Browsing by Author "Perera, W. P. R. T."

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Adsorptive removal of Cd (II) from aqueous solutions by sand/graphite oxide nano-composites: characterization, isotherm, and kinetic studies
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Perera, W. P. R. T.; Perera, P. L. R. A.; Kumarasingha, A. R.; Liyanage, J. A.
Core-shell absorbent granules were developed by coating commercial sand gravels with graphite oxide (few-layer oxidized graphene sheets). Graphite oxide (GO) is synthesized chemically from vein graphite, a rare form of high-purity natural graphite (NVG). Modified Hammer's method was followed in order to synthesize graphene oxide from the NVG. Repeated coatings of graphite oxide on the sand followed by low temperature (120 0C) thermal pyrolysis resulted in core-shell granules with a hierarchical structure in which sand gravels are covered by graphite oxide layers. Five times GO coated water stable sand/graphite oxide nano-composites (M-S/GO) were developed for further adsorption studies. The adsorption performance and mechanism of Cd (II) removal were investigated and FT-IR, SEM, EDX, and XPS were used to characterize the (M-S/GO) as spectroscopic and microscopic characterization methods. Optimization studies were carried out to find the effective pH of the media, dosage, initial concentration of Cd (II), and contact time that reached the equilibrium. Apart from that, the models of kinetics (pseudo-first order and pseudo-second order), and isotherms (Langmuir and Freundlich) were introduced. Characterization findings indicated that un-uniform graphene oxide coatings had been constructed on the sand surface and the surface of the nano-composite comprised of oxygen-based functional groups. Under optimum conditions (0.08 g/L of dosage, 65 mg/L initial Cd concentration, 120 min of contact time), the M-S/GO removed 93.8% of Cd (II) from simulated water at pH 8.0 (30 ± 2 ℃) and the process reached equilibrium after 120 minutes. The adsorption capacity of Cd (II) was augmented when increasing the pH of the medium up to pH=8, and then it tended to reduce. Further, the experimental data have been fitted with the Langmuir isotherm model indicating that monolayer adsorption of Cd (II) occurs on the surface of M-S/GO. Apart from that, M-S/GO had a maximum adsorption capacity (mg/g) (Qmax) value for Cd (II) adsorption (16.12 mg/g) than sand and GO, the equilibrium parameter (RL) value in this study was 0.071, which indicates that Cd (II) adsorption onto the surface of the M-S/GO is favorable. The experiment kinetic data were best fitted to a pseudo-second-order kinetic model indicating that Cd (II) has adsorbed onto the surface of the M-S/GO by a chemical sorption mechanism. These findings imply that M-S/GO could be used as an effective adsorbent for removing Cd (II) from contaminated water sources. More research is required to determine the reusability of M-S/GO in the adsorptive removal process.
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 groundwater contamination with environmental toxicants in CKDu endemic area, Polonnaruwa, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Perera, W. P. R. T.; Dayananda, M. D. N. R; Botheju, W. S. M.; Liyanage, J. A.
Chronic Kidney Disease unknown etiology (CKDu) is one of the major health impacts predominantly confined to people in North Central Province in Sri Lanka. The root courses for the disease prevalence have not found yet. Therefore, this investigation was carried out to determine the groundwater contamination with environmental toxicants: Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Zinc (Zn), Arsenic (As), Iron (Fe), Calcium (Ca), Magnesium (Mg) Fluoride (F), Sodium (Na) and Aluminium (Al) in Dimbulagala Grama Niladhari Division (GND) in Polonnaruwa District, Sri Lanka. The study investigated the groundwater quality of Dimbulagala GND in dry zone of Sri Lanka to assess its suitability for drinking purposes. Only Ten working tube wells were found in the studied area and groundwater samples were collected from the tube wells. Basic physicochemical parameters (pH, temperature, conductivity and dissolved oxygen), (Hatch HQ14d) and fluoride content were determined (Orion Star- 2014) onsite. Environmental toxicant concentrations were determined using Inductive Coupled Plasma Mass Spectrometry (ICP–MS, Agilent 7800). Results were analyzed using SPSS statistical software. descriptive statistics were performed on the data set and the Pearson correlation was applied. According to the results obtained from the onsite investigations the mean values of pH, conductivity and fluoride content were 7.78 (+1.28), 520 us/cm (+148) and 1.20 mg/l (+0.32) respectively. The mean value of the fluoride content has exceeded the permissible limit (1.0 mg/L), (SLS 614-2013). It was highlighted that significant toxic heavy metals such as Lead (Pb), Cadmium (Cd), Chromium (Cr) and Arsenic (As) levels as well as other metals like Fe, Cu, Zn, Na, Al have not been exceeded than permissible limits (SLS 614-2013). Statistically evaluation process proved none of the positive correlation is reported between heavy metal concentrations and Fluoride content of the groundwater in the studied area. But a negative correlation was reported between Fluoride and Cr (p= -0.05) in the groundwater in the studied area. Ca and Mg concentrations ranged between 3.43 mg/l to 130.56 mg/L And 6.54 mg/L to 75.32 mg/L respectively. Although mean Ca (10.12 mg/L) and Mg (15.45mg/L) did not exceed the permissible levels (100 mg/L and 30 mg/L for Ca and Mg), 40% and 50% of individual samples for Ca and Mg levels exceeded the permissible levels respectively. There is an urgent need for establishing proper long term drinking water treatment method for the studied area because of long term exposure to heavy metals such as Cd, Pb, Cr, As, and high levels of Fluoride as well as other environmental toxicants can be harmful to people. These findings can be used as a benchmark of raw water quality in the design processes of treatment plants
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 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.
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.
Effect of fertilizer application to the agricultural soil and the determination of soil to plant transfer coefficients of selected elements
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Perera, W. P. R. T.; Dayananda, M. D. N. R.; Botheju, W. S. M.; Liyanage, Janitha A.
Transfer of metals from soil to plant depends on the availability of particular elements in soil and the fertilizer which are applied to the agricultural fields. This study aims to determine the effect of fertilizer application to the agricultural soil and to determine the soil to plant transfer coefficients of selected elements in Eppawala Grama Niladhari Division (GND), Anuradhapura, Sri Lanka. Fifteen soil and rice root samples were randomly collected from paddy fields and composite fertilizer samples were prepared by adding Urea, Muriate of Potash and Rock Phosphate in the ratios which were used by farmers in sampled area. Metals were analyzed by Inductive Coupled Plasma Mass Spectrometry (ICP-MS-Agilent 7800). Mean concentrations of Cr, Fe, Cu, As, Cd, Pb and Zn in fertilizer composites were 445.00±171.00, 114638.00±46722.00, 92.90±38.40, 178.00±109.00, 5.56±3.41, 912.00±534.00 and 2553.00±1452.00 in mg/kg respectively. Mean concentrations of Cr, Fe, Cu, As, Cd, Pb and Zn in soil samples were 0.22±0.03, 135.10±38.90, 1.37±0.16, 0.25±0.30, 0.01±0.00, 0.32±0.07 and 40±10.3 in mg/kg respectively. The transfer coefficients (TC) of different metals were quantified to indicate the lability of metals in soils. Greater TC value indicates relatively poor retention of metal in soil or greater efficiency of plant roots to absorb metal, and low TC is attributed to strong sorption of metal to the soil colloid. TCs from soil to roots for Cr, Fe, Cu, As, Cd, Pb and Zn were 62.14, 260.04, 46.93, 6.94, 21.26, 14.14 and 3.37 respectively. It indicates that rice roots absorb higher amounts of metals in soil colloids which are resulting mostly from the fertilizer applications. It can be concluded that considerable amount of metals coming from the fertilizers are remaining in the soil and the efficiency of absorbing metals from plant roots is higher than the retention of metals in soil as having greater Transfer Coefficients.
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.
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.
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 spatial distribution of fluoride in drinking water sources in CKDu prevalence areas in Sri Lanka using GIS
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Dayananda, M. D. N. R.; Botheju, W. S. M.; Perera, W. P. R. T.; Liyanage, J. A.
Chronic Kidney Disease of unknown etiology (CKDu) has identified as a significant health burden in rural dry zone areas in Sri Lanka. Fluoride is recognized as a nephrotoxic contaminant which deteriorates the renal functions progressively and the drinking water could be the major source which is responsible for the disease occurrence. Therefore, the present study attempted to investigate the spatial distribution of fluoride in drinking water sources in CKDu prevalence hotspots in Sri Lanka using Geographical Information System (GIS). Triplicated drinking water samples were collected from 30 sampling locations (from dug wells) in each Grama Niladhari Division (GND) including Wewelketiya GND in Anuradhapura district, Ambagaswewa GND in Polonnaruwa district, Naminigama GND in Mathale district and Buddhangala GND in Ampara district (Reference site) in dry season, Sri Lanka (February – March, 2019). Fluoride contents of collected samples were analyzed using ion chromatography (Metrom Eco_IC instrument). Spatial distribution patterns were interpolated using inverse distance weighted (IDW) and spatial autocorrelation (Moran’s Index- MI) tools in ArcMap 10.2.2 software. Results indicated that the mean fluoride levels of the collected water samples of Ambagaswewa and Wewalketiya areas were 1.37 ± 0.66 mg/L and 1.26 ± 0.65 mg/L respectively and those results exceeded the Sri Lankan drinking water standards (SLS 614: 2013) (1.0 mg/L) but the mean fluoride levels relevant to Naminigama area (0.82 ± 0.59 mg/L) complied with the SLS standards. Further 80% of the samples in Ambagaswewa GND and 95% of samples in Wewalketiya GND were highly contaminated with fluorides which were exceeded the SLS standard limits. Significantly higher Fluoride concentration levels were shown in Ambagaswewa GND (P= 0.103) and Wewalketiya GND (P= 0.704) compared to the reference area of the study.As well as fluoride concentration of the reference area was evenly distributed (MI= -0.005) in very low levels compared to the selected hot spots. Fluoride distribution were clustered with higher levels (MI = 0.31) in Wewalketiya GND, and Fluoride levels were evenly distributed with higher levels in Ambagaswewa GND and Naminigama GND with the Moran’s Indices of -0.12 and -0.07 respectively. It can be concluded that fluoride can be one of the risk factors affecting the prevalence of the CKDu. As the people are at a risk with the long-term exposure to the high fluoride concentrations, it is very essential to innovate a proper and affordable drinking water treatment technology for the affected areas and findings of this study can be used as background water quality data in the design process
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.
Study of aqueous calcium ion adsorption competence by coreshell adsorbent granules engineered from sand/graphene oxide nanocomposite
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Premasinghe, Niroshan; Perera, W. P. R. T.; Fernando, W. S. K.; Liyanage, Janitha A.; Kumarasinghe, A. R.
In water treatment, sand unit processes are frequently used to remove turbidity. In order to enhanced the performance of the sand, a surface modification was done using graphite oxide. The core-shell granules were fabricated using graphite oxide coated river sand. Graphite oxide was derived from high purity vein graphite in Sri Lanka. Repeated coating of graphite oxide on the sand followed by low temperature (110 °C) thermal pyrolysis yield hierarchical core-shell structure where several layers of graphite oxide covered the sand particulates. Mineralogical and physicochemical characterization of the novel adsorbent was carried out by Energy Dispersive X-Ray attached to Scanning Electron Microscopy (SEM-EDX), Fourier-Transform Infrared Spectrometry (FTIR), and X-ray Powder Diffraction (XRD). The operational parameters such as contact time, initial calcium ion concentration, adsorbent dose and initial pH of the solution were evaluated in batch procedures at room temperature (26±2 °C) using Five time GO/sand combination which observed as the most effective combination for calcium ion removal from hard water. Characterization studies reveal that uneven coatings of graphene oxide present on the surface of Nanocomposite is containing oxygen-based functional groups (C-O, C=O, O-H) in addition to C-C groups. Optimization studies showed that, the most effective dosage of the adsorbent is 5.0 g with initial calcium ion concentration 50 mg/L. It appears that there was no significant effect on the calcium ion removal over a wide range of pH 4-10 and the process began to reach equilibrium after 20 minutes. Finally, super sand granules show high partiality towards calcium ions and it will be important for the treatment of the hard water and the multiple coated GO/sand combination can be used to regulate excess water calcium and turbidity simultaneously.
Surface modified graphene-based nanocomposite for selective molecular sieving and adsorption of aqueous ions
(2024) Perera, W. P. R. T.
Even if, granular media filtration demonstrates efficacy in diminishing water turbidity, its constrained surface functionalities and inherent physical attributes limit its capacity to efficiently adsorptive removal of contaminants from aqueous environments. Concurrently, graphene oxide (GO), employed across various adsorptive removal endeavors targeting toxic metals and molecules, presents challenges in recovery following dispersion within aqueous matrices. Addressing this shortfall, we have engineered a GO/sand composite (M-GO/S) via coating GO on purified sand without using a binding agent to optimize contaminant removal efficacy in aqueous systems. This innovation not only reduces water turbidity but also enhances the mechanical integrity of GO and activates the sand's surface. When graphene oxide (GO) is applied to the surface of sand, it perturbates the local hydrogen-bonded structure of the sand, exposing the Si-OH sites for chemisorption. M-GO/S achieves fluoride removal efficiency exceeding 70% at a pH of approximately 6.30, as per the Hill adsorption model. In tests using simulated water samples, the M-GO/S composite significantly reduced solution turbidity by 87%, lowering it from 0.08 to 0.01 NTU. These findings suggest that M-GO/S is an effective material for simultaneously reducing both fluoride levels and turbidity in water. M-GO/S outperformed commercial coal powdered activated carbon by removing 75% of calcium ions from simulated hard water (pH 8), indicating superior efficacy. The detection of (-O-Ca-O-) chemical bonds on the nanocomposite's surface post-calcium ion equilibration reveals chemical interactions. This highlights the M-GO/S nanocomposite as a promising option for hard water treatment. The M-GO/S nanocomposite effectively adsorbed toxic metals such as Pb (52 mg/g), Cr (37 mg/g), Cd (40 mg/g), and Ni (21 mg/g) and silanol groups acting as active sites for ion exchange. Graphene oxide's adsorption mechanism is driven by its oxygen-rich functional groups (hydroxyl, epoxide, and carboxyl), which boost its affinity for metal ions via complexation, electrostatic attraction, and cation exchange. The M-GO/S composite, leveraging the synergistic surface properties of sand and GO, effectively removes not just cations and anions but also cationic and anionic molecules. Its notable adsorption capacity for substances like Methylene Blue (259.5 mg/g) and MCPA (47.3 mg/g) indicates that this composite may serve as a promising material for molecular sieving. Developing a chemical-free synthesis method for GO is essential for the large-scale production of M-GO/S, aimed at extensive water purification applications.
Toxic metal contamination in food chains via paddy plant; A study in CKDu endemic area in North Western Province, Sri Lanka
(Faculty of Graduate Studies - University of Kelaniya, Sri Lanka, 2024) Gunathilaka, V. H. N. M.; Perera, W. P. R. T.; Perera, P. L. R. A.; Kadigamuwa, C.C.; Liyanage, J. A.; Premaratne, W. A. P. J.
This study addresses the urgent need for a comprehensive risk assessment of toxic metal contamination in the food chain via paddy plants in CKDu-affected areas emphasizing the health hazards associated with the transfer of toxic metals from soil to paddy grains and evaluating the health risk of consuming rice through different risk indices. Twenty composite paddy soil samples and twenty paddy plant samples with rice grains in the exact locations were collected from paddy areas in Nikawewa Grama Niladhari division during the Maha growing cycle in 2023. The analysis of Cr, Pb, As, Cd, Ni, and Cu was conducted using inductively coupled plasma-mass spectrometry (ICP-MS). Descriptive statistics revealed the average metal concentrations in rice grains as: Cr(637.42±157.44 μg/Kg), Pb(262 ±62.35 μg/Kg), As(39.29±11.97 μg/Kg), Cd(1836±192 μg/Kg), and Cu(1567 ±466 μg/Kg). Cr, As, and Cu levels in rice grains remained within WHO/FAO and codex limits. However, average Pb and Cd levels surpassed permissible limits (Pb-200 μg/Kg, Cd- 50 μg/Kg; WHO). Nevertheless, the Target hazard quotient(THQ) values of Cr and Cd were greater than 1. The estimated Daily Intake(EDI) values of Cr(3.15 μg/Kg/Day) and Cd(9.15 μg/Kg/Day) are higher than Tolerable Daily Intake(TDI) values. The transfer factors(TF) for toxic metals in the soil-root system were determined as follows: Cr-0.069, Pb-0.30, As-0.67, Cd-0.49, Ni-0.10, Cu-0.23. Toxic metal transfer factors in the soil-root system were evaluated, indicating greater uptake by plant roots. When considering a metal transfer from roots to rice grains, Cd had a transfer factor greater than 1, indicating potential accumulation in grains, while Cr exhibited a notable increase in transfer factor compared to the soil-root system. The risk of toxic metal transfer from soil to paddy grains warrants concern due to potential human exposure and related health risks, including Chronic Kidney Disease, from the consumption of contaminated rice grains.