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1.
Occurrence of baddeleyite (ZrO2) which is a rare mineral has been recorded in ferromanganese
nodules of Central Indian Ocean Basin (CIOB). The mineral occurs either as independent isolated
sub-rounded to elliptical grains or in clusters forming fine subhedral crystals (<3 mm) within ferromanganese
concretionary growth bands. The mode of occurrence, textural features and chemistry of the
mineral suggest detrital and possibly an authigenic origin for baddeleyite. For authigenic origin it is
proposed that zirconium might have got released either from the terrigenous sediments or the altered
seafloor rocks forming halogen complexes and subsequently it has re-precipitated in the form of baddeleyite
within manganese nodules under oxic to sub-oxic conditions. 相似文献
2.
Laterites are ubiquitous in Kerala and are developed over different rock types. The laterite profiles developed over gabbro, granophyre of the Ezhimala Complex are discussed here.
The principal mineral assemblages of the laterites are kaolinite, gibbsite, goethite, hematite and quartz with minor amounts of zircon. Amorphous ferric hydroxide, Al-hydroxide and Al-silicate are also present. Samples from various units of the weathering profile have been analysed for major and trace elements. Major-element data show a steady depletion of Si and enrichment of sesquioxides and TiO2 during weathering. It is also observed that the more the content of the mobile elements (Si, Mg, Ca, K, Na) in the parent rock, the greater is its depletion during lateritisation. The trace elements Co, Cr, V, Cu and Ni show an enrichment while Zn and Ba show depletion over both the rock types. Pb shows almost a consistent behaviour. 相似文献
3.
Lal C. Ram Nishant K. Srivastava Ramesh C. Tripathi Sanjay K. Thakur Awadhesh K. Sinha Sangeet K. Jha Reginald E. Masto Swapan Mitra 《Environmental Geology》2007,51(7):1119-1132
The maximum concentration of the majority of the trace metals in the leachates from shake and column test of lignite fly ash
(LFA) was within the prescribed limits; however, total dissolved solids, total hardness, cations and anions (except K+), being above the prescribed limits, may lead to the increase in the hardness and salinity in the soil on the disposal of
LFA. Present generation of huge amount of fly ash from thermal power plants (TPPs) is a big challenge concerning contamination
of soil, crop produce and surface and ground water bodies due to the presence of some of the toxic trace metals in it. The
leaching behavior of alkaline LFA (pH, 10.94), from TPP of Neyveli Lignite Corporation (NLC), India, was investigated by shake
and column tests using water and sodium acetate buffer. The leaching of trace metals from LFA was governed by their concentrations,
association with the ash particles, leaching duration and pH of the leachate (most influencing parameter). The leaching of
metals followed the order: buffer column > aqueous column > aqueous shake > buffer shake test. 相似文献
4.
Muhammad Hassaan Swapan Kumar Bhattacharya Manoj Joseph Mathew Numair Ahmed Siddiqui 《Arabian Journal of Geosciences》2017,10(8):192
Subsidence and thermal history analysis are carried out in order to investigate the Cenozoic basin development of the southwestern (Tenggol Arch and basinal side) part of the Malay basin. Structurally, the southwestern part consists of normal faults and horst and graben geometry. Tectonic subsidence curves show that the basinal side is more active than the Tenggol Arch due to movement along normal faults. Cenozoic development initiated with the deposition of sedimentary Units M & L (Oligocene) and the activation of the Tenggol fault on the basinal side. Several periods of accelerated and slow subsidence are observed during the Oligocene to Middle Miocene that could be associated with changes in regional stresses caused by pulsating plate movement. The Malay Basin experienced inversion throughout the Middle to Late Miocene related to mantle induced slab avalanche effect, causing relatively higher tectonic subsidence rates on the Tenggol Arch compared to the basinal side, suggesting that the Tenggol Arch is less affected by inversion than the basinal side. After a period (Late Miocene) of non-deposition, the basin was reactivated (Pliocene to recent) due to thermal relaxation with thick sedimentation. Paleo heat flows estimated utilizing a novel technique introduced in this study and present day heat flow calibrated using BHT data further supports our results, in that increase in heat flow is related to rapid tectonic subsidence. An anomalously high heat pulse affected the basin during inversion and could be the cause of meta-sediment formation whereas present heat flows, although high compared to average basins, shows decreasing trend from the inversion period. 相似文献
5.
The satellite-derived wind from cloud and moisture features of geostationary satellites is an important data source for numerical weather prediction(NWP) models. These datasets and global positioning system radio occultation(GPSRO)satellite radiances are assimilated in the four-dimensional variational atmospheric data assimilation system of the UKMO Unified Model in India. This study focuses on the importance of these data in the NWP system and their impact on short-term24-h forecasts. The quality of the wind observations is compared to the short-range forecast from the model background. The observation increments(observation minus background) are computed as the satellite-derived wind minus the model forecast with a 6-h lead time. The results show the model background has a large easterly wind component compared to satellite observations. The importance of each observation in the analysis is studied using an adjoint-based forecast sensitivity to observation method. The results show that at least around 50% of all types of satellite observations are beneficial. In terms of individual contribution, METEOSAT-7 shows a higher percentage of impact(nearly 50%), as compared to GEOS, MTSAT-2and METEOSAT-10, all of which have a less than 25% impact. In addition, the impact of GPSRO, infrared atmospheric sounding interferometer(IASI) and atmospheric infrared sounder(AIRS) data is calculated. The GPSRO observations have beneficial impacts up to 50 km. Over the Southern Hemisphere, the high spectral radiances from IASI and AIRS show a greater impact than over the Northern Hemisphere. The results in this study can be used for further improvements in the use of new and existing satellite observations. 相似文献
6.
Abhijit Bhattacharyya Sukumar Biswas Barun K. Chatterjee Mala Das Pradipta K. Das Tapan K. Das Tarun K. De M.H. Engineer Rabi N. Mukherjee Sibaji Raha S.C. Roy Swapan K. Saha A.K. Sen Bikash Sinha Debapriyo Syam 《Astrophysics and Space Science》1997,250(2):313-326
A Total Solar Eclipse (TSE) was observed from Diamond Harbour (lat. 22.2°N, long 88.2°E) on 24 October 1995. The variation of -ray intensity was measured in the energy range of 0.3–3.0 MeV for different time spans throughout the period of the eclipse. A CR-39 detector was used to look at the change in the fluxes of neutral and charged particles. The maximum drop ( 25%) in the intensity of -ray was observed in the range 2.5–3 MeV during TSE. The CR-39 results showed the appearance of a good number of tracks and a small variation of proton and neutron flux of 10% which was not significant statistically. Low energy -ray fluxes at sea level originate from the secondary electron-photon components of cosmic rays in the atmosphere; its modulation by TSE is interpreted as follows. The cooling of the atmosphere in the path of the umbra induces a reduction of the height of the main production layer of the nuclear component, as a result of which, fewer µ± mesons (from the decay of the± mesons) decay to e±. This leads to a small reduction in the flux of electron-photon component at sea level which originates from this branch; the main branch of e - component from 0 decay remains nearly unaffected. As the total mass of air remains the same, little or no change in the slow proton or the neutron flux at sea level is expected. These are consistent with the present observations. For a better understanding, further studies of this new phenomenon during future TSE are suggested. 相似文献
7.
A desert in the delta: Participatory assessment of changing livelihoods induced by commercial shrimp farming in Southwest Bangladesh 总被引：2，自引：0，他引：2
In recent years, shrimp aquaculture, which is undertaken largely in the tropical countries, has experienced spectacular growth in response to expanding global demand and higher economic return. Shrimp exports bring substantial foreign exchange to the producing countries and also generate employment for various stakeholders related to this industry. Despite a number positive aspects (e.g., foreign exchange, employment and food) of shrimp farming, the industry has serious negative environmental impacts. Because of the degradation of natural resources, commercial shrimp farming imposes socio-economic costs on rural resource-reliant communities as their traditional means of food production and livelihoods are displaced. Bangladesh produces 2.5 percent of the global production of shrimp. The country earned about 400 million dollars (U.S.) from shrimp exports during 2004-2005, up from only US$3.17 million in 1971-72. Bangladesh is suffering because of unplanned expansion of this aquaculture and increasingly called as “a desert in the delta”. The purpose of this paper is to identify the impact of commercial saltwater shrimp farming on rural livelihood patterns in southwest Bangladesh using different Participatory Research methods. The authors suggest that vulnerabilities in livelihoods of the rural communities increased due to narrowing down agricultural production, income sources and natural supply of food. Other socio-economic impacts (e.g., landuse patterns, homestead and family structure, daily movement pattern and activities, drinking water, and law and order) also followed as a reaction to the changing ecological conditions. It is also found that economic benefits from shrimp cultivation to the communities was minimal or even negative due to the polarization and outflow of profits, which is augmenting the threat of poverty. 相似文献
8.
C K Unnikrishnan John P George Abhishek Lodh Devesh Kumar Maurya Swapan Mallick E N Rajagopal Saji Mohandas 《Journal of Earth System Science》2016,125(5):935-944
Surface level soil moisture from two gridded datasets over India are evaluated in this study. The first one is the UK Met Office (UKMO) soil moisture analysis produced by a land data assimilation system based on Extended Kalman Filter method (EKF), which make use of satellite observation of Advanced Scatterometer (ASCAT) soil wetness index as well as the screen level meteorological observations. Second dataset is a satellite soil moisture product, produced by National Remote Sensing Centre (NRSC) using passive microwave Advanced Microwave Scanning Radiometer 2 measurements. In-situ observations of soil moisture from India Meteorological Department (IMD) are used for the validation of the gridded soil moisture products. The difference between these datasets over India is minimum in the non-monsoon months and over agricultural regions. It is seen that the NRSC data is slightly drier (0.05%) and UKMO soil moisture analysis is relatively wet during southwest monsoon season. Standard AMSR-2 satellite soil moisture product is used to compare the NRSC and UKMO products. The standard AMSR-2 and UKMO values are closer in monsoon season and AMSR-2 soil moisture is higher than UKMO in all seasons. NRSC and AMSR-2 showed a correlation of 0.83 (significant at 0.01 level). The probability distribution of IMD soil moisture observation peaks at 0.25 m3/m3, NRSC at 0.15 m3/m3, AMSR-2 at 0.25 m3/m3 and UKMO at 0.35 m3/m3 during June–September period. Validation results show UKMO analysis has better correlation with in-situ observations compared to the NRSC and AMSR-2 datasets. The seasonal variation in soil moisture is better represented in UKMO analysis. Underestimation of soil moisture during monsoon season over India in NRSC data suggests the necessity of incorporating the actual vegetation for a better soil moisture retrieval using passive microwave sensors. Both products have good agreement over bare soil, shrubs and grassland compared to needle leaf tree, broad leaf tree and urban land cover types. 相似文献
9.
Alqadhi Saeed Mallick Javed Talukdar Swapan Ahmed Mohd. Khan Roohul Abad Sarkar Showmitra Kumar Rahman Atiqur 《Natural Hazards》2022,111(1):641-660
Natural Hazards - Co-occurrence events of droughts and heatwaves characterized by abnormal low soil moisture (SM) and high temperatures may cause more significant impacts on society and natural... 相似文献
10.
Khan Nafis Sadik Roy Sujit Kumar Mazumder Md. Touhidur Rahman Talukdar Swapan Mallick Javed 《Natural Hazards》2022,114(1):883-906
Natural Hazards - The confluence of the Ganges, Jamuna, and Padma rivers is one of the most dynamic in the world, an internationally important research area because of the confluence of two of the... 相似文献