IRSPAS 2018
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/19084
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Item Development of a digestion technique for the determination of selected heavy metals in soil and sediments(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Wekasinghe, K.; Subramanium, S. S.The objective of this study was to develop a new method on soil digestion techniques because some metal ions such as Cd, Pb, Cu, Cr and Zn are chelated by many soil-organic matter and complexes are inaccessible using previously studied techniques. This method development as well as the analysis of total contents of Cd, Pb, Cr, Cu and Zn in soil and sediment were conducted in selected areas in Medawachchiya, Sri Lanka which is an area that is mostly affected with Chronic Kidney Disease of unknown etiology. In this regard, the random soil samples were taken from cultivated and uncultivated paddy fields and the banks of the tanks. Sediments were collected randomly from the banks of the tanks. Three different digestion methods were used to analyze the heavy metals in soil to select the best digestion method for heavy metal analysis in soil for further studies. All three digestion methods have different combinations and quantities of concentrated acids (i.e., HNO3 and HCl) and H2O2. The heating methods were varied by using hot plate for one of the techniques (i.e., Gallenkamp) and microwave (i.e., Mars6 microwave digester) for the other two techniques. The digestion timing and temperature programming used are different in the three techniques. The results obtained using the Flame absorption spectrometer (i.e., GBC 2000, SavantAA) were analyzed. The results obtained for each technique were compared. Method spike recovery was conducted for the three methods to compare the difference, accuracy and effectiveness of each digestion processes. The concentration variation of heavy metals were as follows; Cd 1.0 mg/kg - 2.0 mg/kg, Cr 20 mg/kg - 60 mg/kg, Pb 10 mg/kg - 24 mg/kg, Zn 20 mg/kg - 110 mg/kg and Cu had the highest variation 20 mg/kg -170 mg/kg. Variation of the above values occur due to the variation of sample areas and environmental factors surrounding them. Further, the spiked method recovery for Zn suggests that the microwavebased digestion is more suitable for the analysis in soil. Results showed that the concentrations of Cu, Cr, Pb and Zn in soil were recorded within the permissible limits set by WHO. The Method LOD and LOQ suggests that the values obtained for Cd were not on the detectable limits and the use of GFAAS or any other sensitive analytical instrument is required for the analysis.Item Analysis of selected, commercially available inorganic fertilizers and soil NPK content in Puhudivula; Medawachchiya(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Sahlah, M. A. H. F.; De Silva, R. C. L.The increased prevalence of CKDu confined to specific geographical regions and among specific occupational groups of Sri Lanka has drawn the attention of scientific community in recent years. This study was conducted to investigate possible contributions of inorganic fertilizer usage on the disease prevalence at Puhudivula; Medawachchiya. Five commercially available fertilizer samples (Urea, TSP, MOP, TOP and Chili mix) most commonly used in the study area were analyzed for their NPK content and trace metal amounts. The NPK composition, calcium content and physiological properties of soil were also analyzed in five selected sites. The total nitrogen amounts were determined using standard Kjeldahl procedure. Total phosphate content of fertilizers was analyzed using ammonium vanadomolybdate method while both total phosphate and inorganic phosphate amounts in soil were determined using molybdenum blue method. The potassium and calcium amounts were determined using flame photometry. The percentage NPK compositions of the analyzed fertilizer samples agree with the percentage compositions listed by the manufacturers for each fertilizer. However, less total nitrogen and less phosphate percentages were measured in Urea and TSP respectively. The NPK composition of soil followed N% > K% > P% order with overall mean concentration of NPK between 279.4-1537.3 mg/kg, 32.4-193.7 mg/kg and 3.0-25.5 mg/kg respectively. The mean calcium concentration in soil was high, ranged from 537.27-1007.75 mg/kg. The trace metals Cd, Pb, Cr, Zn, Cu and Fe in fertilizer samples were analyzed using Atomic Absorption Spectrometer. From the analyzed trace metals, Fe exhibited a remarkable presence in all analyzed fertilizers except Urea with an overall mean concentration >1550.0 mg/kg and the mean concentrations of Cd, Pb and Cr followed the phosphate percentage by weight. Cd and Pb mean concentrations ranged from 0.23-1.80 mg/kg and 0.94-7.17 mg/kg respectively and were below the WHO maximum acceptable concentrations. According to the results, the addition of fertilizers did not increase the heavy metal levels in soil significantly unless it accumulates, and the excessive use of inorganic fertilizers mainly the ammonium-based fertilizers in already nitrogen enriched soils indicates to be causing the acidification of soils and it is evident that it may be mobilizing the calcium ions from its immobile form. This study provides new data to relevant authorities to limit the excessive annual fertilizer input on these lands through proper NPK analysis prior to application.