Outwelling of total alkalinity and dissolved inorganic carbon from the Hooghly River to the adjacent coastal Bay of Bengal

The seasonal variability of the lateral flux of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) of the tropical Hooghly estuary is analyzed in this work. In situ observations of water temperature, salinity, dissolved oxygen, TAlk, and pH were measured in four different stations of the Hooghly estuary. It was measured once every month during 2015-2016, and subsequently, DIC was estimated. A carbon budget was constructed to quantify carbon flows through the freshwater-marine continuum of the Hooghly estuary, and plausible impacts on the adjacent coastal ocean, the northern Bay of Bengal, were examined. The biogeochemical mass balance box model was used to compute the seasonal flow of carbon flux, and subsequently, the annual budgeting of lateral fluxes of TAlk and DIC to the adjacent coastal ocean was carried out. The net annual TAlk and DIC flux from the Hooghly estuary to the adjacent coastal ocean were 4.45 ± 1.90 × 10¹¹ mol and 4.59 ± 1.70 × 10¹¹ mol, respectively. The net annual DIC flux of the Hooghly estuary is about 30 to 60 times higher than surface area integrated air-water CO₂ flux, which is an indication of promoting acidification in the adjacent coastal ocean. The present study indicates that the lateral DIC flux has increased substantially in the Hooghly estuary during the last two decades. The increase in inorganic carbon load in the Hooghly estuary due to the enhanced discharge of inorganic and organic matter load in the upper reaches of the estuary led to this increase in lateral DIC flux. The results strongly establish the need of having such regional studies for better understanding the estuarine carbon dynamics, and its role in controlling the adjacent coastal ocean dynamics.

CO2 fluxes from aquaculture ponds of a tropical wetland: Potential of multiple lime treatment in reduction of CO2 emission

Partial pressure of CO₂ in water [pCO₂(water)] and air-water CO₂ flux were estimated in two aquaculture ponds (one received no lime treatment (NTP) and in the other lime treatment was performed (LTP) four times a year) every month throughout an annual cycle, situated in East Kolkata Wetlands, a Ramsar Site in eastern India. It was hypothesized that lime treatment can potentially lower the pCO₂(water) in aquaculture ponds and hence make these aquatic bodies sinks for CO₂. The results portrayed that NTP acted as a source of CO₂ throughout the year (annual mean: 1929 ± 1397 μmol m^-2 h^-1), whereas, LTP acted as CO₂ sinks post lime addition (monthly mean ranged from -366 ± 16 to -449 ± 32 μmol m^-2 h^-1), though the effect of lime addition was found to diminish by the next month and it acted as source for CO₂ in the months when no lime treatment was done (LTP annual mean: 1010 ± 1617 μmol m^-2 h^-1). Lime treatment increased the pH level and reduced the turbidity which facilitated optimum photosynthesis and the productivity increased rapidly. Beyond the critical pH value of 8.9-9.0, the pCO₂(water) values became under-saturated with respect to atmospheric CO₂ concentration. The effect of lime treatment was not found to prevail in the following months as a steady source of sewage from the Kolkata metropolis which feeds these aquaculture constantly bring in a huge carbon source both in inorganic and organic form. As soon as the flocculation effect of the lime dies off, the water column starts becoming turbid again which aids in converting the system into a net heterotrophic one from a net autotrophic. Based on the results we could successfully accept our hypothesis that lime treatment can not only reduce the CO₂ emission but also make the system a CO₂ sink.

Monitoring of Chilika Lake mouth dynamics and quantifying rate of shoreline change using 30 m multi-temporal Landsat data

Coastal erosion is one of the major and serious concerns for coastal communities residing in the low lying areas, especially near to estuary delta regions. These regions see lots of anthropogenic activities such as economic development, infrastructure and human settlement especially in rapidly developing countries such as India. Shoreline change is a natural process that occurs in coastal areas. But due to the stresses happening in the coast because of anthropogenic activities, understanding how shorelines change over time is important for sustainable management of coast. A crucial aspect of shoreline change monitoring is to identify the location and change over time which can be achieved by developing monitoring strategies using satellite remote sensing data. Performing shoreline change analysis using long term satellite records will help us to understand how shorelines respond to coastal development over time. In the present study we investigate shoreline erosion and accretion rate using three temporal Landsat scenes acquired over a thirty year period for the years 1988, 2000 and 2017. Digital Shoreline Change Analysis System (DSAS) an extension of ArcGIS software was used to compute rate of change statistics by calculating End Point Rate (EPR) values. We observed that Chilika coast is experiencing both erosion and accretion process with very high erosion rate of -13.6 m/yr and accretion of 13.5 m/yr, at Chilika Lake mouth. The average erosion and accretion rate of -1.13 m/yr and 1.41 m/yr were recorded for the study region.

Structural examination of the nickel site in chromatium vinosum hydrogenase: redox state oscillations and structural changes accompanying reductive activation and CO binding

An X-ray absorption spectroscopic study of structural changes occurring at the Ni site of Chromatium vinosum hydrogenase during reductive activation, CO binding, and photolysis is presented. Structural details of the Ni sites for the ready silent intermediate state, SI(r), and the carbon monoxide complex, SI-CO, are presented for the first time in any hydrogenase. Analysis of nickel K-edge energy shifts in redox-related samples reveals that reductive activation is accompanied by an oscillation in the electron density of the Ni site involving formally Ni(III) and Ni(II), where all the EPR-active states (forms A, B, and C) are formally Ni(III), and the EPR-silent states are formally Ni(II). Analysis of XANES shows that the Ni site undergoes changes in the coordination number and geometry that are consistent with five-coordinate Ni sites in forms A, B, and SI(u); distorted four-coordinate sites in SI(r) and R; and a six-coordinate Ni site in form C. EXAFS analysis reveals that the loss of a short Ni-O bond accounts for the change in coordination number from five to four that accompanies formation of SI(r). A shortening of the Ni-Fe distance from 2.85(5) A in form B to 2.60(5) A also occurs at the SI level and is thus associated with the loss of the bridging O-donor ligand in the active site. Multiple-scattering analysis of the EXAFS data for the SI-CO complex reveals the presence of Ni-CO ligation, where the CO is bound in a linear fashion appropriate for a terminal ligand. The putative role of form C in binding H(2) or H(-) was examined by comparing the XAS data from form C with that of its photoproduct, form L. The data rule out the suggestion that the increase in charge density on the NiFe active site that accompanies the photoprocess results in a two-electron reduction of the Ni site [Ni(III) --> Ni(I)] [Happe, R. P., Roseboom, W., and Albracht, S. P. J. (1999) Eur. J. Biochem. 259, 602-608]; only subtle structural differences between the Ni sites were observed.

Examination of the nickel site structure and reaction mechanism in Streptomyces seoulensis superoxide dismutase

Superoxide dismutases are metalloenzymes involved in protecting cells from oxidative damage arising from superoxide radical or reactive oxygen species produced from superoxide. Examples of enzymes containing Cu, Mn, and Fe as the redox-active metal have been characterized. Recently, a SOD containing one Ni atom per subunit was reported. The amino acid sequence of the NiSOD deduced from the nucleotide sequence of the structural gene sodN from Streptomyces seoulensis is reported and has no homology with other SODs. X-ray absorption spectroscopic studies coupled with EPR of the Ni center show that the Ni in the oxidized (as isolated) enzyme is in a five-coordinate site composed of three S-donor ligands, one N-donor, and one other O- or N-donor. This unique coordination environment is modified by the loss of one N- (or O-) donor ligand in the dithionite-reduced enzyme. The NiSOD activity was determined by pulse radiolysis, and a value of kcat = 1.3 x 10(9) M-1 s-1 per Ni was obtained. The rate is pH sensitive and drops off rapidly above pH 8. The results characterize a novel class of metal center active in catalyzing the redox chemistry of superoxide and, when placed in context with other nickel enzymes, suggest that thiolate ligation is a prerequisite for redox-active nickel sites in metalloenzymes.

An experience with diagnostic paracentesis in 100 cases of acute abdomen

Prognosis of acute surgical conditions of abdomen of both traumatic and non-traumatic origin depends on accurate diagnosis and early surgical intervention. However, the diagnosis in acute abdomen is quite difficult. The problem becomes more complex when 24 hours services of radiology and laboratories are not available. Abdominal tap gives a valuable clue to diagnosis. A 10 ml syringe fitted with a 20 gauge intravenous needle was used for the purpose. Both the flanks and the four quadrants of the abdomen were selected for site of the tap according to the suspected pathology. Results were indicated as positive when abnormal fluid (clear, turbid, purulent, bloody, serosanguinous, bile stained and urine, etc) were aspirated. Accurate diagnosis were made in 84.3% in blunt abdominal trauma and 76.47% in non-traumatic acute abdomen. High incidence of accurate results were obtained in gastroduodenal perforations (92%), ruptured ectopic gestation (100%) and burst amoebic liver abscess (100%). The procedure is very simple which could be done at bed side without much disturbance to the severely ill patients. It is safe and free from any complications even if the bowel is also punctured during the tap.

Nerve abscess in lepromatous leprosy. A case report and a discussion of pathogenesis

An instance of nerve abscesses developing in a patient with lepromatous leprosy is reported. The pathogenesis of nerve abscess in lepromatous leprosy is briefly discussed. It appears that such abscesses may develop (i) from an ENL lesion in the nerve during ENL reaction, (ii) because of exacerbation of existing lepromatous lesion, (iii) arise as an "exacerbation nodule", (iv) due to quiet necrosis in a lepromatous granuloma, or (v) it may be iatrogenic.