Browsing by Author "Premaratne, W. A. P. J."

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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.
Assessment of derivative spectrophotometry for analyzing competitive adsorption of brilliant green and methylene blue using multiple coated graphite oxide/sand composite
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Sakalasuriya, D. D.; Perera, P. L. R. A.; Perera, W. P. R. T.; Sakunthala, K. A. D. D.; Premaratne, W. A. P. J.; Liyanage, J. A
Wastewater from industrial sectors such as paint production and textile processing are often contaminated with multiple dye pollutants. The simultaneous presence of multiple dyes like Brilliant Green (BG) and Methylene Blue (MB) poses significant challenges for treatment technologies. These dyes not only contribute to environmental degradation but also pose significant health risks, including allergic reactions and cancer due to their toxicity and persistence in ecosystems. A major challenge in treating dye mixtures is the accurate identification and quantification of multiple dyes due to overlapping absorption spectra. This research aims to enhance the resolution of spectral data using derivative spectrophotometry, enabling more distinct identification of overlapping dye components. In this study, the competitive adsorption of MB and BG onto multiple coated graphite oxide/sand (MGO/S) composite was examined. The determination of dye concentrations was carried out using first order derivative (1D) spectrophotometry. Kinetic and isotherm evaluations were conducted under optimal conditions: pH 7.0, 0.09 g of M-GO/S, and a contact time of 20 minutes in binary dye systems. The 20-minute contact time was sufficient to reach equilibrium, as extended durations showed no significant change in adsorption results from preliminary experiments. The experiment was triplicated. The equilibrium adsorption of MB and BG dyes onto M-GO/S showed an inverse relationship with their initial concentrations, signifying the competitive adsorption dynamics where the dyes compete for the available adsorption sites. In a binary mixture of 10 mg/L BG and MB, significant peak overlap at 625 nm and 664 nm hinders precise concentration measurement using zero-order spectra. First-order derivative spectrophotometry resolves this by identifying the adsorption peaks of MB at 625.6, and 503 nm, and BG at 443.2, 445.6, 525.6 and 664.2 nm. Simultaneous determination of BG and MB was achieved at 443.2 nm (1D443.2) (R2=0.9982) and 625.6 nm (1D625.6) (R2=0.9958), respectively. The characteristic parameters of regression equation for the 1D method and obtained coefficient of determination for individual BG and MB were also studied. Therefore, the application of derivative spectrophotometry has proven to be an effective method for quantification of simultaneous adsorptions of BG and MB onto multiple coated graphite oxide adsorbent. This technique allows for precise differentiation and quantification of each dye in the presence of the other, enhancing the understanding of their adsorption dynamics. The results demonstrate that derivative spectrophotometry can improve the accuracy and efficiency of multipollutant adsorption studies.
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.
A comparison of food contamination by heavy metals/metalloids in CKDu prevalent areas and a reference area; A study in Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, J. A.; Premaratne, W. A. P. J.
During the past two decades, so many studies have been involved in exploring the relationship between the prevalence of chronic kidney disease of unknown etiology (CKDu) and exposure to toxic metals. These studies revealed signs of chronic low levels of toxic metal exposure in Sri Lanka. To assess the risk of negative health effects and propose appropriate public health interventions, novel research studies will be very beneficial. This assessment was performed to study the toxic metal contamination status in domestic rice, leafy vegetables, legumes, and citrus fruits in the CKDu prevalence area in north central province in Sri Lanka and to compare those levels with a reference area in the Eastern province in Sri Lanka where CKDu is not prevalent. CKDu hot spots areas Maradankulama- Mahakanadarawa in the Anuradhapura district, Sri Lanka was selected for sampling and Buddhangala Grama Niladhari area in Ampara district was selected as a reference site. Food samples, including (Oryza sativa; n=25, Centella asiatica; n=25, Citrus crenatiflora; n=18, Vigna radiata; 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 in both areas and the collected food samples were digested by microwave digestion according to the standard procedures and the concentrations of metal ions in food samples, including Cadmium, Nickel, Chromium, Copper, Iron, Manganese, Lead, Zinc, Arsenic, and Calcium, were measured using Inductive Coupled Plasma technique (ICP). As a results of the study, 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 radiata have 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. However, none of the food samples collected from the reference areas has exceeded the permissible limits of analyzed heavy metals/metalloids. THQ (Target Hazard Quotient) values of Cr have exceeded the threshold values for all food species. Furthermore, Pb is also regarded as a toxic element and THQ values of Pb in Oryza sativa and Vigna radiate are noticeably high. Meanwhile, THQ values of the food samples in the reference areas have not exceeded the threshold values. According to the outcome of the study, there is a noticeable difference reported in toxic metals contamination status between the CKDu-prone areas and the reference area. Therefore, the consumption of analyzed rice, leafy vegetables, and legumes was estimated to be risky, and their regular consumption may boost the likelihood of CKDu prevalence in those areas. Further studies are required to monitor and assess heavy metals and metalloids in soil, and fertilizers to find the pathways of contamination of food by toxic metals.
Development of a liquid fertilizer system from bio-slurry waste and natural resources: A case study on early growth of chili (Capsicum annum L.)
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Ranaweera, A.D. P. S.; Karunawardana, W. A. L. S.; Abeysinghe, D. T.; Premaratne, W. A. P. J.
Hydroponics or soil-less culture is a technology for growing plants in nutrient solutions that supply elements needed for optimum plant growth with or without use of an inert medium to provide mechanical support. Hydroponics offer opportunities to provide optimal conditions for plant growth and therefore, higher yields can be obtained as compared to open field agriculture. Here we aim to develop a liquid fertilizer system using a bio-slurry waste obtained from biogas reactor, selected animal waste, wood ash and dolomite. Five liquid biofertilizer systems (M1, M2, M3, M4 and M5) were developed by mixing different ratios of bio-slurry waste obtained from biogas reactor, cow dung, poultry waste, wood ash and dolomite. A control experiment was carried out with Albert solution, a commercial chemical liquid fertilizer. The liquid fertilizer systems were tested using 12 Chili (Capsicum annum L.) plants in each treatment and treated with a continuous hydroponic cultivation system for 12 weeks in triplicate. The pH in hydroponic systems varied from 6 to 8. At the end of the 12 weeks’ plant growth was monitored by measuring the height of the plant. Chili plants grown in fertilizer mixture M4 (bio slurry waste: 36.0 L, cow dung: 600.0 g, poultry waste: 600.0 g, wood ash: 75.0 g, dolomite: 75.0 g) gave the highest growth rate (50.3±3.0 cm) and the highest harvest (28.8±1.2 g) among the five developed biofertilizer systems. This M4 fertilizer system has the highest N (49.0±0.2 ppm), P (9.9±0.1 ppm) and K (434.2±0.8 ppm) content. Fertilizer system M1 which has only bio-slurry waste showed the lowest growth rate (37.4±1.6 cm) and the lowest harvest (16.1±0.6 g). M1 has the lowest nutrients content (N: 28.3±0.1 ppm, K: 349.0±0.7 ppm, P: 4.5±0.1 ppm) among the five liquid fertilizers. The control, Albert solution which has N (10.6%), K (16.3%) and P (9.3%) showed a growth rate of 46.0±5.4 cm and a harvest of 30.1±1.6 g. Therefore, it can be concluded that added natural ingredients improve the effectiveness and quality of the liquid fertilizer with high content of nutrients. Therefore, M4 liquid fertilizer system has the potential to be developed as an economical, effective, eco-friendly fertilizer system for the hydroponic cultivation of chili plants compared to commercial chemical liquid fertilizers.
Development of a new slow release biomass fertilizer system using urea incorporated crape-jasmine plant bark particles
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Premaratne, W. A. P. J.; Thisera, P. A. U. D.
Urea is one of the fast release nitrogen (N) fertilizers that dissolves within few days with sufficient amount of water in soil matrix. The excessive use of urea can weaken the overall health of the plant and lead to adverse environmental issues such as eutrophication. Slowrelease fertilizers may overcome these complications. In this research, a new slow release fertilizer system was developed using urea incorporated Tabernaemontana divaricata (Apocynaceae) plant, which is commonly named crape-jasmine. New fertilizer system was prepared from crape-jasmine bark particles (< 5 mm) after treating with a saturated solution of urea. Crape-jasmine plants were obtained from Rathmalagara estate, Madampe in Coconut Research Institute (CRI), Sri Lanka. The release patterns of nitrogen from urea incorporated crape-jasmine bark particles (10 g) in a soil matrix (200 g) were investigated using columns with deionized water (pH 6.7). Parallel studies were carried out to evaluate the leaching patterns of commercially available three nitrogen fertilizers sold in Sri Lanka in the soil matrix using the columns. Control reactions were carried out with urea in a soil matrix and soil matrix alone. Each experiment and analysis was carried out in triplicate. According to the experimental results, the level of nitrogen (N) in leaf, mid rib, root, bark and stem of the plant varied from 5,313 mg/kg to 12,740 mg/kg. It was found that phosphorous (P) and potassium (K) content in the plant varied from 268 mg/kg to 1,805 mg/kg and from 289 mg/kg to 906 mg/kg respectively. Nitrogen content was increased by more than five-fold giving the maximum value of 72,240 mg/kg after crape-jasmine chips were treated with saturated urea.The initial nitrogen content in the bark was 12,565 mg/kg. Experimental results indicated that within 24 hours, more than 80% of the nitrogen was eluted from urea and commercially available fertilizers in the soil matrix given. But, only 24% of nitrogen was eluted from urea incorporated crape-jasmine bark particles within 24 hours. After 15 days, eluted nitrogen amount was recorded as only 50% from the incorporated crape- jasmine bark particles indicating that N was released in a slow release pattern. Therefore, crape-jasmine can be identified as a potential N fertilizer carrier and urea incorporated crape-jasmine bark particles can be further developed as a new slow release biomass fertilizer system.
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.
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.
Evaluation of nutritional properties and toxicity levels in commercial fertilizers sold in Sri Lankan market
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Medagoda, S. M. C. R.; Premaratne, W. A. P. J.
When plants cannot absorb adequate nutrients from the soil, the plant growth becomes retarded. Plants require nutrients in optimum levels in order to continue normal growth. To meet this requirement, fertilizers are used as an external source to provide nutrients plants need in correct proportions at the right times. In this study, seven brands of mineral fertilizers sold in the Sri Lankan market as NPK fertilizers were investigated over a period of six months in 2017 to determine their nutritional properties and other physicochemical parameters. A parallel study was conducted to investigate the dissolution properties of these commercial fertilizers in a soil matrix in order to identify their leaching kinetics. In addition to that, a quantitative study was carried out to determine the toxic metal levels of these commercial fertilizers. According to the experimental results, the nitrogen (N), phosphorous (P), and potassium (K) percentages in commercial fertilizers varied from 4.5 - 9.9%, 3.2 - 5.7%, and 2.6 - 18.1%, respectively. The release patterns of nitrogen from commercially available fertilizers sold in Sri Lanka (10 g) in a soil matrix (200 g) were investigated using columns with deionized water (pH 6.7). Control reactions were carried out with urea in a soil matrix and a soil matrix alone. Each experiment and analysis was carried out in triplicate. According to the experimental results, within 24 hours, more than 80% of the nitrogen was eluted from urea. But, nitrogen elution within 20 days varied from 30% to 78% in commercially available fertilizers in the soil matrix due to different dissolution kinetics. The concentration levels of Cd (0.44 - 0.93 mg/kg), Pb (6.2 - 17.8 mg/kg), Cr (5.2 - 9.9 mg/kg), Cu (1.9 - 37.9 mg/kg) and Fe (116.1 - 457.8 mg/kg) were found in the commercial fertilizers. The findings obtained from above study can be used in further studies to determine the relationship between heavy metal contents in fertilizers and health effects caused by exposure to these fertilizers.
Evaluation of quality parameters and heavy metals in selected cosmetic products in Sri Lankan market
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) De Silva, J. H. I. G.; Premaratne, W. A. P. J.
Cosmetic products play a significant role in personal care routines worldwide, including in Sri Lanka. Concerns regarding the quality and safety of products have grown due to the potential presence of harmful chemicals and inconsistent product formulations. This study focuses on the analysis of selected cosmetic products commonly available in the Sri Lankan market, assessing their quality attributes, and detecting possible toxic metal contaminants. Four brands of skin creams sold in Sri Lankan market have been investigated for a period of one year (June 2021-June 2022). All analyses were done in triplicates for each sample. Samples have been selected under three categories, sun creams (S1-S4), moisturizing creams (S5-S8) and whitening creams (S9-S12). These samples were obtained from four brands. pH, Non-volatile matter, water content and toxic metals were analyzed. All physicochemical parameters were analyzed according to the test methods given by the SLSI. Heavy metals were analyzed using ICPMS. Range of pH at 27±2oC in selected creams was (5.7 ± 0.09 to 7.8 ± 0.14). According to the specification for skin creams (SLS743:2021), the acceptable range of pH at 27±2oC in creams is 4.5- 8.0. pH value of all the skin care cream samples were statistically in acceptable pH range. Nonvolatile matter at 105oC percent by mass in selected creams was (9.90 ± 0.08 to 24.90 ± 0.07). According to the specification for skin creams (SLS743:2021), acceptable Non-volatile matter at 105oC, percent by mass (minimum value) of skin creams is 15. Nonvolatile matter of S1, S2, S3, S4, S6, and S7 were 10.6. ± 0.11, 9.5 ± 0.42, 11.2± 0.08, 14.20 ± 0.34, 9.90 ± 0.08 and 11.10 ± 0.06 respectively and all six samples were not complied with the acceptable (minimum) level. The water content percentage by mass in selected creams was (70.40 ± 0.59 to 87.60 ± 0.53). According to the specification for skin creams (SLS743:2021), acceptable Water content, percent by mass (maximum value) of skin creams is 85. The water content of all samples was below the acceptable (maximum) level except S4 sample (87.60 ± 0.53). Some of metal concentrations were tested under metal analysis, Aluminium 9.2 ± 0.18 - 224.9 ± 3.24 mg/kg, Zinc 2.90 ± 0.09 – 19866.7 ± 1423.21 mg/kg, Calcium 88.1 ± 5.2 – 2647.8 ± 87.1 mg/kg, Potassium 15.4 ± 0.16 – 3645.8 ± 4.97 mg/kg, Sodium 142.3 ± 2.9 – 7960.2 ± 845 mg/kg), Molybdenum 0.33±0.01 - 3.09 ± 0.06 mg/kg, Magnesium 9.10 ± 0.04 - 250.00 ± 168.13 mg/kg, Vanadium 0.34 ± 0.01 - 2.41 ± 0.06 mg/kg. Some metals were not detected, and some results were below LOQ level. According to the specification for skin creams and lotions (SLS743:2021), acceptable maximum value of Lead, Arsenic, Mercury, Cadmium concentration in skin creams are 10 mg/kg, 3 mg/kg, 1 mg/kg and 3 mg/kg respectively. As, Cd, Pb, and Hg level were below the recommended limits according to the SLS standard. According to the results obtained from this study, all the tested samples were in acceptable quality and as the recommendation; further research can be conducted to determine the chemical concentrations which can damage the function of skin.
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.
Exploring the toxic metal contamination and unveiling the risks in staple grains grown in a CKDu hotspot in Sri Lanka
(Faculty of Graduate Studies - University of Kelaniya, Sri Lanka, 2023) Perera, M. A. S. N.; Perera, W. P. R. T.; Perera, P. L. R. A.; Kadigamuwa, C.C.; Liyanage, J. A.; Premaratne, W. A. P. J.
Toxic metals in dietary grains could pose health risks from direct ingestion. This investigation aims to analyze the concentrations of toxic metals in selected dietary grains and conduct a comparative risk assessment in a region endemic to Chronic Kidney Disease of Unknown etiology(CKDu) in a non-endemic region. Six household fields in the CKDu endemic region in Nikawewa Grama Niladhari Division(GND) and three in the reference region; Wewagedara GND were selected for sampling. Inductively Coupled Plasma-Mass Spectrometry(ICP-MS) was used to determine Arsenic (As), Cadmium (Cd), Lead (Pb), Chromium (Cr), Copper (Cu), and Zinc (Zn) in composite samples collected from both GND areas (pulses; [(Vigna radiata; n=20), (Vigna unguiculata; n=20), (Vigna unguiculata subsp.; n=20)] cereal; [(Oryza sativa; n=30)]. Descriptive statistics revealed average As concentrations in samples as follows; Oryza sativa (38.60±13.84 g/kg,) Vigna unguiculata (3.25±1.96 g/kg), As was undetectable in samples of Vigna radiate, and Vigna unguiculata subsp. in CKDu endemic area. The average As concentrations of Oryza sativa in the reference area was 5.56±1.87g/kg and As was not detected in other grain species. All values complied with FAO/WHO & Codex permissible limits (As-100-200 g/kg). The estimated Daily Intake (EDI) value of As (0.257 g/kg/day) in Oryza sativa in the endemic area did not exceed the Tolerable Daily Intake (TDI) (As-0.3 g/kg/day). The average concentrations of Cd and Pb were reported in the CKDu endemic area; Oryza sativa (Cd-1276.92±234.42 g/kg, Pb-419.31±98.78 g/kg), Vigna radiata(Cd-571.31±60.71 g/kg, Pb-344.15±93.75 g/kg), Vigna unguiculata (Cd-1354.33±265.34 g/kg, Pb-408.56±22.20 g/kg), and Vigna unguiculata subsp.(Cd-1546.23±355.23 g/kg, Pb-408.63±115.14 g/kg) and exceeded FAO/WHO permissible limit(Cd-400 g/kg, Pb-300 g/kg). But those values were within the limits in the reference areas. However, Cu, Cr, and Zn remained within FAO/WHO safe limits in both regions. A health risk can be generated owing to long-term consumption of staple grains grown in Nikawewa GND; CKDu endemic area.
Graphite oxide / TiO2 advanced hybrid material using Sri Lankan graphite: Synthesis and characterization.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Premaratne, W. A. P. J.; Fernando, K. D. G.
Sri Lanka has deposits of vein graphite consisting of a high crystallinity and high purity (> 99 % of carbon). Graphite being a lamellar structure that is both electrically and thermally highly conductive, allows it to be a versatile material for use in hybrid materials and nanocomposites. Graphite oxide (GO) which has a lamellar structure and is derived from graphite is a promising material for the synthesis of nanocomposites. In this study, the synthesis of GO/TiO2 hybrid material was carried out at low temperature using GO formed from Sri Lankan vein graphite and titanium oxysulfate (TiOSO4) as reactants. Here we investigated the intercalation of nano-TiO2 particles in the d-spacing of the lamellar structure of exfoliated GO from Sri Lankan vein graphite. Hummers’ method was used to oxidize vein graphite to produce GO using potassium permanganate (KMnO4) at 20 °C. Exfoliated graphite oxide (GO) was then used to intercalate with TiO2 synthesized using a sonication method. Raw materials, intermediate products, and the hybrid material were analyzed using X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) to observe material characteristics and their physical and chemical properties. Graphite showed high crystallinity at the (002) plane at 26.5 degrees. For GO this (002) plane was shifted to a value of 9.84 degrees, indicating the expansion of the d-spacing. For the GO/TiO2 hybrid material, the d-spacing has been reduced due to the shift of the (002) peak to a value of 11.48 degrees. SEM images obtained at 25 kV showed that the growth of TiO2 on the composite surface was in agglomerate form with a particle size range of 100-500 nm. FTIR indicated a strong peak at 1580 cm-1 for vein graphite. There were multiple peaks for GO at 1580 cm-1, 1680 cm-1, 3400 cm-1, 1100 cm-1, and 1400 cm-1 indicating the presence of oxygen containing groups. The GO/TiO2 hybrid material showed few extra peaks with small intensity in the Raman spectra at 640 cm-1, 510 cm-1, and 400 cm-1. Photocatalytic activity of TiO2 intercalated GO hybrid material was investigated using a methyl orange solution. The degradation of methyl orange in the presence of hybrid material was studied by employing UV-visible spectrophotometry and compared with pure nano-TiO2 (< 25 nm). The results showed that after 60 minutes, the advanced hybrid material (GO/TiO2) degraded 95% of methyl orange while nano-TiO2 has only degraded 46% under UV irradiation.
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.
Investigation of heavy metal concentrations and distribution in road dust from large and small urban areas in Gampaha district, Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Wijesinghe, L. O.; Premaratne, W. A. P. J.
Heavy metal contamination has become one of the major problems in metropolitan areas all around the world. Gampaha district in Sri Lanka is one such hotspot that experiences extensive heavy metal contamination. Road dust contains several types of potential pollutants resulting from diversified anthropogenic sources which are observed commonly in urban areas. Acceleration of anthropogenic activities leads to the increment of heavy metal levels in the earth's crust. Therefore, heavy metal content analysis in road dust is a worthwhile measure to evaluate the pollution level of the environment. This indicates toxic heavy metal levels in living systems and therefore the potential threat to human health. This investigation was carried out by selecting twelve sampling sites from large and small urban areas in the Gampaha district. Sampling sites lie in the GPS range of 6.96920 °N to 7.022829 °N and from 79.912284 °E to 80.049099 °E. Six sampling sites from highly polluted large urban areas in the vicinity of Kandy- Colombo main road (A1) and six sampling sites from less polluted small urban areas away from the A1 main road in Gampaha area were selected. Dust samples were collected by the wiping method and analyzed in triplicate for six consecutive weeks from July to August 2020. There was no significant change in the rainfall during the study period. Samples were analyzed for pH, conductivity, moisture, phosphorous content and organic matter. Contents of five heavy metals Pb, Cu, Zn, Cr and Fe in the samples were determined using Atomic Absorption Spectroscopy (AAS). The factors that favor accumulation of heavy metals in the environment were investigated and analyzed. Fe content in road dust samples from both large and small urban areas was very high (14.2×104, 9.5×104 mg/kg respectively) The road dust from large urban areas contained reasonably high Pb (71.1 mg/kg) and Zn levels (108.8 mg/kg) compared to the levels in small urban areas (15.1, 86.0 mg/kg respectively). Cr (52.0, 25.1 mg/kg) and Cu (6.8, 0.6 mg/kg) were relatively abundant in almost all the samples. The results revealed that Pb, Cu, Zn, Cr and Fe levels were higher in road dust from large urban areas compared to small urban areas.
Investigation of metal concentrations in indoor and outdoor dust in Kelaniya area, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Silva, K. D. M.; Premaratne, W. A. P. J.
Urban dust is often contaminated with heavy metals and has become one of the major problems in metropolitan cities which is difficult to be controlled. Kelaniya area in Sri Lanka is one such vulnerable location. Anthropogenic activities have contributed exclusively for the elevation of heavy metal concentrations in atmospheric dust and in the earth’s surface. Analysis of both indoor and outdoor dust therefore becomes an important tool in the prediction of the extent to which air pollution has taken place in a particular area. This can help to relate the threat for human health by toxic elements and to identify its impacts. This investigation was carried out by selecting two major locations at the vicinity of the Kandy- Colombo main road (A1) in Kelaniya area including the premises of University of Kelaniya which is located very close to the A1 main road. The sites lie in the GPS range of 6.969674 °N to 6.975092°N and from 79.913546°E to 79.923919°E. Ten sampling sites from indoor and outdoor locations were selected. Samples were collected as triplicates for six consecutive months from June to November 2018. They were analyzed for pH, conductivity, moisture, phosphorous content and organic matter. Concentration levels of five heavy metals Pb, Cu, Zn, Cr and Fe were also determined using atomic absorption spectroscopy. The preliminary factors that favor the persistence of heavy metals in the environment were investigated and analyzed. It was observed that acidic dust and organic nature favor heavy metal deposition. Among the heavy metals, Fe content was very high (1614-6134 mg/kg) in the dust samples. Cr levels (1.92-10.58 mg/kg) were very low. Pb content (21.09-84.52 mg/kg) was reasonably high. Zn level (14.72-42.48 mg/kg) and Cu level (6.0-45.0 mg/kg) were relatively abundant in almost all the samples. A good positive correlation was observed in between Pb- Zn, Pb-Fe and Pb-organic matter than other combinations assuring to a correlation coefficient greater than 0.5 in every instance. These results suggest that components of positive correlation have arisen from a common source and that dust comprised of high Zn or Fe concentration have a higher probability of Pb contamination
Investigation of toxic metals contamination status in red raw rice (Bg 350) grown in North Central province in Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Kumari, M. K. J. K.; Premaratne, W. A. P. J.; Perera, P. L. R. A.; Perera, W. P. R. T.; Liyanage, J. A.
Red raw rice consumption is high due to its nutritional properties. The chemical components of food are correlated with their ability to sustain better human health. Rice is the staple food of Sri Lanka. Although it is a good source of nutrients in a diet, its consumption can also lead to exposure to toxic metals due to environmental pollution. Rice is grown extensively in the North Central Province (NCP) where the prevalence of chronic kidney disease of unknown origin (CKDu) is high. This study was aimed to determine the toxic metal content such as Arsenic (As), Cadmium (Cd), and Lead (Pb) in domestically grown red raw rice in NCP and assess the risk of these values to human health. A total of 35 samples of red raw rice were obtained from farmers in NCP during Yala growing cycle in 2021 based on the eight sampling sites. As, Cd and Pb levels were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The potential health risk was estimated by Estimated Daily Intake (EDI). The mean Pb levels in red raw rice were higher than the FAO/WHO allowable limits (Pb-200 μg/kg) in all the selected areas except the Rambewa area. The highest mean Pb concentration was recorded in the Horowpathana area as 429.93100.93 μg/kg. As and Cd values were within FAO/WHO allowable limits (As-200 μg/kg, Cd-400 μg/kg). The highest mean value of as was recorded in the Medirigiriya area, and it was 97.7218.19 μg/kg. The highest Cd level was recorded in the Horowpathana area as 60.7024.39 μg/kg. The estimated daily intake (EDI) values are also significantly lower than the Tolerable Daily Intake (TDI) (Pb-250 μg/day, Cd-62 μg/day, As-3 μg/day). Dietary exposure is the most common route through which these toxic metals enter the human body. Long term consumption of red raw rice causes to accumulate the toxic metals in body tissues and generates adverse health effects of residents in selected CKDu prevalent areas in NCP. It is suggested that further studies are needed to get a more comprehensive idea on the public health concerns of toxic metals due to red raw rice consumption in Sri Lanka.
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.
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.
The role of ascorbic acid in optimizing optoelectronic performances of CdS thin films
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Danansuriya, D. B. U. I.; Hetti Arachchige, K. A.; Manilgama, T. T. D.; Kalingamudali, S. R. D.; Premaratne, W. A. P. J.; Jayathilaka, K. M. D. C.; Wijesundara, L. B. D. R. P.; Kumarage, W. G. C.
Cadmium sulfide (CdS), a widely studied (II-VI) group semiconductor, has long captivated the scientific community due to its potential applications in photovoltaic (PV) devices. However, optoelectrical properties of n-CdS, such as flat band potential, and optical band gap, are crucial for enhancing solar cell efficiency. This study explores the tunability of these properties in CdS thin films through chemical bath deposition (CBD) with a mild reducing agent ascorbic acid (C6H8O6). A series of CdS thin films were deposited on fluorine-doped tin oxide (FTO) glass substrates by using various concentrations of ascorbic acid (0, 0.1, 0.01, and 0.001 mol.dm-3). The deposition chemical bath consisted of 0.1 mol.dm-3 cadmium sulfate (CdSO4) and 0.2 mol.dm-3 thiourea (CS(NH2)2) as cadmium and sulfur sources, respectively. The deposition process was conducted at 80 °C for one hour at a pH of 11. Post-deposition, the CdS films were etched in the non-conductive side of the FTO with diluted hydrochloric acid (HCl), followed by annealing at 300 °C for one hour in air. All the electrical measurements were performed in a photoelectrochemical cell comprising a CdS/0.1 mol.dm-3 Na2S2O3/Pt half-cell with an active area of 1 cm². An Ag/AgCl electrode served as the reference for all characterizations. The short-circuit current density (JSC) has shown a significant increase with decreasing ascorbic acid concentration, achieving a 155.6% enhancement with a concentration of 0.001 mol.dm-3 compared to untreated CdS. Conversely, with increasing ascorbic acid concentration the opencircuit voltage (VOC) and the flat band potential (VFB) decreased. The highest reported photocurrent power (VOC×ISC) was observed in films deposited with 0.001 mol.dm-3 ascorbic acid, showing a 150.2% improvement over untreated CdS. Scanning electron microscopy (SEM) analysis revealed that ascorbic acid-treated CdS films exhibited aggregated nanoscale particles, whereas untreated films displayed larger clusters. Consequently, the photocurrent enhancement is attributed to these morphological changes that cause higher effective surface area in the ascorbic-treated CdS thin films compared to the untreated CdS. Furthermore, Mott-Schottky analysis confirmed that all deposited films retained n-type characteristics. This study demonstrates that the electronic properties of n-CdS can be finely tuned through ascorbic acid treatment, making it a promising approach for fabricating thin film solar cells with high light-to-current conversion efficiency. The ability to control and enhance these properties is invaluable for advancing PV applications and achieving higher solar cell performances.