iPURSE 2015
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- ItemSpatial variability of soil properties in a calcic red latosol soil scape in the nothern area of Sri Lanka(University of Peradeniya, Sri Lanka, 2015-11-06) Nerogini, S.; Vitharana, U.W.A.; Karunainathan, T.The information on the spatial variability of soil properties is vital for the better management of soil and to increase the crop productivity. This study was conducted to explore the short-scale spatial variability of selected chemical and physical soil properties of a Calcic Red Latosol soil scape in the Alaveddi area in the Jaffna district. The study area consisted of 2.5 ha and samples were collected within the plough depth (0- 30 cm) by using stratified random sampling scheme. This was achieved by firstly defining a sampling (spacing 29 x 29 m) grid. Subsequently, a random sample was added within each grid cell. The variability of soil clay content, silt content, sand content, organic matter (OM), pH (soil to water ratio of 1:2.5) , electrical conductivity (EC) (soil to water ratio of 1:5) were investigated for all the samples (n=40) and available phosphorous, exchangeable potassium were investigated for selected samples (n=9) by means of classical and geo statistical analysis techniques. The coefficient of variation of properties ranged from 4% (pH) to 32% (clay content). The experimental variograms calculated for soil properties were best fitted with spherical model. According to the relative nugget effect (RNE -ratio of nugget to the sill) of variograms, the clay content, sand content, silt content, electrical conductivity and organic matter exhibited a highly spatially structured variability (RNE < 25 %), whereas a medium structured variability was observed for soil pH (RNE 25-75 %). The observed spatial dependencies of soil properties indicated that sampling space for future studies can be ranged from 20 m (pH) to 70 m (sand). The maps of texture, OM further illustrated a strong short-scale spatial variability indicating the potential of site-specific soil management in the study area.
- ItemP-T-t Evolution of calc-silicate rocks in the South-Western highland complex of Sri Lanka(University of Peradeniya, Sri Lanka, 2015-11-06) Sameera, K.A.G.; Perera, L.R.K.Recent studies on calc-silicate rocks from the Southwestern Highland Complex of Sri Lanka have renewed the interest on the reconstruction of the P-T-t and fluid evolution in this part of the island. Present study is another contribution to understand the P-T-t path and fluid conditions of the calc-silicate lithologies around Galle and Middeniya-Embilipitiya areas in the Southwest. Based on petrography and mineral assemblages, the studied calc-silicate lithologies can be subdivided into three main groups; Group I – wollastonite-bearing but grossularite-absent assemblages, Group II – grossularite-bearing but wollastonite-absent assemblages, Group III - both wollastonite and grossularite-absent assemblages. Formation of different assemblages is possibly a result of peak metamorphic P, T conditions, the chemistry of protoliths, graphite precipitation and response to fluctuation of level during prograde path. Critical reaction textures in Group I lithologies indicate breakdown of, (1) wollastonite calcite + quartz, (2) wollastonite + dolomite → calcite + diopside, (3) scapolite → calcite + quartz + plagioclase, (4) alkali feldspar + wollastonite → scapolite + quartz + K+, that are important in re-constructing the P-T-t evolution of the terrain. Diopside rims around quartz in Group II assemblage suggest the reaction, (5) dolomite + quartz → diopside + CO2. In addition, local occurrences of fluids involving reaction textures such as myrmekitic intergrowth of plagioclase + quartz between calcite + K-feldspar and replacement of diopside by hornblende have been observed in calc-silicate rocks from the study area. Peak metamorphic assemblage of the Group I suggests a stabilization temperature of about 800-8500C at 5 kbar, and 0.2 in the fluid phase. The retrograde reactions (1), (2) and (3) suggest isobaric cooling (IBC) following peak metamorphism during which internal fluid buffering prevailed. But the IBC reaction anorthite + wollastonite → grossularite + quartz, noted from elsewhere was not present in the studied samples perhaps due to lower lithostatic pressure in the study area. The reactions (4) and (5) suggest isothermal decompression (ITD) following the IBC path, and other fluid involving reactions noted in the study area suggest both hydration and influx during final stages of metamorphic evolution. The retrograde reaction textures in the studied calc-silicates and the inferred IBC and ITD P-T-t segments for the Southwestern Highland Complex correlate well with the results of previous P-T-t studies of calc-silicate, pelitic and mafic rocks in the Highland Complex. Further, presence of grossularite-absent assemblages, the reaction textures (1), (3) and (4), and the inferred P-T-t path for the study area strongly correlate well with mineral assemblages, reaction textures and P-T- t evolution in the Kerala Khondalite Belt within the Trivandrum Block of Southern India.
- ItemImpacts of sea level rise and bed level accretion on residence time of Negombo lagoon, Sri Lanka(University of Peradeniya, Sri Lanka, 2015-11-06) Pushpakumara, P.K.P.; Nandalal, K.D.W.; Weerakoon, S.B.Water quality of an aquatic system is highly influenced by residence time (RT), which indicates how long a constituent is retained inside the system. This paper focuses on the effect of climate change induced future sea level rise (SLR) and associated bed level variations on RT of Negombo lagoon, Sri Lanka. The hydrodynamic behaviour of the lagoon was numerically simulated using Delft3D surface water modelling suite. The time required to drop the concentration of a constituent to of its original value was calculated as the RT of the lagoon. Anticipated maximum SLR of 79 cm at the end of the 21st century, predicted by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, was considered as the future sea level of the lagoon. Three bed level accretion conditions, namely, no bed level accretion, accretion of the lagoon bed level by 50% of the SLR (partial bed level accretion condition) and accretion of the lagoon bed level similar to the SLR (full bed level accretion condition), in response to the anticipated SLR were considered. RT was calculated for each bed level variation under low (5.64 ) and high (41.93 ) streamflow conditions. Model predicted RTs of the lagoon at present are 22.4 days and 12.4 days under low and high streamflow conditions, respectively. Under the absence of bed level accretion, RT is increased up to 32.2 days (+43.7%) and 17.8 days (+43.5%) due to SLR in low and high streamflow periods, respectively. Under partial bed level accretion, RT is decreased up to 18.1 days (-19.2%) and 12 days (-3.2%) in low and high streamflow periods, respectively. RT is decreased up to 13.4 days (-40.2%) and 8.5 days (-31.5%), under full bed level accretion, in low and high streamflow periods, respectively. The results reveal that the climate change induced future SLR and the associated bed level accretion influence the RT of the lagoon altering the lagoon water quality.
- ItemFluoride uptake by native and modified cattle bones from aqueous medium by batch adsorption(University of Peradeniya, Sri Lanka, 2015-11-06) Gunathilake, B.A.P.T.; Iqbal, M.C.M.; Sumanasinghe, V.A.Fluoride is found in excess compared to the WHO recommended levels in drinking water in the Kandy district. Health hazards such as dental fluorosis, skeletal fluorosis, crippling fluorosis and metabolic defects in lipids, proteins and vitamins are caused due to excess Fin drinking water. Among several defluoridation techniques, adsorption is the most effective and common method. The objective of this study was to investigate the effectiveness of the natural, economically feasible and eco-friendly materials such as plant leaves and cattle bones for removing fluoride ion from drinking water using batch adsorption method. Bio-adsorbent materials were collected and rinsed initially with tap water, and then with deionized water. Cleaned materials were air dried for 48 h and oven dried at for 48 h. Dried materials were sieved to obtain particle size between 250 – 350 μm. Batch adsorption experiments were conducted. A mass of 0.2 g of different adsorbents was added in 50 mL of 3 mg fluoride solution and shaken at 80 rpm in orbital shaker for 3 h. Thereafter, suspension was filtered and final Fconcentration was determined by fluoride ion-selective electrode. Chemical and physical modifications such as base treatment and bone char preparation were done to enhance the adsorption efficacy. Native bones were heated at 500oC for 3 h in muffle furnace to prepare bone char (BC). Effect of contact time and dosage were determined for chemical modification and effect of pH, kinetic studies, isotherm studies, desorption and adsorbent characterization for BC were carried out. adsorption on BC was maximum between pH 4-7 and equilibrium time for BC was 12 h. Pseudo second order kinetic model and Langmuir isotherm model described adsorption of on BC. The highest desorption was given with 0.1 M NaOH. BC enhances the efficacy of defluoridation from aqueous medium and is a cost effective and eco-friendly biosorbent.
- ItemInteraction of ferrous ions and free chlorine on microbiological quality of drinking water(University of Peradeniya, Sri Lanka, 2015-11-06) Munasinghe, T.S.; Abayasekara, C.L.; Chandrajith, R.; Jayawardana, A.University of Peradeniya has a nearly 60 year’s old water distribution network that consists mainly iron pipelines, most of which are now corroded to a large extent, adding iron rust to water. The aim of this study was therefore to investigate the possible consumption of free chlorine that added in to water for disinfection by iron dissolved from pipes. If free chlorine is reduced due to iron, the available amount of free chlorine would not be sufficient for the disinfection of microorganisms in water. A laboratory simulated study was carried out to investigate the possible reaction between ferrous ion and free chlorine in water using a series of and free chlorine mixtures. The effect of the reaction on the inhibition of microorganisms were also determined by spiking Serratia spp. (a total coliform) and Escherichia coli (a fecal coliform) into known mixtures of and free chlorine. The and free chlorine contents were measured spectrophotometerically while viable microbial count was assessed using membrane filtration technique that followed a confirmation tests. Furthermore free chlorine and microbiological quality were determined periodically using 27 water samples that were collected from various points of the University network. The results of this study indicated a rapid reaction between and free chlorine. The rate of free chlorine reduction was directly proportional to the amount of in water. Although inhibition of Serratia spp. and E. coli was observed due to free chlorine in water, the effect reduced drastically with increasing in water. Serratia sp. decreased gradually with the ascending chlorine levels at levels of 0.2 and 1.0 mg/L. Total inhibition of Serratia sp. were observed at 2 and 3 mg/L of while E. coli was inhibited at levels of 1.0, 2.0 and 3.0 mg/L. The content in the water distribution network of University of Peradeniya were ranged from <0.01 mg/L to 0.64 mg/L (desired value is <0.3 mg/L), while the desired free chlorine level (0.2 mg/L) was observed only at two locations (Faculty of Veterinary Science and Meewathura treatment plant). Total coliforms were detected in samples collected from Upper Hanthana, Marcus Fernando Hall, University Temple, Science Faculty, Mars Hall and Medical Faculty, while fecal coliforms were detected only in a sample from Marcus Fernando Hall. The results of microbiological test showed that water distributed from the Kandy Municipal Council and Meewathura plants are suitable for drinking, but water distributed from the Upper Hanthana plant was not suitable for human consumption according to the World Health Organization (WHO) Standards (0/CFU per 100 ml for both total and fecal coliforms) and Sri Lankan Standards (3/CFU per 100 ml for total coliforms and 0/CFU per 100 ml for fecal coliforms). The possible reason behind the unsuitable microbiological quality of water may be related to the reaction between and free chlorine in water. It was also noted that, a high level of in water was inhibitory to microorganisms in water and remove bacteria by formation of clumps.