Browsing by Author "Navarathna, C."

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    Intrusion of heavy metals/metalloids into rice (Oryza sativa L.) in relation to their status in two different agricultural management systems in Sri Lanka.
    (Groundwater for Sustainable Development, 2021) Navarathna, C.; Pathiratne, S.; de Silva, D.; Rinklebe, J.; Mohan, D.; Mlsna, T.
    The contentious results of elevated As and Cd levels, in both Sri Lankan rice and in agrochemicals have recently raised tremendous attention. These claims could not standalone due to the study’s poorly designed sampling and analytical methodologies. In this work, selected traditional Sri Lankan rice and hybrid rice varieties were cultivated (under fertilized and organic conditions) using a split-plot design during Yala (May to August) and Maha (September to March) seasons in two regions: Anuradhapura and Kurunegala. As, Cd, Cr, Hg, Pb, and Se contents were determined in harvested rice grain and straws for Chronic Kidney Disease of unknown etiology (CKDu) risk assessment. In addition, analysis of these elements in water, soil, and agrochemicals was used to estimate their geochemical behavior. The majority of agrochemicals and fertilizers had Cd, Cr, and Pb. Grain Cd contents in rice varieties were ranged from not detectable to 158.9 μg kg􀀀 1 in both cultivation seasons, and soil was sought to be the primary Cd source. As, Se, Hg, and Pb were also not detectable in both rice grain and straws. Native variety Pachcha Perumal rice grain showed a low Cd accumulation in both seasons at both regions. Kuruluthuda and Madathawalu showed a moderate accumulation versus other varieties. Cultivating and consuming these native traditional rice varieties practicing organic farming could be a possible way to combat CKDu risks. The correlations (between the rice grain Cd content and farming condition, location, or season of cultivation) were tested linear regression to fit data on to Freundlich model, and no distinct statistical correlations were observed (p > 0.05). Mean chromium contents (38.5–112.1 μg kg􀀀 1) detected in the rice grain were not alarming. Soil, irrigation water, and agrochemicals were free from As and Hg. However, rice straws contained substantial amounts of Cd. Therefore, use of it as organic manure should be limited.
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    A Novel Technique to Digest Biochar for Metal Analysis
    (4th International Conference on Advances in Computing and Technology (ICACT ‒ 2019), Faculty of Computing and Technology, University of Kelaniya, Sri Lanka, 2019) Wathudura, P.D.; Peiris, C.; Navarathna, C.; Kaumal, M.N.; Gunatilake, S.R.
    Biochar (BC) is a low cost carbonaceous adsorbent material widely used for the removal of toxic metal ions from aqueous systems due to their highly porous nature and presence of various functional groups. Depending on the feedstock used to produce these carbonaceous materials, the trace metal content may vary. Various digestion techniques have been incorporated to analyze the metal content of BC though a proper method has not yet been established. This study was focused on finding a suitable method to totally digest the carbonaceous material and to evaluate the matrix effect. Both open vessel and microwave digestion methods were carried out for BC derived from tea waste, king coconut husk, Douglas fir and steam activated coconut shell biochar (CSBC) using mixtures of 69% nitric acid (NA), fuming nitric acid (FNA), 98% sulfuric acid (SA) and 30% hydrogen peroxide (HP) and their turbidity were measured. Lowest turbidities for open vessel digestions were observed for SA/HP mixture for low-temperature pyrolyzed BC with no external heating (2.04 – 7.90 FNU). Microwave digestions provided satisfactory turbidity levels for NA, NA/SA mixture, FNA and FNA/SA mixture for all types of carbonaceous material (1.58 – 20.97 FNU). The matrix effects were compared using cadmium, copper, lead and zinc using flame atomic absorption spectrophotometry. Digestion mixture containing only fuming nitric acid showed the lowest matrix effect for cadmium (1.2) for CSBC and copper (2.4) for CSBC while the mixture containing only nitric acid shows lowest matrix effect (7.6) for zinc with respect to Douglas fir BC. Recovery study confirmed the suitability of FNA as a suitable digestion mixture incorporated with microwave energy.