Coastal Agriculture and Its Challenges: A Case Study in Gosaba Island, Sundarban, India

Agriculture is the main economic activity in Sundarban to sustain the basic livelihood of rural people. In recent decades, the nature of agriculture mainly cropping patterns, crop productivity, and agricultural land use is gradually changing because of various natural as well as anthropogenic factors. The frequent occurrence of climatic extremes over the Bay of Bengal has been directly or indirectly affected the agricultural system of the delta. In the wake of the 2009 cyclone Aila, the crop production in Gosaba rapidly declined due to high salinity and low pH in the soil. Most of the agricultural land remains a seasonal fallow due to the shortage of freshwater during the dry season. The direction of the surface slope has been altered by the unsystematic construction of embankment and haphazard construction of closure in river channels. The saucer-shaped appearance of the island causes massive drainage congestion induced waterlogging problem in the agricultural field. Waterlogging causes crop damage and low productivity. Farmers continue to face substantial monetary loss and entrapping in poverty. To overcome these issues, climate-resilient cropping strategy, proper maintenance of the drainage system, and adaptation of modern land reshaping techniques for diversified agriculture systems are urgently needed for the profound agro-based economic future of the delta

Geo-historical Appraisal of Embankment Breaching and Its Management on Active Tidal Land of Sundarban: A Case Study in Gosaba Island, South 24 Parganas, West Bengal

The embankments act as a life line for deltaic people of the Sundarbans. The reclamation of immature land through the construction of embankment without proper planning has been increasing the vulnerability of embankment breaching due to various natural and anthropogenic causes. The construction and maintenance of embankments are difficult tasks without prior knowledge about the mode of vulnerability and ground situations of the sites. To understand the scenario of embankment breaching and its recent management strategy, an intensive field survey was conducted to comprehend the underlying reasons for embankment breaching and its management techniques at the ground level. The modern techniques were also incorporated to identify the vulnerable sites of river bank erosion. The study reveals that the southern part of the delta is more vulnerable due to intensive river bank erosion. To understand potential capabilities of these embankments to combat against fluvio-hydrological challenges, a sequential change of embankment construction from historical past to present and recent scientific engineering model of Aila Dam has been chalked out in this study. The present study is an attempt to understand the geo-historical perspectives of embankment construction and to identify the vulnerable coastal zone of Gosaba Island of Sundarban. The study also aims to illustrate the modern techniques of embankment management for its longevity in such a dynamic land.            &nbsp

Syntheses, crystal structures, and magnetic properties of metal-organic hybrid materials of Mn(II)/Co(II): three-fold interpenetrated alpha-polonium-like network in one of them

Three new 1,4-phenylenediacrylate bridged Mn(II) and Co(II) complexes with the molecular formulae {[Mn2(phen)4(H2O)2(ppda)]∙(ppda)∙2(H2O)}(1), {[Co(ppda)(dpyo)(H2O)3]∙4(H2O)}n (2), and {[Co(ppda)(bpe)]∙(0.5H2O)}n (3) [phen = 1,10-phenanthroline; ppda = 1,4-phenylenediacrylate; dpyo = 4,4´-dipyridyl N,N´-dioxide; bpe = 1,2-bis(4-pyridyl)ethane] have been synthesized and characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structural determination reveals that complex 1 is dinuclear, 2 is a 1D polymeric chain, while 3 is a three-fold interpenetrated α-polonium-like network. Hydrogen bonding interactions, formed by coordinated and/or lattice water molecules with ppda oxygen, and staking interactions of aromatic rings lead to a 3D supramolecular architecture in both complexes 1 and 2. Low temperature magnetic study shows antiferromagnetic coupling in all the complexes. In addition, their electronic and fluorescent spectral properties have also been investigated

1D, 2D, and 2D Parallel Interpenetrated Dicarboxylato Bridged Co(II) Metal Organic Frameworks: Synthesis, Crystal Structure, Fluorescence Sensing and Band Gap Calculation

Metal organic frameworks of Co(II), {[Co(bphz)1.5(tp)(H2O)2] c53.2H2O}n (1), {[Co(bphz)(ip)] c5(bphz)0.5}n (2), and [Co(bpp)(ppda)(H2O)2]n (3) [where bphz=N,N\u2032-bis-pyridin-4-ylmethylene-hydrazine; tp=1,4-benzenedicarboxylate; ip=1,3-benzenedicarboxylate; bpp=1,3-bis(4-pyridyl)propane; ppda=1,4-phenylenediacrylate] have been synthesized and characterized by single crystal X-ray diffraction and spectroscopic studies. Complex 1 is a ladder like 1D polymeric chain, 2 is a 2D porous sheet, while 3 is a 2D parallel interpenetrated network. The band gap of complexes has been calculated using solid state reflectance spectra, and results show that complexes act as semiconductor. In dispersed methanolic solution complexes 1\u20133 exhibit intense fluorescence at room temperature. The complexes were tested with several aromatic compounds such as benzene, nitrobenzene, o-nitrotoluene and p-nitrotoluene, etc., in dispersed methanol medium. Results show that complex 3 selectively senses nitro aromatic compounds and this behavior has been explained on the basis of PET and RET mechanisms

Spatio-temporal Change of Drainage Network at Human-Nature Interface and Its Future Implication to the Estuarine Environment in Gosaba Island, Sundarban, India

Gosaba C.D. Block is an active tidal island of the Indian Sundarban. In this island, human-induced modification of the natural drainage system poses serious threats to the estuarine environment. It was started during the British colonial period through the construction of embankment to protect the reclaimed coastal land from saline water ingression. The rapid growth of population over the last few decades has triggered the changes in the drainage network and also altered the land use land cover of the study area. The human encroachment on the drainage area has hampered the sedimentation process as well as water circulation in the delta. As a result, the island is gradually transforming into saucer-shaped form, which aggravates various coastal threats like flood inundation, waterlogging and embankment breaching during extreme environmental events. To study the spatio-temporal change of the drainage network pattern from 1955 to 2018, different multi-temporal satellite images, US Army Toposheet, Census of India Report (2001 and 2011) and Human Development Report (2014) have been used as a source of secondary data for the analysis in ArcGIS environment. In addition to this, instrumental surveying has been done to measure the slope direction in relation to land use land cover and a questionnaire survey was conducted to understand the livelihood status of people influenced by various coastal threats and risks due to the drainage congestion. The study reveals that population density has gradually increased in recent decades and is negatively correlated with the drainage density on the island. The choking of the surface drainage canals has increased the problem of waterlogging in agricultural fields, which affected their productivity. Therefore, a strategy for management of the drainage network needs to be urgently implemented in order to protect the life and livelihood of rural people from various coastal threats

The supramolecular assembly of tetraaqua-(pyridine-2,5-dicarboxylato)- copper(II) complex: Crystal structure, TD-DFT approach, electronic spectra, and photoluminescence study

The copper(II) complex, {[Cu(2,5-pdc)(H2O)4]\ub7H2O} (1) [2,5-pdc = pyridine-2,5-dicarboxylate], has been synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The metal shows a distorted octahedral coordination sphere and in solid state the complex forms a 3-D supramolecular network via hydrogen bonding and off-center anti-parallel \u3c0\u2013\u3c0 stacking interactions between py rings. At room temperature, 1 exhibits fluorescence in methanolic solution [\u3bbex = 226 nm, \u3bbem = 309, 330, and 341 nm]. The geometry optimization at the B3LYP/LanL2DZ level led to a five-coordinate copper having a distorted square pyramidal geometry. The electronic spectrum of this compound is compared with the results obtained by employing density functional theory (DFT) and time dependent density functional theory calculations

Tetracarboxylato-bridged copper(II) complexes with ancillary N-chelating ligands: Syntheses, crystal structures and effect of aromatic compounds on the fluorescence property

Two Cu(II) complexes [Cu2(1,10-phen)2(H2O)4(cbtc)].6H2O (1) and {[Cu2(2,20-bipy)2(cbtc)].6H2O}n (2) [1,10-phen = 1,10-phenanthroline; 2,20-bipy = 2,20-bipyridine; cbtc = 1,2,3,4-cyclobutane tetracarboxylate tetraanion], were synthesized and characterized by elemental analysis, IR, single crystal X-ray crystallography and thermal analysis. The structural determination reveals that complex 1 is dinuclear, while 2 is a 1Dpolymeric chain built by a bridging cbtc ligand. Hydrogen bonding interactions, formed by coordinated and/or lattice water molecules with cbtc oxygens, lead to a supramolecular architecture in both structures. Complex 1, which exhibits intense fluorescence (kex = 262 nm, kem = 358 and 373 nm) at room temperature, was tested with several aromatic compounds, such as m-toluidine, aniline, nitrobenzene, etc. in MeOH\u2013 CHCl3 (1:1) solution. The results show that a pronounced fluorescence quenching and enhancement is observed in the presence of nitrobenzene andm-toluidine, respectively. Thermogravimetric analysis shows that complex 2 undergoes a reversible deaquation\u2013rehydration process

Bis-chelated-(3-methoxy-2-oxo-benzaldehyde)–copper(II) complex: Synthesis, crystal structure, fluorescence property, DFT calculation, and catecholase activity

Reaction of Cu(NO3)2·3H2O and 2-hydroxy-3-methoxybenzaldehyde (HL) in methanolic medium results [CuL2]·4H2O (1) [L- = 3-methoxy-2-oxo-benzaldehyde]. The complex was characterized by elemental analysis, IR, single crystal X-ray structure determination and DFT calculation. The X-ray single crystal structure determination reveals that 1 is a discrete mononuclear four coordinated complex with the metal in square planar coordination geometry and four lattice water molecules. The complex form dimer around the center of symmetry with short Cu

Cu(II) complexes of pyridine-2,6-dicarboxylate and N-donor neutral ligands: Synthesis, crystal structure, thermal behavior, DFT calculation and effect of aromatic compounds on their fluorescence

Two copper(II) complexes [Cu(pdc)(im)] (1) and {[Cu(pdc)(2-ap)(H2O)].2H2O} (2) [pdc, pyridine- 2,6-dicarboxylate; im, imidazole and 2-ap, 2-aminopyridine] have been synthesized and characterized by elemental analysis, IR spectroscopy, X-ray crystallography, and thermal analysis. Complexes 1 and 2 show a square planar and square pyramidal Cu(II) coordination sphere, respectively, and in solid state form hydrogen bonded 3D supramolecular networks. Both the complexes exhibit fluorescence in water\u2013 methanol solution at room temperature [kex = 261 nm, kem = 317 and 361 nm, quantum yield = 0.0149 for 1; kex = 278 nm, kem = 351 nm, quantum yield = 0.0031 for 2]. The effect of the presence of different aromatic compounds such as m-toluidine, aniline, nitrobenzene, p-cresol, phenol, etc., on the fluorescence of these copper complexes in solution has been inspected. Results indicate that complex 2 behaves as a fluorescence sensor for p-cresol, but loses its fluorescent properties in association with phenol. The optimized geometry from density functional theory (DFT) study shows a good agreement with the X-ray structural data. The electronic and IR spectra of these compounds are compared with results obtained by employing DFT and time-dependent density functional theory (TD-DFT) calculations