Browsing by Author "Shanika, K.K.A."

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    Assessment of Nitrate and Phosphate Levels in Natural Water Bodies in Badulla District
    (Uva Wellassa University of Sri Lanka, 2020) Siriwardhana, R.G.H.L.; Rangika, G.D.N.; Shanika, K.K.A.; Wijewardana, Y.N.S.
    Water plays a significant role in human life and the environment. Due to the application of pesticides and weedicides in agricultural activities and dumping of solid wastes on open dumpsites, water resources are now in danger near urban and also rural areas of Badulla district. With the rainfall and widely spanned streams, it is very easy to contaminate the water resources in some areas of the Badulla district. The objective of this study was to identify the NO3 - and PO4 3- concentrations of selected natural water bodies in the Badulla district. Water samples were collected from natural water bodies located in all 13 divisional secretariat divisions including Haldummulla, Haputhale, Bandarawela, Ella, Welimada, Uva-Paranagama, Soranathota, Hali-Ela, Lunugala, Passara, Meegahakiula, Kandaketiya, and Badulla during the period from January to December 2019. Onsite measurements of temperature, pH, conductivity, and dissolved oxygen were measured using portable pH, Dissolved Oxygen (DO), and conductivity meters respectively. Laboratory analysis was conducted to determine NO3 - and PO4 3- concentrations using a UV spectrophotometer. The results were compared with the Sri Lanka Standards (SLS 614:2013) for potable water. The results revealed that NO3 - concentrations of all water samples were lying under the SLS potable water quality standards. PO4 3- concentrations of many water samples exceed the maximum permissible level of 2 mg L-1 for potable water. The water sample collected from “Narangahakiula” in Meegahakiula division showed the highest PO4 3- concentration value of 17.6 mg L-1 and all the water samples collected from Soranathota, Ella, Bandarawela, Welimada, Uva Paranagama Meegahakiula, Kandaketiya and some other water samples collected from Haldummulla and Passara showed higher PO4 3- concentration values more than the permissible level. The study indicates that the pollution potential of downstream areas where the catchment is disturbed by human activities. Keywords: Physico-chemical parameter, PO4 3- , NO3 - , Water quality, Water pollution
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    Development of Novel Super Absorbent Polymer Using Banana Pseudo Stem Waste to Increase Water Retention Capacity of Agricultural Soils
    (Uva Wellassa University of Sri Lanka, 2020) Perera, L.S.S.; Shanika, K.K.A.; Wijewardana, Y.N.S.; Senevirathna, M.A.S.R.
    Water scarcity of agricultural fields for irrigation is a huge problem in many parts of Sri Lanka especially in dry zone where it covers 70% of the agriculture production. The objective of this study is to prepare a novel environmentally friendly Super Absorbent Polymer (SAP) using cellulose that extracted from banana pseudostem fibers and study the water retention capacity of SAP amended agricultural soil (AS). Cellulose was extracted from banana pseudo stem fibers by alkaline pretreatment and cross-linked with 3.75% w/w citric acid in the presence of water. Cellulose and prepared SAP was confirmed using Fourier Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD) measurements. The water retention capacity of SAP was investigated with distilled water (DW) and tap water (TW). The water retention ability was examined by soil without SAP and amending SAP concentrations of 0.25, 0.50, 0.75, and 1% w/w for depths of 0-10, 10-20, and 20-30 cm. Soils with dry bulk densities of 1.78, 1.69, and 1.76 g cm-3 in the dry zone and 1.12, 1.34, and 1.35 g cm-3 in the intermediate zone were used to the SAP amendment. The absorption peak at 1724 cm-1 was attributed to ester linkage due to anhydride formation and Full Width at Half Maximum values in XRD patterns for both cellulose and SAP were decreased from 3.020 to 2.950 with increased the crystallinity which confirm the cross-linking of SAP. FTIR and XRD results showed that the banana pseudo stem is a source for cellulose extraction. The maximum water retention capacity of SAP was 67.4 g/g for DW and 57.4 g/g for TW. SAP amended soils showed a significant increase in overall water retention than AS without SAP. The evaporation test showed that 0.75% is the best SAP concentration for water retention in all selected AS. It is needed to test water retention capacity for wet zone AS to get an overall idea about the effect of prepared SAP as the dry and intermediate zone AS showed the significant increase in water retention with the SAP amendment. Keywords: Super Absorbent Polymer (SAP), Banana Pseudo Stem, Cross-linking, Evaporation Test, Agricultural Soils (AS)
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    Understanding the Effect of Unsaturated Hydraulic Conductivity of Surface Soils on Landslide Triggering: A Case Study in Yahalabedda Landslide Risky Area, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Shanika, K.K.A.; Nirujan, B.; Wijewardana, Y.N.S.; Herath, H.M.S.K.; Galagedara, L.W.
    Hydraulic conductivity (K) is one of the most important soil properties for rainfallinduced landslide triggering. Yahalabedda receives higher rainfalls in Northeast and Southwest monsoon seasons and considered a potential landslide risky area in Sri Lanka. The objective of this study was to evaluate the unsaturated K (Kunsat) of surface colluvium soils using a minidisk tension infiltrometer together with relevant basic soil properties. Field investigations were conducted at three soil depths; 0, 30, and 60 cm of a prepared soil profile in September 2019. The infiltration test was conducted at each soil depth using three tension levels of -0.03, -0.02, and -0.01 m. The Kunsat has been calculated using the Kunsat = C1/A, where C1 is the slope of the curve of the cumulative infiltration versus the square root of time, and A is a value relating the van Genuchten parameters for a given soil type to the suction rate and radius of the infiltrometer disk. Kunsat increased with the soil profile depth for each tension value. Kunsat values for -0.03 m tension, are 1.35 × 10-6, 2.62 × 10-6 and 7.77 × 10-6 m s-1 ; for -0.02 m tension, are 2.13 × 10-6, 3.91 × 10-6 and 1.02 × 10-5 m s -1 and for -0.01 m tension, are 4.23 × 10- 6, 7.86 × 10-6 and 1.42 × 10-5 m s-1 for 0, 30 and 60 cm depths, respectively. Kunsat increases with decreasing the tension values at each depth as expected. 0 and 30 cm depths show nearly the same bulk density (1.0 g cm-3 ), while the 60 cm depth shows higher bulk density (1.1 g cm-3 ). The soil texture is clay loam for the entire soil profile while the uniformity coefficient (Cu) is higher (6.8) in upper soil resulting in a lower chance to interlock between soil particles and higher pore spaces. As the Kunsat increases with the depth, more water will be percolated to deeper soils resulting in the increasing soil weight in deeper soils and the landslide risk. The study reveals that the Yahalabedda area has a threat to landslide triggering in rainy seasons. Keywords: Minidisk tension infiltrometer, Hydraulic conductivity, Infiltration, Landslide risky soils
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    Variability of Unsaturated Hydraulic Conductivities of Landslide Risky Soils in Uva Province of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Nirujan, B.; Shanika, K.K.A.; Wijewardana, Y.N.S.; Galagedara, L.W.
    Localized slope failures resulting in massive landslides can occur during the rainy season in the central highlands of Sri Lanka. The objective of this research was to measure and assess the variability of the field hydraulic conductivities using a minidisk tension infiltrometer. The selected sites were located in Uva Wellassa University of Sri Lanka, Haputale, Haldummulla, and Meegahakiula which are located in the Uva province of Sri Lanka. Using the minidisk infiltrometer, infiltration rates were measured for soil depths of 0-5, 30-35, and 60-65 cm under suction levels of -3, -2, -1, and -0.5 cm. Soil core samples were collected to measure bulk densities of respective soil depths while the soil textural class was identified using the simple method of feeling by hand. The field moisture content was measured using the oven-dry method. Sieve analysis was performed to identify particle size distribution and coefficient of uniformity. Field hydraulic conductivity values were calculated using infiltrometer readings with respect to each suction rate and soil texture class for all three depths. Textural classes of tested soils were identified as clay loam to sandy clay loam and the coefficient of uniformity value is ranging from 4.4 to 6.8. The gravimetric moisture content of soil samples ranged from 0.021 to 0.233 g g-1 for all sites and bulk density ranged from 1.0 g cm-3 to 1.5 g cm-3 . The highest unsaturated hydraulic conductivity 6.9 × 10-5 m s-1 was observed in Meegahakiula soil at -0.5 cm suction at a gravimetric moisture content of 0.212 g g-1 for 60-65 cm depth. The lowest hydraulic conductivity 1.0 × 10-6 m s-1 was observed in the Uva Wellassa University site at -3 cm suction at a gravimetric moisture content of 0.040 g g-1 for 0-5 cm depth. Identifying relationships between hydraulic conductivity and the soil properties individually and developing prediction equations to demarcate landslide risky areas are expected to be done in the future. Keywords: Slope failure, Hydraulic conductivity, Suction, Minidisk infiltrometer