Shoreline Change Near Gopalpur Port, East Coast of India

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Ecological health assessment of a coastal ecosystem: Case study of the largest brackish water lagoon of Asia

This study focuses on the ecological health assessment of Chilika, a shallow lagoon present in east coast of India, through nutrient stoichiometry and trophic state index (TSI). Multivariate statistical analysis such as ANOVA, Pearson's correlation, Principal Component Analysis (PCA), and Discriminant Analysis (DA) were employed for data interpretation. Nutrient stoichiometry revealed that the Chilika Lagoon experiences phosphorus limitation with regard to nitrogen and silicate (N:P:Si = 16:1:16) throughout the study period. As per the computed TSI values, the southern sector (SS), central sector (CS), and outer channel (OC) were assigned with a mesotrophic status, whereas the northern sector (NS) was assigned with the eutrophic status. From PCA, total nitrogen was found to be negatively correlated with salinity and positively correlated with silicate, thus indicating that the major source of nitrogen in the lagoon was freshwater ingress by rivers with high silicate content. DA indicated that it was successful in discriminating the groups as predicted

Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9g€¯mm to global mean sea level, with the rate of mass loss rising from 105g€¯Gtg€¯yr-1 between 1992 and 1996 to 372g€¯Gtg€¯yr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9g€¯Gtg€¯yr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86g€¯Gtg€¯yr-1 in 2017 to 444g€¯Gtg€¯yr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9g€¯Gtg€¯yr-1) and, to a lesser extent, from the Antarctic Peninsula (13±5g€¯Gtg€¯yr-1). East Antarctica remains close to a state of balance, with a small gain of 3±15g€¯Gtg€¯yr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)

Kinetics and mechanism of the reaction of sulphur(IV) with <i>trans-bis</i>(aqua)(N,N' -salicy lidiniminato-<i>ortho-</i>phenylenediamine cobaltate (III) : The <i>trans</i> effect of <i>S</i>-bonded sulphite

53-60The reaction of trans-(aqua)(hydroxo)(N,N'-salicylidiniminato-ortho-phenylenediamine) cobaltate(III) with SO2 results in the formation of S-bonded monosulphito complex, trans-[Co(salophen) (OH2)(SO3)]- as the primary product; the CoIII-S bond formation is concerted with CoIII-O bond breaking. At 25°C, I = 0,5 mol dm-3 (NaNO3), the rate and activation parameters for this process are: kSO2 = (4.8) × 108 dm3 mol-1 s-1, ΔH± = 23.6±3.2 kJ mol-1 , ΔS± = - 0.14±16.7 J K-1 mol-1. The aqua-sulphito complex further undergoes substitution of the aqua ligand by imidazole and SO32-; the formation of the imidazole complex, trans-[Co(salophen)(imH)(SO3)ris, however, reversible. The rate data indicate that the trans effect of the S-bonded sulphite in trans-[Co(salophen)(OH2)(SO3)]- is only marginally stronger for the aqua ligand substitution by imidazole and SO32- than in the case of its salen analogue reported earlier. The kinetic inertness of trans[Co(salophen)(OH2)(SO3)]- towards H+ catalysed aquation in comparison to its salen analogue (kHsalen/kHsalophen= 104 at 25°C) demonstrates the effects of rigidity and extended electron delocalization by the salophen moiety. The rate constants of base hydrolysis of trans[Co(salophen)(OH)(SO3)]2- at [OH-]T = 0.01-0.5 , I= 0.5 mol dm-3 (25°C) obeys kobs = ko + kOH [OH-] with k0 = (0.89±0.04 ) × 10-3 s-1 and kOH =(6.4±0.6) × 10-3 dm3 mol-1 s-1. A finite value of ko indicates that the trans-labilising action of the coordinated OH group is stronger than that of the bound SO32- .It is suggested that the second order rate constant kOH, is associated with a mechanism which involves the formation of a reactive C-conjugate base from the aldimine function , H-C=N-R

Redox and substitution reactions of <i>trans</i>-(diaqua)(N, N'-ethylenebis(salicylideneaminato)cobalt(lll) with hexacyanoferrate(ll, lll): A proton coupled electron transfer reaction

1062-1067The electron transfer between trans-[Co(Salen)(OH2)2]+ (Salen N, N'-ethylenebis(salicylideneaminato) and (Fe(CN)6]4- involved a binuclear species, [(OH2)Colll(Salen)- (NCFeIlCN5)]3-, as an intermediate. The kinetics of the formation of this binuclear species and the one formed by the reaction of the title complex with [FeCN6]3- have been studied at 20-35°C (I = 0.5 mol dm- 3); the data are consistent with the Id mechanism. Both spontaneous and H + coupled paths are identified for the electron transfer within the binuclear species of hexacyanoferrate(II) which further undergoes electron transfer with [FeCN6]4- via a second order path

Electron transfer between aquapentaamminecobalt(lll) and sulphur(IV) in aquo-organic solvent media: Delineation of solvent effects

260-267The kinetics of intramolecular electron transfer between COIIl and SIV in O-sulphitopentaamminecobalt(III), (NH3)5 CoOSO+2, have been investigated in aquo-organic solvent media comprising dipolar protic cosolvents (methanol, n-propanol, isopropanol, tert-butanol, and ethyleneglycol) and dipolar aprotic cosolvents (acetonitrile, ethylene carbonate) at 25-40°C. Rate acceleration is generally observed with increasing mole fraction (Xorg) of the cosolvent except for ethyleneglycol + water. Correlation of rate (In ksred) with Xorg GE (Gibbs excess free energy), ENT and dielectric constants of the solvent mixtures using multiparameter regression indicates that preferential solvation and solvent structural effects are important in controlling the reactivity. The correlation of rate with solvent hydrogen bonding acidity (α), basicity (β) and polarizability (π*)for acetonitrile+water {ln ksred=(2.5±0.4)-(2.0±0.6)α +(0.2±0.4)β-4.0±0.4)π*} indicates that the electron transfer rate conformed well with the Taft model of solvation. The activation enthalpy and entropy versus Xorg plots display extrema at low Xorg,∆.H+ versus ∆S+ plot is linear indicating that the solvent structure effects on these parameters are mutually compensatory

Electron transfer between aquapentaamminecobalt(III) and sulphur(IV) in aquo-organic solvent media: delineation of solvent effects

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Kinetics and mechanism of the reaction of <em>trans-(diaqua)(N,N' - </em>ethylene bis-(salicylidineiminato)cobalt(III) with ascorbic acid

947-960The kinetics of the reactions of trans-[Co(Salen)(OH2)2]+ (Salen = N.N¢-ethylene bis (salicylidineiminate) ·jth ascorbic acid (H2Asc) have been studied under varying conditions of pH, [ascorbic acid]T, and temperature at .5 mol dm-3 ionic strength. The initial fast reactions observed in the stopped flow time scale are due to the complex formation between the reactants. This occurs in two phases i.e., the formation of the trans- [(2 ua)(ascorbato)CoIII(Salen)] and its transformation to the corresponding ascorbate chelate. The rate constants are the activation parameters for the formation of the monobonded and chelate ascorbate complexes are reported. T low values of ΔH+ and negative values of ΔS+ for the complexation reaction favour associative interchange mechanism(la). The hydroxide in trans-[Co(Salen)(OH)(OH2)] marginally accelerates substitution of the aqua and by HAsc- and the trans-[Co(Salen)(OH)(AscH)]- is considered to undergo fast internal proton transfer to .nerate trans-[Co(Salen)(OH2)(Asc)]- which undergoes chelation of the Colll centre by the bound ascorbate noiety; the latter reaction is, however, 15 times slower than the corresponding reaction of trans- [Co(Salen)(OH2)(AscH)]. The faster complexation reactions are followed by the slow redox reactions. The rate constant for the internal reduction of Colll by the coordinated ascorbate in the chelate [Co(Salen)(AscH)] is 5 - 10 times (25°C – 45°C) faster than the same for [Co(Salen)(Asc)]-. This trend in reactivity is due to the low value of ΔH for the former although the high negative value of ΔS compensates at least partly the overriding effect of the activation enthalpy. The internal redox occurs via innersphere mechanism. We also have observed a redox path involving trans-[Co(Salen)(OH2)(AscH2)]+ and H2Asc for which electron transfer most likely involves outersphere mechanism

Geochemical distribution of forms of phosphorus in marine sediment of Bay of Bengal, southeast coast of India

1132-1141Sediment samples were collected from three transects in the continental shelf region (up to 30km offshore) between Chennai to Marakkanam. Sedimentary parameters such as sand, silt, clay and organic carbon percentage were analyzed in order to find out their relation with various phosphorus fractions.  Sediment was found to be predominantly sandy in nature with low silt and clay content. Among all the fractions (loosely bound- Lo-P, calcium bound- Ca-P, iron bound- Fe-P, aluminum bound- Al-P and organically bound- OP), Ca-P fraction constituted the largest portion (71.38%) followed by OP (16.16%). Bioavailable fractions of phosphorus ranged from 9.3 to 36.2% (avg. 20.9%) of the total phosphorus (TP) during the present study. Total phosphorus content in the offshore sediments ranged between 469.35 and 1219.34 mg/kg with an average of 824.66 mg/kg. The abundance of the major forms of P in the surface sediments of Kalpakkam coast followed the order: Ca-P > OP > Al-P > Lo-P > Fe-P. Cluster analysis clearly showed that all the three transects were different from each other as they formed three different clusters

New record of an epizoic diatom, Pseudohimantidium pacificum on two species of copepods from the Indian Ocean

1331-1334Pseudohimantidium pacificum Hustedt and Krasske, 1941, an epizoic diatom was found on the copepod genera Corycaeus Dana and Euterpina acutifrons Dana from the coastal waters of Southwestern Bay of Bengal. The present report forms the first record of the epibiont Pseudohimantidium pacificum from the Indian coast and the Indian Ocean