International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Remediation of cadmium contaminated montane forest soils (Horton Plains): Will rubber (Hevea brasiliensis) nut shell and rice husk bio char be effective remediating agents?(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) De Silva, J. S. R.; Yapa, P. I.; Bandara, R.; Seneviratne, M. A.Horton Plains, one of the two montane forests in Sri Lanka, which provides habitats to many endemic species of plants and animals, has been severely affected by forest dieback. Previous research has identified a direct link between soil pollution with Cadmium (Cd) (through atmospheric pollution) and the phenomenon of forest dieback. As a consequence, forest dieback is increasing proportionately to the soil pollution. As such, it is imperative to protect Horton Plains, and this study focuses on identifying a cost-effective remediation technique to neutralize soil Cd, and thereby reducing forest dieback. This experiment was conducted for a period of three months. Soil samples were collected from Horton Plains, mainly Thotupolakanda site, which shows more than 90% severity of forest die back. Three soil amendments were used in this research as; bio char prepared using (i) rubber nut shells, (ii) rice husks, and (iii) bio char occurring naturally in Horton Plains. Along with the control treatment (only soil), this experiment consisted of four treatments, of 5 replicates. Treatments were added to the soil samples and available Cd was extracted using standard methods in literature, and the Cd concentrations were analysed using the Atomic Absorption Spectrophotometer. Horton Plains forest soil used for the study showed the pH of 5.4 and the Cation Exchange Capacity (CEC) was 210 c moles kg -1 of soil. The soil was highly rich with organic matter and the soil organic matter (SOM) content has reached 13.4%. Immobilization of Cd added to the soil was observed and it was significant (p <0.03). However, the control (only soil) has also shown its ability to immobilize soil Cd. Thus, it appears that the presence of extraordinary level of SOM and active natural sorbents in SOM such as humic acid and fulvic acid have masked the effect of all the biochar treatments. The amount of Cd used for spiking the soil was 0.1 μg and the minute quantity may have been immobilized by the SOM. However, the study proved the possibility of neutralizing Cd toxicity in the soil by using natural sorbents. Other treatments did not show that much of Cd neutralizingItem Effect of phosphorus fertilizers and soil amendments on cadmium accumulation in maize (Zea mays L.) seeds(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Wanninayakea, P. C. U.; Yapa, P. N.; Malaviarachchi, M. A. P. W. K.; Hettiarachchi, R. P.Phosphorus (P) is important for plant growth and metabolism. Higher percentage of phosphorus (up to 80%) is immobile or unavailable to uptake by plants because of adsorption, precipitation, leaching and conversion to organic forms. As a result, about 30 million tons of phosphorus fertilizer is used in agriculture worldwide every year. Phosphorus fertilizers contain cadmium (Cd) as a contaminant at different levels from trace amounts to high. Once accumulated in agricultural products, Cd can enter the human body resulting in severe health issues. Therefore, investigating the effect of different types of P fertilizers on Cd uptake and accumulation in maize seeds was the main focus of this study. A field trial was carried out at Field Crop Research and Development Institute in Mahailluppallama. Eppawela rock phosphate (ERP) and triple super phosphate (TSP) were separately applied as P fertilizers, with four amendments namely compost, biochar, dolomite and arbuscular mycorrhizal inoculants (AMF) in a randomized complete block design with three replicates. Amount of Cd in soil and accumulated in seeds were determined using Atomic Absorption Spectrophotometry and the data was analyzed using a two-factor factorial design. Available soil Cd and total seed Cd amount were significantly higher (p<0.05) in TSP treatments compared to ERP treatments, with and without the amendments. Addition of organic amendments compost, biochar and dolomite to the soil significantly reduced seed Cd level compared to treatments without the amendments. There was no colonization of AMF in TSP applied soil, while 25-60% colonization was recorded with ERP. Therefore, conclusion of the study was that ERP contribute to lower Cd accumulation in maize seeds and with the addition of compost and biochar with ERP, cadmium accumulation was further reducedItem Sensitivity of four freshwater animal species to copper and cadmium under tropical temperature exposure(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Heshani, A.L.S.; Pathiratne, A.Copper and cadmium are two common pollutants in Sri Lankan freshwater ecosystems. Water quality criteria for these metals focusing on the protection of freshwater species in Sri Lanka are yet unavailable. Formulating water quality criteria based on tropical species sensitivity distribution analysis would require credible ecotoxicity data (especially at early life/young stages) under tropical temperature exposure for a range of freshwater species belonging to different trophic levels. Thus, objective of the present study was to generate freshwater ecotoxicity data for copper and cadmium for tropical temperature exposures using four freshwater native/model test organisms: two crustaceans, Daphnia magna and Moina macrocopa, the fish Poecilia reticulata and the tadpoles of Duttaphrynus melanostictus representing primary and secondary consumers. Based on the range finding tests, the animals were exposed separately to a series of concentrations of Cu2+ (D . magna 50-300; M . macrocopa 1-150; fish 25-300; tadpole 10-300) or Cd2+ (D . magna 10-200; M . macrocopa 1-150; fish 25-300; tadpole 100-500) in μg/L along with the controls (in triplicate/quadruplicate exposure medium, n=10 animals per replicate) at 280C - 300C under static-renewal conditions (hardness ≤ 66 mg/L as CaCO3) following standard OECD toxicity testing protocols. The sensitivity of the crustaceans (neonates) for different concentrations of Cu2+ and Cd2+ exposure was assessed based on percentage neonates immobilized whereas the sensitivity of P . reticulata (fry 5-10 mm total length) and D . melanostictus (Gosner stage 25 tadpoles) was evaluated based on percent mortality. Concentrations of copper and cadmium in the exposure media were determined using atomic absorption spectrophotometry. Ecotoxicity thresholds were estimated based on concentration-toxicity response relationships using USEPA software, ‘Toxicity Relationship Analysis Program’. Estimated 48 hour median effective concentration (EC50) of copper for immobilization of the crustaceans, D . magna and M . macrocopa were 117 and 15 μg/L respectively whereas corresponding values for cadmium were 45 and 12 μg/L. Estimated 96 hour median lethal concentration (LC50) values of copper for the fish, P . reticulata and the tadpole, D . melanostictus were 63 and 72 μg/L respectively. Corresponding LC50 values for cadmium were 76 and 431 μg/L. The most sensitive species for copper and cadmium was the crustacean, M . macrocopa . The highest tolerance for cadmium was shown by the amphibian, D . melanostictus tadpole whereas D . magna showed the highest tolerance to copper. Additional ecotoxicity data for copper and cadmium focusing on more tropical freshwater species are needed for derivation of water quality criteria for tropical freshwater life protection.Item A study on sorption of Cd(II) onto chitosan derivatives.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Samaranayaka, K. A. S.; Rajapakse, C. S. K.Pollution of water sources, specially drinking water sources, is becoming a serious problem in the world today. Unlike organic pollutants, heavy metals are non-biodegradable and even trace amounts of some of the heavy metals such as cadmium is highly toxic and may cause deleterious health effects in humans. In recent years the search for efficient, readily available and more affordable adsorbents that have high metal-binding capacities for the removal of toxic heavy metals in drinking water has intensified and in this research, chemically modified chitosan [cross-linked chitosan beads (CLCB) and physically modified chitosan] and chitosan coated activated carbon (CCAC) were prepared and their sorption properties for Cd(II) uptake were studied. Chitosan derivative CLCB was prepared using glycerol diglycidyl ether as the cross linking agent and composite bio-adsorbent CCAC has been prepared by coating chitosan onto commercially available activated carbon to improve their mechanical strength and metal adsorption ability compared to that of unmodified chitosan. The modified adsorbents were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The equilibrium data were evaluated using Langmuir, and Freundlich isotherms and adsorption equilibrium data of Cd(II) adsorption onto CLCB and CCAC at 30 0C were correlated with the Langmuir isotherm model. The maximum monolayer adsorption capacity; Langmuir constant, qo obtained for adsorption of Cd(II) onto CLCB and CCAC were 79.4 μg/g and 84.0 μg/g, respectively, which were significantly higher than the values for the adsorption of Cd(II) onto unmodified chitosan. The kinetic data were fitted with the pseudo second order model for initial Cd(II) concentrations of 50 μg/L. The findings from this research indicate that the CLCB and CCAC have enhanced Cd(II) sorption abilities compared to that of unmodified chitosan. Therefore, the modified chitosan derivatives could be used as efficient bio-adsorbents to remove Cd(II) from polluted drinking water.