Browsing by Author "Vithana, P. V. A. S."

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Abundance and distribution of microplastics in Muthurajawela wildlife sanctuary and Pamunugama beach, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Sandaruwan, U. A. C.; Vithana, P. V. A. S.; Sithumini, W. E. B. K.; Samaraweera, B. G. K. N. D. B.; Tharani, T.; Gallage, C.V.; Subasinghe, K.; Vidanage., S. P.
Microplastics (MPs), defined as plastic particles less than 5 mm, are increasingly recognized as a global environmental threat impacting marine and terrestrial ecosystems. This study investigates the prevalence, distribution and characteristics of MPs in the lagoon and coastal sediments of Muthurajawela Wildlife Sanctuary and Pamunugama Beach in Sri Lanka, areas interconnected through the Negombo Lagoon. Sediment samples were collected from 14 locations (06 from the Muthurajawela lagoon and 08 from the Pamunugama beach) distributed in both in low-tide line and mid-tide line identified through systematic sampling method. From each location, three replicate samples were collected to form a composite sediment sample and 20g of oven-dried sediment was used for analysis of MPs after performing a density separation on the sieved sample. The abundance, size, and shapes of MPs were examined using a stereomicroscope using “Optica TCB5.0” software. Observed MPs were divided into two size ranges: 5 mm – 1.1 mm and 1 mm – 0.5 mm and defined as “large MPs” and “small MPs” respectively. MPs were divided into five categories of shapes: fragments, filaments, films, foams and pellets. Findings indicated a higher abundance of MPs in Pamunugama Beach sediments (79.3 ± 10.3 MPs/Kg) compared to Muthurajawela lagoon (58.0 ± 10.8 MPs/Kg). In Muthurajawela, smaller MPs were more prevalent (79.87%) than larger MPs (20.12%), with a statistically significant difference (p<0.05; Two-sample T test) while Pamunugama Beach showed no significant difference in the abundance of large and small MPs. The abundance of total MPs was not significantly different between low and mid-tide lines at both study sites suggesting a low spatial variability in abundance (p>0.05; Two-sample T test). The most common MP shape in Muthurajawela was filaments (78.8%), while fragments (61.53%) dominated Pamunugama Beach. The study also underscores the impact of the MV X-Press Pearl ship disaster on Pamunugama Beach, contributing to the higher MP levels observed. MPs in Muthurajawela were primarily filament-shaped, likely sourced from urban wastewater and industrial activities, whereas Pamunugama Beach exhibited more fragment-shaped MPs due to recreational activities and natural fragmentation processes driven by coastal dynamics. These findings provide critical baseline data for long-term monitoring and highlight the need for targeted mitigation strategies. Future research should focus on the ecological impacts of MP pollution, particularly on wetland birds and other wildlife in these regions. Comprehensive studies examining the sources, pathways, and ecological consequences of MPs will further inform conservation efforts and policy decisions, ultimately contributing to the protection of Sri Lanka's unique coastal and wetland ecosystems.
Comparison of adsorption characteristics of Ni(II) on fibres of Agave americana and areca nut husk
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wickramasinghe, W. R. M. N. R.; Vithana, P. V. A. S.; Karunathilaka, R. M. M. K.; Priyantha, N.
Heavy metal contamination is of major concern at present due to its adverse impacts on humans and the environment. Among many heavy metal remediation methods, biosorption has become attractive in the recent past due to its low-cost and environmentally sustainable nature. Nevertheless, fibrous biosorbents have not been much explored, especially for the removal of Ni(II) species. Though Ni is a micronutrient that contributes to certain cellular functions in the human body and plants, higher concentrations of it could impose adverse health effects as well as ecological damage. Hence, Ni remediation should be carried out before releasing industrial effluent to the environment. This work is thus based on a comparative study to investigate the adsorption potential of Agave americana fibre and Areca nut husk fibre for the removal of Ni(II) ions from aqueous solutions. This study aims to optimize experimental parameters varying one parameter at a time throughout a broad range keeping others constant for the two biosorbents separately. Both Agave americana fibre and Areca nut husk fibre exhibit significant adsorption capacities toward the adsorption of Ni(II) ions with average removal of 90.39% and 93.27%, respectively, in batch experiments, conducted using 10 mg L-1 Ni(II) solution under optimized conditions of 60 min shaking time, 20 min settling time, ambient pH, ambient temperature and 150 rpm agitation speed for an optimum dosage of 20.00 g L-1 of the biosorbents. Adsorption isotherm studies, conducted using Ni(II) solutions of initial concentrations in the range from 10 mg L-1 to 350 mg L-1, show that the Langmuir model is a better fit for the two types of fibre with higher regression coefficients of 0.9836 and 0.9937 than those of the Freundlich model for Agave americana and Areca nut husk fibre, with the maximum adsorption capacities of 1.03 mg g-1 and 1.68 mg g-1 respectively. These studies could be extended for the design of treatment plants for large-scale removal of Ni(II) ions from contaminated water.