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    A novel potentiometric ion selective sensor based on piperine for determination of Fe3+ ions
    (2018) Haputhanthri, M.; Perera, L.H.R.
    Iron plays a vital role in humans as iron deficiency cause anemia and overload of iron leads to haemochromatosis. In plants, chlorosis is a common plant disorder that arises as a result of iron deficiency, whilst excess iron leads to toxicity due to the formation of oxygen radicals. As a consequence, there is an imperative need for determination of iron in its ionic form and even in complex matrices. The purpose of this study is to develop a potentiometric solvent polymeric membrane ion selective electrode (ISE) using piperine, to be used efficiently in routine analysis of iron. The ISE was calibrated according to the Nernst equation, correlating the Fe3+ concentration with the potential of the ISE measured with respect to a Ag/AgCl reference electrode. Selectivity coefficients were measured using the separate solution method. The electrode exhibits a linear response towards Fe3+ ions in the citrate buffer medium over a concentration range of 110-4 to 1M (detection limit 6.3×10-5 M) with a Nerstian slope of 20.5 mV per decade. The electrode can be successfully used in the pH range 3.15 - 7.85 with a life-time of 3 months. It has fairly good discriminating ability towards Fe3+ ions among some other metal ions such as K+, Ca2+, Mg2+, Cu2+, Ba2+, Co2+, Al3+ and Cr3+ with selectivity coefficient of -2.11, -9.02, -10.38, -8.34, -8.12, -8.79, -8.41 and -3.69, respectively. Developed Fe3+ ISE was used to determine Fe3+ concentration in a pharmaceutical sample and the results produced by the sensor were comparable with those obtained using AAS. It proves the fact that, this sensor can be developed into a simple, cost effective alternate method in determining Fe3+ ion concentrations in biological and analytical samples.
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    Sediment modelling in Nillambe Oya, Sri Lanka
    (Department of Zoology and Environmental Management, University of Kelaniya, Kelaniya, Sri Lanka., 2016) Gunawardena, M.P.; Najim, M.M.M.
    Sedimentation in surface water bodies is a major problem worldwide as well as in Sri Lanka especially in the upper Mahaweli catchment. To address these issues, proper monitoring of sedimentation is necessary, but daily monitoring and data collection are greatly time consuming and costly. Therefore, development and application of models for accurate simulation of these variations will be a vital requirement for management of these ecosystems. Therefore, the present study was done with the objectives of calibrating and validating the HEC-HMS 3.5 and HEC-RAS 4.1.0 models based on climatic, sediment and landuse data and applying the calibrated models to predict sediment variations. With the purpose of addressing this issue, combination of HEC-HMS 3.5 and HEC-RAS 4.1.0 models were used to simulate flow and sediment changes in the Nillambe Oya, which is located in the upper Mahaweli catchment with typical landuse patterns of the central highlands of the mid and up country wet zone of Sri Lanka. During the period from May 2013 to September 2013; flow was measured and water samples were analysed for sediment in nine selected days. Rainfall data, other meteorological data, flow and sediment data were obtained from the Environment and Forest Division of the Mahaweli Authority and the Meteorology Department of Sri Lanka. HEC-HMS 3.5 and HEC-RAS 4.1.0 models which are developed by the United States Army Corps of Engineers were used to simulate flow and sediment of the Nillambe Oya. The HEC-HMS 3.5 model was used to generate flow which is needed for HEC-RAS 4.1.0 model in order to perform simulation of sediment in Nillambe Oya. Daily flow data for five years (from October 1991 to September 1996) were used to calibrate the HEC-HMS 3.5 model and another set of flow data for five years (from October 1994 to September 1999) were used to validate the model. HEC-RAS 4.1.0 model was calibrated using sediment data collected and analysed in five days along with flow and other meteorological data. The validity of the calibrated model was evaluated using sediment data collected in the other four days. The calibrated and validated HEC-HMS 3.5 model reliably predicted the flow in Nillambe Oya. The HEC-RAS 4.1.0 model simulates only the sediment derived from river scouring and it cannot simulate the sediment resulting from watershed erosion. According to the model simulations, the sediment concentration derived from river scouring varies from 6.9% to 10.3% when compared to the total sediment load. On average, 92% of the sediments carried by the river is resulted from watershed soil erosion. Therefore, proper watershed management actions should be taken in order to reduce the sediment load carried by the Nillambe Oya and also to minimise the impact of sedimentation of the Nillambe reservoir.