Browsing by Author "Ariyawansha, J. M. M. S."

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    Comparison of sensitivity of Lemna perpusilla (minute duckweed) to chromium, nickel, and zinc ions
    (Faculty of Science, University of Kelaniya Sri Lanka, 2022) Ariyawansha, J. M. M. S.; Pathiratne, A.
    In recent times, the pollution of tropical aquatic ecosystems due to heavy metals has become a great issue. The major sources of heavy metal pollution in aquatic ecosystems are effluents from metal-based industries and municipal wastewater. Duck weeds (Lemna species) are widely used in the treatment of wastewater and sewage effluents as they have the ability to absorb nutrients in the wastewater effectively. The species, Lemna minor and L. gibba generally represent temperate areas while L. perpusilla is native to Southeast Asia. Objective of the present study was to compare the sensitivity of L. perpusilla to chromium (Cr), nickel (Ni), and zinc (Zn) ions under tropical temperature exposure based on standard laboratory ecotoxicity tests. Growth reduction of L. perpusilla under Cr, Ni, and Zn exposure was assessed using a standard ecotoxicity procedure with a range of metal ion concentrations (Cr6+: 0, 12, 30, 60, 90 and 120 mg/L; Ni2+: 0, 0.03, 0.06, 0.15, 0.30 and 0.60 mg/L; Zn2+: 0, 0.1, 0.25, 0.5, 1.0 and 2.0 mg/L). Toxicity thresholds of Cr6+, Ni2+ and Zn2+ for the duckweed L. perpusilla under tropical temperature exposure (27°C - 29°C) were estimated based on multiple endpoints (total number of fronds, percentage of green fronds and green frond area). Triplicate test vessels were used for each concentration and the controls. The average specific growth rate and percent inhibition growth rate for each treatment and control replicate were determined. Metal contents in the exposure media were analytically verified using atomic absorption spectrophotometry. One way ANOVA followed by Dunnett’s test was used to estimate the lowest observed effect concentration (LOEC) for each endpoint. Effective concentrations of metals at different percentile effect levels (EC50, EC20, EC10 and EC5) were estimated through nonlinear regression modelling using USEPA Toxicity Relationship Analysis Program software. Based on different endpoints used for the toxicity assessments, lowest observed adverse effect concentrations (7 day LOAEC) for growth reduction of L. perpusilla for Cr6+, Ni2+, and Zn2+ were estimated as 21 mg/L, 0.06 mg/L, and 0.26 mg/L, respectively. For growth reduction of L. perpusilla, the most sensitive 7-day effective concentration for 10% effect (EC10) for Cr6+, Ni2+, and Zn2+ were 21 mg/L, 0.021 mg/L, and 0.2 mg/L, respectively. In conclusion, the sensitivity of L. perpusilla to the three metal ions followed the decreasing order: Ni2+ > Zn2+ > Cr6+. This study revealed that L. perpusilla is more sensitive to Ni2+ than Cr6+ and Zn2+. Of the three metals tested, Cr6+ exposure could be most tolerated by L. perpusilla.
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    Selecting suitable locations to establish a ground solar farm in Trincomalee District in Sri Lanka using GIS
    (Faculty of Science, University of Kelaniya Sri Lanka, 2023) Senadeera, T. S. M.; Bandara, W. M. J. Y.; Herath, H. M. A.; Ariyawansha, J. M. M. S.; Weerasinghe, V.P.A.
    Renewable energy is energy derived from natural sources that are regenerated at a higher rate than consumed. One of the examples of the most effective renewable energy sources is solar energy, which is derived from the sun. Solar energy can be extracted directly or indirectly for human use. With the rapid growth in energy demand, solar energy has led to an increased interest in power generation. In Sri Lanka, solar energy investments have developed rapidly in recent years. The ground solar farm is one of the solar energy harvesting types for electricity generation, especially at the industrial level. Our main focus is to provide an additional power supply to the National Grid of Sri Lanka, and this study focuses on utilising Geographic Information Systems (GIS) to identify suitable areas for establishing a ground solar farm in the Trincomalee District, Sri Lanka. Trincomalee District has a tropical wet and dry climate with high sunlight. According to that Trincomalee District was selected as the study area by considering solar irradiation and by focusing on the cumulative solar power plant capacity in Sri Lanka. According to the literature review, various factors can be useful for selecting locations for a ground solar farm. Land surface temperature, slope, land use, and proximity to roads were selected as criteria for this case study. The separate criterion maps were generated and they were reclassified according to the requirements, and those were used with Analytical Hierarchical Process (AHP) to find the weights for overlay analysis in GIS. The resulting final factor map shows a land area of 24.47 km2 for Trincomalee District as highly suitable for establishing a ground solar farm. This case study aims to reduce the overconsumption of natural resources that are used to produce energy and to ensure the protection of the environment through using renewable energy.