Geochemical Transactions最新文献

This study investigates the trace element concentrations in the surface waters of four north-joining Himalayan tributaries of the Ganga river (Ramganga, Ghaghara, Gandak, and Kosi), highlighting the combined effects of geogenic processes and anthropogenic activities on trace element chemistry and water quality. A knowledge gap exists in understanding the sources of trace elements in these tributaries and the contribution of trace elements from these tributaries to the Gangariver. The novelty of the study lies in its assessment of sources, human health risks, and ecological impacts. The investigation was conducted by assessing trace element concentrations and comparing them with national and international standards. Various human health and ecological risk indicators, including the Heavy Metal Pollution Index (HPI), Hazard Quotient (HQ), Health Index (HI), Chronic Daily Intake (CDI), and the Potential Ecological Risk Index (PERI), were applied. The results reveal high concentrations of copper (Cu), zinc (Zn) and lead (Pb) in the Ramganga, indicating contamination from industrial activities in the catchment. Although most trace element concentrations are within safe limits, Pb concentration in the Ramganga exceeds the limit prescribed by WHO. The Ramganga shows the highest health risks, with a HI_total of 1.876 for adults and 1.616 for children. In contrast, the Ghaghara, Gandak, and Kosi exhibit lower but moderate contamination levels. HPI values for these rivers- 93.74 for the Ghaghara, 83.95 for the Kosi, 83.13 for the Gandak, and 80.43 for the Ramganga—indicate that although contamination is below critical thresholds, targeted mitigation strategies are needed. The findings provide valuable insights into trace metal sources and their implications for human health and ecological risks, and emphasize the need for frequent monitoring and pollution control measures for maintaining sustainable water quality in these tributaries.

The quality of water can significantly affect the regional water resources due to scarcity of potable water in industrial area. The purpose of this study was to explore potentially toxic trace elements (PTEs) contamination and their seasonal variations in different water sources within the coal mining area of the Mahan River command area, Central India. To achieve this, 96 water samples were collected across two distinct seasons and analysed for PTEs. The results indicate that during the pre-monsoon season, the concentrations of Mn (18%), Cu (4%), Pb (8%), Ni (18%), Cd (2%), Al (4%), Cr (2%), and Fe (30%) exceeded permissible limits. In the post-monsoon season, Mn (15%), Pb (6%), Ni (15%), Cd (2%), Al (15%), Fe (46%) and Ba (4%) surpassed the standards. The multiple groundwater pollution indexical methods further revealed that 14% [Heavy metal pollution index (HPI)], 14% [Heavy metal evaluation index (HEI)], 18% [Contamination index (CI)], 14% [the entropy-weight based HM contamination index (EHCI)] and 20% [Heavy metal index (HMI)] of the samples exceeded permissible thresholds during the pre-monsoon season. Similarly, during the post-monsoon period, 10% (HPI), 10% (HEI), 15% (CI), 15% (EHCI) and 17% (HMI) of the samples were above acceptable limits. The relationship between the pH of water and the total load of dissolved metals is established using Caboi plot, confirming that mine water from mine water from Bhatgaon Underground (UG), Mahamaya UG, and Mahan Opencast (OC) [PR40, PR41, PR42, PR43, PR47, and PR48], surrounding rivers, and groundwater sources, exhibited an “Acid-High Metal” characteristic. This suggests significant contamination from acid mine drainage and mineral dissolution. Apart from the anthropogenic inputs, geogenic and environmental processes are responsible for the current distribution of PTEs and their seasonal variations.

In anoxic subsurface environments, low Fe(III) bioaccessibility greatly limits in situ biodegradation of petroleum hydrocarbons (PHCs). Ferric ammonium citrate is a soluble compound that has the potential to increase the bioaccessibility of Fe(III). However, in neutral to alkaline environments, Fe(III) hydrolysis can produce Fe(III) (oxyhydr)oxides that may subsequently transform or recrystallize to relatively stable and less bioaccessible phases. Accordingly, the objective of this study was to elucidate the transformation and fate of Fe(III) contributed by ferric ammonium citrate in a gasoline-contaminated subsurface environment that was undergoing in situ bioremediation. Ferric ammonium citrate, together with sodium tripolyphosphate, magnesium sulphate, and nitric acid, was continuously injected into the contaminated groundwater for about 22 weeks. Colloids in the groundwater (solid particles retained on a 0.45 (upmu)m filter) and soil cores were collected from the site. Fe speciation in these samples was characterized using X-ray absorption near edge structure (XANES) and Fourier transform infrared (FTIR) spectroscopy. The groundwater colloids (GWCs) contained mostly octahedrally coordinated Fe(III), but the subsoils contained both octahedrally coordinated Fe(III) and Fe(II). The fraction of Fe(II) in the subsoils generally increased after about 22 weeks of continuous amendment injection. Ferric ammonium citrate did not persist in the PHC-contaminated subsurface: the Fe(III) it contained was transformed to solid phases. Fe(III)-organic-matter (Fe(III)-OM) complex/coprecipitate and sulfate green rust were the major phases present in the GWCs; akaganeite, chloride green rust, vivianite, ferrihydrite, Fe(III)-silicate, and magnetite were present as minor phases. The subsoils contained three major phases: Fe(III)-OM complex/coprecipitate, magnetite, and calcium ferric silicate. The presence of major Fe(II) phases in the subsoils strongly indicate that secondary Fe(III) phases (especially Fe(III)-OM complex/coprecipitate) served as terminal electron acceptors during the microbial degradation of PHCs in the contaminated subsurface.

A series of the calcium-nickel carbonate solid solutions [(Ca_1−xNi_x)CO₃] were synthesized and their dissolution in N₂-degassed water (NDW) and CO₂-saturated water (CSW) at 25 °C was experimentally investigated. During dissolution of the synthetic solids (Ni-bearing calcite, amorphous Ca-bearing NiCO₃ and their mixtures), the Ni-calcite and the Ca-NiCO₃ dissolved first followed by the formation of the Ni-bearing aragonite-structure phases. After 240–300 days of dissolution in NDW, the water solutions achieved the stable Ca and Ni concentrations of 0.592–0.665 and 0.073–0.290 mmol/L for the solids with lower Ni/(Ca + Ni) mol ratios (X_Ni), or 0.608–0.721 and 0.273–0.430 mmol/L for the solids with higher X_Ni, respectively. After 240–300 days of dissolution in CSW, the water solutions achieved the stable Ca and Ni concentrations of 1.094–3.738 and 0.831–4.300 mmol/L, respectively. For dissolution in NDW and CSW, the mean values of log IAP (Ion activity products) in the final stable state (≈ log K_sp, Solubility product constants) were determined to be − 8.65 ± 0.04 and − 8.16 ± 0.11 for calcite [CaCO₃], respectively; − 8.50 ± 0.02 and − 7.69 ± 0.03 for the synthetical nickel carbonates [NiCO₃], respectively. In respect to the bulk composition of the (Ca_1−xNi_x)CO₃ solid solutions, the final log IAP showed the highest value when X_Ni = 0.10–0.30. Mostly, the mean values of log IAP increased with the increasing X_Ni in respect to the Ni-calcite, the Ni-aragonite and the amorphous Ca-Ni carbonate. The plotting of the experimental data on the Lippmann diagram for the (Ca_1−xNi_x)CO₃ solid solution using the predicted Guggenheim parameters of a₀ = 2.14 and a₁ = − 0.128 from a miscibility gap of X_Ni = 0.238 to 0.690 indicated that the solids dissolved incongruently and the final Ca and Ni concentrations in the water solutions were simultaneously limited by the minimum stoichiometric saturation curves for the Ni-calcite, Ni-aragonite and the amorphous Ca-Ni carbonate. During dissolution in NDW, the Ni²⁺ preferred to dissolve into the water solution and Ca²⁺ preferred to remain in the solid, while during dissolution in CSW for the solids with higher X_Ni, the Ca²⁺ preferred to dissolve into the water solution and Ni²⁺ preferred to remain in the solid. These findings provide valuable insights into understanding the mechanisms governing Ni geochemical cycle in natural environments.

Green rusts (GR) are mixed-valence iron (Fe) hydroxides which form in reducing redox environments like riparian and wetland soils and shallow groundwater. In these environments, silicon (Si) can influence Fe oxides’ chemical and physical properties but its role in GR formation and subsequent oxidative transformation have not been studied starting at initial nucleation. Green rust sulfate [GR(SO₄)] and green rust carbonate [GR(CO₃)] were both coprecipitated from salts by base titration in increasing % mol Si (0, 1, 10, and 50). The minerals were characterized before and after rapid (24 h) aqueous air-oxidation by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fe extended x-ray absorption fine structure spectroscopy (EXAFS), and N₂-BET surface area. Results showed that only GR(SO4) or GR(CO3) was formed at every tested Si concentration. Increasing % mol Si caused decreased plate size and increased surface area in GR(CO3) but not GR(SO4). GR plate basal thickness was not changed at any condition indicating a lack of Si interlayering. Air oxidation of GR(SO4) at all % mol Si contents transformed by dissolution and reprecipitation into lepidocrocite and goethite, favoring ferrihydrite with higher % Si content. Air oxidation of GR(CO3) transformed into magnetite and goethite but increasing Si caused GR to oxidize while retaining its hexagonal plate structure via solid-state oxidation. Our results indicate that Si has the potential to cause GR to form in smaller particles and upon air oxidation, Si can either stabilize the plate structure or alter transformation to ferrihydrite.

Graphical Abstract

The magmatic complex along the Marsa Alam-Idfu transect, Central-Eastern Desert of Egypt, represents the northern segment of the Arabian–Nubian Shield (ANS), which developed within the framework of the East African Orogen. The basement rocks of the Arabian-Nubian Shield have been developed through three distinct phases of magmatic activity: the island-arc, the syn-orogenic, and the post-orogenic phases. Transitioning of the magmatic phases from the syn-orogenic to the post-orogenic, identifies changing the tectonic regime from a compressional to an extensional setting. The scarcity of comprehensive regional geochronological data that rely on precise isochron methods, such as the zircon U-Pb technique, could limit the comprehensive understanding of this region’s geological and tectonic history. That would raise a number of uncertainties ranging from the timing of the different magmatic activities and timing of changes in the tectonic regime to the existence of the pre-Pan-African crust in the CED. Our study provides new insights into the aforementioned uncertainties through zircon U-Pb dating of different rock units along the Marsa Alam-Idfu transect, CED, Egypt. The resulting ages ranged from 729 ± 3 Ma to 570 ± 2 Ma, constraining the temporal evolution of the ANS in the studied region into (1) the island-arc phase, represented by a metamorphic sample with an age of 729 ± 3 Ma. (2) the syn-orogenic phase, represented by calc-alkaline and alkaline granitic samples with ages ranging from 699 ± 4 Ma to 646 ± 2 Ma. These two phases indicate initiation of the compressional subduction regime in the CED since 729 ± 3 Ma and being dominated till 646 ± 2 Ma. (3) the post-orogenic phase, represented by metavolcanics, volcanic rocks, and alkaline plutonic samples with ages ranging from 623 ± 3 Ma to 570 ± 2 Ma. This phase suggests dominance of the compressional-to-extensional tectonic transition setting from 623 ± 3 Ma to 600 ± 1 Ma along with the Dokhan volcanism and activation of post-collision tensional regime activated at 582 ± 3 Ma. Our findings discourage the proposed dominance of the island-arc and syn-orogenic phases in the CED and the classical restriction of older magmatic activity to calc-alkaline granitic rocks and younger magmatic activity to alkaline granitic rocks. Additionally, we identified evidence of local magmatic sources by dating five grains with Mesoproterozoic (pre-Arabian–Nubian Shield) xenocrysts with ages ranging from 1549 ± 4 to 1095 ± 25 Ma.

Interfacial processes involving metal (oxyhydr)oxide phases are important for the mobility and bioavailability of nutrients and contaminants in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning, and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy to study the molecular-scale interfacial processes that influence surface complexation in ferrihydrite-water systems containing aqueous ({text {MoO}_4}^{2-}). We validate the utility of this approach by calculating surface complexation models directly from simulations. The reactive force-field captures the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption and proton transfer. We find that upon hydration and adsorption, ferrihydrite restructures into a more disordered phase through surface charge equilibration, as revealed by simulations and high-resolution X-ray diffraction. We observed how this restructuring leads to a different interfacial hydrogen bond network compared to bulk water by monitoring water dynamics. Using umbrella sampling, we constructed the free energy landscape of aqueous ({text {MoO}_4}^{2-}) adsorption at various concentrations and the deprotonation of the ferrihydrite surface. The results demonstrate excellent agreement with the values reported by experimental surface complexation models. These findings are important as reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions.

Graphic Abstract

Clean river water is an essential and life-sustaining asset for all living organisms. The upper Ganga and Yamuna river system has shown signs of rejuvenation and tremendous improvement in the water quality following the nationwide lockdown due to the coronavirus pandemic. All the industrial and commercial activity was shut down, and there was negligible wastewater discharge from the industries. This article addresses the water quality assessment from the study area, which is based on the original data of physical parameters, major and trace elements, and stable isotopes (hydrogen and oxygen) systematics during the nationwide lockdown. The impact of the lockdown could be seen in terms of an increase in dissolved oxygen (DO). Water samples were collected from the Upper Ganga and Yamuna river basins (Alaknanda, Bhagirathi, and Tons rivers) during an eight-week lockdown in Uttarakhand, India. We discussed the signs of rejuvenation of riverine based on physical parameters, major ions, trace elements, isotopic ratios, and water pollution index (WPI). Results reveal that the water quality of the entire upper basins of the Ganga has significantly improved by 93%, reflecting the signs of self-rejuvenation of the rivers. Multivariate analysis suggests a negative factor loading for an anthropogenic element (({NO}_{3}^{-})), implying that they contribute little to the river water during the lockdown. Further, bicarbonate (({HCO}_{3}^{-})) is a dominant element in both river basins. The geochemical facies are mainly characterized by the (({{Ca}^{2+} :{Mg}^{2+} : HCO}_{3}^{-})) type of water, suggesting that silicate rock weathering dominates with little influence from carbonate weathering in the area. The positive factor loadings of some cations, like({HCO}_{3}^{-}),({Ca}^{2+}), and ({Mg}^{2+}) reflect their strong association with the source of origin in the lockdown phases. Stable isotopic reveals that the glaciated region contributed the most to the river basin, as evidenced by the low d-excess in riverine water compared to anthropogenic contributions. Rivers can self-rejuvenate if issues of human influence and anthropogenic activities are adequately resolved and underline our responsibility for purifying the ecosystem. We observed that this improvement in the river water quality will take a shorter time, and quality will deteriorate again when commercial and industrial activity resumes.

δ-MnO₂ is an important component of environmental minerals and is among the strongest sorbents and oxidants. The crystalline morphology of δ-MnO₂ is one of the key factors affecting its reactivity. In this work, δ-MnO₂ was initially synthesized and placed in an acidic environment to react with Mn²⁺ and undergo a crystalline transformation. During the transformation of crystalline δ-MnO₂, kinetic sampling was conducted, followed by analyses of the structures and morphologies of the samples. The results showed that at pH 2.5 and 4, δ-MnO₂ nanoflakes spontaneously self-assembled into nanoribbons via edge-to-edge assembly in the initial stage. Subsequently, these nanoribbons attached to each other to form primary nanorods through a face-to-face assembly along the c-axis. These primary nanorods then assembled along the (001) planes and lateral surfaces, achieving further growth and thickening. Since a lower pH is more favorable for the formation of vacancies in δ-MnO₂, δ-MnO₂ can rapidly adsorb Mn²⁺ directly onto the vacancies to form tunnel walls. At the same time, the rapid formation of the tunnel walls leads to a quick establishment of hydrogen bonding between adjacent nanoribbons, enabling the assembly of these nanoribbons into primary nanorods. Therefore, in a solution with the same concentration of Mn²⁺, the structure transformation and morphology evolution of δ-MnO₂ to α-MnO₂ occur faster at pH 2.5 than at pH 4. These findings provide insights into the mechanism for crystal growth from layer-based to tunnel-based nanorods and methods for efficient and controlled syntheses of nanomaterials.

Quarrying of rock aggregates generates produced water that, if not handled properly will be a source of pollution for nearby water bodies, thus affecting the chemistry of the water. This study examined the chemistry, impact of quarrying activities on water resources and the health consequences/risks posed by ingestion of the water by humans in the Akamkpa quarry region in southeastern Nigeria. Thirty (30) water samples consisting of pond water, stream water, hand dug wells, and borehole samples were collected and analyzed for their physicochemical parameters using standard methods. The results obtained from the analyses indicated that the water was moderately acidic, fresh, and not salty, with many parameters below the recommended standards with Ca²⁺, and HCO₃⁻ being the dominant ions present in the water resources. Rock weathering processes including silicate weathering as illustrated by hydrochemical facies, cross plots, and Gibbs diagrams are the dominant mechanisms influencing the quality and major ions chemistry of the water resources with minor contributions from dissolution, anthropogenic activities, and ion exchange. Ca-Mg-SO₄-Cl and Na–K-HCO₃⁻ are the most important water types. Although the water quality index shows that the water is suitable for human use and irrigation, the mean values of As, Cd, Pb, and Se are above the acceptable limits. Additionally, the calculated contamination factor revealed the water resources are moderate to highly contaminated by As, Cd, Cr, Mo, Pb, Sb, and Se, and are therefore unsuitable for consumption with regards to these parameters. However, the residual sodium carbonate and water hazard index (WHI) values showed that 38% to 90% of sites in the quarry area were unsuitable for cultivation, 10–30% were in the low to medium impact category, and 60% were classified as risky and are from high to very high impact category. A non-cancer study of inhabitants living in the vicinity of the quarry area indicated that 6.7% of the sites have values greater than one, indicating that it may endanger the health of the people. Therefore, constant monitoring of the water quality is recommended as long-term use of contaminated water can harm humans, plants, and soils.