RESCON 2022

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Spatial and temporal variation of tree biomass in tropical rainforest of southwest Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Herath, H.M.S.I.; Wijekoon, P.; Ediriweera, E.P.S.K.
Although tropical rain forests hold large amounts of carbon, there is uncertainty about the quantity and distribution stored in forests. The Above Ground Biomass (AGB) of forests provides estimates of the carbon pools, as 50% of AGB is carbon. Hence, the availability of reliable AGB estimates is important. This study was carried out in the 25-ha Sinharaja Forest Dynamic plot (FDP). This study aims to estimate the AGB in the FDP and analyze the spatial and temporal variation of the AGB of the FDP over 25 years. The stems of the selected species were analyzed at eight different diameter classes. The 20 most dominant species in the FDP were selected for analysis based on the Important Value Index (IVI). The estimated AGB of the selected species were analyzed at eight different diameter classes. The ANOVA repeated ANOVA and Kruskal-Wallis test were used to understand the significance of temporal variation and the variation of AGB across diameter classes. The total AGB in each quadrat was obtained in Mg ha⁻¹ and they were analyzed and visualized through spatial maps at a scale of 0.04 ha to understand the spatial variation of AGB. Further, AGB gains and losses over the years were calculated. Even though a change in AGB was observed over the years, the temporal variation of the overall AGB was not significant. However, the AGB change at diameter classes was highly significant. The spatial variability within the plot was high, and the spatial variation at 0.04 ha level over the years was statistically significant (p < 0.05). Most of the quadrats (80%) had AGB < 60 Mg ha⁻¹, and around 42% of quadrats contained AGB < 20 Mg ha⁻¹. The overall distribution of AGB in the FDP was positively skewed. Further, the total AGB in the FDP has decreased with time, indicating its role as a carbon source rather than a carbon sink.
Synchronization of multi-manufacturer multi-buyer integrated inventory supply chain model
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Hisam, M.S.M.; Juman, Z.A.M.S.; Daundasekera, W.B.
The manufacturer–buyer integrated inventory supply chain system is common practice and evolving into a significant factor in the more highly competitive environment encountered in today's global economy. Coordination between the manufacturer and the buyer offers benefits economically for both parties. Notable attention has been given to single-manufacture, single-buyer and single-manufacture multi-buyer integrated inventory systems with consideration of various realistic factors in the literature. This study was motivated by a real-world problem where six tea manufacturing factories produce a brand of tea and distribute their two buyers. However, to the best of our knowledge, only a few studies investigated multimanufacturer multi-buyer integrated inventory systems in previous research. Further, we assumed manufacturers transfer the lot just after its production and buyers have limited storage capacity to accommodate the required inventory. So, we first develop a multi-manufacturer multi-buyer integrated inventory model by accounting for realistic factors such as capacity limitation of buyer storage. In our study, manufacturers produce a homogenous product and supply it to all buyers to satisfy their demands. Besides, we consider unequal batch size transferring policy and assume the batch sizes follow geometric series. Then, we derive an optimal solution technique for the model to obtain the minimum total cost. Further, a sensitivity analysis is performed, and real-world tea distribution data is solved to support the analytical findings.
Based on modified ant colony algorithm for researching the minimum weight spanning tree
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Niluminda, K.P.O.; Ekanayake, E.M.U.S.B.
A Minimum Weight Spanning Tree (MWST) is a mathematical technique for connecting a set of points with the least amount of connecting lines. The MWST problem is among the most fundamental and intensely studied problems in network optimization, with a wide range of theoretical and practical applications. A common and well-known problem in combinatorial optimization is the MWST problem. The MWST visits all vertices in the same related portion as the starting node. In this study, several strategies are considered to solve the generalized MWST problem, and a novel approach is used to solve the MWST. MWST can be obtained using the well-known Prim and Kruskal algorithms. These algorithms can be divided into two groups according to the implementation. MWST is divided into two types: line-based MWST and node-based MWST. Prim's algorithm is node-based, whereas Kruskal's is a line-based algorithm. However, in this paper, we present a method for solving the MWST problem using a Modified Ant Colony Optimization (MACO) algorithm. Ant Colony Optimization (ACO) is a probabilistic method and a type of metaheuristic that has gained widespread use for solving combinatorial optimization problems, as well as a technique for determining the shortest path between two points. It is based on how ants behave as they travel from their nest (colony) to a food source in search of food. The algorithm has been improved in this unique way by modifying the ACO algorithm and including the transition rule and pheromone update rule. A comparable result can be obtained by applying Prim's and Kruskal's algorithms.
Open vehicle routing problem with moving shipments at the cross-docking terminal
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gnanapragasam, S. R.; Daundasekera, W.B.
Vehicle Routing Problem (VRP) plays a vital role in supply chain (SC) management. The cross-docking (CD) strategy was introduced in the 1930s to reduce up to 70% of warehousing at traditional distribution centres in SCs. The research on integrating VRP with CD (VRPCD) was initiated in 2006. Open VRP (OVRP) is one of the variants of VRP, and it is more suitable for organizations which outsource the fleets of vehicles from third-party logistics (3PL) companies. In this study, one of the internal operations at the CD terminal (CDT), moving shipments (MS) from receiving doors to the shipping doors of CDT, is integrated with VRPCD. Consequently, this study considers open VRPCD with MS at CDT (OVRPCDMS). As an additional feature in this study, two sets of fleets of vehicles with two different capacities are added for pickup and delivery processes separately. Furthermore, the service cost at each customer and at receiving and shipping doors of CDT is considered when calculating the total cost of transportation. Moreover, the asymmetric distance between any two customers is assigned by incorporating a characteristic of one-way routes between cities in real-life transportation. The objective of this study is to minimize the total transportation cost which incurs travelling costs between customers, service cost at customer points, service cost at the receiving and shipping doors of CDT, cost of moving shipments inside the CDT and finally, the cost of hiring fleets of vehicles from 3PL. To solve the OVRPCD-MS problem, a mixed integer linear programming (MILP) model is developed. The programming models was implemented in LINGO (version 18) optimization software. The branch and Bound algorithm is employed to solve ten small-scale instances generated randomly. The applicability of the proposed MILP model is observed. The required fleets of vehicles to be hired and the run time to reach the optimal solution is determined. The study revealed that the average run time is exponential for small-scale instances. Thus, it can be concluded that this proposed model can be used for the last time in the planning of similar, small-size instances. At the same time, the combinatorial nature of VRP makes OVRPCD-MS as NP-hard problem. Therefore, this study recommends that heuristic or metaheuristic methods are more appropriate for the medium and large-scale instances of OVRPCD-MS to reach near-optimum solutions. This further recommends incorporating additional constraints to the OVRPCD-MS model, such as time windows for each customer, budget allocations for fleets of vehicles and temporary storage capacity at CDT to cover a broader spectrum of a study under investigation.
Skew-t replicated measurement error model for method comparison data
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Duwarahan, J.; Nawarathna, L.S.
Method comparison studies are designed to determine whether the two methods of quantifying a continuous variable are compatible enough to be used interchangeably. The linear mixed-effects model is often used to model method comparison data when the methods have the same measurement scale. During the data collection, Measurement Errors (MEs) will occur in observations of covariates and response variables, and these mistakes may be caused by using different measuring scales or methods. If these MEs are not considered, the conclusion will be misleading. This study discusses the framework for modelling method comparison data for quantitative measurements with the MEs, called the 'Measurement Error Model' (MEM). These models generally assume normality for true covariates and errors. However, these assumptions are frequently violated in practice due to the skewness and heavy tails. The key objective of this research is to develop a Skew-t Replicated Measurement Error Model (ST-RMEM) under skew-t distribution for true covariate and t distribution for errors with a matching degree for analyzing the degree of similarity and agreement between the two methods. Further, the Skew-Normal RMEM (SN-RMEM) and Normal RMEM (N-RMEM) models were considered for comparative purposes. The expectation- maximization (EM) approach was used to fit the model. The simulation research was carried out to validate the proposed methodology using sample bias (BIAS), standard deviation (SD), root mean square error (RMSE), and coverage probability (CP) measures. These values under ST-RMEM were better than the N- RMEM and SN-RMEM in all cases. Moreover, this methodology is demonstrated by analyzing subcutaneous fat data. In addition, the Total Deviation Index (TDI) and Concordance Correlation Coefficient (CCC) were utilized to assess method agreement. The CCC estimate for ST-RMEM is 0.990, with a lower bound of 0.984, while the TDI estimate for ST-RMEM is 0.034, with an upper bound of 0.050, suggesting good agreement amongst the methods. These results indicate that our suggested model works well for analyzing replicated method comparison data with measurement errors, skewness, and heavy tails, which are frequent in many fields such as medical research, epidemiological studies, economics, and the environment.
Responses for paleocene-eocene thermal maximum: evidenced by calcareous nannofossil assemblages of the Mannar basin, offshore Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Wijesinghe, W.M.H.M.; Wijenayake, A.U.; Dharmapriya, P.L.; Gyawali, B.R.; Malaviarachchi, S.P.K.; Kularathna, E.K.C.W.
The Paleocene-Eocene transition, spanning about ~170 to ~217 kyr, records a significant and extreme global warming event known as Paleocene-Eocene Thermal Maximum (PETM). PETM is marked by temperature elevations across ocean water columns and lateral temperature increments in the tropics to high latitude regions. The effects of these climatic events have been discussed by many researchers as a bloom of many biotic assemblages. In this research segment, we focused on identifying the paleoclimatic changes associated with the Mannar Basin during the period of PETM by using calcareous nannofossil assemblage. The samples were deep-marine carbonate-rich sediments selected within the depth of 2,400 – 2,605 m at 25 m intervals from the Dorado-North Hydrocarbon Exploration well drilled in the Mannar Basin, Sri Lanka. Simple smear slides were prepared and observed under the polarized microscope with an oil-immersion objective lens (magnification 1000x). Based on the calcareous nannofossil stratigraphy, the age determined for the section is Late Paleocene to Early Eocene (P/E), which traverses from biozone NP8 to zone NP10 and the subzones of NP9; NP9a and NP9b were identified. Calcareous nannofossils discovered at the P/E boundary are distinguished by a considerable rise in warm water taxa (e.g., Sphenulithus, Discoaster, Ericsonia, Fasiculithus). The pre-PETM and post-PETM periods were characterized by the presence of cold-water taxa (Coccolithus, Toweius and Chiasmolithus). The study samples showed evidence for an increasing temperature of the ocean surface, with an increase in the relative abundance of dissolution-resistant forms (D. multiradiatus and F. tympaniformis) and the decrease in the relative abundance of cold-water taxa (C. pelagicus and T. pertusus) during the PETM, while ceasing of the event could be inferred by the increasing of cold-water species (e.g., Coccolithus, Toweius and Chiasmolithus) upon reaching the Early Eocene.
Distribution and abundance of common coot (fulica atra) and common moorhen (gallinula chloropus) in the Jaffna Peninsula, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rajkumar, P.; Wijesundara, C.S.
The Common Coot (Fulica atra) is a less common breeding resident in the lowlands of the Northern part of Sri Lanka, while the Common Moorhen (Gallinula chloropus) is a locally rather common breeding resident in the lowlands throughout the country. The significant extents of mangroves, lagoons, and ponds in the Jaffna Peninsula provide ideal habitats for both these species. Their distribution and abundance have not been studied in the area, and this may hinder the conservation activities of these species. Hence, the objective of the present study was to determine the distribution and abundance of these species in the Jaffna Peninsula. Point counts are used in this study, which was undertaken from 2013 to 2018. To observe birds, binoculars (8×40 and 10×42) and a spotting scope (25×50) were used. Peak observation hours were between 0630-0830 h and 1530-1830 h, and counts of these birds were taken monthly. Each of the 12 sites was visited multiple times throughout the study period. The total number of individuals averaged 1,724 for the Common Coot and 116 for the Common Moorhen from the 12 sites during the study period. The main sites frequented by these birds included mangrove areas such as Sarasalai, Anthanathidal, Nagar Kovil, Kudarappu and Mamunai-Chempiyanpattu, and paddy areas associated with ponds such as Nunavil, Maravanpulavu, and major ponds in the Jaffna town. The highest number of common coots (532) was recorded from the Anthanathidal area. These two species have also been recorded in the Island areas of Jaffna. The study showed that both are rare resident birds in the Jaffna Peninsula compared to other waterbird species. However, the Jaffna breeding population of both species does not currently appear to be exposed to any serious threats. The wetland areas of the Jaffna Peninsula are potentially good birding destinations, which provide opportunities for ecotourists to enjoy many rare resident species like these. Hence, more attention should be given to the conservation and ecology of such species.
Heavy metal and radioactive contaminants in selected cosmetic and personal care products in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gamage, S.G.; Mahagamage, M.G.Y.L.
Cosmetic and personal care products (PCPs) are highly utilized products among the general public. Since the demand for more efficient products has emerged over the last few decades, product manufacturers have experimented with different chemicals and production processes. Ultimately, end products contaminated with various toxic metals have created numerous adverse health impacts and environmental consequences. Therefore, this study examined the presence of toxic metals in selected cosmetics and PCPs in the Sri Lankan market. Based on the questionnaire survey, five categories of products: face wash (FW), facial scrubs (FS), baby creams (BC), shaving creams (SC), and skin creams (SK) were identified for the study. From each category, three samples from three highly utilized brands were taken (n=45). Each product (0.200 ± 0.001 g) was digested in 4 ml of Aqua Regia solution and injected into ICP-MS. The analyses revealed that toxic metals: Cr (0.15 – 1.67 mg kg⁻¹), Cd (0.04 -0.19 mg kg⁻¹), As (0.02 – 0.15 mg kg⁻¹ ), and Pb (0.06 – 2.86 mg kg⁻¹) were present in many products. Further, the highest levels of Cr, Cd, As and Pb were detected in SC1, SK3, SK1/SK3 and SC1 samples, respectively. However, these limits were within the maximum permissible levels specified by the local regulatory body. Alarmingly, Uranium-238, a radioactive element, was detected in four product categories (FS, BP, SC and FW) in a range of 0.01 – 0.04 mg kg⁻¹ . Additionally, large amounts of Mn, Fe, Cu, Zn, and Ag were observed in many products. Bioconcentration and biomagnification of such elements in the environment could cause many unforeseen impacts in the future. Hence, regular monitoring of products must be a requirement in the production process, and the regulatory authorities should ensure all cosmetics and PCPs are healthy and environmentally friendly.
Effect of liquid handwash on soil bacterial flora
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Arunodi, D.M.S.; Rathnayake, I.V.N.
Frequent use of liquid handwash as a preventive measure against COVID-19 raises concern about its toxic effects on the soil microbiota. This study aimed to investigate the effect of four selected handwash products on soil bacteria over time. Composite soil samples were spiked with selected handwash at two different concentrations (12.5 and 25.0 ml kg⁻¹). It was assumed that nearly 25-50 persons wash their hands on 1 kg of soil, and 0.5 ml was taken as the volume that one person uses per wash when taking from a dispenser. Handwash samples were diluted before soil spiking, and one soil sample (300 g) was used for each concentration. A control soil sample was maintained without spiking, and all samples were incubated at room temperature (27 °C). Soil bacterial counts of each sample were obtained after the 7ᵗʰ, 14ᵗʰ, 21ᵗʰ, and28ᵗʰ days using the pour plate method. After a serial dilution, 10-6 to 10-10 dilutions were plated in triplicate on nutrient agar, incubated at room temperature for 24 h, and bacterial counts were taken. The relative growth of test samples based on Colony-Forming Units per gram of soil (CFU g⁻¹) was calculated. A repeated measures ANOVA was conducted to evaluate the null hypothesis that there is no change in the bacterial count with handwash concentrations in all products over time. There was significant evidence to reject the null hypothesis, and it was revealed that handwash concentrations had a significant effect on bacterial growth (p<0.05) in all products. The posthoc pairwise comparison revealed significant differences between each concentration and time (p<0.05). A decreasing pattern of bacterial counts was observed when handwash concentration and time increased. This may be due to the collective toxic effect of ingredients present in tested handwash products on soil bacterial flora.
Bioremoval of five laboratory dyes in aqueous solutions using green algae, chlorococcum aquaticum
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rupasinghe, M.H.K.T.; Athukorala, A.D.S.N.P.; Jayasundara, K.B.
Dyes are one of the frequent contaminants in science laboratory wastewater which are highly water soluble, potentially toxic and carcinogenic. Their negative impact on aquatic and soil ecosystems urges treating laboratory effluents before discharge. Conventional removal of laboratory dyes from wastewater is a costly process. As an alternative, the current study investigated the potential use of phytoremediation to decolourize and detoxify five laboratory dyes: rose bengal, safranin, congo red, bromothymol blue and methylene blue using microalgal species Chlorococcum aquaticum. The percentage decolourization was determined using UV visible spectrometry with 400 nm – 800 nm for 14 days. The experiment was repeated twice. The microalgal species demonstrated a decolourization percentage above 50% for all dyes, except for safranin, with the highest colour reduction of 90% with methylene blue within 14 days. The percentage of live cells of C. aquaticum monitored using light microscopy indicated that a tolerance of over 85% was observed for all dyes except safranin after the investigation period. The reduction in toxicity of the dyes by C. aquaticum determined using a seed germination assay showed that there was no significant difference among percentage seed germination (p=0.11 – 0.95 for 5 dyes) in seeds treated with dye solutions with and without C. aquaticum at day 0. However, a significant increase in the percentage of seed germination (p<0.0001) was observed in seeds treated with dye solutions incubated with C. aquaticum from day 0 to day 14 for all dyes, while no significant change (p=0.22 – 1.00 for 5 dyes) was observed between day 0 to day 14 with the dye solutions without the algae added. This study revealed that C. aquaticum has the potential to decolourize and detoxify the five laboratory dyes tested, and therefore the method developed can be extended as a dye remover/detoxifier from laboratory wastewater.
Microplastics in commercially bottled water in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Kapukotuwa, G.K.; Premathilake, B.A.P.C.; Jayasena, N.; Rajakaruna, R.S.
Microplastics (MPs) are micro-sized plastic particles (< 5 mm) which have been detected in freshwater systems and in drinking water over the globe. MPs are conveyed through air and rainwater, contaminating natural water sources. This study quantified MPs in commercially bottled water in Sri Lanka. Bottled water was purchased from the market, and the samples were filtered through a 0.45 μm membrane filter to isolate MPs. The membrane filter was examined and enumerated under the Stemi508-ZEIZZ dissecting microscope at 40× magnification. The MPs were classified according to their colour, form, and shape. Confirmation of detected particles as MPs and identification of polymer type was performed using FTIRspectroscopy. A Generalized Linear Model (GLM) with a negative binomial distribution was used to determine whether the concentration of MPs varied by the brand of bottled water. The major water source of bottled water was tube wells, followed by dug wells and spring water. All the bottles (n = 35) had MPs ranging from 3 - 19 MPs/l. The sizes ranged from 5 - 5,000 µm. Most MPs were present in the form of fibres (81%), followed by films (10%) and fragments (8%). Half of the MPs were transparent. Twelve types of polymers were identified, of which polyvinyl-alcohol, polyacrylamide, polyethene and polyethene-terephthalate were the most abundant. Brands, where the water sources were dug wells, contained a higher abundance of MPs compared to tube wells (GLM; z = -3.06, p = 0.002) and spring water (GLM; z = -3.18, p = 0.001). Further, it is likely that bottled water is contaminated with MPs during the manufacturing process. Our study stresses the importance of further investigation of MP contamination of bottled water due to its potential health risks.
Inexpensive filter to remove toxic heavy metals from wastewater using Sri Lankan red earth
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rathnayake, R.M.I.M.; Weedagama, W.L.A.C.I.; Koralegedara, N.H.; Chandrajith, R.; Athurupana, B.; Balasooriya, N.W.B.; Senaratne, A.
Bioaccumulation of heavy metals and metalloids poses both acute and chronic health issues in humans and animals. Hence, removing these toxic heavy metals from contaminated water is essential. The currently available treatment methods are costly and sometimes not appropriate for the current needs. Considering the high cost associated with advanced water purification technologies, developing low-cost and site- specific methods to remove heavy metals is an urgent need. Natural red earth (RE), mainly composed of iron-aluminium oxide-coated quartz sand, is found in the north-northwestern coastal belt of Sri Lanka. The size fraction <180 μm of RE is well-known for its metal adsorption ability. However, the use of the fine fraction of RE in water filtration may lead to certain practical issues, such as clogging the filter media and contamination of purified water with particles. Hence, this study examined the use of RE as a water filter media to overcome the aforementioned difficulties. Column adsorption experiments were performed using the medium-sized sand fraction (125 - 500 μm) of RE. Cylindrical, plastic columns (width =5.5.cm, length=30 cm) were filled alternatively with 125-250 μm, and 250-500 μm size RE fractions as layers. Synthetic wastewater (arsenic ~ 3 mg/l, chromium ~ 3 mg/l) was passed through the column against gravity at a rate of 15 ml/min for 10 h. Filtered samples were collected at every 15 min intervals and analyzed for As and Cr by inductively coupled plasma mass spectrometry (ICP-MS). Almost complete removal of both As (III/V) (from 3 to 0.0031 mg/l) and Cr (III/VI) (3 to 0.0060 mg/l) was confirmed by ICP-MS data. Hence, the medium-sized sand fraction of RE can be used as an effective filtering medium to remove As and Cr from contaminated water. Experiments are underway to determine the lifespan of the RE column.
Whole-rock geochemical signatures of dolerite dykes in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Munasinghe, S.A.; Dharmapriya, P.L.; Malaviarachchi, S.P.K.; Kumarasiri, S.A.T.D.; Samaranayake, S.A.
So far, dolerite dykes have solely been reported from the Vijayan Complex (VC) of Sri Lanka. Samples of two localities have been geochemically analyzed for whole-rock major and trace element concentrations. Here, we present the whole-rock major and trace element geochemistry of seven Sri Lankan dolerite samples collected from five localities (two samples each at Wahawa, Rukkamputur, and one sample from Gallodai in the Vijayan Complex; one each in the Highland Complex - close to Badulla, and Wanni Complex - close to Kurunegala) to unravel the tectonic setting, nature of source magma and crustal contamination of dolerite magmatism. In the SiO₂ vs Na₂O + K₂O diagram, the composition of dolerite magma varies from basalt to basaltic andesite and was plotted within the region of the sub-alkaline magma series. Major and trace element geochemical discrimination diagrams (AFM, Jensen cation plot, and Nb/Y vs Rb/Y diagram) of different magma series indicate tholeiite affinity and are differentiated through fractional crystallization. The wide ranges in MgO (3.03-7.47wt %), and patterns of other major trace elements (such as Fe₂O₃, TiO₂, and SiO₂) and compatible trace elements (such as Ni and Cr) with MgO indicate the typical trends of fractional crystallization. Chondrite normalized rare earth element (REE) patterns indicate enrichment of LREE relative to MREE and HREE. Chondrite normalized REE patterns and Primitive Mantle (PM) normalized incompatible trace element patterns of dolerites are mainly comparable with those of continental basalts. The pronounced negative Nb, Ti, and positive Pb anomalies in the PM normalized diagram and Nb/La ratios of <1 represent the signals of crustal contamination of parent magma. In tectonic discrimination diagrams (Y vs Cr, Zr/4-2*Nb-Y), dolerites fall in the within- plate basalt (WPB) field and continental basalt region. Hence, the studied dolerites indicate their origin from a differentiated contaminated-tholeiitic magma in an intra-continental tectonic setting.
Dormancy breaking methods: in-situ and ex-situ conservation of Sri Lankan endemic wild rice oryza rhizomatis
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Thasajini, N.; Orsenigo, S.; Wijayasinghe, T.W.M.M.; Jayasuriya, K.M.M.G.; Kumarage, M.N.G.M.V.; Mondoni, A.
Sri Lanka consists of five wild rice species. Among them, Oryza rhizomatis is endemic and distributed only in the low-country dry zone of Sri Lanka. According to the previous literature, some of the recorded populations of this species are declining due to natural and anthropogenic processes. Thus, this study was conducted to determine the conservation status and the seed biology of O. rhizomatis. Ex-situ conservation data were gathered from seed banks (43), the national herbarium (2) and literature (46) and were confirmed using field surveys. Seed germination and the effect of dormancy-breaking treatments were studied using freshly collected seeds. A field survey revealed that 13 out of 46 previously recorded populations have disappeared in the wild. Only 28% of the existing populations were inside protected areas, while only 26% of the population was conserved ex-situ. Thus, high priority should be given to the in-situ and ex-situ conservation of O. rhizomatis. Seeds were identified as dormant since no germination was observed for intact fresh seeds. Percentage mass increments, after 48 h of imbibition of scarified and non-scarified seeds, were not significantly different, revealing that seeds have no physical dormancy. The embryo had not developed prior to germination; thus, physiological dormancy could be the possible dormancy class. Chemical treatments with HNO₃, KNO₃ and H₂O₂did not significantly improve seed germination. Only 12% and 9% of seeds germinated after exposure to wet heat at 45 and 50 ⁰C, respectively. Only 5% of seeds germinated after dry storage at -20 ⁰C. Nevertheless, 80% of seeds germinated when they were physically scarified just above the embryo, revealing their physiological dormancy. However, a more feasible dormancy-breaking treatment must be identified to assist the propagation of this species. Since this is an endemic and high-priority species for in-situ and ex-situ conservation, further studies must be conducted on seed germination and dormancy-breaking treatments.
Classification system for urban green spaces: a case study from Colombo city, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Abeysinghe, U.M.; Hewawasam, H.U.C.P.
Urban Green Space (UGS) is a land area that is partly or wholly covered with grass, trees, shrubs, or other vegetation in urban areas. These UGSs provide multiple ecosystem services such as air and water purification, climate regulation, disaster risk reduction, habitat for species and biodiversity enhancement. Further, they present diverse opportunities to mediate the adverse effects of climate-induced disasters while simultaneously improving human health, well-being, and economic and social benefits. Strategic planning and management are vital in obtaining the optimal benefits of UGSs, and the absence of clear demarcation and proper classification of UGSs makes sustainable development goals unachievable. Thus, this study spatially mapped existing UGSs with clear demarcations using Sentinel 2 Level-A satellite images and ArcGIS 10.2. A systematic classification system was also developed for UGSs in Colombo city, Sri Lanka as a model. This would enable planners to devise effective urban management plans to create a climate- resilient city in the future. Based on the past literature, field observations, topographic maps, land-use maps, and high-resolution satellite images, a list of criteria and sub-criteria was used to develop the UGS classification system. The main criteria used for the classification are the structure and functionality of urban UGSs. Normalized Difference Vegetation Index (NDVI; using Band 8 and Band 4) technique was utilized for UGS extraction. Vegetated areas were further classified based on their vegetation density by using NDVI threshold values. The extent of UGS in the Colombo Municipal Council area is 35.4% of the total land extent. The analysis defined four categories of urban green spaces: parks and conservation green spaces (15% of total UGS), shadings and greenways (21%), community green space (13%), and residential and amenity green spaces (51%). This systematic classification of UGSs can be a first step towards categorizing urban green spaces and addressing issues in sustainable city development in the future.
Total arsenic and arsenic species in selected marine food fish by HPLC-ICP-MS and assessment of toxicity
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Jayakody, J.A.K.S.; Edirisinghe, E.M.R.K.B.; Senevirathne, S.A.; Senarathna, L.
The toxicity of Arsenic (As) is mainly dependent on the As species and oxidation status. Thus, the total As concentration does not provide accurate information about the toxicity in the matrix. The objective of the present study was to assess the actual toxicity of As species in selected marine food fish to ensure safety for human consumption. Ten species (n=3 per each) of fish were collected from the Trincomalee fish market, and total As in fish muscles was determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after microwave digestion. Arsenic species were selectively separated and determined using High-Performance Liquid Chromatography (HPLC) hyphenated to ICP-MS following water bath extraction with 30 mmol dm⁻³ nitric acids. An anion exchange column was used for the separation of the five As species, including arsenobetaine (AsB), arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) with 1 mL/min isocratic elution (run time-12 min) of 10 mM Ammonium phosphate (pH - 8.6) as the mobile phase. The employed operating conditions for ICP-MS- HPLC successfully separated and consecutively eluted AsB, AsIII, and AsV in all samples. The level of total Arsenic in the present study varied from a minimum of 0.547±0.038 mg/kg in Carangoides fulvoguttatus to a maximum of 13.403±1.075 mg/kg in Nemapteryx caelata. In all the species studied, the predominant As the compound was AsB which accounted for 83.2 to 99.4% of the total As ranging from 0.473-13.323 mg/kg. AsIII and AsV were found at low levels, whereas MMA and DMA contents were not detected in any sample. The concentration of inorganic As (sum of AsIII + AsV) ranged from 0.007 (Carangoides fulvoguttatus) to 0.040 (Nemapteryx caelata) mg/kg. Inorganic As concentrations in all the studied fish species were below the maximum admissible limit 2 mg (inorganic As)/kg, indicating that the species tested are safe for human consumption in terms of inorganic As.
Root morphological and anatomical responses in selected rice (oryza sativa l.) varieties against excess iron (Fe ²⁺)
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Mudalige, H.M.M.Y.; Masakorala, K.
Roots are the primary sensors of toxicity; their responses to excess Fe²⁺ can be used as biomarkers in the selection of Fe²⁺ toxicity tolerance rice varieties. Therefore, this study aimed to analyze root morphological and anatomical responses of selected rice varieties to excess Fe²⁺. Two selected rice varieties from a preliminary study as tolerant (Ld408) and susceptible (Ld365) to excess Fe²⁺ were examined for morphological and anatomical responses. Seven-day old seedlings of both varieties were exposed to different levels of Fe²⁺ [150 mg l ⁻¹ (control), 450 mg l ⁻¹ , 650 mg l ⁻¹ , 850 mg l ⁻¹ , 1,050 mg l ⁻¹ and 1,250 mg l ⁻¹ ] at pH 5.5 for seven days. The experiment was carried out in a modified flood and drain hydroponic system according to the randomized block design (RBD). The number of roots and length of the roots per plant were recorded, and the fully developed air channels in the root cortex were counted in the cross sections of the roots under the high power of the trinocular compound microscope. Data were analyzed by two-way ANOVA followed by Tukey’s posthoc test using statistical software MINITAB 17. Ld365 showed a significant (p<0.050) reduction in the number of air channels in the tested Fe²⁺ levels higher than 650 mg l ⁻¹ . In contrast to Ld365, Ld408 showed Fe²⁺ level-dependent significant increase (p<0.050) in the number of fully developed air channels in the root cortex. This indicates a high root oxidation power in tolerant plants in order to form an iron plaque as a defence mechanism against excess Fe²⁺ uptake. Both varieties showed a significant (p<0.050) increase in root number with Fe²⁺ stress. Comparatively, a higher number of roots was exhibited by Ld408 in all treatments compared to Ld365,suggesting a higher oxidation power of roots in Ld408. However, Ld365 reported a significant (p<0.050) reduction in root length compared to Ld408 against Fe²⁺ toxicity indicating a reduction of root growth in Ld365 under excess Fe²⁺ . Overall results inferred that morphological and anatomical responses of rice roots are variety-specific in response to Fe²⁺ stress.
Applicability of clean and fertility indices as tools in determining compost quality
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gallage, A.W.R.; Masakorala, K.
With the increasing demand, the release of low-quality compost to the market under different brand names has become a significant issue. Since different inputs, such as agricultural waste, and municipal solid waste, are used in composting, there is a potential threat of containing heavy metals in compost. Therefore, it is crucial to have a mechanism to assess the nutrient composition and heavy metal contents to determine the quality of products. The study examined the applicability of the clean index (CI) and fertility index (FI) as tools to ensure the quality of compost in the market. Based on the results of a preliminary survey, eight commonly available compost brands in the market of the Southern Province, Sri Lanka, were collected and analyzed. The FI was calculated on the basis of the chemical properties, total organic carbon (TC), total nitrogen (TN), total phosphorus (TP), total potassium (TK) and carbon to nitrogen ratio (C: N), which were determined according to the standard methods. The CI was calculated by considering heavy metal contents (Zn, Cu, Cd and Pb), which were determined using Atomic Absorption Spectroscopy (AAS). To assure the quality, either a marketable class (A, B, C and D) or a restricted use class (RU-1, RU-2 and RU- 3) was determined by considering both FI and CI values. The FI values varied from 2.10 to 4.50 with a mean value of 3.19, while CI values varied from 3.64 to 5.0 with a mean value of 4.55 (on a scale of 5). According to the results, 37.5% of tested brands were categorized under the restricted use class, RU-1, due to low fertilizing potential or low FI values, while 62.5% of brands were categorized under marketable classes due to their acceptable levels of heavy metals and fertilizing potentials. Hence, overall results highlight the significance of using FI and CI as tools in ensuring the quality of compost before being released to the market.
CYTO-genotoxicity assessment of wastewater from automobile service station by using the Allium cepa test
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Madushika, W.A.S.; Hemamali, K.K.G.U.; Masakorala, K.
Automobile service stations produce wastewater (WW) on a large scale with a combination of toxicants such as different types of hydrocarbons, detergents, etc. Therefore, the characterization of the potential cytotoxicity of WW before being discharged from automobile service stations is important. The study aimed to assess the cyto-genotoxic potential of wastewater generated in automobile service stations by using the Allium cepa test, which is widely used in the cyto-genotoxicity characterization of toxicants. Healthy, surface sterilized A. cepa bulbs grown in distilled water for 48 h under the dark were transferred to a series of treatments with 6.2, 12.5, 25.0, 50.0 and 100% WW and incubated for 48 h. Distilled water was used as the control. After the 48 h incubation period, the number and elongation of roots, mitotic index (MI) and frequencies of different types of aberrations were evaluated as endpoints. The complete randomized block design (CRB) was employed with three replicates per treatment and control. The data recorded from the endpoints were analyzed by one-way ANOVA followed by Tukey’s posthoc test. The root number showed the contamination level-dependent significant reduction in treatments compared to the control (23.00±0.57), and the lowest (6.67±0.57) was recorded from the treatment with 25.0% WW. There were no visible roots in the 50.0% and 100%. The calculated mitotic index (MI) showed the contamination level-dependent downward trend, and the lowest value (36.9%) was recorded from the 100% WW compared to the control (82.5%). The higher frequencies of nuclear aberrations (NA), such as nuclear lesions, nuclear buds, binuclear cells and micro nucleus and chromosomal aberrations (CA), such as chromosomal bridges, chromosomal fragments, were recorded from the undiluted WW (100%), and the contamination level-dependent decrease in the cells with aberrations was observed in lower contamination levels. The highest frequency of aberrant cells (61.2%) was recorded from undiluted WW (100%). The calculated IC₅₀ values (6.25%) were based on the inhibitions in root number, and the calculated MI inferred the potential cytotoxicity. Different types of NAs and CAs observed in the study inferred the potential genotoxicity even at the low level of contamination of WW, highlighting the significance of treating WW before being released into the environment.
GIS-based soil erosion vulnerability mapping in Welimada Divisional Secretariat in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Medawela, R.M.S.G.N.; Rathnayaka, N.M.; Perera, M.S.M.; Nagaruby, N.; Weerasinghe, V.P.A.
Soil erosion is a major environmental issue in watersheds in Sri Lanka. It is a severe problem in the up and mid-country with steep slopes, high-intensity rainfall, and unplanned land uses to reduce soil nutrients. Soil erosion is a particular concern in the hill country where the watersheds of major rivers are located. Welimada Divisional Secretariat is in Welimada electorate in Badulla District of Uva Province. Mountains are around in this part of the country, and 70% of the population, which counts 100,365 are living in agriculture. The objective of this case study is to develop a soil erosion vulnerability map for Welimada DSD, Sri Lanka. The main causative factor for soil erosion is rainwater runoff. Apart from that, some anthropogenic activities also affect soil erosion. Soil loss was estimated using the Revised Universal Soil Loss Equation (RUSLE) model. Digital Elevation Model, land use map, soil map, and rainfall data were used to create the soil erosion vulnerability map. Collected data were analyzed using GIS. Based on this study, Welimada DSD was classified into three soil erosion hazard classes as low (0≤25 t ha-1 yr⁻¹ ), moderate (>25-50 t ha⁻¹ yr⁻¹ ), and high soil erosion (<50-161.10 t ha⁻¹ yr⁻¹ ). The 45.5% area of Welimada DSD falls into the low soil erosion hazard category, while 41.0 and 13.5% area of Welimada DSD fall into moderate and high soil erosion hazard categories, respectively. The annual mean average soil loss in Welimada DSD was estimated as 32.81 t ha⁻¹ yr⁻¹ . Moderate and highly eroded areas in the Welimada area are prone to high soil erosion. Steep topographic features, poor vegetation cover and poor land management practices, and high rainfall rate may contribute to the high erosion. Those lands require soil conservation measures and regular maintenance to prevent further soil erosion that can lead to agricultural yield reduction.

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