Some observations from the data taken in and around Kharagpur during the onset of the monsoon, 1990

During MONTBLEX 1990, various observational platforms were operated at Kharagpur and the nearby Kalaikunda Air Base. Using the data from all the platforms, one can draw the following conclusions. The temperature and wind data obtained from various sensors have overall compatibility. Sodar wind data indicate the presence of a low level jet at around 300 m above ground. The inversion height may be evaluated from the vertical profile of the sodar back-scatter echo intensity. The sub-synoptic or synoptic scale convergence modulates the inversion height and the presence of cloud-base within the inversion height in turn modulates the sensible heat and momentum fluxes.     

Utility of orbital surveillance system for snow monitoring in the Indian context

Since snow covered areas in the Himalayas contribute significantly to the discharge of the major rivers of North India, snow monitoring is essential for effective control and management of the available water resources, particularly in the lean period. As accumulation and melting of snow are dynamic processes the need arises for periodic monitoring. Conventional survey methods are time consuming and expensive due to adverse terrain conditions and weather. As such, updating information at reasonably frequent intervals calls for a strategy invoiving remote sensing techniques. Potentials of such techniques such as aerial and orbital photography and multispectral scanning systems as also microwave sensing systems are briefly discussed. Particular emphasis is laid on a Landsat type surveillance system, which is at the operational stage. As a case study demonstrating the system capability an area in the Sutlej catchment has been analysed on Landsat imagery acquired in October and December, 1972. The snow covered area is found to be considerably more in the December, 72 imagery. Such a map overlaid on a contoured 1:250,000 base updated every month can be useful input attempts at watershed modelling incorporating other dynamic features also.     

Assessing redox properties of standard humic substances

Redox properties of humic substances (HS) control important biogeochemical processes. Thus, accurate estimation of redox properties of HS is essential. However, there is no general consensus regarding the best available measurement method of HS redox properties. In this study, we compared several common HS redox property measurement methods using anthraquinone-2,6-disulfonate (AQDS) as model compound, and standard Elliot soil humic acid (1S102H, ESHA), reference Pahokee peat (1R103H, PPHA), and Suwannee River natural organic matter (1R101N, SRNOM) as representative HS. We found that the H₂/Pd reduction method followed by incubation with ferric citrate (FeCit) reagent was incomplete, and the H₂/Pd reduction method followed by incubation with potassium ferricyanide (K₃Fe(CN)₆) was insensitive. Stannous chloride (SnCl₂) reduction followed by titration of excess stannous (Sn²⁺) by potassium dichromate (K₂Cr₂O₇) was found to be most accurate. These findings will help in future investigations on detailed characterizations of functional groups of HS responsible for oxidation/reduction reactions.     

An experiment on the magnetic hysteresis and remanence of Rajmahal basalts

Summary Hysteresis curves of Rajmahal Trap basalts in Bihar are drawn and their coercivities obtained. The experimental arrangements and the procedure are described. The initial remanent magnetisation curves of the specimens are also drawn with the help of the same arrangement. Coercive forces of the rock specimens tested range from 70 to 237 oersteds. The values of saturation magnetisation and remanent magnetisation of two typical specimens are also given.     

Post-Cyclone Sidr illness patterns in coastal Bangladesh: an empirical study

After the landfall of Cyclone Sidr along the southwestern coast of Bangladesh on November 15, 2007, emergency and public health personnel within and beyond Bangladesh anticipated a massive outbreak of water-borne and other diseases in most affected areas. Fortunately, such an outbreak did not occur. The objectives of this paper are to examine the extent and pattern of illnesses experienced by Cyclone Sidr survivors in the aftermath of its landfall and to investigate household and individual-level factors associated with such illnesses. Based on face-to-face interviews conducted among 277 randomly selected Sidr survivors living in the four most severely impacted coastal districts, this study found that the post-cyclone incidence of water-borne, respiratory, and other diseases was not unusually high. Only 52 persons suffered Sidr-related illnesses, and their illnesses were significantly associated with household income, and gender and age of the Sidr survivors. A major outbreak of such diseases was largely avoided because of the proper distribution of food and safe drinking water, as well as the timely implementation of health care intervention measures. This important finding will aid relevant authorities in successfully responding to outbreaks of diseases following a future extreme event in Bangladesh and perhaps elsewhere.     

Impact of multispecies diatom bloom on plankton community structure in Sundarban mangrove wetland,India

A multispecies bloom caused by the centric diatoms, viz. Coscinodiscus radiatus, Chaetoceros lorenzianus and the pennate diatom Thalassiothrix frauenfeldii was investigated in the context of its impact on phytoplankton and microzooplankton (the loricate ciliate tintinnids) in the coastal regions of Sagar Island, the western part of Sundarban mangrove wetland, India. Both number (15–18 species) and cell densities (12.3 × 10³ cells l⁻¹ to 11.4 × 10⁵ cells l⁻¹) of phytoplankton species increased during peak bloom phase, exhibiting moderately high species diversity (H′ = 2.86), richness (R′ = 6.38) and evenness (E′ = 0.80). The diatom bloom, which existed for a week, had a negative impact on the tintinnid community in terms of drastic changes in species diversity index (1.09–0.004) and population density (582.5 × 10³ to 50 × 10³ ind m⁻³). The bloom is suggested to have been driven by the aquaculture activities and river effluents resulting high nutrient concentrations in this region. An attempt has been made to correlate the satellite remote sensing-derived information to the bloom conditions. MODIS-Aqua derived chlorophyll maps have been interpreted.     

Nitrite reduction by Fe(II) associated with kaolinite

Interactions of iron (Fe) with the nitrogen (N) cycle have emerged and contain elements of abiotic and biological reactions. One such abiotic reaction which has received little study is the reactivity of NO₂ ^? and Fe(II) associated with a major clay mineral, kaolinite. The main objective of this study was to evaluate the reactivity of NO₂ ^? with Fe(II) added to kaolinite under anoxic conditions. Stirred batch reactivity experiments were carried out with 10 g L^?1 kaolinite spiked with 25 and 100 µM Fe(II) at pH 6.45 in an anaerobic chamber. Approximately 500 µM NO₂ ^? was added to initiate the reaction with Fe(II)-loaded kaolinite. The rate of nitrite removal from solution was 2.4-fold slower in the high Fe(II) treatment when compared with the low Fe(II) treatment. A large portion of the NO₂ ^? removed from solution was confirmed to be reduced to N₂O_(g) in the Fe(II)-kaolinite slurries. However, NO₂ ^? reduction was also noticed in the presence of kaolinite-alone and to somewhat lesser extent in the presence of dithionite-citrate-bicarbonate (DCB)-treated kaolinite. Chemical extractions coupled with infrared spectroscopy suggest that Fe(III) oxide mineral impurities and structural Fe(III) in kaolinite may participate in NO₂ ^? removal from solution. Furthermore, a magnetite mineral was identified based on X-ray diffraction analysis of untreated kaolinite and DCB-treated kaolinite. Our findings reveal a novel pathway of NO₂ ^? transformation in the environment in the presence of Fe(II) associated (sorbed and impurity) with kaolinite.