Conservation of biodiversity of the coastal resources of Sundarbans,Northeast India: an integrated approach through environmental education

The Indian Sundarbans, a diversified coastal wetland on the southern fringe of the State of West Bengal, harbors a luxuriant biodiversity and acts as a potential refuge of living marine resources. Girdled with thick mangrove foliage, this estuarine delta system offers an excellent nursery ground for most of the brackishwater finfish and shellfish. Since supply of hatchery-produced tiger prawn seed (Penaeus monodon) is highly inadequate in West Bengal, the aquaculture farms of this region largely depend on the supply from natural resources. Being motivated by a regular cash income, the majority of coastal people from Sundarbans have adopted prawn seed collection as their profession almost throughout the year as an important source of earning. The users are neither trained nor guided at any stage from collection to marketing and are fully dependent on traditional methods. They first sort out the tiger prawn seeds (mainly the postlarval stage PL 20) accounting only 0.25-0.27% of the total catch and thereafter the major portion of the haul are thrown away on the beach flats or the tidal mudflats. This wasted by-catch contains the juveniles of economic and uneconomic varieties of finfish and shellfish along with a bulk of holoplankters and meroplankters (non-target species). This practice causes several ecological and occupational consequences, namely, (i) the huge destruction of the pelagic biota that can lead to severe stock depletion as well as hamper the energy transference through the marine ecosystem food webs; (ii) constant dragging of nets along the coast and tidal creeks paves the way for soil erosion, uprooting the mangrove seedlings and saltmarsh vegetation; (iii) the water quality is deteriorating in the catchment areas due to mud erosion and (iv) due to constant contact with the seawater, the collectors are affected with waterborne diseases, skin infections, reproductive tract disease in women and many other contagious diseases.This paper, in addition to identifying the challenge to environmental quality and resource abundance, emphasizes the need for grass-root public education so that local people come to understand, support and implement sustainable resource conservation and environmental protection activities now and in the future. As a follow-up course of action, the authors have initiated a general awareness program for developing consciousness among the coastal people regarding proper use of natural resources. Initiatives are taken for educating coastal people by holding workshops and seminars with the use of educational resource materials. Exclusive awareness camps and grass root level training for coastal people are also being proposed as a future course of action by means of exhibitions, audiovisuals etc. It is proposed that local government bodies come forward to mitigate this problem with scientific and rational approaches and to take proper actions towards conservation.     

Study of dems derived from ERS-1/2 SAR and SRTM data

The DEM of the Bhuj earthquake affected area of 50 x 50 km was generated using the ERS-1/2 SAR tandem data (May 15—16,1996). Region growing algorithm coupled with path following approach was used for phase unwrapping. Phase to height conversion was done using D-GPS control points. Geocoding was done using GAMMA software. A sample data of DEM of Shuttle Radar Topography Mission (SRTM) of the Bhuj area is made available by DLR Germany. The intensity image, DEM and Error map are well registered. The spatial resolution of this DEM is about 25 m with height accuracy of a few meters. The DEM derived through ERS SAR data is prone to atmospheric affects as the required two images are acquired in different timings where as SRTM acquired the two images simultaneously. An RMS height error of 12.06 m is observed with reference to SRTM though some of the individual locations differ by as much as 35 m.     

Assessment of geo-coding and height accuracy of the dem derived from preliminary data sets of x-band srtm

The first data set of X-band Digital Elevation Model (DEM), derived from Shuttle Radar Topography Mission (SRTM), of Gujarat Earthquake affected area was processed to assess the geo-coding and height accuracy. A detailed survey of the study area was carried out using Differential-GPS systems to get accurate control points. Though, it is the first data set processed without Attitude and Orbit Determination Avionics, the geo-coding and height accuracy is good. It is observed that there is an average shift of-1.5 pixels in Latitude and 2.5 pixels in Longitude with 1.5 pixels Standard Deviation (STD). A comparison of SRTM and Differential-GPS heights indicates that there is a bias of 7.4 m with STD of 3.4 m. This is in agreement with the height errors reported by the Deutschen Zentrums fur Luft- und Raumfahrt (DLR) in Height Error Map (HEM) data set.     

Geochemistry of coexisting hornblende and biotite from the Ambalavayal granite,Kerala

Major and trace element geochemistry of coexisting hornblendes and biotites from the Ambalavayal granite, northern Kerala, are presented. The hornblendes correspond to edenitic composition, whereas the biotites correspond to annite. The hornblendes typically show high Al₂O₃ contents (9·69–11·89%) comparable with those from anorogenic granites. The biotites are characteristically low Mg-type, similar to those reported from alkaline rocks. The distribution coefficients calculated for all the major and trace elements are presented and an evaluation of the nature of variation indicate near-chemical equilibrium conditions during the crystallization of the two minerals. The hornblende-biotite tie lines in the Fe³⁺?Fe²⁺?Mg compositional triangle, lie parallel to those of buffered biotites, indicating crystallization in an environment closed to oxygen and well above the Ni?NiO buffer. It is inferred that thefH₂O increased towards the residual stage andfO₂ values were high, in the range of 10^?15 bars.     

Radioelement geochemistry of alkali granites of the Kerala region,south-west India

Th, U and K abundances in four alkali granites of the Kerala region, south-west India, are presented. The plutons show high radioelement levels, correlatable with those of alkali granites in other regions. The nature of variation is consistent with the correlation of Th and U with accessory phases like sphene, zircon, allanite, apatite and monazite. A geochronologic correlation is also observed between the alkali granites and the Th-bearing beach placers of the region. The petrogenetic features of the alkali plutons, their taphrogenic association, Pan-African affiliation and high Th/U levels suggest that the alkali plutons are favourable locales for radioelement exploration.     

Lateritisation as a possible contributor to gold placers in Nilambur Valley, southwest India

Panning for placer gold in the river beds of Punna Puzha and Chaliyar Puzha in the Nilambur Valley, southwest India, has been in vogue among the local people for the last few centuries. The auriferous quartz veins and reefs associated with the Precambrian migmatitic gneisses of the region had been mined for several years. Of late, Au is also being recovered from the laterite matrix of gravels in the old river terraces and from the residual laterites overlying the gneisses. The size of Au nuggets associated with the laterites is much higher (0.5 mm) than that of the Au in vein quartz (0.2 mm) and the associated heavy minerals in the placers (0.2 mm). The Au nuggets show surface and internal textures characteristic of redeposition under low-temperature conditions. Our field and laboratory investigations suggest that dissolution, transport and redeposition of Au occurred in Nilambur concomitant with the lateritisation process.     

Productivity optimisation in weak sedimentary formations for improved coal production and roof stability—an approach

Far-field peak particle velocity (PPV) measurements were made in the roof while blasting in coal development drivages at Tandsi Mine, Western Coalfields Limited, India. The roof was fragile at this mine and was posing constant support problems for mining, resulting in low productivity. The PPV measurements have been used to decipher the damage zone in the roof. The extent of damage obtained has been compared to establish the threshold limits for the damage zone. Conversely, the maximum charge per delay that can be exploded is calculated and a suitable blast design has been recommended for maintaining the roof stability and pull. A roof vibration predictor equation has been developed that shows a consistent trend indicating that it may have future use in a similar geo-mining setup. The blast pattern recommended has reduced the damage extent, though marginally, but helped in improving pull. Critical PPV for incipient rock damage in underground coal mine development drivages under fragile roof were computed. The PPV level for incipient crack growth was found to vary from 500 to 800 mm/s while for overbreak it varied from 800 to 1200 mm/s. It was also observed that the location of cut holes, charge concentration and firing sequence were found to be responsible for the difference in their damage potential.     

Ophiolites-Geodynamic and environmental implications:Preface

Ophiolite studies over the decades have played a crucial role in better understanding of mid-ocean ridge and subduction zone processes,mantle dynamics and heterogeneity,fluid-rock interactions in both sub-oceanic and sub-arc upper mantle,and the mechanisms of continental growth in accretionary and collisional belts.The continued interest in ophiolites as a topic of multi-disciplinary research in Earth Sciences has resulted in a wealth of new data,syntheses,and ideas from ophiolites around the world.