Browsing by Author "Ghosh A.K."
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Item Carbon Sequestration in Revegetated Coal Mine Soil: A Chronosequence Study in the Gevra Opencast Project, Chhattisgarh, India(wiley, 2024) Singh P.; Ghosh A.K.; Masto E.; Kumar S.; Pradhan C.Coal, contributing to over 70% of India�s energy production, is intrinsically linked to significant land degradation, notably from mining operations. One of the adverse effects of coal mining is the greenhouse gas emissions from coal combustion, fallen biomass, and mineralization of exposed soil organic matter (SOM). This degradation often results in a significant reduction of SOM content in disturbed soils, which can potentially be countered by targeted soil restoration and strategic revegetation. This study, based in Gevra Coal Mines, Chhattisgarh, probes into the intricacies of soil carbon (SOC) sequestration, focusing on the roles played by plant litter quality and decomposition rates. Through the analysis of different carbon parameters from soil samples collected under the three native plant species - Azadirachta indica, Dalbergia sissoo, and Gmelina arborea, the research underscores that litter quality, more than quantity, is pivotal to effective carbon sequestration. As vegetation gets restored, a resistant SOC pool accumulates, which further contributes to long-term SOC sequestration. With time, SOC molecules undergo humification, becoming more aromatic and stable. The molecular properties of these molecules play a critical role in defining soil quality in reclaimed areas. Spectroscopic methodologies, such as FT-IR and UV-vis, emerged as valuable tools to discern SOC molecular attributes and their dynamics. Of the tree species studied, D. sissoo demonstrated superiority in both quality and quantity of sequestered carbon. In conclusion, the research reaffirms the indispensable need for robust afforestation measures in coal mining areas. As vegetation gets restored, not only is carbon effectively sequestered, but soil health is gradually revived, emphasizing the role of strategic revegetation in post-mining landscapes. � 2025 John Wiley & Sons Ltd.Item Electrical and magnetic properties of double perovskite Y2-xCaxCoMnO6 (x = 0.1, 0.2, 0.5)(Springer, 2024) Kumar D.; Alam M.; Singh P.; Dixit S.; Ghosh A.K.; Chatterjee S.The crystal structure, electronic, magnetic, and transport properties of the hole substituted (Ca2+) and partially B-site disordered double perovskite Y2-xCaxCoMnO6 system are studied. At room temperature, the samples demonstrated a monoclinic perovskite structure with a space group P21/n which was confirmed by Rietveld refinement of X-ray diffraction data. Ultra-violet visible analysis of these samples shows a direct band gap including gap energy near about 1.50�eV. X-ray photoemission spectroscopy measurement shows that component Co and Mn ions exist in a mixed state (Co3+, Co2+, Mn3+, and Mn4+). All samples exhibit semiconducting/insulating, and electrical conduction can be explained by Mott�s 3-D variable range hopping and small polaron hopping fitting. The magnetization numerical value decreases observed with increases in Ca concentration appears to be caused by increases in antiferromagnetic (AFM) phases. The double perovskite Y1.9Ca0.1CoMnO6 and Y1.8Ca0.2CoMnO6 show ferromagnetic transition at transition temperatures Tc~ 70�K and Tc~ 68�K, respectively. The analysis of the samples� zero fields cooled DC magnetic susceptibility as a function of temperature reveals Griffiths-like singularity features that arise as the concentration of Ca increases in the parent system. The Griffith-like phase exists in the sample Y-site with Ca-substitution is independent of the structural disorder caused by the John�Teller active Mn3+ions in sample Y1.5Ca0.5CoMnO6. Field-dependent magnetization shows meta-magnetic behavior at low-temperature regions in Y1.9Ca0.1CoMnO6 and Y1.8Ca0.2CoMnO6. As the concentration of Ca increased from Y1.8Ca0.2CoMnO6 to Y1.5Ca0.5CoMnO6 meta-magnetic behavior disappeared. � The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Item Heavy Metals in the Sediments of the Chilika Lake, India: Contamination, Source and Toxicity Analysis(Springer Nature, 2024) Panda D.; Ghosh A.K.; Ballesta R.J.; Espinosa M.T.R.; Pradhan S.N.; Patra A.Lakes are multifunctional waterbodies in terrestrial hydrosphere ecosystems and sediment plays a key role in the liquid�solid junction. The rapid economic development in the post-industrial era had manifold heavy metal concentration compared to background values. The non-lithogenic forms of heavy metals possess toxicity to living beings through bioaccumulation and bio-magnification processes. Chilika Lake (India) is a diversified hotspot region and habitat for many endangered species. Over the years, the lake was affected by anthropogenic activities. So, the present study was undertaken to study the dynamic relationship between heavy metals (Cr, Ni, Cd, and Pb) and sediment matrix and their mobilization behavior to the water phase influenced by sediment properties (pH and TOC). A sequential extraction procedure (SEP) was used to evaluate each chemical form's metal content. The ecological risk of metals was assessed by contamination factor (CF), geo-accumulation index (Igeo), Nemerow index (Iin), pollution load index (PLI), potential ecological risk index (PER), ratio of primary phase to secondary phase (RSP), and mobility factor (MF). Source identification (PCA) was done to chalk out the remedial plan. The spatial distribution revealed greater heterogeneity in metal concentration in the lake. Sediment properties control the mobility of metals thus protecting their quality. The mean concentration (mg kg?1) of metals follows the order of Cr (54.35) > Ni (34.95) > Pb (19.53) > Cd (0.93). The dominance of metal content in the labile fraction was found in Cd (97%) and Pb (70%), which indicates a toxic effect on biota. The average value of MF follows the order of Cd (48%) > Pb (13%) > Cr (11%) > Ni (9%) indicating a dynamic equilibrium between sediment and aqueous phase. Source analysis indicates that Cr and Ni came mostly from natural sources, while Cd and Pb originate from man-made activities. The study revealed that the majority of threat is coming from Cd and Pb. Thus, regular monitoring of sediments, treatment of influx water, use of high-quality fuel in the motorboats and the development of a drainage system are essential to eliminate heavy metal toxicity. � The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Observation of the multiple magnetic phases in double perovskite Pr1.8La0.2CoFeO6(Elsevier B.V., 2024) Kumar D.; Singh P.; Alam M.; Kumar S.V.; Dixit S.; Bandyopadhyay K.; Dwivedi G.D.; Saha S.; Ghosh A.K.; Chatterjee S.The structural and magnetic properties of the double perovskite Pr1.8La0.2CoFeO6 have been investigated. The X-ray diffraction study shows that the system acquires room-temperature orthorhombic phase with the Pnma space group. The X-ray photoemission spectroscopy (XPS) measurement confirmed that the B-site ions are present in mixed valence states i.e. Co has been found in Co2+ and Co3+ valance states whereas Fe has been found in Fe3+/Fe4+. Magnetic measurements of the system confirm the existence of several fascinating magnetic behaviors, such as long-range canted antiferromagnetism withTN ? 271 K, giant exchange bias, and re-entrant cluster glass phase (TG ? 33 K). Field-dependent magnetization shows a large spontaneous exchange bias; HSEB? 1.8 kOe and giant conventional exchange bias, HCEB? 2.4 kOe at 5 K. Antiferromagnetic materials with large exchange bias can be utilized in high-density spintronic devices. Temperature-dependent Raman study demonstrates that the observed phonon mode exhibits anomalous behavior close to the magnetic transition temperature. Analysis of anomalous softening of phonon mode below TN, clarifies the presence of significant spin-phonon coupling while the magnetostriction effect does not play any significant role in the observed phonon anomaly. � 2024Item Revegetating Mine Soils with Different Tree Species Influences Molecular Characteristics of Soil Organic Matter(Taylor and Francis Ltd., 2024) Singh P.; Ghosh A.K.; Kumar S.; Kumar M.; Yadav S.; Nagargade M.; SeemaAlthough molecular characterization of soil organic carbon is crucial for understanding its dynamics, studies on reclaimed coal mine soil are comparatively limited. Therefore, the primary objective of this study was to ascertain the influence of tree species on the soil organic carbon content and molecular characteristics of soil organic carbon in a chronosequence of reclaimed coal mine soil. To investigate the effects of reclamation time on soil organic carbon characteristics, a chronosequence of three coal mine soil was used, each exhibiting different ages of reclamation: 8, 14, and 25 years. Along a re-vegetation age gradient of 8 to 25 years, the total soil organic carbon content increased. Within the 25 years of restored soil, the FTIR absorption intensities were lowest within the range of 2,920 and 2,850 cm?1, while they were highest within the range of 1,685, 1,425, and 1,285 cm?1which indicates presence of aromatic C=C. This shows that aromatic compounds contributed more significantly to the composition of soil organic carbon compared to aliphatic structures. Based on molecular characteristics, it is suggested that the soil organic carbon in 25-year old revegetated coal mine soil consists of aromatic and recalcitrant carbon. Among three tree species Dalbergia sissoo can be used for reclamation as quality and quantity of carbon found was higher under this tree species. In conclusion, the results indicated that the molecular properties of soil organic carbon were extremely important for understanding the dynamics of soil organic carbon in a restored coal mine soil chronosequence. � 2024 Taylor & Francis Group, LLC.Item Structural, dielectric, and electrical transport properties of La2FeMnO6 double perovskite for multifunctional applications(Elsevier Ltd, 2024) Meena B.R.; Alam M.; Chatterjee S.; Ghosh A.K.The polycrystalline La2FeMnO6 has been prepared by the solid-state reaction method. The Rietveld refinement of X-ray diffraction (XRD) data confirms a single-phase double perovskite cubic structure. The vibrational modes have been investigated by the Raman and Fourier transform infrared (FTIR) spectroscopy. The X-ray photoemission spectroscopy (XPS) measurement reveals the presence of mixed valence states of Mn and Fe cations. The dielectric, impedance, modulus, and AC conductivity measurements of La2FeMnO6 have been done over temperature range (125�300 K) and frequencies (1 kHz - 1 MHz). This material exhibits a high ?? (?1826) with a low dissipation factor near room temperature. The NTCR (negative temperature coefficient of resistance) characteristics of both resistivity and impedance showed the semiconducting nature of the sample. Grains and grain- boundaries play important role in the process of electrical conduction. The Cole-Cole plots follow the RC equivalent circuit and verify non-Debye-type relaxation. The value of the exponent �s� suggests the non-overlapping small polaron tunneling (NSPT) process in La2FeMnO6. The NTCR characteristic of this material, with good stability factor, thermistor constant, and sensitivity factor may be useful for NTC-type thermistor. � 2024Item Wafer scale growth of single crystal two-dimensional van der Waals materials(Royal Society of Chemistry, 2024) Gautam C.; Thakurta B.; Pal M.; Ghosh A.K.; Giri A.Two-dimensional (2D) van der Waals (vdW) materials, including graphene, hexagonal boron nitride (hBN), and metal dichalcogenides (MCs), form the basis of modern electronics and optoelectronics due to their unique electronic structure, chemical activity, and mechanical strength. Despite many proof-of-concept demonstrations so far, to fully realize their large-scale practical applications, especially in devices, wafer-scale single crystal atomically thin highly uniform films are indispensable. In this minireview, we present an overview on the strategies and highlight recent significant advances toward the synthesis of wafer-scale single crystal graphene, hBN, and MC 2D thin films. Currently, there are five distinct routes to synthesize wafer-scale single crystal 2D vdW thin films: (i) nucleation-controlled growth by suppressing the nucleation density, (ii) unidirectional alignment of multiple epitaxial nuclei and their seamless coalescence, (iii) self-collimation of randomly oriented grains on a molten metal, (iv) surface diffusion and epitaxial self-planarization and (v) seed-mediated 2D vertical epitaxy. Finally, the challenges that need to be addressed in future studies have also been described. � 2024 The Royal Society of Chemistry.
