Browsing by Author "De Silva, S.N."

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    Characterizing of Vein Quartz Occurrences in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2012) Piumalee, W.D.H.; Cooray, J.T.; De Silva, S.N.
    Sri Lanka endowed with vast potential and exquisite varieties of industrial minerals. Unique physical and chemical properties of high grade quartz as a raw material for high-tech products. The characteristics of vein quartz vary with the geological environment, and although it is primarily composed of silicon dioxide, gaseous, liquid, solid trace elements can occur within crystals or between crystal boundaries. In Sri Lanka, silica is available in two forms as free silica and combined with other elements and compounds. Quartz with extreme purity over 99 percent of Si02 is found in many parts of Sri Lanka as discordant veins and they are mainly confined to the central Highlands. Highland/Vijayan complexes boundary zone. Contain vein quartz apart of the deposits within Highland complex. The origin and provenance of vein quartz in Sri Lanka is highly a debatable aspect.
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    Geophysical Techniques and Geochemical Analysis for Identification of Potable Groundwater — A Case study from Morawewa Area
    (Uva Wellassa University of Sri Lanka, 2018) Arangajanan, S.; De Silva, S.N.; Attanayake, A.N.B.; Samaranayake, S.A.
    Appropriate accessibility to drinking water is a major concern throughout the world. Having access to safe drinking water leads to improvements in health of communities while achieving local (SLS) and international (WHO) Standards, which is a basic measuring-yard of the development of a nation. Dry-zone of Sri Lanka has recently suffered due to lack of drinking water availability and this trend is set to be climbed for damaging heights, as time passes. This study was carried out selecting Morawewa as a sample area, which is situated in the North Central part of Sri Lanka and adjoining the Trincomalee district, bounded by latitude 8° 35' 0" - 8° 38' 0" North and the longitude of 80° 50' 0" - 81° 04' 0" East. The present study aims to detect the groundwater potential in Morawewa area of Trincomalee District, Sri Lanka using electrical measurement and geochemical analytical methods. Electric resistivity data interpretation was carried out by using Schlumberger configuration with electrode spacing (AB/2) of 100 m distance. The resistivity curves were analyzed with curve matching techniques along with the help of RESIST Software. The results of quantitative interpretation of geophysical data indicated that the layer system having minimum of two layers to a maximum of three layers in the area and the maximum depth to the bedrock was 17.9 m. Hence based on the range of resistivity values and graph trending, the weathered and fractured zones were interpreted. The contacts between certain saturated and dry formation zones having different resistivity values were identified from the interpreted resistivity curve and the range of resistivity value. Moreover, geochemical analysis revealed phosphate contamination in the dug well water samples.
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    Identification of Near Surface Water Flow Path in Kanniya Hot Water Spring
    (Uva Wellassa University of Sri Lanka, 2018) Chathuranga, H.D.N.; Subasinghe, N.D.; Premachandra, N.P.; De Silva, S.N.; Samaranayake, S.A.; Bandara, H.M.D.A.H.
    Although Sri Lanka is not located in an active volcanic region or in the vicinity of an active plate margin, the country possesses unexplored geothermal resources with potential for development as a source of renewable energy. As the present trend for geothermal prospects of low-enthalpy metamorphic terrains become a focus overriding conventional magmatic provenances, Sri Lanka is well placed to explore the same. Prospects for low to medium temperature geothermal resources can be expected to spread across the hot springs belt of Sri Lanka. Low to medium temperature geothermal resources have direct applications in food processing, fruit drying, refrigeration and recreational activities. Delineating the source characters of prospective geothermal fields in geological perspectives would be the initial step towards addressing this untapped energy source. Thorough geological mapping along with geophysical applications would pave the way for such source characterization. Geochemical analysis further provides necessary clues on the potential of the source, its provenance and temperatures. Among many geothermal fields that are scattered in the SE to eastern region of the island, Kanniya site was selected for this study. Objective of this study was to identify the near surface water flow path in Kanniya hot water spring which is one of the major hot spring fields located in Sri Lanka near Trincomalee. One-Dimensional and TwoDimensional resistivity survey and magnetic survey were used for subsurface layer mapping of the area and the results were synchronized with the elevation model. The results showed that the flow path is in Northeast - Southwest direction line receiving from beneath a quartz hump. According to the topography of the area, water flow is towards the sea in Northeast direction. Therefore, it is possible to conclude that the near surface water flow path in Kanniya hot water spring is towards the Northeast direction. Presumably the quartz layer acts as a conduit for such flow, due to its high permeability character.
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    Identifying Leachate Plumes Using Geophysical Methods: A Case Study from Open Municipal Solid Waste Dumpsite in Badulla
    (Uva Wellassa University of Sri Lanka, 2018) Dulmini, K.K.V.; Samaranayake, S.A.; De Silva, S.N.; Udagedara, D.T.; Bandara, H.M.D.A.H.; Perera, K.V.G.S.
    Badulla dumpsite is one of the major open municipal dumpsites in Sri Lanka. However the dumpsite has not been constructed according to the modern engineering techniques and it has no liner to prevent seepage of leachate. Therefore leachate pockets can be built up in the subsurface and they can flow directly to a nearby surface water body (Badulu oya) through surface and subsurface channels, due to elevation difference. Therefore mapping leachate plumes and their flow paths have high interest in the environmental management and prevention of surface water pollution. Hence in this study leachate flow paths were delineated by using resistivity imaging with controlled inversion parameters and magnetic mapping techniques. The geophysical findings of the leachate characters, were supplemented with physico-chemical parameter analysis of collected leachate samples from solid waste dumpsite and leachate drainage channel. Leachate plumes were demarcated by 2D resistivity technique, and a unique correlation was established between ground magnetic results and resistivity imaging. 3D resistivity contour plot synthesized by 2D resistivity imaging profiles, confirms that leachate plumes and their flow paths are confined to near surface, almost throughout the dumping area. Moreover high electric conductivity values of leachate produce unique signature in resistivity image. Chemical parameters such as biochemical oxygen demand, chemical oxygen demand and phosphate are above the tolerance limits for the discharge of industrial wastewater into inland surface waters. This study reveals the appearance of subsurface leachate plumes in Badulla dump site and their flow paths. It is recommended to build a retaining wall in the identified direction of leachate flow path down to the depth of bedrock in order to prevent seepage of leachate to Badulu oya and accumulated leachates should be treated prior to discharge.