ICAPS 2024

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Facile synthesis of cyclic polyphenylene oxide as an electroactive supramolecule
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wadumethrige, S. H.; Rathore, R.
Heteroatom containing polymers such as polyphenylene sulfides, polyanilines, and polyphenyl ethers are known to have high chemical and thermal stability. Polyphenyl ether is one of the most important engineering plastics and their structures contribute to the toughness, strength, and thermal performance. Although various substituted polyphenyl ethers are studied for their enhanced polymer properties, supramolecular polyphenyl ethers are largely unexplored. Therefore, the objective of this research is to synthesize and study a cyclic polyphenylene oxide. In this study a supramolecular ether structure, cyclic polyphenylene oxide with six phenoxy units was successfully synthesized by using N,Ndimethylglycine prompted Ullmann coupling, characterized by 1H/13C NMR spectroscopy, and the redox properties were evaluated by cyclic voltammetry. The cation radical was generated by using NOSbCl6 and studied using NIR spectroscopy. The cyclic voltammogram of cyclic polyphenylene oxide shows three oxidations (1.53, 1.78, 1.83 V vs SCE). The first oxidation is reversible, and the others are quasi reversible. The reversibility of the first oxidation at 1.53 V vs SCE predicts the potent use of the cyclic polyphenylene oxide in secured repeated redox processes in molecular electronics. The absorption band around 1600 nm in the cation radical spectrum suggests the coupling between aryl groups. The availability of reversible oxidations and interactions between aryl groups suggest that the cyclic polyphenylene oxide is a promising candidate for applications in emerging areas of molecular technology.
Investigating the effluent quality of a sewage treatment plant in the Kelaniya area: A temporal analysis
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Jayasekara, J. M. P. M.; Najim, M. M. M.
Sewage treatment focuses on effectively removing contaminants from sewage to produce an effluent that is safe for discharge into the environment or reuse. Monitoring the effluent quality of a wastewater treatment plant is crucial for maintaining the treated effluent quality. There are growing concerns about the potential environmental impacts of the selected sewage wastewater treatment plant (SWWTP). However, there is a lack of comprehensive research to assess the actual impact of SWWTP on the local environment. Hence, the current study investigated the quality of the effluent of the selected SWWTP. This study was conducted by analysing variations of effluent quality parameters over 6 months (August 2023 to January 2024). Water samples were collected monthly and analysed for key water quality indicators using APHA methods. Temperature, pH, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), conductivity, salinity, and flow velocity were measured as key water quality indicators. The values of each parameter were compared with the tolerance limits for the discharge of wastewater or effluent into Inland Surface Waters presented by the National Environmental (Protection and Quality) Regulations. The temporal variations of the studied parameters of water samples were statistically analysed using a One-way ANOVA. Results suggest that COD values exceeded the standard values in August (654±16.8 mg/L), October (336.5±35.4 mg/L), November (273±16.8 mg/L), and January (95.2±11 mg/L). TSS values exceeded the standard values in August (87±14.2 mg/L) and October (60±1.74 mg/L) and Dissolved oxygen did not reach the standard values in October (4.47±0.09 mg/L) and November (4.46±0.03 mg/L). Nitrate concentration exceeded the standard values in August (16±1.14 mg/L) and January (13.54±1.04 mg/L). All the other parameters lay within the range of standard values. The cluster analysis of water quality parameters was used to identify the similarities between the sampling sites, and it revealed that effluent released into the environment in August has very different water quality values than other sampling months. All the parameters except pH exhibit significant temporal fluctuations. Low DO level suggested limitations in the aeration process or overload of the organic matter. Low DO levels can affect microbial activities and chemical reactions. Ultimately this can lead to elevated levels of COD and BOD. In addition, sand filtration and carbon filtration are not sufficient to remove soluble organic matter in the water. Therefore, it can be concluded that this treatment plant has some environmental implications due to high COD, TSS, DO, and nitrate levels. Further analysis of each step of the wastewater treatment plant is needed to thoroughly understand the causes of variations in the water quality parameters.
Evaluating heavy metal accumulation in Scylla serrata (mud crabs) inhabiting the Negombo lagoon, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Dias, B. C. G.; De Silva, D. S. M.; Amarathunga, A. A. D.; Bakir, A.; McGoran, A. R.; Sivyer, D. B.; Reeve, C.
A multitude of anthropogenic and industrial uses lead to the extensive dispersion of heavy metals in aquatic environments. The protracted presence and poisonous nature of heavy metals inflict negative impacts including organ malfunction and the inactivation of enzymes in aquatic organisms. The bottomdwelling mud crabs are frequently used as bioindicators for evaluating such heavy metal contamination in lagoons and estuaries. Therefore, the main emphasis of this study was on the amounts of heavy metals found in the meat of the Scylla serrata mud crab that lives in Negombo Lagoon, Sri Lanka. Due to their great sensitivity, mud crabs, bottom dwelling crustaceans that live in the bottom zones of lagoons, are frequently utilized as indicators for evaluating heavy metal contamination. Mud crab samples (n = 42) were randomly collected from the Negombo Lagoon from March to May 2023. Three replicates, 1 g each, of the flesh from each crab sample, were treated to acid digestion (conc. HNO3 and H2O2) and analysed separately using an atomic absorption spectrophotometer (AAS). Cu, Fe, Mn, and Zn were found to be the most common heavy metals in crab flesh based on the metal analysis. The amounts of Cd and Cr were not detectable. Zn (0.70 ± 0.24 mg/L) was the most prevalent heavy metal in the meat, followed by Mn (0.08 ± 0.07 mg/L), Cu (0.15 ± 0.12 mg/L), and Fe (0.46 ± 0.30 mg/L). The study's findings support the notion that the mud crabs living in the Negombo Lagoon have heavy metals in their meat. A recent study offers strong proof that heavy metals are present in mud crabs, a popular edible shellfish in Sri Lanka. The Negombo Lagoon's whole food chain may be affected by this contamination.
Change detection of vegetation cover in Kurunegala district by using remote sensing approach
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Imbulana, I. B. A. C.; Jayasinghe, V. S.; Peramune, P. R. S. N.; Samaraweera, S. A. P. T.; Weerasinghe, V. P. A
The amount of vegetation cover has reduced over time due to the rapid increase in population, expansion and intensification of agricultural activities, and unsustainable use of resources worldwide. This leads to significant negative impacts on the ecosystems. Although several studies have been carried out on vegetation change in Sri Lanka, there is little or no information available in Kurunegala District. Therefore, the objective of the present study was to assess the extent of changes in areas with healthy vegetation cover in Kurunegala District of Sri Lanka, through examining the Normalized Vegetation Index (NDVI) over a period of 10 years from 2013 to 2023. NDVI was employed to determine the growth condition of vegetation. Remote sensing data from Landsat-8 OLI/TIRS images were used to perform NDVI analysis. The area was classified into no vegetation and vegetation and the values above 0.3 were considered as the vegetation. The obtained NDVI maps were reclassified, and the resulting maps were converted to vector maps. The final values were used to compute the area under no vegetation and vegetation. The results of the present study indicated a significant vegetation cover change between 2013 and 2023. The results revealed a conversion of 1424.95 km2 area from no vegetation to vegetation and a conversion of 550.57 km2 area from vegetation to no vegetation. In addition, 669.98 km2 of no vegetation area and 2253.35 km2 of vegetation area have remained unchanged. The vegetation area, which was initially 2804.32 km2 in 2013, had expanded to 3678.79 km2 in 2023, reflecting a 31.18% transformation of no vegetation areas to vegetation areas. Thus, it can be concluded that the vegetation cover area in the year 2023 had increased compared to 2013. However, NDVI does not differentiate between various types of vegetation, such as agricultural crops and forests, which is a limitation of this study. Enhancing sustainable land management, strengthening environmental policies, promoting community involvement and continuous monitoring are crucial for further expansion of the vegetation cover in Kurunegala District
Intracellular peloton colonization and mycorrhizal associations in epiphytic orchid roots
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Disanayaka, D. M. H. A.; Thathsarani, Y. K. D. D.; Edirisinghe, P.; Senanayake, S. P.
Orchids are highly valued for their esthetic beauty and economic significance, playing a vital role in the global floriculture industry. In their natural habitats, orchids heavily depend on mycorrhizal associations, which influence seed germination, protocorm growth, and nutrition. Despite their importance, understanding these associations remains a challenge. In Sri Lanka, there is limited knowledge exists on the root-associated fungal species interacting with epiphytic orchids and their ecological roles. Exploring the endophytic fungal microbiome in these orchids helps in identifying fungi that form mycorrhizae in epiphytic habitats, paving the way for effective cultivation and developing novel conservation strategies. Intracellular entangled hyphal coils that colonize within the cortex of the roots of epiphytic orchids are known as pelotons. Knowledge of the presence and the distribution of pelotons is crucial for understanding the symbiotic relationships between orchids and mycorrhizal fungi. Therefore, the objective of this study was to investigate the distribution of pelotons in the roots of selected epiphytic orchids. In the present study, sixteen wild-grown and cultivated epiphytic orchid roots belonging to genera, i.e. Dendrobium, Arachnis, and Vanilla were randomly collected from four study sites in tropical lowland, wet and intermediate zones in Sri Lanka. Microscopic imaging of microtome sections was employed to observe the peloton colonization within the randomly sampled orchid roots. Longitudinal and cross-sectional analyses of six orchid root samples revealed sparse colonization of fungal hyphae. Extensive peloton colonization was observed only in the roots of two specimens of Dendrobium sp. and in one specimen of each Arachnis sp. and Vanilla sp. indicating the presence of mycorrhizal fungi in the roots. However, peloton colonization was not found in all the sampled roots of the studied genera. Furthermore, microscopic observations showed that intracellular pelotons were predominantly colonized in the cortex at approximately two centimeters beyond the tip of the roots that are adhered to the substrate. Pelotons were observed as thin hyphal masses ranging from circular and irregular to elongated shapes with hyphae often knotted or spiraled in various dimensions. The study highlighted that wild Dendrobium sp. from Avissawella, Western province, exhibited the highest peloton colonization (5–6 per root cortical cell) with both circular and elongated shapes. In contrast, Arachnis sp. had one irregularly shaped peloton per root cortical cell. Dendrobium sp. from Mahawa, Northwestern province showed both circular and irregular pelotons while Vanilla sp. from Kelaniya, Western province displayed the lowest colonization with irregular pelotons. Irregularshaped pelotons are predominantly found except in Dendrobium sp. from Mahawa, Northwestern province underscoring geographic and genus-specific influences on peloton morphology. These findings enhance the understanding of mycorrhizal associations in orchids and provide valuable information for future research on orchid-mycorrhizal symbioses and their ecological significance.
Block encryption and decryption of a sentence using decomposition of Generalized Peterson graph
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Dilushani, S. A. S.; Wijesiri, G. S.
In the modern digital era data breaches and cyberattacks threaten the integrity of global communications more frequently. Cryptography stands as the frontline defense, safeguarding sensitive information against unauthorized access. Encryption and decryption are two cryptographic techniques that conceal and transmit critical information to authorized individuals without the interference of a third party in a network. Cryptography relies on mathematical concepts such as number theory, graph theory, group theory, probability theory, statistics and algebra. Graph theory enhances cryptographic security by utilizing the complexity of graphs, which pose significant challenges to potential attackers. There are mainly two types of cryptographic algorithms as private key cryptosystem and public key cryptosystem. This research introduces a novel cryptosystem utilizing the Generalized Peterson graph GP (7,2). After analyzing various generalized Peterson graphs GP(7,2) was selected for its properties in graph decomposition. We use graph decomposition theories to develop the cryptosystem. The main advantage of choosing GP (7,2) is that, by decomposing GP (7,2), 𝐶7, 𝑃4, 2 copies of 𝑃2and 3 copies of 𝑆3 can be generated. An encryption and decryption scheme utilizing GP (7,2) is proposed, incorporating these subgraphs to enhance cryptographic operations. Security is further enhanced by employing 10 lists of arithmetic progression as coding tables. Additionally, the binary digit labeling for path 𝑃4 and an encoding table for frequently used symbols are introduced to increase the robustness of the cryptosystem. An algorithm is developed and tested to validate the proposed methodology, confirming its effectiveness and reliability. Results indicate that the proposed methodology effectively encrypts, and decrypts sentences of variable lengths, showcasing its flexibility compared to other graph based cryptosystems in the current literature. In conclusion, goal of this research was to propose a new private key block crypto system which is based on graphs and graph theory concepts and which could potentially address the limitations in the current literature such as complexity of graph decomposition becoming exponentially difficult with the number of words in the sentence getting higher. And this proposed methodology can be further improved as well. An open area for future work involves expanding the symbol set to include more characters, such as upper and lower case letters, special characters and numbers. This enhancement would accommodate a wider range of inputs in real world scenarios. The decomposition of a Generalized Peterson graph has been chosen, and future work will explore different types of graph techniques to make the cryptosystem stronger and more difficult to hack.
Placental abnormalities observed among stillbirths, Kandy district, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Alahakoon, A. M. S. S.; Rathnayake, C.; Tennakoon, S.; Karunakaran, K.
Stillbirths are a major concern of the health system of a country as it is a tragic event both for the mother and the society. The placenta of a stillborn baby may have evident anatomical and physiological changes that deviate from the typical appearance of a healthy placenta. These variations could be a cause for the foetal demise in utero. Our study aimed to determine remarkable gross abnormalities identified among placentae of stillbirths. A cross-sectional study was conducted in the National Hospital Kandy, Teaching Hospital Peradeniya, Base Hospital Gampola, and District General Hospital Nawalapititya, for one year from April 2017. The placentas, including umbilical cords of stillbirths that completed 22 weeks of period of amenorrhoea were examined to assess the presence of abnormalities. All consecutive cases were included in the study from the beginning for one whole year. Of 213, placentae that had irregular shapes were 4 (1.9%), and all had complete cotyledons. Two (0.9%) had succenturiate lobes, and one (0.5%) had incomplete membranes. Retroplacental blood clots were observed in 48 (22.5%). Placental infarcts were seen in 25 (11.7%). Among the 211 umbilical cords observed, 195 (92.4%) depicted normal insertion at the placental site. Abnormal insertions observed were battledore (n=13, 6.2%), furcate (n=2, 0.9%) and velamentous (n=1, 0.5%). The number of true umbilical cord knots, nuchal entanglement, umbilical cord hemorrhages, and two cord blood vessels were 4 (1.9%), 24 (11.4%), 46 (21.8%), and 1 (0.5%) respectively. The mean umbilical cord length was 39.4cm. Our study found apparent gross abnormalities in the placentas and umbilical cords among stillbirths. Hemorrhages in both placentae and the umbilical cord, and placental infarcts showed higher incidences compared to other changes. Direct impact on the foetus can be found in the cases of true cord knots ceasing blood supply to the foetus, as well as nuchal entanglement that was leading to asphyxia. Furthermore, the mean cord length in the study was shorter than the normal average length. In-depth laboratory investigations are needed to determine their direct or indirect association with stillbirth. Moreover, national-level values for umbilical cord length must be made for future references and better evaluation.
Assessment of cytotoxic and genotoxic effects on Mahaweli river surface water samples contaminated with Gohagoda landfill leachate using Allium cepa bioassay
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Abhayarathna, I. D.; Yatawara, M. D. M. D. W. M. M. K.
Landfill leachate that potentially contains toxic compounds harms humans and the environment. Therefore, landfill leachate must be appropriately treated and disposed to avoid its environmental damage. However, conventional physicochemical analysis alone may not be adequate to evaluate the biological effects, therefore, conducting bioassay toxicity tests and traditional methods would be more appropriate. The present study assessed the potential toxic effect of Mahaweli River surface water samples contaminated with Gohagoda landfill leachate by a plant-based bioassay, Allium cepa. Moreover, the physio-chemical parameters have been tested. Surface water samples were collected from the river where the leachate was released into the Mahaweli River from the leachate outlet on five occasions, covering wet and dry seasons from September 2023 to January 2024. The A. cepa root tips were exposed to collected samples and the bioassay was carried out according to a standard method with some modifications. Aged tap water was used as the control. The statistical analyses were performed as appropriate in MINITAB-19. The study revealed that the A. cepa bioassay indicated significant cytogenotoxic effects on the leachate contaminated surface water compared to the control, evidenced by a percentage decrease in mitotic index (44.60%, 48.81%, 20.99%, 44.41% and 16.91%), the higher number of total nuclear abnormalities (165.20‰, 159.70‰, 154.20‰, 182.86‰ and 162.26‰), and higher number of chromosomal aberrations (352.40‰, 328.10‰, 258.00‰, 254.08‰ and 291.90‰). The presence of toxic substances in the leachate contaminated surface water, suggests a clear cytotoxic effect on exposed organisms. This is further supported by observing various nuclear abnormalities such as bi nuclei, micronuclei, and nuclear buds, predominantly in samples collected from leachate contaminated water, compared to control. These abnormalities indicate genetic damage and potential mutagenic effects, likely stemming from the discharge of leachate into the Mahaweli River. Moreover, chromosomal aberrations, including vagrant chromosomes, chromosomal bridges, and spindle disturbances, underscore the genotoxicity of the leachate. These abnormalities reflect structural changes in chromosomes and spindle apparatus, which can lead to disruptions in cell division and genetic instability. The significantly higher occurrence of these aberrations in leachate contaminated samples compared to control water samples highlights the detrimental impact of leachate contamination on the environment. All the COD and BOD5 values obtained for the leachate-contaminated water exceed the CEA tolerance limit values for all five sampling events. The findings highlight that the leachate discharged directly and significantly impacts the water quality at the leachate discharging point of the Mahaweli River. Further research is recommended to confirm the toxic effects of drained leachate on sensitive aquatic organisms in the Mahaweli River since they provide a better understanding of the risks associated with drained leachate. In addition, strict leachate management measures are recommended to minimize river contamination with this leachate.
Color development and growth performance of Xiphophorus hellerii fed with experimental feeds incorporated with Tagetes erecta petal meal and whole meal of Euphausia sp
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Pathirathne, H. A. K. M.; Parakrama, M. G. I. S
The color intensity of ornamental fishes contributes greatly in determining the value, marketability and demand of the fish. Growth enhancement of fish, leading to reduction of the duration of culture period, could reduce production cost. Therefore, color manipulation and growth enhancement have become priorities of ornamental fish farmers. The use of suitable ingredients in feed formulation and feeding the fish have displayed the potential to achieve those goals ethically and effectively. Therefore, during the present study two experimental feeds were prepared by incorporating Tagetes erecta (marigold) petal meal (Treatment 01) and whole meal of Euphausia sp. (krill; Treatment 02) to the same ingredients used to prepare the control feed. Three groups of Xiphophorus hellerii (Swordtail fish) were maintained separately under equal conditions, except feeding with 03 different feeds, over 84 days. At the end of the experimental period, color intensity was measured using the red value scale in ImageJ software, where a lowest red value indicates strongest color intensity. The fish fed with Marigold feed exhibited the significantly lowest (p < 0.05) red value (117.37 ± 2.35), indicating the deepest intensity of red color and the highest red value (159.32 ± 2.92) was recorded for the control group (having the lowest color intensity. The highest percentage weight gain was recorded for the fish in Treatment 02 (78.90 ± 0.01%) followed by Treatment 01 (56.49 ± 0.01%) and the lowest weight gain (52.22 ± 0.04%) was observed in control treatment (p < 0.05). Significantly (p < 0.05) highest specific growth rate (SGR) (1.85±0.05%) was observed in treatment 02 followed by treatment 01 (0.99±0.01%) while the control treatment had the lowest (0.88 ± 0.06) SGR value. Percentage ash content in marigold petal incorporated feed was significantly higher (16.67 ± 0.31; p < 0.05) than those of control and krill meal based feed (both feeds had the same value; 13.33 ± 0.40). The food conversion ratio of treatment 01 (1.96 ± 0.08) was higher than those of treatment 02 (1.44 ± 0.21) and the control treatment (1.76 ± 0.10). Marigold petal incorporated feed had contributed to a more pronounced development of red color confirming that it could be used for red color enhancement in Swordtail fish. Krill meal had demonstrated that growth promotion in Swordtail fish could be achieved by incorporating krill meal into the feed.
Efficient dye removal from wastewater by using expired rice grain derived biochar: A sustainable solution for water purification
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ranaweera, D. M. S. U.; Vithanage, M.; Ranaweera, S. A.
The accumulation of waste dyes in aquatic systems poses significant risks to human and animal health due to their hazardous and carcinogenic nature. Dyes also interfere with photosynthesis by reducing sunlight penetration in deep water. Although various methods have been developed to remove color contaminants from aqueous systems, there remains a need for cost-effective, environmentally friendly, and efficient adsorbents. Over 350,000 kg of expired rice is disposed of annually from warehouses in Sri Lanka. Because of the rich composition of nutrients in rice, they can be used as raw material to produce biochar. In this study, the remediation of Methylene Blue (MB) from simulated wastewater using biochar produced by pyrolysis of expired rice grains was investigated. Two types of biochar were prepared: non-modified (NMRG) and modified (MRG) through KOH activation. The efficiency of MB removal by these variants was evaluated. FT-IR spectra confirmed the modification of the rice biochar surface with various functional groups through alkali treatment, and Scanning Electron Microscopy (SEM) micrographs showed the opening of meso and macropores in the biochar due to KOH activation. Batch adsorption studies were conducted to determine the effects of MB concentration, pH, temperature, and contact time on MB removal. The optimum pH was found to be pH 4 for both NMRG and MRG, with an optimum contact time of 2 hours. The maximum MB adsorption was observed for a 2000 ppm MB solution at an optimum temperature of 30 °C. Experimental results indicated that MRG exhibited the highest adsorption capacity of approximately 169.93 mg/g with an 84.97% removal rate, while NMRG showed an adsorption capacity of 41.75 mg/g with a 20.88% removal rate. Thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS), and Gibb’s free energy (ΔG) were evaluated for both adsorbates. The ΔS and ΔH values for NMRG were 0.01 kJ mol⁻¹ K⁻¹ and 5.25 kJ mol⁻¹, respectively, whereas, for MRG, these values were 0.13 kJ mol⁻¹ K⁻¹ and 8.55 kJ mol⁻¹, indicating an increase in randomness during adsorption. The enthalpy values revealed the endothermic nature of the process, with MB uptake enthalpy for NMRG and MRG at 5.25 kJ mol⁻¹ and 8.55 kJ mol⁻¹, respectively. The Gibbs free energy for MRG was a large negative value (-30.45 kJ mol⁻¹), while for NMRG, it was a small positive value (8.89 kJ mol⁻¹), suggesting that adsorption was mainly governed by chemisorption. The Intra-Particle Diffusion model indicated that adsorption occurred through both intra- and inter-particle diffusion. The Toth isotherm and the Redlich-Peterson models were identified as the best-fit models for NMRG and MRG, with R² values of 0.99.
Characterization of the water quality in the Rekawa lagoon, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) De Silva, K. V. N. T.; Wijeyaratne, W. M. D. N.
Rekawa lagoon is located in the Hambantota district in the Southern province of Sri Lanka. The lagoon is of high ecological and socio economic significance and is heavily utilized for aquaculture and fisheries purposes. The present study was conducted to assess the pollution status of selected sites in Rekawa lagoon in terms of water quality indices. The data was collected from five sampling sites in the lagoon; Site A: canal mouth, Site B: adjacent to residential areas, Site C: adjacent to agricultural lands, Site D: adjacent to hotels and shrimp farms, Site E: adjacent to mangrove forests. The water samples from each sampling site were analysed monthly for a period of six months from August 2023 to January 2024 to measure the water pH, salinity, turbidity, conductivity, DO (Dissolved Oxygen), TDS (Total Dissolved Oxygen), BOD5(Biological Oxygen Demand), temperature and Cr, Cd, Pb concentrations taking 5 replicates for each sample. In-situ parameters such as pH, salinity, turbidity, conductivity, DO, TDS, temperature were measured using multiparameter. The BOD5 values were measured according to APHA 2017. Heavy metal concentrations were measured using GBC SavantAA. The spatial and temporal variation of water quality parameters were assessed using one – way ANOVA followed by Tukey’s pairwise comparison by Minitab 17 software. Water quality index (WQI) was calculated from the water quality data. The WQI reflects moderate confidence due to the absence of microbiological parameters. The results of the present study indicated significant spatial variations of temperature, salinity, EC (Electrical Conductivity), pH, DO, BOD5, Cr, Cd, Pb and Zn concentrations. The highest mean surface water temperature was recorded at site C (32.5±0.11oC), highest mean surface pH at site A (8.35±0.06), highest mean conductivity at site A (28.48±0.28 mS/cm), highest mean water salinity at site A (10.31±0.21‰), highest mean DO at site A (8.09±0.01 mg/L), highest mean BOD5 at site C (4.77±0.02 mg/L), highest mean chromium concentration at site D (1899.00±0.00 ppb), highest mean cadmium concentration at site D (10.01±0.00 ppb), highest mean lead concentration at site D (157.02±0.00 ppb) and highest mean zinc concentration at site D (281.00±0.00 ppb). Salinity, EC, pH and temperature showed significant temporal variations among the sites. The highest mean surface water temperature was recorded in August, October and November (32.5 oC), highest mean salinity in August (12.00 ‰), highest mean conductivity in November (28.80 mS/cm) and highest mean pH in August (8.11). The highest WQI was recorded at site D (51.8) while the lowest was recorded at site E (26.6). According to the WQI the site D was categorized as poor while the other sites were categorized as good. The high load of organic pollutants released by the hotels and restaurants in the vicinity was identified as a possible cause for the degradation of water quality at site D as many point source wastewater outlets were identified at this site. Therefore, it is recommended to conduct adequate water quality monitoring and management activities in the Rekawa lagoon to ensure the continuous ecological and economic benefits acquired from the lagoon and to prevent the possible degradation.
Naphthalene appended diethylenetriamine based ligands and their platinum complexes as cancer theranostic agents
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Edirisinghe, L. G.; Perera, I. C.; Perera, N. T.
Dual action compounds with both diagnostic and therapeutic properties are extremely beneficial in treating cancers. Naphthalene sulfonamides are known fluorescent species due to the conjugated aromatic systems and they show sigma receptor targeting potential when bonded to diethylenetriamine. Here we present two new naphthalene sulfonamide ligands N(SO2-1-naphthalene) dien (L1) and N(SO2- 2-naphthalene)dien (L2) with their platinum complexes [Pt(N(SO2-1-naphthalene)dien)Cl]Cl (C1) and [Pt(N(SO2-2-naphthalene)dien)Cl]Cl (C2). The ligands L1 and L2 were synthesized by derivatizing the central N atom of diethylenetriamine, unlike the conventional ligands reported by derivatizing the terminal N atom of diethylenetriamine. All the compounds were synthesized in good yields and characterized using spectroscopic methods; UV-Visible, FTIR and 1H NMR spectroscopy. UV-Visible spectra of all compounds show absorption peaks due to n→π* electronic transitions in the region of 225-235 nm and absorption peaks corresponding to π→π* transitions were observed within the region of 265-300 nm. FTIR spectra aided to identify special functional group vibrations such as S-N bond vibrations and 1H NMR spectra were used in elucidating the structures of synthesized ligands and complexes. All of these species bear highly conjugated fluorophores (1-naphthalene and 2-naphthalene) which empower them as potential fluorescent imaging agents in diagnosis of cancer. By using Swiss TargetPrediction server, the biological targets for these two ligands were identified and sigma opioid receptor (SIGMAR-1) showed the highest probability showing their potential to act as cancer therapeutic drug leads. Moreover, both ligands obey the Lipinski rules ensuring their drug likeness. The structures of the ligands were geometrically optimized using the Gaussian 16 programme package, B3LYP/6-31G(d) level of theory. Theoretical molecular docking studies were performed to calculate binding affinities of ligands to the protein SIGMAR-1 (PDB ID: 5HK2) by AutoDock Vina wizard in PyRx 0.9.4 software, resulting -6.4 kcal/mol and -5.5 kcal/mol binding affinities for L1 and L2, respectively. Equipped with both therapeutic and diagnostic properties these compounds may serve as potential theranostic agents in the battle against cancer.
A comparative study of the effect of salinity on egg laying preference, egg hatchability, and larval survival of Aedes aegypti and Aedes albopictus (Diptera: Culicidae): a laboratory assessment
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Madhushani, M. H.; Chandrasekara, W. U.
Mosquitoes are notorious vectors that transmit pathogenic diseases, including dengue hemorrhagic fever. Since the salinity level affects the breeding behaviour of mosquito vectors, a laboratory assessment was conducted to study the variation of egg-laying preference, egg hatchability, and larval survival of two dengue vector mosquitoes, Aedes aegypti and Aedes albopictus, by exposing them to predetermined periods at varying salinity levels. In this assessment, the egg-laying preference, egg hatchability and larval survival of laboratory-raised Ae. aegypti and Ae. albopictus colonies were measured respectively at 5-day intervals for 25 days at 0 ppt, 5 ppt, 10 ppt, 15 ppt, and 20 ppt salinity levels (n = 3 each). The egg-laying preference, egg hatchability, and larval survival data, each against the salinity level, exposure period and the mosquito species, were analysed by 3-way ANOVA, while the differences in the measured parameters between the two species were analysed by a two-sample ttest. Results revealed that the egg-laying preferences of the two mosquito species did not differ significantly from each other (Ae. aegypti 34.73 ± 6.4 and Ae. albopictus; 35.01 ± 5.9) (p > 0.05). Both species laid eggs from the 5th day upon exposure to the test solutions, and the number of eggs gradually increased with the increasing exposure period. Neither species laid eggs at 15 ppt and 20 ppt salinity levels (p < 0.05). The hatchability of Ae. aegypti eggs (12.9 ± 1.2) were significantly higher than that of Ae. albopictus eggs (9.7 ± 0.6) (p < 0.05). The eggs of neither species hatched at 15 ppt and 20 ppt salinity levels (p < 0.05). The larval survival of both species was statistically similar to each other (p > 0.05), but the survival of both species gradually decreased with the increasing exposure period. The larvae of both species did not survive in 15 ppt and 20 ppt salinity levels (p < 0.05). Since the Aedes mosquitoes thrive in areas close to human dwellings, the addition of common table salt into discarded water-filled containers, both indoors and outdoors, to make the water salinity above 10 ppt (<10 g salt in 1 litre of water) could be used as a promising alternative vector control method in integrated vector management programmes.
Supercapacitor assisted LED (SCALED) lighting system with grid connection
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Kumara, W. R.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
Photovoltaic (PV) systems are increasingly popular as the world shifts to sustainable energy. Generally, there are three main types of PV systems. The SCALED system consists of a PV panel, a Supercapacitor (SC) bank, and an LED. Utilizing the Supercapacitor-Assisted Loss Management (SCALoM) theory, the SCALED system integrates an SC bank and LED bulb to reduce energy loss during charging. Solar energy is stored in the SC bank and released to ensure the LED remains powered. However, the current SCALED system, with oversized solar panels and SC banks, is inefficient if it can't power LEDs at night or in adverse weather. To address this, an innovative approach is proposed by integrating the SCALED system with the grid for reliable energy storage and continuous LED illumination. In this innovative method, the SC bank and LED are connected in series with PV panels or grid connection in the SC charging loop. The system has two identical loops connected in parallel with the PV panels or grid. One SC bank charges while the other discharges, ensuring the LED bulbs remain powered. An electronic switching network with two SC banks manages four operational modes to optimise energy utilisation. These modes include alternating charging and discharging loops. A microcontroller-based control circuitry operates the system, which connects to the grid via a Switch Mode Power Supply (SMPS). A current sensor measures the current of the solar panel output. During adverse weather, the system switches to the grid when the output current drops solar panels below a threshold, isolating the solar panel. In the Developed SCALED system, MOSFETs efficiently manage power flow between the SC bank and LEDs, minimizing losses. Microcontrollers optimize energy use by controlling MOSFETs and monitoring voltage, and current levels, ensuring reliable LED operation even in adverse conditions. This improves overall system efficiency and reliability. When the solar panel output current exceeds the threshold value, the system will connect the solar panels and isolate the SMPS from the system. The system achieves a high charging efficiency of around 95%. Operational in all weather conditions and at night, the system ensures consistent LED illumination, enabling normal user operation regardless of weather during day and night.
Computer vision-based approach to floating waste detection
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Rathsara, K. M. A. C. D.; Sandaruwan, K. D.
Water pollution, especially from floating waste like plastics, metals, and organic matter, poses a severe threat to aquatic ecosystems and environmental health. This study aims to develop a computer visionbased model for detecting floating waste in water bodies, utilizing recent advancements in deep learning to enhance detection accuracy and efficiency. This paper presents a study toward the development and implementation of the You Only Look Once model (YOLOv8n) to improve accuracy and efficiency in detecting floating waste. The primary objective is to develop a better model for the detection of various floating waste of concern, including glass, metal, plastic, and water hyacinth. The Research involves collecting datasets from publicly available sources as well as web scraping to collect additional images. After data collection, several preprocessing steps were applied, including cleaning and normalization to ensure consistency across the dataset. Data augmentation techniques were used to increase the diversity of images and improve model reliability. Finally, the dataset was labeled using annotation tools. The YOLOv8n model was trained on this dataset with iterative parameter optimization and various experiments to improve detection performance. Experiments included creating a model from scratch, fine-tuning it, using a pre-trained model, and transferring weights to new configurations. The experiments demonstrate that the YOLOv8n model is highly effective for detecting floating waste. The model achieved a mean average precision (mAP50) of 0.932, with a precision of 0.904 and recall of 0.852, indicating strong accuracy in detection. The YOLOv8n model has shown exceptional performance, particularly in detecting water hyacinth, highlighting its effectiveness and efficiency in floating waste detection. Moreover, the model has the ability to detect floating waste precisely and potentially can also be used in real-time applications for monitoring the water environment. These findings have a huge potential for real-world applications involving rapid responses in aquatic environments and further conservation. Future work will focus on further training with iterative adjustments and dataset augmentation to improve the adaptability and accuracy of the model across different water conditions. This includes expanding the dataset through additional data collection efforts and increasing the diversity and number of identification classes. This study contributes to the wider discourse of environmental conservation by calling for innovation in technological solutions to reduce the adverse effects of floating waste in aquatic environments and also promotes sustainable management of water resources.
Antibacterial efficacy and phytochemical properties of Citrus crenatifolia (Heen Narang) and Citrus reticulata (Jama Narang)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Salwathura, I. A.; Deraniyagala, N. G. I. A.; Fernando, N. H.; Perera, M. D.; Perera, E. H. L.; Ranasinghe, H. A. K.
The Citrus family encompasses various plant species known for their antibacterial properties. Various parts of Citrus plants have been used in traditional Sri Lankan medicine for an extended period. Citrus reticulata was selected for its established antibacterial properties, providing a foundation to further investigate its potential alongside the less-researched Citrus crenatifolia. The present study was conducted to investigate the antibacterial properties of C. crenatifolia and C. reticulata found in Sri Lanka. Active phytochemicals were extracted from the peels, using the reflux method employed in an aqueous medium. The antibacterial properties of plant extracts were assessed using the well diffusion method against six common bacterial pathogens; Staphylococcus aureus (ATCC 23235), Pseudomonas aeruginosa (ATCC 15442), Proteus mirabilis (ATCC 35659), Klebsiella pneumoniae (ATCC 13883), Escherichia coli (ATCC 25922) and Enterococcus faecalis (ATCC 29212). Double distilled water was used as the negative control, while commonly used antibiotics (ampicillin, penicillin, gentamicin, vancomycin, augmentin, and ciprofloxacin) served as the positive controls. A McFarland standard was employed for each test microbe. The diameter of inhibition zones was measured after incubation, and statistical analysis was performed using the SPSS software package. The independent sample t-test revealed that there was no significant difference between the mean values of the control and both peel sample extractions for all tested bacteria. (p = 0.115). There was no statistically significant difference in antibacterial activity among the six microbes according to the One-Way ANOVA test for C. reticulata (p = 0.271). But there was a statistically significant difference in the antibacterial activity of C. crenatifolia (One-Way ANOVA: p = 0.021). Tukey’s Post-Hoc analysis of C. crenatifolia extract showed a significant difference in the mean inhibition zone diameters between S. aureus and P. aeruginosa (p = 0.044) as well as S. aureus and K. pneumoniae (p = 0.049). The antibacterial activities of both extracts were supported by the presence of phytochemicals such as alkaloids, steroids, flavonoids, phenol, and tannins which showed combination effects. Anyhow, saponins were not detected in both extracts. The present findings highlight the potential of C. crenatifolia and C. reticulata extracts as valuable sources of antibacterial agents, warranting potential applications in the field of microbial control. Further investigation to elucidate its specific mechanisms of action is recommended.
Isolation, characterization, and application of phosphate-solubilizing fungi as a biofertilizer for plant growth promotion
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Jayathilake, K. M. P. I.; Manage, P. M.; Idroos, F. S.
Plants require major nutrients such as nitrogen and phosphorus for their optimal growth. Phosphorus is an essential macronutrient, yet its availability in soil is often limited due to its insoluble form. Soil microbes can convert insoluble phosphate into soluble phosphate through various mechanisms. Phosphate-solubilizing fungi (PSF) play a vital role in this process, contributing to the phosphorus requirements of plants. Hence, the present study aimed to isolate, characterize, and utilize PSF as a biofertilizer. The PSF strains were isolated from compost soil in Karadiyana (6°48′ 51.8′′ N, 79° 54′ 17.0′′ E) using Pikovskaya's agar (PVK) medium. The phosphate solubilizing index (PSI) was determined by observing halo zone formation after a 7-day incubation period. Phosphate solubilizing efficiency was assessed using PVK broth supplemented with 0.5% tricalcium phosphate following 7 days of incubation at 160 rpm (28 oC). The isolated fungal strains were introduced to a developed potting medium containing compost, coir dust, and soil in a 1:1:1 ratio. Mung bean (Vigna radiata) was selected as the experimental plant. Plant growth parameters (shoot length, root length, wet weight, and dry weight) were measured to determine the effect of the isolated fungal strains. These parameters were recorded after 30 days. Genotypic identification of the isolated strains was performed using the Internal Transcribed Spacer (ITS) region. The strains were confirmed as Fusarium proliferatum, Aspergillus niger, and Aspergillus flavus. A. niger demonstrated the highest phosphate solubilizing efficiency (296.8 ± 0.2 μg/mL) after 6 days of incubation, with a PSI of 2.15 ± 0.1. Fungi-inoculated pots showed a significant increase in shoot length, root length, wet weight, and dry weight compared to the control (n = 9, p < 0.05). Potting media inoculated with A. niger showed the best results, with the highest root length (11.8 ± 0.5 cm), shoot length (16.7 ± 0.5 cm), wet weight (0.6381 ± 0.03 g), and dry weight (0.1060 ± 0.02 g) was recorded. This study suggests that the potting media containing F. proliferatum, A. niger, and A. flavus exhibited significant roles in phosphate solubilization and plant growth promotion, indicating their potential to be used as an effective biofertilizers.
Investigation of using diatomaceous earth variants as fillers in rubber composites: cure characteristics and tensile properties
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) De Costa, N. B. J.; Egodage, S. M.; Maddumaarachchi, M.
Diatomaceous earth (DE) generally made of fossilized diatom exoskeletons, is well-known for its high porosity and potential usage as a rubber filler alongside silica. This study characterizes various grades of DE such as amorphous, crystalline, crystalline brewery waste, and ground brewery waste to reduce the particle size, compared to silica. This research aims to identify their morphological properties and impact on the cure characteristics and tensile properties of natural rubber vulcanizates. First, rubber formulation was optimized to provide a baseline for the cure characteristic tests. The ground waste DE was thus prepared by ball-milling crystalline waste DE for 3 hours at 300 rpm in a laboratory scale ball mill. The fillers were then characterized extensively using established techniques such as Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), X-ray diffraction (XRD), X-ray fluorescence Spectroscopy (XRF), and Fourier-Transform Infrared Spectroscopy (FTIR). Rubber composites were formulated with 55 phr of each filler. As the next step, amorphous and crystalline waste DE was mixed with silica in proportions of 25%, 50%, and 75% of DE-based filler to silica by weight to prepare rubber composites. Cure characteristics were obtained using a Moving Die Rheometer (MDR) at 150 °C for 30 minutes, and ultimate tensile strength was measured with a Universal Testing Machine according to ASTM D412 standards (die cut-C) at a strain rate of 500 mm/min. The results revealed that ball milling was ineffective in reducing the particle size of crystalline waste DE at the given conditions. 100% Amorphous DE-filled composite showed inferior cure characteristics, with a low cure rate index and low cross-link density. Nevertheless, composites with 25% amorphous DE blended with silica demonstrated higher ultimate tensile strength compared to composites with 100% silica, explained by the positive synergistic effect from particle size and increased surface area of amorphous DE. However, loadings of more than 25% of amorphous DE to silica caused reduced tensile properties due to lower filler density. Waste DE-loaded composites showed reduced tensile properties due to both larger particle size and agglomeration. In conclusion, amorphous DE exhibited positive synergism with silica when used as a rubber filler, enhancing tensile properties due to higher cross-link density facilitated by smaller particles and increased filler-matrix interactions due to the nano-roughness of DE. Composites loaded with waste DE showed significantly reduced tensile properties due to pronounced agglomeration. The optimal loading of amorphous DE as a filler was determined to be 25% of DE with silica, providing a balance between improved tensile properties with higher reinforcement. This study emphasized the potential of using amorphous DE as a bio-based filler in rubber composites, highlighting the need for optimization of filler loading to mitigate agglomeration and optimize the material performance. These findings could contribute to innovating sustainable materials in polymer composites.
Biovalorization of agro-food wastes for the production of melanin pigment via a submerged fermentation process using Aspergillus niger: as a sustainable approach
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Rasna, N. F.; Jayathilake, K. M. P. I.; Manage, P. M.; Idroos, F. S.
Biovalorization harnesses biological processes to convert waste materials into value added products, encouraging sustainability and resource efficiency. The current study aims to explore and optimize a sustainable method for the production of melanin pigment through the submerged fermentation (SMF) process by utilizing banana peel waste, affected Sesbania grandiflora leaves and stem wastes, and used tea dust waste using Aspergillus niger. The pH, moisture content, total organic carbon, and total ash contents of collected food wastes were measured using standard methods. Fungal cultures were incubated under the submerged fermentation process, at 25 °C with an agitation speed of 160 rpm for 14 days. Subsequently, the fungal-produced pigment was extracted using 1.0 mol/L KOH and subsequently characterized using physicochemical tests with water, organic solvents, alkaline and acidic solutions, and an oxidizing-reducing agent. Further, the pigment was confirmed based on ultraviolet-visible spectroscopic analysis and Fourier-transform infrared spectroscopic (FTIR) analysis. The extracted pigment was tested for toxicity, antibacterial, and antioxidant properties to the determination of the distinctive characteristics and quality of the extracted pigment, hence enabling their industrial use. The pigment yield from banana, Sesbania, and tea wastes were 597.2 ± 21.5 mg/L, 395.4 ± 39.1 mg/L, and 135 ± 12.9 mg/L, respectively. Compared to the control setup, a significant difference (p < 0.05) was observed between the pigment yields produced by A. niger when utilizing different types of food waste. In the physico-chemical analysis, the blackish brown colour of the pigment served as primary evidence for melanin. The pigment was insoluble in water and organic solvents (acetone, chloroform, ethanol, and sodium acetate), but it was readily soluble in KOH and NaOH, precipitated with HCl, and decolorized with H₂O₂. The UV-Vis spectrum indicated that the pigment possessed a λmax around 213–216 nm. The FTIR spectrum showed broad bands around 3000– 3500 cm⁻¹ (OH), 2924.7 and 1032.6 cm⁻¹ (saturated carbon and C-O), 2830–2930 cm⁻¹ (CH2 and CH3), 1500–1650 cm⁻¹ (aromatic C=C or C=O), 1320 and 1390 cm⁻¹ (C-N), and 1210–1230 cm⁻¹ (C-OH). The extracted pigment exhibited low toxicity to mung beans (4.4–6.7%) compared to the positive control (100% extraction solvent). In the antibacterial activity assay, inhibition zones ranged from 2.1 ± 0.1 to 2.6 ± 0.1 cm for Staphylococcus aureus and 2.1 ± 0.1 to 2.5 ± 0.1 cm for Escherichia coli. The antioxidant assay demonstrated an increase in the percentage of DPPH inhibition with increasing pigment concentration, suggesting the pigment's ability to scavenge free radicals. This study proposes a sustainable approach for the production of fungal-based pigment (melanin) through a submerged fermentation process utilizing agro-food wastes with Aspergillus niger strain, which was not documented in previous studies.
A preliminary study to investigate the impact of geographical variation on phytochemical content and antioxidant properties of selected green leafy vegetables
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Dahanayaka, L. W.; Kadigamuwa, C. C.; Mapa, S. T.
Green leafy vegetables (GLVs) are rich sources of phytochemicals with significant therapeutic potentials including antioxidant activity, mitigating non-communicable diseases. The phytochemicals and antioxidant properties may vary depending on many factors including geographical location. This preliminary study aimed to analyze the variation of these properties in two selected GLV species; Ipomea aquatica and Alternanthera sessilis with geographical location. Plant samples were acquired from different geographical locations (low-country dry zone – Jaffna, up-country intermediate zone – Welimada/Ella, low-country wet zone – Kalutara/Hikkaduwa) cultivated under organic farming practices. A pot study (with controlled growth conditions) was carried out at Gampaha (low-country wet zone). Edible plant parts were cleaned, oven-dried at 45 ºC, ground, and the methanolic extracts were prepared. Each experiment was carried out in triplicates. The total flavonoid content (TFC) and the total phenolic content (TPC) were determined by the aluminium chloride colorimetric assay and Folin-Ciocalteu method respectively. 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric ion-reducing antioxidant power (FRAP) assay were used to determine the antioxidant activity. For statistical analysis, the one-way analysis of variance (ANOVA) test which indicates significant differences among locations, and Tukey’s post hoc test to identify statistically significant differences between locations (p < 0.05) were carried out. A. sessilis showed significant differences towards all experimented aspects (chlorophyll, carotene, TFC, and FRAP) except TPC and DPPH. I. aquatica showed significant differences in chlorophyll and TFC. However, several locations were not significantly different in some aspects. TPC in A. sessilis from Jaffna and Ella were not significantly different from Hikkaduwa, while DPPH of Hikkaduwa and Gampaha were not different from Jaffna. The carotene content of I. aquatica did not show any significant difference between Kalutara and Gampaha samples. The TPC of I. aquatica was not significantly different in the samples of Jaffna, Welimada, and Gampaha. The difference in DPPH inhibition was not significant in Jaffna and Gampaha, while FRAP was not significantly different between Kalutara and Jaffna as well as Welimada and Gampaha. The results indicate that geographical location has contributed to the variation of some experimented aspects. Furthermore, the highest TFC for both plants was recorded from Jaffna samples, while the highest DPPH activity was recorded with the high-altitude locations (Ella and Welimada). No such pattern was observed with other variables. These results evidence the possible variations in the phytochemical composition and antioxidant activity of GLVs depending on the geographical location. This knowledge can be used to establish comprehensive research to investigate the correlation of geographical variations with phytochemical and antioxidant properties, guide agricultural practices, select better cultivation sites, improve the quality of herbal medicines, and enhance the nutritional value of GLVs.