au–Mo–W–Sn) greisen (Breves deposit) and Cu-(Au–Mo–F) veins (Gameleira and Alvo 118 deposits) are associated with the A-type magmatism that affected the entire central Amazonian Craton. These deposits are, in contrast, related to an intracratonic silicic large igneous province (SLIP) and have no relation to the Archean Carajás cratonic lithosphere keel rift evolution. The CMP is directly related to the thinning of the lithosphere above a mantle plume, beneath a sub-continental lithospheric mantle (SCLM) keel.

Spatial variation and source identification of heavy metals in sediments in Shaanxi section of Weihe River, Northwest China.

In order to understand the spatial variation of heavy metals in Shaanxi section of Weihe River, the contents and sources of Cd, Co, Cu, Pb, Sb, As, Ni, Cr, Zn, Mn in sediments at 17 sampling sites in Shaanxi section of Weihe River and its tributaries were analyzed. The results showed that the average contents of Cd, Co, Cu, Pb, Sb, As, Ni, Cr, Zn, Mn were 0.10, 1.24, 11.73, 11.95, 24.90, 24.91, 29.31, 54.18, 72.74, 626.85 mg·kg-1, respectively. Except for that of Cd being greater than 1, the coefficient of variation for each of other heavy metals was less than 0.5. The peak contents of Cd, Pb and Cr were found at the sampling site of Bahe River, of Co and Mn at Heihe River, of Cu and Zn at Qingjiang River, and of Sb, As and Ni at Shawang Ferry, Xianyang Railway Bridge and Linjia Village, respectively. According to the results of correlation analysis, principal component analysis and cluster analysis, the elements of Cd, Co, Cu, Pb, Ni, Cr, Zn and Mn mainly originated from industrial and domestic sources, but Sb and As mainly originated from agricultural and geochemical sources.

Heavy Metals in Macrozoobenthos and Sediments of the Coastal Zone of the Eastern Gulf of Finland

The Zn, Cd, Pb, Cu, Mn, and Fe concentrations in sediments, bottom waters, and benthic macroinvertebrates (Amphipoda, Bivalvia, Gastropoda, Hirudinea, and Oligochaeta) collected at six coastal stations in the Eastern Gulf of Finland were determined with the aim to reveal the features of heavy metals bioaccumulation in the macrozoobenthos. It was shown that benthic macroinvertebrates accumulate Mn, Fe, and Zn more actively than Pb, Cu, and Cd, while Hirudinea and Oligochaeta worms have enhanced accumulative capacities as compared to amphipods and mollusks. A close relationship was found between the Zn and Pb concentrations in the sediments and amphipods, but for the other elements no reliable relationship was observed. It was recommended to use organisms of other trophic levels along with zoobenthos and data on heavy metal concentrations in sediments for chemical monitoring of coastal waters.

Heavy Metals Accumulation in River Water and Sediment Core at Kelantan River Tributaries of Gua Musang, Kelantan

Several rivers around Gua Musang had been suspected as polluted area due to waste discharge from ore mining and palm oil factories located near the rivers. However, more evidence is needed to support the statement. Therefore, this study had been carried out to determine the water quality of Aring, Lebir and Relai Rivers at Gua Musang, Kelantan via its physiochemical parameters. Elemental concentrations of Fe, Al, Mn, Zn and Pb were determined in both water samples and sediment cores collected from Aring, Lebir and Relai Rivers to evaluate the accumulation trend of the heavy metal. The pollution level of heavy metals in Aring, Lebir and Relai Rivers were then investigated by using geo-accumulation index. The heavy metals of sediment were analysed by Atomic Absorption Spectrometer (AAS) after being digested by an acid mixture of HNO3/HCL (1:3; v/v). This study shows that Aring, Lebir and Relai Rivers need to treated before direct consumption. The horizontal spatial distribution of heavy metals in water and sediment suggests that the rivers were contaminated with Mn, Fe, Al and Zn. Although Aring Rivers shows the highest concentration of Mn in both water and surface sediment, the inconsistent trend of vertical profiling of heavy metals through sediment cores shows Lebir River has the highest Fe, Pb, Zn and Al geoaccumulation while Relai River has the highest Mn geoaccumulation.

Geochemical approach to the genesis of the Oligocene-stratiform manganese-oxide deposit, Chiatura (Georgia)

The Chiatura deposit is considered to be among the largest deposits of metallurgical grade manganese ore in the world, yet its geochemistry is poorly known, which is the focus of this paper. The Oligocene sedimentary Mn deposit is located in the Chiatura region of central Georgia and formed in a restricted arm of the Paratethys on stable crystalline basement during a regressive-transgressive cycle. An Oligocene basal conglomerate is overlain by sandstone that is in turn overlain by the ore deposits. The Chiatura sedimentary deposits form horizontal beds, 1.5 to 4 m thick, average 2 m, of which 1 to 1.5 m is high-grade ore, covering an area of some 150 km2. The Chiatura deposit contains three types of ore, primary oxide ores, carbonate ores, and oxidized carbonate ores and this paper focuses on the oxide ores. The common manganese minerals in the oxide ore are manganite, pyrolusite, braunite, and psilomelane, and less commonly bixbyite, rhodochrosite, and vernadite. Eighteen manganese-oxide and four wall-rock (low manganese content) samples were analyzed for geochemistry and found on average 36.6 wt% MnO, 2.45 wt% Fe2O3, 23.5 wt% SiO2, 5.88 wt% Al2O3, 3.84 wt% CaO for major oxide concentrations. The mean main trace element concentrations of the samples are 3944 ppm Ba, 946 ppm Sr, 511 ppm Ni, 150 ppm Zn, 94 ppm V, 84 ppm Cu, and 55 ppm Co. These element concentrations are generally low and indicate an enrichment assemblage of V, Ni, Co, Cu, Zr, As, Ba, Cd, Pb, and Zn. The total rare earth element (REE) concentrations of the deposits vary from 83 ppm to 521 ppm (mean 199 ppm). The Post-Archean Australian Shale (PAAS)-normalized REE concentrations have similar trends and show heavy REE (HREE) enrichments. All manganese-oxide samples show negative Ce (mean 0.58) and generally positive Eu (mean 1.20) anomalies, except for four samples. These geochemical data indicate that the Chiatura deposit precipitated rapidly in oxic seawater with a characteristic negative Ce anomaly. The carbonate and mixed ores compared to the oxide-hydroxide ores formed in a deeper-water environment of the shallow sea. Further, both Pb isotopic data and chemical discrimination diagrams show that the Chiatura deposit was affected by both hydrothermal activity located in deeper water, and by terrestrial input. The manganese metals in the oxide ores were syngenetically transported to the area of mineralization from deeper waters than the region where the carbonate ores formed.

Geochemical focusing and sequestration of manganese during eutrophication of Lake Stechlin (NE Germany)

Significant sedimentation of manganese (Mn) in form of manganese oxides (MnOx) and the subsequent formation of authigenic calcium-rich rhodochrosite (Mn(Ca)CO3) were observed in the seasonally stratified hard water Lake Stechlin in north-eastern Germany. This manganese enrichment was assumed to be associated with recent eutrophication of the formerly oligotrophic lake. The mechanisms and processes involved were examined by analysing: (i) short sediment cores obtained from seven locations along a depth transect ranging from 69.5 m (the deepest point) to 38 m; (ii) sediment traps located at 20 m and 60 m water depths; (iii) water column profiles; and (iv) porewater profiles at 69.5 m and 58 m depths. Sedimentary Mn enrichment was observed at water depths below 56 m and increased to more than 25 wt% at the deepest site. Between 2010 and 2017, Mn accumulation at the deepest site was 815 g Mn m−2. Transfer of Mn from the shallower towards the deepest parts of the lake was initiated by reductive dissolution of MnOx and diffusion of dissolved Mn from the sediment to the overlying water column. Manganese was then dissipated via turbulent mixing and subsequently oxidised to MnOx before being transported towards the deepest zone. Transformation of the redeposited MnOx to Mn(Ca)CO3 favoured the final burial of Mn. We show that eutrophication and the areal spreading of anoxic conditions may intensify diagenetic processes and cause the spatial redistribution of Mn as well as its effective burial. Contrary to many previous findings, we show that increases of Mn and Mn/Fe can also be used as indicators for increasing anoxic conditions in previously oligotrophic lakes.

Source identification and human health risk assessment of heavy metals in water sources around bitumen field in Ondo State, Nigeria

The concentrations of Cr, Cu, Fe, Mn, Pb, Ni, V and Zn in sediment, surface and groundwater were determined in a total of 180 samples acquired bi-monthly for one year to evaluate the impact of bitumen spills. Principal component analysis (PCA) and cluster analysis (CA) were also used to identify the possible sources of contamination. The concentrations of heavy metals in groundwater, surface water and sediment as follows: Fe > Mn > Zn > Cu > Pb > Ni > V > Cr, Mn > Fe > Zn > Cu > Pb > Ni > V > Cr and Mn > Fe > Zn > Pb > Ni > V > Cu > Cr respectively. The average concentrations of Fe, Pb and Mn in groundwater were found to be above the World Health Organization (WHO) drinking-water quality standard of 0.1, 0.003 and 0.4 mg L−1 respectively. Multivariate analysis suggests significant intrusions of two diagnostic heavy metals (Ni and V) into groundwater samples indicating the migration of these trace metals from bitumen into the water sources. Data from this study showed that the child hazard quotient (HQ) for Pb and Mn were all ≥1, contributing up to 55.5% towards the Hazard Index (HI). Furthermore, Cr, Pb and Ni in groundwater were the predominant contributors towards carcinogenic risks with Ni contributing an average of 81.7% towards the aggregate cancer risk. These results showed significant petroleum contamination that could lead to heavy metal bioaccumulation in residents with a potential threat to public health. Conclusively, these results provide a useful reference for water system management of metals in Agbabu environment.

An optimized HNO3 and HBF4 digestion method for multielemental soil and sediment analysis using inductively coupled plasma quadrupole mass spectrometry

A robust and reliable analytical procedure for the determination of trace (mg∙kg−1) and ultra-trace elements (μg∙kg−1) in soil and sediments by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) was optimized. Aliquots of ∼200 mg of two certified reference materials (IAEA Soil-7, soil and IAEA SL-1, lake sediments) were digested in nitric acid (HNO3) purified twice by sub-boiling distillation using a microwave-heated high-pressure autoclave. Incremental addition of tetrafluoroboric acid (HBF4, 0.1–2 mL) to HNO3 was evaluated for yield. The selection of appropriate proportions of digestion acids was crucial to obtain accurate results. Digested samples were analyzed for a range of trace elements including those that are potentially toxic (Ag, Cd, Pb, Sb, and Tl), plant micronutrients (Cu, Fe, Mn, and Zn), those enriched in bitumen (Mo, Ni, and V), and lithophile elements (Al, Ba, Co, Cr, Rb, Sr, Th, Ti, Y, and Zr). Nitric acid alone proved to be sufficient to completely liberate Cd, Co, Cr, Fe, Mn, Ni, Pb, V, and Zn in both soil and sediments (87%–120% recovery). For almost all the other elements, addition of HBF4 was needed for improved recovery. A combination of 3 mL of HNO3 and 1.5 mL of HBF4 was optimal to fully liberate an extended list of elements including Ba, Sb, and Sr from both the reference materials. Conservative lithophile elements (Th, Ti, Y, and Zr) could not be completely recovered with the proposed method, requiring hydrofluoric acid for complete dissolution of recalcitrant minerals.

Heavy metal pollution and ecological risk assessment in the Maowei sea mangrove, China

The level and ecological impact of heavy metal pollution in the Maowei Sea mangrove are poorly understood. This work first investigated the distribution and ecological risk of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn in Maowei Sea mangrove sediments. The results showed that heavy metals were mainly concentrated in the top 10 cm of mangrove stands, declined up to 20 cm deep, and were constant afterwards. Exceptionally, Mn concentration increased significantly with depth in the mudflat. Multiple environmental risk indices indicated that the investigated area was broadly contaminated by heavy metals and that Cd was the dominant contributor to potential ecological risks. However, the biological toxicity posed by these metals was negligible. Multivariate analyses implied that Cd, Co, Cr, Cu, Ni, Pb, and Zn originated mainly from anthropogenic sources, whereas Mn was primarily from natural processes. These findings could provide insightful information for future management of this mangrove.

Heavy metal contamination and ecological risk assessment in water and sediments of the Halda river, Bangladesh: A natural fish breeding ground

This study reports the mass fractions of Al, Cr, Mn, Fe, Co, Zn, As, Ni, Cu, Cd, Hg, and Pb in water and sediments of the Halda river, Bangladesh, and studies the distribution, contamination, and potential ecological risks of the metals and metalloid. The average mass fractions of As, Cd, and Pb are relatively higher in sediments compared to those in background values, whereas Al, Fe, Mn, and Pb concentration fractions in water are higher than the international guideline values. The results of the different contamination indices indicate that Halda river sediments are minorly contaminated by As and Pb and moderately to considerably contaminated by Cd. The ecological risk assessments indicate considerable to high ecological risk due to Cd. Multivariate statistical analysis reveals the origin of the contaminants in the river, and indicate that Cr, Zn, Pb, and Cd are from anthropogenic activities while the other metals originate from natural lithogenic actions.