Environmental geochemistry of the Pichavaram mangrove ecosystem (tropical), southeast coast of India   总被引：3，自引：0，他引：3  

A. L. Ramanathan  V. Subramanian  R. Ramesh  S. Chidambaram  A. James 《Environmental Geology》1999,37(3):223-233

 Spatial and temporal geochemical variations of various parameters in the water and sediment of a relatively small mangrove situated on the southeast coast of India were examined in detail for the first time. The water quality generally reflects the impact of seawater and the Vellar estuary (mixing effect) aided by evaporation and in situ biological productivity. The depletion and fluctuation of dissolved silica are controlled by biological processes. Nitrate and phosphate are contributed by fertilizer input from adjoining agriculture fields. Total suspended matter (TSM) shows an erratic range and trend due to deforestation and resuspension processes. Sand and silt constitute 70–90% of the sediments. Statistical analysis of the sediments shows the prevalence of a moderately high-energy environment with very effective winnowing activity. Organic matter content is higher in the mangrove sediments in comparison to adjacent estuaries. Water and sediment show fluctuations in their chemical concentration, but no specific trends could be identified. Heavy metals are also enriched in the mangrove sediments, indicating their unique chemical behavior and the existence of trapping mechanisms. Factor analysis and correlation analysis of water and sediments show the complexity of the system and the multitude of contributing sources. The core sediment chemistry suggests the depletion of metal input due to the damming of the detrital inputs. The Pichavaram mangrove seems to be relatively unpolluted, since the anthropogenic signal observed is small and acts as a sink for heavy metals contributed from a multitude of sources without an adverse effect. Received: 5 November 1997 · Accepted: 30 March 1998  相似文献   

Sedimentary nutrient dynamics in a tropical estuarine mangrove ecosystem     

M. Bala Krishna Prasad  A.L. Ramanathan 《Estuarine, Coastal and Shelf Science》2008

Mangrove sediments play a pivotal role in the nutrient biogeochemical processes by behaving as both source and sink for nutrients and other materials. Surface and core sediments were collected from various locations of the Pichavaram mangrove (India) and analyzed for grain size distribution, nutrients and stable N isotope (δ¹⁵N) signatures in order to understand the spatial and vertical distribution of nutrients and biogeochemical processes of the C, N, P and S in this ecosystem. Sand is the dominant fraction followed by silt and clay. Spatial distribution of nutrients is controlled by the external and internal loadings, whereas vertical distribution is largely driven by the in situ microbial activities. Interior mangrove sediments contain higher concentrations of organic carbon (OC) than the estuarine sediments reflecting high rates of organic matter retention. Finer fractions of sediment hold ∼60% OC due to high surface area. At some sampling points, moderately high δ¹⁵N signatures were observed and this may be because of agricultural runoff and aquaculture effluents.  相似文献   

Hydrogeochemical processes in the groundwater environment of Muktsar,Punjab: conventional graphical and multivariate statistical approach   总被引：4，自引：0，他引：4  

Manish Kumar  Kalpana Kumari  Umesh Kumar Singh  AL. Ramanathan 《Environmental Geology》2009,57(4):873-884

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Phosphorus fractionation in sediments of the Pichavaram mangrove ecosystem,south-eastern coast of India     

Rajesh Kumar Ranjan  AL. Ramanathan  Rita Chauhan  Gurmeet Singh 《Environmental Earth Sciences》2011,62(8):1779-1787

Present study examined phosphorus dynamics through delineation of source as well as availability of phosphorus and its fractionation within the intertidal sediments of Pichavaram mangrove ecosystem. Twelve sediment samples and two cores were collected from the mangrove forest along with estuarine area (Vellar-Coleroon) during January 2005. Sediments were analyzed for total phosphorus and its fractionation using operationally defined chemical sequential extraction scheme (SEDEX). Dissolved phosphorus (in water) and total phosphorus (in sediments) concentrations were high in the Vellar region of Pichavaram mangrove area due to pollution load from nearby villages and agricultural fields. However, the spatial variation in dissolved phosphorus were insignificant (at significance level = 0.05). The results for the phosphorus fractionation (post-tsunami) were compared with earlier studies (pre-tsunami). It was observed that all phosphorus fractions (except adsorbed-phosphorus) showed a highly significant (at significance level = 0.05) increase in concentration after the tsunami event. There was significant decrease in the adsorbed phosphorus concentration as a result of tsunami. The changes were more pronounced for organic phosphorus which increased by almost twofold following the event. These variations were attributed to change in salinity, increase in dissolved oxygen as well as the retreat of tsunami water carrying the waste load. The vertical distribution of phosphorus through core sediments showed that mixing after tsunami had altered the different phosphorus fraction and its availability. Overall, the study indicated that the fluvial weathering along with litter degradation and anthropogenic sources controlled the biogeochemistry of phosphorus in this mangrove ecosystem. Observed changes in the concentrations are a result of altered physico-chemical characteristics caused by tsunami.  相似文献   

Preliminary studies on the characterization of clay minerals in the Sundarban mangrove core sediments,West Bengal,India     

K. Rajkumar  AL. Ramanathan  P. N. Behera  S. Chidambaram 《Arabian Journal of Geosciences》2014,7(2):537-544

Clay mineral found in rivers, estuaries, and marine sedimentary environments is an important group of minerals which is the by-product of chemical weathering. The main constituents of this fine-grained sediment include mudstones, clay stones, and shales. This is probably the first report of a Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) investigation on the clay minerals to characterize them in the Sundarban mangrove core sediments of Moipith Matla and Belamati Island. This study was carried out in the selected stretch for FTIR and SEM analyses. The study reveals the dominant association of kaolinite with subordinate amount of quartz, illite, and chlorite. The abundance of kaolinite, illite, chlorite, and clay with quartz helps in increasing the sediment in the island region. The geochemical and mineralogical evolution of mangrove sediment results in the interaction of biotic and abiotic parameters, whose balance is conditioned by the climate that governs the hydrologic regime, the sedimentation dynamics, and of the organic matter. This study on the characterization of clay provides substantial impact in the water-holding capacity, productivity, and mineralogical and chemical transformation in order to establish much more and intermediate equilibrium between marine influence and continental contribution, as a part of the estuarine environment.  相似文献   

Characterization of clay minerals in the Sundarban mangroves river sediments by SEM/EDS     

K. Rajkumar  A. L. Ramanathan  P. N. Behera 《Journal of the Geological Society of India》2012,80(3):429-434

Clay minerals, byproducts of chemical weathering, are important group of minerals found in rivers, estuaries, and marine sedimentary environments, which include mudstones, clay stones, and shales. In the present study, FTIR and SEM investigation on the clay minerals in Sundarban mangrove core sediments collected from Moipith Matla and Belamati Island are carried out. The study indicated the dominant association of kaolinite with subordinate amount of quartz, illite and chlorite. The abundance of kaolinite, illite chlorite and clay with quartz helps in increasing sediment in the islands region. The geochemical and mineralogical evolution of mangrove sediments are results of the interaction of biotic and abiotic parameters, whose balance is conditioned by the climate that governs the hydrologic regime, the sedimentation dynamics and the organic matter. This study on the charaterstation of clay provides us with substantial impact in the water holding capacity, productivity and mineralogical and chemical transformation in order to establish much more and intermediate equilibrium between marine influence and continental contribution, as part of the estuarine environment, than to the tropical climate conditions.  相似文献   

Short note: Applications of third-order statistics for the automatic time picking of seismic events     

Karthik Srinivasan  Luc T. Ikelle 《Geophysical Prospecting》2001,49(1):155-158

We present a new automatic time-picking method based on third-order statistics, namely bicoherence correlation. Contrary to conventional methods, which are based on second-order statistics (i.e. cross-correlation or neural-network trainings), our method is less sensitive to coloured noise as well as the bandwidth of the signal. Bicoherence correlation can also be used for autotracking events in seismic data for an interpretation.  相似文献   

Urban growth analysis using spatial and temporal data     

H. S. Sudhira  T. V. Ramachandra  Karthik S. Raj  K. S. Jagadish 《Journal of the Indian Society of Remote Sensing》2003,31(4):299-311

Urban growth identification, quantification, knowledge of rate and the trends of growth would help in regional planning for better infrastructure provision in environmentally sound way. This requires analysis of spatial and temporal data, which help in quantifying the trends of growth on spatial scale. Emerging technologies such as Remote Sensing, Geographic Information System (GIS) along with Global Positioning System (GPS) help in this regard. Remote sensing aids in the collection of temporal data and GIS helps in spatial analysis. This paper focuses on the analysis of urban growth pattern in the form of either radial or linear sprawl along the Bangalore — Mysore highway. Various GIS base layers such as built-up areas along the highway, road network, village boundary etc. were generated using collateral data such as the Survey of India toposheet, etc. Further, this analysis was complemented with the computation of Shannon’s entropy, which helped in identifying prevalent sprawl zone, rate of growth and in delineating potential sprawl locations. The computation Shannon’s entropy helped in delineating regions with dispersed and compact growth. This study reveals that the Bangalore North and South taluks contributed mainly to the sprawl with 559% increase in built-up area over a period of 28 years and high degree of dispersion. The Mysore and Srirangapatna region showed 128% change in built-up area and a high potential for sprawl with slightly high dispersion. The degree of sprawl was found to be directly proportional to the distances from the cities.  相似文献   

Qualitative and quantitative assessment of TanDEM-X DEM over western Himalayan glaciated terrain     

Pratima Pandey  Surendar Manickam  Avik Bhattacharya  AL. Ramanathan  Gulab Singh  G. Venkataraman 《国际地球制图》2017,32(4):442-454

Glaciers have a high impact in the socio-economic sectors including water supply, energy production, flood and avalanches. A high precision digital elevation model (DEM) is required to monitor glaciers and to study various glacier processes. The present study deals with the qualitative and quantitative evaluation of the DEM generated from the bistatic TanDEM-X data by comparing it with GPS, Ice, Cloud, and land Elevation Satellite (ICESat) data and standard global DEMs such as Shuttle Radar Topography Mission (SRTM) and Advanced Space-borne Thermal Emission and Reflection Radiometer Global DEM (ASTER GDEM). The study area consists of highly undulating glaciated terrain in western Himalaya, India. The results reveal that TanDEM-X is slightly better than SRTM both qualitatively and quantitatively, whereas ASTER GDEM showing maximum discrepancy among the three DEMs. The Root Mean Square Error (RMSE) of the TanDEM-X DEM with respect to GPS is 3.5 m at lower relief and 11.9 m at glaciated terrain, against 6.7 and 12.5 m for SRTM and 9.3 and 19.8 m for ASTER GDEM, respectively, for the same sites. On an average, for the whole study area, the RMSE of TanDEM-X is 7.9 m, SRTM is 9.3 m and ASTER GDM is 14.2 m. The RMSE of TanDEM-X, SRTM and ASTER GDEM with respect to ICESat are 16.3, 19.9 and 101.1 m, respectively. It is evident from the analysis that though SRTM is closer to TanDEM-X in terms of accuracy in the mountainous terrain, however, TanDEM-X will be more useful for studying glacier dynamics and topography.  相似文献   

Ageostrophic instabilities in a two fluid system with rotation     

N. Ramanathan  D. B. Rao 《Journal of Earth System Science》1984,93(4):387-397

The stability of synoptic scale waves formed on a frontal surface is studied including nongeostrophic effects with the basic flow subjected to both vertical and horizontal shear. Spectral method is used to obtain the desired solutions. The stability characteristics of the developed unstable modes are presented as a function of shears of the basic flow. With the inclusion of barotropic shear the spectrum of instabilities increase. The lower speeded member of the mixed mode (gravitational-rotational) pair is influenced by the barotropic shear in the basic current and it appears at lower vertical shears. The structure of the height perturbations are utilized to distinguish the various unstable modes developed in the system together with their stability characteristics. This investigation has shown that the ageostrophic effects can be a significant factor in the development of synoptic scale waves on a frontal surface.  相似文献