http://dr.lib.sjp.ac.lk/handle/123456789/10718 Wed, 07 Jan 2026 06:05:58 GMT 2026-01-07T06:05:58Z http://dr.lib.sjp.ac.lk/handle/123456789/10891 Estimation of Recreational Value of Horton Plains National Park in Sri Lanka: A Decision Making Strategy for Natural Resources Management Rathnayake, R. M. W.; Gunawardena, U. A. D. P. Horton Plains National Park (HPNP) is an area of high biodiversity and exceptional endemism receiving high visitation (166,613 visitors in 2009), both by local and foreigners. Although, tourism causes negative impacts on the environment, environmental valuation could be used for taking decisions on natural resources management. The study shows that the recreational value of HPNP is Rs. 51.68 million rupees per year, but the total economic value could be many times higher than this. Calculations showed the maximum revenue from the park could be obtained if the entrance fee is raised to Rs. 472.00. This may however reduce the present visitor number by 65%, but it will improve the total revenue of the park by 314 %. These differences strengthen the common argument by both officials and the public regarding insufficient allocation of man power and funds for natural resources management. Sat, 01 Jan 2011 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/10891 2011-01-01T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/10885 Estimation of Above Ground Tree Biomass and Carbon of Pinus caribaea (Morelet) Subasinghe, S.M.C.U.P.; Munasinghe, G.B. Forests in Sri Lanka contribute to the mitigation of global climate change through sequestrating a net amount of carbon dioxide and also maintaining carbon stocks as forest biomass. This study was conducted using an empirical method to understand the biomass and stored carbon by forest plantations in Sri Lanka. Further, in this study, the possibility of predicting the above ground tree biomass and carbon of Pinus caribaea (Morelet) was investigated. A 27 year old P. caribaea plantation was selected from the Low Country Wet Zone in Sri Lanka and the data were collected using 0.05 ha sample plots. Without felling trees, a core sample was obtained from the stem and biomass and carbon of that sample was used to estimate the stem biomass and carbon through volume measurements. The canopy biomass and carbon were estimated using samples of primary, secondary and tertiary branches and leaves. The total above ground tree biomass and carbon were estimated by adding the stem and canopy values together. It was found that, for 27 year old P. caribaea, the average above ground tree biomass was 368.9 kg and the carbon was 215.9 kg which is 58.5% from the biomass. The amount of carbon in the canopy was 64.5% from the canopy dry mass. The carbon percentages of the primary, secondary and tertiary branches and leaves were 61.7, 59.1 and 79.6 respectively. The total above ground tree carbon for a 27 year old P. caribaea plantation was 103.6 T ha-1. Then regression models were developed to identify the relationships of biomass and carbon with stem volume. A relationship between biomass and carbon was also developed for the selected species. Finally, mathematical models were developed to predict biomass and carbon using some other tree variables such as diameter and height, without felling the trees. Sat, 01 Jan 2011 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/10885 2011-01-01T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/10880 Solar Radiation Alters Toxicity of Carbofuran: Evidence from Empirical Trials with Duttaphyrnus melanostictus Wijesinghe, M.R.; Jayatillake, B.A.D.M.C.; Ratnassoriya, W. D. In the present study we investigated the potential of natural solar radiation to alter the toxicity of a commonly used carbamate pesticide, carbofuran, on tadpoles of the Common Asian Toad Duttaphrynus melanostictus. A single exposure trial was conducted over 96 hrs with three concentrations (150, 250 and 500 μgl-1) of photo-irradiated and non-irradiated carbofuran. Results show that photo-irradiation markedly reduced the toxicity of carbofuran as evident by its effects on three end points, i.e. mortality, growth and swimming activity. The mortality of tadpoles exposed to irradiated carbofuran was significantly lower than those exposed to the non-irradiated pesticide. Both treatment and control tadpoles showed a hormetic response for mortality. Tadpoles in irradiated tanks were also larger and more active than those in the control tanks. Photo-altered toxicity was evident at all three tested concentrations. The results of this study therefore signals caution when directly linking results of empirical trials to field scenarios and highlight the necessity to evaluate toxic effects of compounds under variable environmental conditions. Sat, 01 Jan 2011 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/10880 2011-01-01T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/10879 Lead and Cadmium Removal from Aqueous Medium Using Coir Pith as Adsorbent: Batch and Fixed bed Column Studies Amarasinghe, B.M.W.P.K. Coir pith was used as an alternative to commonly available adsorbents for heavy metal ion removal from aqueous solutions. Batch and fixed bed column experiments were conducted to study adsorption characteristics of Cd and Pb onto coir pith. Coir pith is an effective adsorbent for Pb and Cd removal. The adsorbent dose, metal ion concentration and the solution pH affects the degree of adsorption. The maximum adsorption was observed at solution pH values above 5. The equilibrium data was satisfactorily fitted to Langmuir and Freundlich isotherms. Pb showed higher adsorption capacity compared to Cd under the experimental conditions. Kinetic studies revealed that Pb and Cd uptake was fast within first 10 to 15 min of contact time and data fits to pseudo second-order model. Breakthrough curve data fits to linear Bed Depth Service Time (BDST) model and bed capacities for Pb and Cd were 41 and 28 mg/ g of coir pith respectively. Sat, 01 Jan 2011 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/10879 2011-01-01T00:00:00Z