Symposia & Conferences
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/10213
Browse
15 results
Search Results
Item Enhancing methylene blue removal efficiency using rice-husk derived, modified activated carbon via magnetic particle integration(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Sakunthala, K. A. D. D.; Perera, P. L. R. A.; Perera, W. P. R. T.; Premaratne, W. A. P. J.; Liyanage, J. A.The extensive use of synthetic dyes in industries has increased environmental pollution, reducing oxygen levels and sunlight penetration in water bodies. Activated carbon (AC) is widely used for removing contaminants. However, the effective recovery and reuse of absorbents in post-treatment present a challenge. Hence, AC integrated magnetic particles (MAC), is seen as a better and innovative alternative due to its easy recovery and minimal environmental impact. This study focused on producing MAC using rice husk and evaluating its effectiveness in Methylene Blue (MB) removal using isotherm and kinetic studies. To produce AC, rice husks were initially washed with DI water, treated with HCl (5% v/v) for 24 hours, and dried at 383 K. Physical activation was carried out at 400°C for 2 hours. Synthesised AC was then mixed with FeSO4 (FeSO4: DI water =1:7.5) and freshly prepared FeCl3 (FeCl3: DI water = 1:72) mixture, stirred at 60-70°C for 30 min, and adjusted to pH 10 using NaOH (10 M). After mixing for 60 min, mixture was left for 24 hours at room temperature, washed with DI water and ethanol, followed by vacuum filtration and overnight drying at 50°C to yield MAC. Characterization was done using Fourier Transform Infrared Spectroscopy (FT-IR). Proximate analysis was carried out and the yield percentage of MAC was calculated. Batch adsorption studies were conducted to optimize parameters such as initial MB concentration, adsorbent dosage, contact time, and pH, for MB removal. Subsequently, under optimized conditions, isotherm and kinetic experiments were conducted. All experiments were duplicated and performed at room temperature. The FT-IR analysis of MAC revealed distinctive features: additional bands at 635.2 cm⁻¹ and 882.7 cm⁻¹, indicating the presence of stretching and bending vibrations of Fe-O bonds. Additionally, a band at 1105.7 cm⁻¹ suggested potential Fe-O-C interactions, confirming the integration of magnetic particles onto the AC surface. In batch adsorption studies, MAC (0.0212 ± 0.0001 g) had optimal MB removal at pH (7.01 ± 0.01) and an initial concentration of 4 mg/L, following 60 minutes of agitation. Adsorption isotherm analysis illustrated an excellent fitting to the Langmuir model (R2=0.9934), revealing monolayer adsorption on a homogeneous surface, with a maximum adsorption capacity (qmax) of 102.04 mg/g. Kinetic studies indicated that the adsorption process followed a pseudo-second-order reaction (R2 = 0.9884), suggesting chemical sorption as the governing mechanism. In conclusion, this study demonstrated the effective integration of magnetic particles with AC derived from rice husks, which enhances the recoverability of the adsorbent in the post-treatment phase due to its magnetic property. Furthermore, this innovative approach ensures effective MB removal from wastewater, providing an eco-friendly and cost-effective solution that advances wastewater treatment technologies without environmental compromise.Item Assessment of heavy metal contamination in surface water, sediment and paddy soil in CKDu endemic regions: A comparative study in Minipe and Dambagolla, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Lakshan, L. M. U.; Sakunthala, K. A. D. D.; Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, J. A.; Premaratne, W. A. P. J.Chronic Kidney Disease of unknown etiology (CKDu) is a major health crisis in Sri Lanka, particularly affecting rural agricultural communities in regions such as the Central and Uva provinces. This study investigated the concentrations of heavy metals, alongside various quality indicators, in water, sediment, and paddy soil within CKDu endemic regions of these provinces. The objective is to determine whether toxic heavy metals present in surface water, sediment, and paddy soil correlate with the upraised CKDu incidence in Dambagolla compared to Minipe. Using a stratified random sampling technique, surface water and sediment samples were collected from three locations: Minipe Anicut, Minipe Canal, and Loggal Oya. Eighteen composite sediment samples (six from each location) and thirteen surface water samples (three from Minipe Anicut, two from Minipe Canal, and eight from Loggal Oya) were collected. Additionally, a total of twelve topsoil samples (six from each location) were collected from paddy fields in Minipe and Dambagolla areas in which higher CKDu prevalence was recorded compared to Minipe. Water samples were analyzed for pH, electrical conductivity (EC), hardness, and phosphate using standard methods. Sediment and soil samples were tested for pH, EC, organic matter, potassium, phosphate, and total nitrogen. Heavy metals (Pb, As, Cr, Cd, Ni) were quantified using Inductively Coupled Plasma–Mass Spectrometry (ICP-MS). All analyses were duplicated. Statistical significance across parameters was assessed through ANOVA and Tukey's pairwise comparisons. Water samples from all locations have maintained pH levels within WHO recommendations. Minipe Anicut samples had relatively lower conductivity (141.1±27.27 μS/cm) while having elevated hardness (65.39±7.58 mg/L) and phosphate levels (12.28±9.67 ppm). Pb, Cr, and Cd were not detected in Minipe Anicut, and Cr was absent in Minipe Canal. Arsenic levels, although within WHO standards, were higher than other metals, particularly in Minipe Canal (4.17±0.03 µg/L) and Loggal Oya (5.25±3.89 µg/L). ANOVA showed no significant differences in heavy metal levels among sites (p>0.05). Sediment samples from Minipe Canal had lower levels of Cr (11.93±0.37 mg/kg) Pb (2.52±1.06 mg/kg), As (0.62±0.30 mg/kg), Cd (0.013±0.010 mg/kg), and potassium, resulting in substantially lower conductivity. In Minipe Anicut and Loggal Oya, heavy metal content followed the order Cd < As < Pb < Ni < Cr, with Minipe Anicut showing slightly higher concentrations. Furthermore, paddy soil analysis showed higher organic matter content in Dambagolla (4.16±0.46%) compared to Minipe (1.22±0.15%), while Minipe had higher heavy metal concentrations and potassium content (p<0.05). The results suggest that agricultural activities, natural geological factors, and localized contamination sources influence the water, sediment, and soil quality in the studied areas. Furthermore, findings reveal that heavy metal concentrations in surface water, sediment, and paddy soil were not significantly linked to the higher CKDu prevalence in Dambagolla compared to Minipe, suggesting greater influence from other critical factors, driving CKDu development in this region.Item Risk assessment of toxic heavy metals in Oryza sativa (rice) from CKDu prevalent areas: Dambagolla and Minipe, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Yasandhika, K. K. G. N.; Perera, P. L. R. A.; Perera, W. P. R. T.; Premaratne, W. A. P. J.; Liyanage, J. A.Chronic Kidney Disease of unknown etiology (CKDu) has been a significant health issue in North Central region in Sri Lanka. One of the suspected contributing factors to CKDu is the contamination of food crops, particularly rice, with toxic heavy metals. This study assessed the risk associated with toxic heavy metals in rice (Oryza sativa; BG- 300) grown in two CKDu prevalent areas, Dambagolla and Minipe. Despite being only approximately 4 kilometers apart and separated by the Mahaweli River, there is a significant difference in CKDu prevalence. In 2023, Dambagolla reported over 50 CKDu patients, whereas Minipe reported fewer than 10. The objective of this study is to evaluate the concentration of toxic heavy metals in rice samples from these areas and to determine if these concentrations correlate with the incidence of CKDu. Twenty rice samples were collected from each paddy field in Dambagolla and Minipe using a random stratified sampling method. Heavy metal analysis, (lead (Pb), arsenic (As), chromium (Cr), cadmium (Cd), and nickel (Ni)), was conducted using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). All sample analyses were duplicated. The data were analyzed to compare the levels of these metals with the maximum permissible levels (MPL) set by the Codex Alimentarius Commission. Additionally, the Target Hazard Quotient (THQ) levels were evaluated, and statistical evaluation was performed using the two-way ANOVA method. In Minipe, the detected levels of heavy metals were Pb (0.315 ± 0.091 mg/kg), As (0.0504 ± 0.01 mg/kg), Cr (0.735 ± 0.086 mg/kg), Cd (1.071 ± 0.087 mg/kg), and Ni (0.247 ± 0.005 mg/kg). In Dambagolla, the detected levels were Pb (0.291 ± 0.06 mg/kg), As (0.093 ± 0.03 mg/kg), Cr (0.388 ± 0.086 mg/kg), Cd (1.124 ± 0.078 mg/kg), and Ni (2.100 ± 0.017 mg/kg). Among the analyzed metals, the mean concentrations of Cd and Pb exceeded the maximum permissible levels (MPL) set by the Codex Alimentarius Commission in both areas. The Target Hazard Quotient (THQ) indexes indicated significant health risks in both areas. In Minipe, the THQ values for Cr (12.26) and Cd (5.355) exceeded threshold values, suggesting a potential health hazard. In Dambagolla, the THQ values for Cr (4.8653), Cd (1.9442), As (18.73), and Pb (3.000) also exceeded threshold values, indicating a significant health concern. Statistical analysis using two-way ANOVA revealed that the concentrations of As and Ni varied significantly between the two areas (p < 0.05). These findings suggest that the elevated levels of Cd and Pb in rice could be contributing to the higher incidence of CKDu in Dambagolla compared to Minipe. The regular consumption of rice could pose significant health risks, potentially contributing to the prevalence of CKDu in these regions. Further investigation is necessary to identify the sources of these heavy metals and to develop strategies to mitigate their impact on public health.Item Development of sand/graphene composite and its application for MCPA pesticide adsorption from water(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Perera, W. P. R. T.; Ruwanthi, N.M.N; Perera, P. L. R. A.; Kannangara, Amila; Premarathna, W.A.P.J; Liyanage, J. A.; Kumarasinghe, A. R.This research endeavours to synthesize a novel adsorbent, sand/graphene oxide composite (MGO/S), achieved through the iterative deposition of graphene oxide layers on river sand employing a thermal annealing process. Scanning electron microscopic (SEM) and Fouriertransform infrared spectroscopy (FT-IR) characterization studies revealed the presence of a nonuniform graphene oxide coating on the surface of the sand and the incorporation of oxygenated functional moieties within the structure. Comparative evaluations show the heightened adsorption capacity of this new composite entity with alternative sorbent materials, such as activated carbon, graphene oxide, and sand to adsorb neutral 2-methyl-4-chlorophenoxyacetic acid (MCPA) pesticide molecule. To analyse the MCPA adsorption parameters, High-performance liquid chromatography (HPLC)was used (Solvent mixture - Acetonitrile: Distilled water (1:1); Flow rate - 1.5µLmin-1; Wave length - 275nm). The retention time for the MCPA was reported as 1.538s. The optimization studies and adsorption modelling were carried out, focusing on the adsorption of MCPA onto the M-GO/S. Accordingly, the optimum concentration, dosage, and contact time were 75 mg/L, 0.05 g, and 105 minutes respectively, at neutral pH values. The investigation of adsorption equilibrium isotherms has highlighted the Freundlich model's (multilayer adsorption) superior explanatory capacity in characterizing the adsorption phenomenon. Concurrently, the analysis of adsorption kinetics has demonstrated a favourable fit with the pseudo-second-order model (with a correlation coefficient denoted as 0.9754), implying a prevailing chemical sorption mechanism underlying the adsorption process. Although MCPA possesses either neutral or negatively charged (upon dissolution) surfaces, the M-GO/S composite exhibits significant adsorption capability towards MCPA. Consequently, the synthesized composite emerges as a viable candidate for effectively mitigating MCPA pesticide contamination from water.Item Assessment of contaminant levels of hazardous toxic metals and subsequent risk analysis in agricultural soil and selected comestibles within a region afflicted by CKDu in Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Perera, M. A. S. N.; Kadigamuwa, C. C.; Gunathilaka, V. H. N. M.; Samaraweera, G. A.; Perera, W. P. R. T.; Perera, P. L. R. A.; Liyanage, J. A.; Premaratne, W. A. P. J.Agricultural commodities constitute a pivotal component of the human daily sustenance, yet they are susceptible to contamination by pernicious heavy metals, notably Hg, Cd, Pb, and As. Consequently, agricultural products represent a substantive source of apprehension for human well-being and health. This study aims to evaluate related risk indices of agricultural soils (n=25) and selected comestible grains, namely Oryza sativa (n=25), Vigna radiata (n=25), Vigna unguiculata (n=25), and Vigna unguiculata subsp. (n=25), within the endemic region of Nikawewa Grama Niladhari Division (GND) in North Western Province (NWP) and the reference region, Wewagedara GND in NWP where no evidence for Chronic Kidney Disease of unknown etiology (CKDu). The concentrations of metals in the collected samples were determined by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and based on that risk indices were calculated. The mean geo-accumulation index (Igeo) for four metals in soil was As - 0.82, Cd - 1.47, Cu - 0.91, and Pb 1.31. That indicates no anthropogenic activities related to As, Cd and Cu while Pb is responsible for moderate pollution in endemic area. Estimated Daily Intake (EDI) values for these heavy metals were calculated with respect to the all grains. EDI means of As and Pb in the endemic and the reference areas for all grain samples were within the Tolerable Daily Intake (TDI) set by United States Environmental Protection Agency (USEPA) (As-0.300 g/kg/day) and World Health Organization (WHO) (Pb-3.600 g/kg/day) while Cd (EDI in endemic area; Oryza sativa-6.385 g/kg/day, Vigna unguiculata-3.386 g/kg/day and Vigna unguiculata subsp.-3.866 g/kg/day) highly exceeded the tolerable weekly intake (TWI) of European Food Safety Authority (EFSA) (Cd-2.5 g/kg/week) in both areas. EDI of Cr in rice samples (1.138 g/kg/day) in endemic area exceeded the TDI set by EFSA (1.0 g/kg/day) and all other values of Cr were below the TDI in both areas. According to the USEPA (intolerable cancer risk (CR) - > 1 x 10-4) cancer risk exist for all these staple grains. Igeo of Pb in the soil, raising concerns about their bioavailability and uptake by the food crops and EDI were indicated the long-term consumption of these foods especially Oryza sativa poses a serious threat to human health. Implementing proper soil management practices, monitoring heavy metal levels in crops, and raising public awareness about safe consumption practices are crucial steps towards mitigating the risk of CKDu.Item Distribution of heavy metals across different tissue types in Etroplus suratensis from Mahakanadarawa reservoir: Investigating dietary implications for CKDu in Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, U. P.; Premaratne, W. A. P. J.; Liyanage, J. A.The escalating cases of chronic kidney disease of uncertain etiology (CKDu) in rural communities, especially in the Maradankulama-Mahakandrawa region of Sri Lanka, stipulate a critical public health investigation. Given the significant dietary reliance on Etroplus suratensis due to geographical and logistical complexities in obtaining sea fish, bioaccumulated toxic metals in this species can be a potential risk factor for CKDu. This study investigated the heavy metal content (As, Pb, Cd, Cr, Ni) in the gut, gill, and muscle tissues of E. suratensis sourced from the Mahakanadarawa Reservoir in the CKDu endemic Mihintale region. To obtain representative E. suratensis samples from across the Mahakanadarawa Reservoir, fish were collected using a randomized sampling method. Multiple random points within the reservoir were pre-determined and fish were caught at each location by local fishermen using appropriate techniques. The captured fish were identified as E. suratensis and 36 samples were separated as gut, gills, and muscles for the toxic metal analysis. The heavy metal content (As, Pb, Cd, Cr, Ni) in these samples was then analysed using inductively coupled plasma mass spectrometry (ICP-MS). To thoroughly compare metal concentrations across tissue types, the non-parametric Kruskal-Wallis ANOVA test was utilized followed by post-hoc Tukey HSD tests. The non-parametric ANOVA assessed statistically significant differences in metal levels between muscle, gill, and gut tissues. Post-hoc Tukey tests then enabled pairwise comparisons between each tissue type to determine which specific metal concentrations differed. There were significant differences between tissue types for concentrations of As, Cd, Cr and Ni (p<0.001). Post-hoc Tukey tests showed As, Cr, Cd and Ni were significantly higher in gut compared to that of muscle and gill tissues (p<0.05), with the order Gut>Gill>Muscle. Pb did not deviate significantly across tissues, however, mean Pb concentrations exceeded the WHO/FAO permissible limits for dietary intake in all tissues, while Cd remained within acceptable levels. Compared to gut and gills, muscle contained relatively low concentrations of As (0.01±0.01) mg/kg, Cr (0.22±0.03) mg/kg, Pb (0.508±0.36) mg/kg, and Cd (0.015±0.13) mg/kg and Ni (0.06±0.01) Although edible muscle in some samples met regulatory limits, frequent consumption of E. suratensis from this CKDu endemic area may pose a health risk, warranting further study on geographical and seasonal variation. Ultimately, this study contributes to the growing body of evidence suggesting that bioaccumulation of toxic metals in fish poses significant CKDu risk factors.Item Health risk analysis of toxic metals via consumption of rice and other food species grown in Mahakanadarawa - Maradankulama areas in Anuradhapura district; A study in Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, J. A.; Premaratne, W. A. P. J.Chronic Kidney Disease of unknown etiology (CKDu) is a heterogeneous disorder that impairs kidney functions and structure. Even though a number of studies were conducted on this issue, a specific reason has not yet been discovered. Unexpected contaminants have harmed crop quality in recent decades, threatening food security and human health. This study was designed to assess the status of toxic metal contamination of frequently consuming food species in selected Maradankulama - Mahakanadarawa Grama Niladari (GN) divisions to evaluate the link between CKDu prevalence and food safety in the selected areas. Maradankulama - Mahakanadarawa GN divisions in Anuradhapura district, Sri Lanka, were selected as the sampling areas. The sampling procedure was conducted in April (2022). Food samples, including (rice grains of Oryza sativa; n=25, leaves of Centella asiatica; n=25, fruits of Citrus crenatiflora; n=18, grains of Vigna radiate; n=10) were collected from the villager’s own paddy fields, and home gardens of the CKDu suspected patients according to the random stratified sampling method and the collected food samples were digested by microwave digestion. (added 8.0 mL of conc. Nitric acid to 0.2 g of food sample and digested) The concentrations of metal ions in food samples, including Cadmium, Nickel, Chromium, Copper, Iron, Manganese, Lead, Zinc, Arsenic, and Calcium, were measured using the Inductive Coupled Plasma technique (ICP). Statistical analysis was done using SPSS Statistics Software. Accordingly, mean As and Pb concentrations of Oryza sativa (As-0.15 mg/kg, Pb-3.10 mg/kg) and Citrus crenatiflora (As-0.15 mg/kg, Pb-0.47 mg/kg), Pb (0.65 mg/kg) and Cd (0.05 mg/kg content in Centella asiatica, and mean concentrations of As (0.14 mg/kg), Pb (9.25 mg/kg) and Cu (57.8 mg/kg) in Vigna radiate exceeded the permissible limits given by the FAO and WHO, 2011 (As-0.1 mg/kg, Pb-0.1 mg/kg, Cd-0.05 mg/kg, Cr-2.3 mg/kg, Cu-40 mg/kg). In addition to Pb, Cd, As, Cr and Cu, other detected metals have not exceeded the permissible limits in all samples. According to the Target Hazard Quotient (THQ) values of Cr exceeded the threshold value of 1 for all food species. In addition to that, Pb is also considered a toxic element, and THQ values of Pb in Oryza sativa and Vigna radiate reported noticeably high values. The total EDIs (Estimated Daily Intake) of Cr, Ni, Cd, As, Cu and Pb for all selected food samples studied have not exceeded the maximum tolerable daily intake (MTDI). Considering the resident’s complete diet, these EDIs can be enhanced. As a result, the consumption of analyzed rice, leafy vegetables, and legumes was deemed unsafe, and their regular consumption may cause a risk for the prevalence of CKDu in selected areas.Item Risk assessment of toxic metal contamination in groundwater and paddy soil; A study in CKDu affected Maradankulama area in Anuradhapura, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Ranasinghe, R. A. H. B.; Premaratne, W. A. P. J.; Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, J. A.Chronic Kidney Disease of Unknown Etiology (CKDu) has emerged as a serious public health concern in Sri Lanka. The North Central Region (NCR) has the highest CKDu prevalence in the country, and the disease is more prevalent among farming communities and people who rely on groundwater as their primary source of drinking water. Meanwhile, heavy metal/metalloids exposure and accumulation are recognized as the causative agent of many acute and chronic diseases in certain vulnerable human tissues, including the kidneys. This study assesses the level of contamination of heavy metals/metalloids in drinking water and agricultural soil in a CKDu endemic area in NCR, Sri Lanka. Fifteen groundwater samples collected from wells were analyzed for pH, EC, hardness, heavy metals, and anion concentration using potentiometric, conductometric, titrimetric, inductively coupled plasma mass spectrometric, and ion chromatographic methods, respectively. From six sampling sites in a paddy field, composite soil samples were collected from the surface, and two depths (30 cm and 60 cm). Soil samples were analyzed for pH, EC, organic matter, potassium, phosphate, and heavy metals using potentiometric, conductometric, titrimetric, flame photometric, colorimetric, and inductively coupled plasma mass spectrometric methods respectively. Accordingly, the mean pH of groundwater is 7.25 and this lies within the guideline values. Mean EC is 662.4 μS/cm and mean hardness is 287.0 mg CaCO3/L. Among fifteen samples, four and five water samples have exceeded the health guideline values for EC and hardness, respectively. Metal content varies in the following order, Cd < As < Cr < Cu < Co < Fe < Ni < Mn < Zn. Pb was not detected in any of the water samples and other metals were found in concentrations well below the standard guideline values. Only one sample and three samples exceeded the guideline value for fluoride and nitrite, respectively. Mean pH, EC, organic matter, potassium, and phosphate in paddy soil is 7.57, 101.8 μS/cm, 1.34%, 148.9 mg/kg, and 24.05 mg/kg respectively. Heavy metal content in soil varies in the following order, Cd < As < Pb < Co < Ni < Cu < Zn < Cr < Mn < Fe. Paddy soil from the very bottom showed the highest pH, Pb, Cd, As, Zn, Ni, Mn, Cr, and Fe content while the highest EC, organic matter and potassium content was detected in topsoil. EC, organic matter, and potassium content decreased with the depth of the soil, and the concentration of Pb, As, Zn, Mn, and Fe increased with the depth. This study reveals the dependence of some soil quality parameters on the depth of the soil profile. Monitoring the soil quality is important to minimize the possibility of heavy metal uptake by rice plants. Low heavy metal concentration in groundwater may not have an acute health effect on humans. But long-term chronic exposure to toxic heavy metals together with high EC, hardness, and fluoride would be a reason to trigger the prevalence of CKDu in Maradankulama area.Item Evaluation of toxic metal contamination in surface sediments and water in Mahakanadarawa tank; Anuradhapura, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Sampath, M.; Perera, R. T.; Perera, R. A.; Liyanage, J. A.; Premaratne, W. A. P. J.Toxic elements, including heavy metals/metalloids, readily contaminate water reservoirs via natural mechanisms such as surface runoff, precipitation, and atmospheric deposition. As a result, some toxic metals can be accumulated in surface sediments in the reservoirs and be incorporated into the food chains. It has become a major issue because various trace elements contaminate water, soil, and sediments, which can have serious health consequences due to their toxicity, persistence, and carcinogenic nature. This study was carried out with the aim of analysing the sediment quality in a major irrigation tank called Mahakanadarawa tank in Anuradhapura district, which is located in a high prevalence of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. Fifteen composite sediment samples (five samples in each of fifteen different locations) were randomly collected around the Mahakanadarawa tank in April (2022). Twenty surface water samples (Triplicated) were collected from the Mahakanadarawa lake using twenty different locations. Concentrations of metal elements including Mn, Co, As, Cd, Pb, Cu, Zn, Na, K, Al, Ca, Mg, Fe, and Ni were determined using inductively coupled plasma mass spectrometry (ICP-MS) and multi-element standards were used for the instrumental calibration. Statistical analysis was done using SPSS Statistics Software. According to the analysis of the sediment samples, none of the analysed toxic metals have exceeded the severe effect level as well as the lowest effect level. Abundancy of the metals in the sediments samples is varied as Fe> Mn > Cr> Zn > Cu >Pb > Ni >Co> As> Cd. The Igeo (Geo Accumulation value) values obtained, and the index values exhibit that the sediment samples have a tendency to transfer to an unpolluted to moderately polluted stage with analysed toxic metals except for Zn and Cd. Owing to the long-term intense applications of the crop fertilisers and pesticides in the area, toxic metals may be transferred and concentrated in the tanks from the agricultural fields. Apart from that, average concentrations values of analysed metals, including toxic metals such as Pb, As, and Cd in surface water, were far below the irrigation standards. Contamination of food chains and worsening the hazardous conditions for aquatic life can occur due to the toxic metal accumulations in the surface sediments. In order to conduct a health risk assessment for the consumption of tank fish from Mahakanadarawa tank, further studies should be performed by conducting several sampling cycles of sediment and water as well as toxic metal contamination status of inland fish in Mahakanadarawa tank also need to be evaluated.Item Synthesis and characterization of silica nanoparticles and graphene oxide/nanosilica composite(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Weerasinghe, M. A. S. N.; Liyanage, J. A.; Kumarasinghe, A. R.Ordinary sand is commonly used for water purification. Graphene oxide (GO) is capable of absorbing various water pollutants such as heavy metals and organic contaminants. The ability and the efficiency of water treatment process is proposed to be enhanced using silica nanoparticles and GO/nanosilica composites. Silica nanoparticles and GO/nanosilica composite were synthesized and characterized. Silica nanoparticles were synthesized using tetraethyl orthosilicate and following the sol-gel method. Graphene oxide was synthesized using the modified Hummers’ method. Silica nanoparticles, graphene oxide membrane and GO/nanosilica composite were characterized using Fourier Transform Infrared Attenuated Total Reflection Spectroscopy (FT-IR ATR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Absorption Spectroscopy (ED-XAS) and X- ray Diffraction (XRD). The size of silica nanoparticles was found to be in the range of 50-110 nm with SEM data, which confirms the synthesis of nano-sized silica particles. The sheet like structure with aggregated and folded surfaces of graphene oxide was observed in the SEM analysis of graphene oxide. The interphase between silica and graphene oxide was observed in SEM analysis of GO/nanosilica composite. FT-IR ATR data supported for the identification of functional groups of silica nanoparticles, graphene oxide membrane and GO/nanosilica composite. The peak at 1093cm-1- for asymmetric stretching of Si-O-Si bonds and the peak at 800 cm-1 for symmetric stretching of Si-O-Si bonds are characteristics peaks of silica. The peaks at 3441 cm-1 for the stretching vibration of hydroxyl groups, at 1739 cm-1 for the stretching vibration of carbonyl groups and at 1391 cm-1 for the stretching vibrations of epoxy groups are characteristics peaks of graphene oxide. The FT-IR ATR spectrum of GO/nanosilica composites showed peaks for both silica and graphene oxide. ED-XAS data showed the presence of corresponding elements in each samples. Data from ED-XAS of silica nanoparticles supported the presence of silicon and oxygen while the ED-XAS of GO/nanosilica showed that the presence carbon, oxygen, silicon as the main elements of the sample. XRD spectrum of silica nanoparticles showed a strong broad peak at 22.22 (2θ). A broad peak for silica was observed in the XRD spectrum of GO/nanosilica composite similar to the XRD spectrum of silica nanoparticles. The data from SEM, FT-IR ATR, ED-XAS and XRD confirms the successful synthesis of silica nanoparticles and GO/nanosilica composite