Geological Survey and Mines Bureau

Bureau, Sri Lanka

Geological Survey and Mines Bureau

Bureau, Sri Lanka
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Wijesekara S.S.R.M.D.H.R.,Sri Lanka Institute of Fundamental Studies | Mayakaduwa S.S.,Sri Lanka Institute of Fundamental Studies | Siriwardana A.R.,Sri Lanka Institute of Fundamental Studies | Siriwardana A.R.,University of Peradeniya | And 4 more authors.
Environmental Earth Sciences | Year: 2014

This study focuses on the characterization of leachate generated from Gohagoda dumpsite in Kandy, Sri Lanka, assessment of its spatial and temporal variations, and identification of subsurface canals and perched water bodies in the wetland system affected by the leachate flow. Leachate samples were collected monthly throughout dry and rainy seasons from different points of the leachate drainage channel over a period of 1 year and they were tested for quality parameters: pH, temperature, electrical conductivity, total dissolved soils, alkalinity, hardness, total solids, volatile solids, total suspended solids, volatile suspended solids, biochemical oxygen demand (BOD5), chemical oxygen demand, nitrate-nitrogen, nitrite-nitrogen, phosphates, ammonium-nitrogen, chloride, dissolved organic carbon, total organic carbon and heavy metals. Sequential soil extraction procedures were performed for the characterization of leachate-affected local soil. A geophysical survey using direct current resistivity technique was conducted at locations downstream of the dumpsite. Leachate characteristics indicated that the leachate is in the methanogenic phase and the results strongly suggest that the leachate may be polluting the river where the leachate is discharged directly. Leachate exceeds the allowable limits of Sri Lankan wastewater discharge standards for many of the parameters. Significant difference (P < 0.05) was observed for most of organic and inorganic parameters among all sampling locations. Many parameters showed a negative correlation with pH. The affected soils showed high heavy metal concentrations. Resistivity study confirmed a confined leachate flow at the near surface with few subsurface canals. However, no separate subsurface plume movement was observed. The results of this research can effectively be used for the establishment of an efficient and effective treatment method for the Gohagoda landfill leachate. © 2014 Springer-Verlag Berlin Heidelberg.

Wijesekara H.R.,Sri Lanka Institute of Fundamental Studies | De Silva S.N.,Geological Survey and Mines Bureau | Wijesundara D.T.D.S.,Geological Survey and Mines Bureau | Basnayake B.F.A.,University of Peradeniya | Vithanage M.S.,Sri Lanka Institute of Fundamental Studies
Environmental Technology (United Kingdom) | Year: 2014

This study presents the use of direct current resistivity techniques (DCRT) for investigation and characterization of leachate-contaminated subsurface environment of an open solid waste dumpsite at Kandy, Sri Lanka. The particular dumpsite has no liner and hence the leachate flows directly to the nearby river via subsurface and surface channels. For the identification of possible subsurface flow paths and the direction of the leachate, DCRT (two-dimensional, three-dimensional and vertical electrical sounding) have been applied. In addition, the physico-chemical parameters such as pH, electrical conductivity (EC), alkalinity, hardness, chloride, chemical oxygen demand (COD) and total organic carbon (TOC) of leachate collected from different points of the solid waste dumping area and leachate drainage channel were analysed. Resistivity data confirmed that the leachate flow is confined to the near surface and no separate plume is observed in the downstream area, which may be due to the contamination distribution in the shallow overburden thickness. The stratigraphy with leachate pockets and leachate plume movements was well demarcated inside the dumpsite via low resistivity zones (1–3 Ωm). The recorded EC, alkalinity, hardness and chloride contents in leachate were averaged as 14.13 mS cm−1, 3236, 2241 and 320 mg L−1, respectively, which confirmed the possible causes for low resistivity values. This study confirms that DCRT can be effectively utilized to assess the subsurface characteristics of the open dumpsites to decide on corridor placement and depth of permeable reactive barriers to reduce the groundwater contamination. © 2014 Taylor & Francis

Ranasinghe P.N.,Woods Hole Oceanographic Institution | Ranasinghe P.N.,Kent State University | Ortiz J.D.,Kent State University | Moore A.L.,Earlham College | And 4 more authors.
Quaternary International | Year: 2013

The 2004 Indian Ocean tsunami highlighted the need to better understand the dynamics of the South Asian coastlines. Very little knowledge on paleo-coastal variability hinders the development of a paleo-tsunami chronology of the western Bay of Bengal. Also, limited sea level records for the southern Bay of Bengal are remarkably different from rest of the Indian Ocean due to alternating highstands and lowstands during mid-late Holocene.This study was undertaken to recognize how the coastal environment in tectonically stable eastern and southeastern coasts of Sri Lanka changed during mid-late Holocene and to derive evidence of sea level variability. Sediment cores were collected from Kirinda and Panama estuaries, Okanda lagoon and Vakarai beach ridge plain, situated on the eastern and southeastern coasts of Sri Lanka. Physical and chemical variations in sediments, caused by the coastal environmental changes occurred due to fluctuating eustatic sea level, were determined using X-ray fluorescence, visible reflectance, magnetic susceptibility and grain size. Chronology of events were developed using AMS 14C dates on bulk organic matter, wood, inorganic carbonate and mollusk shells.Results suggest that key periods of transition in the coastal environment in the studied area occurred between about 7300 and 3000 BP. Submergence of coastal environments by mid-Holocene transgression began around 7300 BP. Barrier development initiated at the end of the submergence phase around 4900 BP. Onset of beach ridge development in areas with high sediment supply took place around 4000 BP and continued later than 2400 BP. Marine influence ended around 3000 BP.These coastal environmental changes suggest that Holocene transgression, which started flooding southeastern coastal lowlands, either slowed or the sea level stabilized around 4900 BP. Sea level fell down to its present level at around 3000 BP by the subsequent slow regression. Some cores carry evidence for a possible pause in the transgression or a short lowstand that ended around 5200 BP. © 2013 Elsevier Ltd and INQUA.

Ranasinghe P.N.,Woods Hole Oceanographic Institution | Ranasinghe P.N.,Kent State University | Ortiz J.D.,Kent State University | Smith A.J.,Kent State University | And 4 more authors.
Holocene | Year: 2013

The southeastern coastal plain of Sri Lanka contains Holocene sediment archives representing the winter monsoon variability because this region is protected from both summer monsoon and cyclonic rainfall. Chemical, biological, mineralogical, and physical climate proxies were studied in sediment cores extracted from three different coastal estuaries and lagoons situated on the southeastern coast to derive winter monsoon variability. These cores displayed minimum influence of sea level-related changes in sediments. Clay normalized proxy records suggest intervals of aridity from >7300 to ~6750, semi-aridity from ~6250 to 4600 yr BP, and aridity from ~4000 to 3000 and ~1100 to <500 cal. yr BP, with a short wet interval from ~6500 to 6250 cal. yr BP, and a wet interval from ~3000 to 1500 yr BP. Our results match the timing of previously published climate events for Holocene variations in the Indian summer monsoon. Wavelet analysis of the detrended climate proxy records identify significant periodicities at: ~20 ~28-32, ~64, ~100, ~128, ~192, ~256 yr in our data. Most of these periodicities are consistent with known solar irradiance cycles, which drive the decadal- to centennial-scale variability of the summer monsoon. Our multiproxy record for mid- to late-Holocene climate in southeastern Sri Lanka documents that Indian winter monsoon variability is statistically similar to Indian summer monsoon variability, suggesting similar forcing mechanisms. © The Author(s) 2013.

Atwater B.F.,University of Washington | Cisternas M.,Pontifical Catholic University of Valparaíso | Yulianto E.,Lembaga Ilmu Pengetahuan Indonesia | Prendergast A.L.,University of Cambridge | And 6 more authors.
Andean Geology | Year: 2013

The Chilean tsunami of 22 May 1960 reamed out a breach and built up a fan as it flowed across a sparsely inhabited beach-ridge plain near Maullín, midway along the length of the tsunami source. Eyewitnesses to the flooding, interviewed mainly in 1988 and 1989, identified levels that the tsunami had reached on high ground, trees, and buildings. The maximum levels fell, from about 10 m to 2 m, between the mouth of the tidal Río Maullín and an inundation limit nearly 5 km inland across the plain. Along this profile at Caulle, where the maximum flow depth was a few meters deep, airphotos taken in 1961 show breaches across a road on a sandy beach ridge. Inland from one of these breaches is a fan with branched distributaries. Today its breach holds a pond that has been changing into a marsh. The 1960 fan deposits, as much as 60 cm thick, are traceable inland for 120 m from the breach. They rest on a pasture soil above two additional sand bodies, each atop its own buried soil. The earlier of the pre-1960 sand bodies probably dates to AD 1270-1400, in which case its age is not statistically different from that of a sand sheet previously dated elsewhere near Maullín. The breach likely originated then and has been freshened twice. Evidence that the breach was freshened in 1960 includes a near-basal interval of cobble-size clasts of sediment and soil, most of them probably derived from the organic fill of pre-1960 breach. The cobbly interval is overlain by sand with ripple-drift laminae that record landward flow. The fan of another breach near Maullín, at Chanhué, also provides stratigraphic evidence for recurrent tsunamis, though not necessarily for the repeated use of the breach. These findings were anticipated a half century ago by description of paired breaches and fans that the 1960 Chilean tsunami produced in Japan. Breaches and their fans may provide lasting evidence for tsunami inundation of beach-ridge plains. The breaches might be detectable by remote sensing, and the thickness of the fan deposits might help them outlast an ordinary tsunami sand sheet.

The present paper concerns a mineralogical characteristic of selected gem deposits. Introductory studies in two localities were conducted since the gem bearing areas occupy one fourth of the area of Sri Lanka, that is a mineralogical and geological phenomenon. Two types of rich deposits situated in central (Ratnapura) and southwestern (Meetiyagoda) parts of the Highland/South-Eastern Complex have been described and presented taking into account their mineralogical curiosities and relatively easy access. They are shown on the geological background of the country mostly built of the Precambrian rocks and three genetic types of deposits: magmatic (pegmatitic), metamorphic and sedimentary.

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