Browsing by Author "Dushyantha, N"

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Assessment of ni phytomining potential in Ginigalpelessa serpentinite deposit, southeast Sri Lanka
(IEEE, 2023-12-09) Dilshara, P; Senarath, S; Ratnayake, N; Abeysinghe, B; Premasiri, R; Dushyantha, N; Ratnayake, A; Batapola, N; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Nickel (Ni) phytomining is an emerging mining technique that uses hyperaccumulator plants to recover Ni from low-grade metal-rich soils such as serpentine. The Ginigalpelessa serpentinite deposit in Sri Lanka contains high concentrations of Ni, Cr, and Co where the phytomining potential is not well-documented. Therefore, the present study determines Ni, Cr, and Co contents in the soil and assesses the relationship between Ni content and plant diversity to identify potential areas for phytomining in the deposit. Thirty-one soil and twenty-five rock samples were collected from the deposit to analyze their metal contents. The abundant plant species were recorded at each location to analyze the plant diversity and species evenness using the Shannon Weiner Diversity Index. Based on soil analysis, Ni concentration in Ginigalpelessa serpentine soil ranged from 4,005 to 17,352 mg/kg which is within the range of global Ni phytomining grade (6,000 – 12,000 mg/kg). Moreover, areas having low diversity (0.0919 - 0.3061) showed high enrichment of Ni (7,000 - 12,000 mg/kg), emphasizing that low diversity areas with high Ni-enriched soils are suitable for in-situ Ni phytomining. However, further studies are required to assess the Ni hyperaccumulation ability of the abundant plant species to implement Ni phytomining in the Ginigalpelessa serpentinite deposit.
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Dynamics of the Madu-Ganga Estuary
De Silva, UHNH; Somasiri, RBHP; Jayasekara, NNL; Ratnayake, AS; Dushyantha, N; Weththasinghe, SM; Samaradivakara, GVI; Vijitha, AVP; Ratnayake, NP; Abeysinghe, AMKB; Dassanayake ABN; Elakneswaran, Y;
Among the estuaries in Sri Lanka, Madu-Ganga Estuary plays a significant role to generate a massive income through tourism. The existing tropical ecosystem attracts the tourists. However, this ecosystem faces problems of environmental deterioration problems which affect the tourism industry and income of the local community. Therefore, this research is mainly focused for understanding hydro dynamics and sediment dynamics process in Madu-Ganga Estuary. The four field visits were carried out to cover southwest and northeast monsoon periods. In situ and laboratory tests were conducted for surface and bottom water samples of Madu-Ganga Estuary to analyse the quality of the water. In addition, grab and core samples and sub-bottom profile data were used to identify sediment distribution patterns of the estuary. Moreover, time series satellite images were used to identify nearshore sediment dynamics along the western coast of Sri Lanka. Results show that a significant variation of water quality parameters under the estuary mouth opened and closed conditions. The spatial variation of chloride content also indicates that estuary mouth opened condition plays a major role to control seawater invasion in this aquatic system. Sub-bottom profile data shows cyclic/seasonal changes in accumulation of sediments in Madu-Ganga Estuary. Time series satellite images indicate that sand can probably receive from the southern region by predominant longshore currents during the southwest monsoon. Further studies are recommended to identify lake ecosystem responses to physicochemical changes and to design seasonal mining capability.
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Exploration for rare earth elements (REES) in different geological formations of Sri Lanka and their recovery potential
(2022-09) Batapola, N; Ratnayake, N; Abeysinghe, B; Premasiri, R; Rohitha, S; Dushyantha, N; Ilankoon, S; Dissanayake, K; Dharmaratne, P
Rare earth elements (REEs) are widely attracting global attention due to their crucial role in the modern lifestyle, especially in the industrial advancement towards a green economy through renewable technologies. This particular group of metals consists of the 15 lanthanides, yttrium (Y), and scandium (Sc). There are two subgroups, namely light rare earth elements (LREEs) from lanthanum (La) to europium (Eu) and heavy rare earth elements (HREEs) from gadolinium (Gd) to lutetium (Lu) and Y (Fig. 1a). Generally, LREEs are more abundant in the mineral deposits when compared to more priced HREEs [1].
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Geochemical exploration for prospecting new rare earth elements (REEs) sources
(2023) Dushyantha, N; Ratnayake, N; Premasiri, R; Batapola, N; Panagoda, H; Jayawardena, C; Chandrajith, R; Ilankoon, IMSK; Rohitha, S; Ratnayake, AS; Abeysinghe, B; Dissanayake, K; Dilshara, P
Rare earth elements (REEs) are globally considered as critical elements due to their indispensable applications in various high-tech industries. With the ever-increasing demand, identified primary REE resources will not be able to fulfil the global requirements and thus exploration and exploitation of secondary REE deposits are essential. This work is designed to prospect REE potential in lake sediments in the proximity of the Eppawala Phosphate Deposit (EPD) in Sri Lanka. In this context, surface and core sediment samples were collected from 2 upstream lakes and one downstream lake (connected to a man-made water canal, namely Jaya-Ganga) with respect to the EPD. In the downstream, the average total rare earth element (TREE), light REE (LREE) and heavy REE (HREE) concentrations of the surface sediments were 1011.3, 904.6 and 66.6 mg/kg, respectively. The corresponding average values in downstream core sediments were 858.7, 719.3 and 100.2 mg/kg, respectively. The results suggested that the downstream lake sediments contained a high TREE content with a significant LREE enrichment compared to the upstream lake sediments. The EPD was identified as the main REE source and Jaya-Ganga, which flows across the EPD, was the main transport medium in this study. Phosphate-bearing minerals, such as fluorapatite and hydroxylapatite, derived from the EPD act as the REE carriers where REEs substitute isomorphous in the mineral lattice. Since REE grade is relatively high compared to some of the reported secondary REE sources, the downstream lake sediments could be a potential secondary source for REEs for future exploitation.
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Navigating risk in Sri Lanka's renewable energy transition: key challenges affecting investment in onshore wind farms
(Faculty of Graduate Studies, 2024) Bakmeewewa, P; Nethmini, N; Pradeepika, M; Kuruppu, G; Dushyantha, N; Dassanayake, S
In alignment with the 13 Sustainable Development Goals (SDGs) that emphasize the transition from fossil fuels to renewable energy [1]. Sri Lanka stands at a pivotal juncture in embracing this transformative trend. The country can significantly reduce its carbon footprint, enhance energy security, and foster sustainable economic growth by investing in renewable energy sources such as wind, solar, and hydroelectric power. With its geographical advantages, Sri Lanka has enormous potential to harness energy from renewable sources like wind, and sunlight. However, as of 2018, only 39% of Sri Lanka’s energy generation has been utilized through renewable energy sources. Located in one of South Asia’s largest monsoon belts, Sri Lanka benefited from excellent wind resources with an estimated 5000 km2 of wind energy potential in 2003 [2].
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Navigating the uncertainty: financial, technological, and geopolitical risks in deep-sea mining ventures
(Faculty of Graduate Studies, 2024) Droohithya, T; Fernando, T; Ranaweera, P; Kuruppu, G; Dushyantha, N; Dassanayake, S
Deep-sea mining (DSM) involves extracting minerals from ocean depths exceeding 200 meters, focusing on resources like hydrothermal vents, ferromanganese crusts, and polymetallic nodules [1]. These resources are rich in valuable metals like cobalt, nickel, rare earth elements, and man-ganese, which are essential for technologies like electric vehicle batteries and renewable energy systems. For instance, as depicted in Figure 1, the electric vehicle market is expected to expand rapidly, leading to an increased need for essential minerals. While the DSM offers an exceptional opportunity to access the minerals, it also raises significant concerns about marine ecosystem degradation, biodiversity loss, and potential conflicts with other marine resource users [3]. The International Seabed Authority (ISA) is currently developing regulations to manage DSM, aiming to balance resource extraction with environmental protection.
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Nearshore sediment dynamics in Sri Lanka
Ratnayake, AS; Weththasinghe, SM; Dushyantha, N; Premasiri, HMR; Ratnayake, NP; Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Coastal environment is a unique morphodynamic system for diverse changes. The present study estimated coastal morphodynamic changes and sediment transportation directions at locations of Uswetakeiyawa beach nourishment and Colombo harbour expansion project areas. In addition, heavy mineral occurrences were studied in beach sediments altogether parameters of mineralogical and geochemical compositions to identify depositional environments. Moreover, time series satellite images were used to identify seasonal coastal sediment accretion and depositional trends. Uswetakeiyawa beach nourishment project area indicates complex sand accretion or erosion, and a net reduction of overall beach widths with reference to the initial field visit. This site records bi-directional sediment transportations by longshore currents during the monsoon periods. Similarly, Colombo harbour expansion project area shows that the cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). The cumulative and site-specific sand accretion and erosion patterns show clear influence with the monsoon seasonality. Beaches were wider during the stormy south-western monsoon, whereas beaches were narrower during fair weather of north-east monsoon. In contrast, ilmenite, zircon, garnet, monazite and rutile were identified as main heavy minerals in beach sediments. The heavy mineral potential of the north-eastern coast was high (average about 45-50% in the Verugal and 70-85% in the Pulmoddai deposits and 3.5-5.0% in the offshore samples from Nilaveli to Kokkilai), compared to the south-western sediments (average about 10% in onshore and 2% in offshore Gin River mouth). Observed high concentrated heavy minerals in beach and low concentrated offshore sediments suggest the panning system in the surf zone to form enriched placer deposits. The whole rock major and trace compositions of beach sediments were marked enrichment of TiO2, Fe2O3, Ce, Cr, Nb, Th and V compared to the average upper continental crust values. The analysis of prominent coastal longshore transport patterns shows that clockwise flows in the eastern and north-western coasts. In the south-western coast, transport directions were divided into two branches of anti-clockwise and clockwise. Therefore, the schematic representation of monsoon-derived longshore currents suggests that the sources of heavy minerals in the Pulmoddai and Verugal deposits may have probably influenced by clastic sediment supply in eastern India and Sri Lanka (the Mahaweli River), respectively. Heavy minerals in the western coast can probably derive from Precambrian metamorphic rocks, and supplied to coast through river systems in Sri Lanka.
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Nickel phytomining potential in serpentine soil of Sri Lanka: an implication for sustainable mining
(2023-08) Dilshara, P; Abeysinghe, B; Premasiri, R; Ratnayake, N; Senarath, S; Ratnayake, A; Dushyantha, N; Batapola, N
The world is experiencing rapid growth of nickel (Ni) demand, especially for lithium-ion batteries used in electric vehicles, while high-grade Ni deposits are being depleted due to expanding economics, growing populations, and disorganized industrialization. Therefore, a major transformation from high-grade low-bulk ores to low-grade high-bulk ores is necessary to secure the future supply chain of Ni [1]. In this context, ultramafic soil is considered a low-grade high-bulk Ni ore, mostly found in tropical countries. However, conventional mining practices are high energy-consuming and generate a tremendous amount of waste, making it impracticable to recover Ni from ultramafic soil. Therefore, phytomining (or farming for metals) is identified as a viable and innovative method for Ni recovery from low-grade high-bulk sources such as ultramafic soil.
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Rare earth element enrichment in intrusive rocks of Sri Lanka as a potential low-grade source
(IEEE, 2022-07) Batapola, N; Ratnayake, R; Abeysinghe, B; Premasiri, R; Rohitha, S; Dushyantha, N; Illankoon, IMSK; Dissanayake, O; Dharmaratne, P; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Owing to the crucial role-playing in the decarbonization of the global economy, the demand for rare earth elements (REEs) is burgeoning while the supply is highly uncertain. This lack of secure supply coupled with high-grade resource depletion has led to increased explorations on potential low-grade resources of REEs. Thus, the present study focuses on the enrichment of REEs in intrusive rocks in Sri Lanka – a prospective low-grade REE resource. We analyzed fifty-five rock samples from a few granitic bodies (Massenna, Thonigala, Arangala), Eppawala Phosphate Deposit (EPD), and Ratthota pegmatite for their REE concentrations. Amongst the studied prospects, EPD (4185 mg/kg), Arangala granite (2183 mg/kg), and Massenna granite (937 mg/kg) had high REE concentrations with increased LREE enrichments over HREEs. However, EPD contains processable REE minerals (apatite and monazite), and REEs can be extracted as a by-product after developing the phosphate fertilizer production flow. Thus, EPD is the highest prospective of all the studied intrusive rocks of Sri Lanka. Compared to global occurrences, although it is low-grade (0. 48 wt% REO, 0.29 million tons REE reserve), such low-grade REE resources could become viable in the future due to the ever-increasing demand and the expected resource depletion of REEs.
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Rare earth element potential in the beach placers along the southwest coast of Sri Lanka
(IEEE, 2021-07) Batapola, N; Dushyantha, N; Ratnayake, N; Premasiri, R; Abeysinghe, B; Dissanayake, O; Rohitha, S; Ilankoon, I; Dharmaratne, P; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
In the recent few years, rare earth elements (REEs) were considered as critical metals with strategic importance due to their high usage in modern technology and green energy applications. Currently, with the unexpected increase of rare earth element (REE) demand and China's market dominance, many REE processing projects are being launched or revived. In this regard, the present work is focused on assessing the REE potential in the beach placers along the southwest coastline in Sri Lanka. The collected 36 beach sand samples from the mean sea-level in the southwest coast during both southwestern and northeastern monsoons were subjected to both elemental and mineralogical analyses. Based on the findings, Galle, Ginthota, Wadduwa, and Thelwatta areas were found with significant contents of REEs ranging from 32.8-1,359.1 mg/kg. Moreover, the results suggest that REE-bearing heavy minerals are heavily concentrated in the beach face due to stronger oceanic currents generated by the strong winds of the southwestern monsoon along with the increased sediment supply by inland rivers. The findings in this study would provide insights for future REE prospecting studies, which is helpful in unraveling the hidden potential of REE resources in Sri Lankan beach placer deposits.
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Sea-level inundation and risk assessment along the south and southwest coasts of Sri Lanka
(Springer, 2020) Palamakumbure, L; Ratnayake, AS; Premasiri, HMR; Ratnayake, NP; Katupotha, J; Dushyantha, N; Weththasinghe & W. A. Panchala Weerakoon, S
Global sea-level changes have been a major topic among scientists. Sea-level changes are not globally uniform. Reconstruction of paleo sea-level changes and monitoring of variations in regional sea-level are important to (i) evaluate future sea-level changes, and (ii) predict risk assessment. In this study, we examined sea-level inundation during the middle Holocene highstands based on paleo sea-level indicators along the south and southwest coasts of Sri Lanka. Besides, future sea-level inundation was predicted considering the calculated sea-level trends based on tidal gauge data and high-resolution surface elevation data. Light Detection and Ranging (LiDAR) is one of the most accurate optical remote sensing methods currently available to obtain high-resolution land surface elevation data. Therefore, in this study, Digital Elevation Models (DEMs) were prepared using LiDAR data for estimating the risk assessment in coastal lowlands. Tide gauge data of Colombo in Sri Lanka (from 2006 to 2017), Gan in the Maldives (from 1995 to 2017), and Hulhule in the Maldives (from 1995 to 2017) showed that sea-level has increased with a rate of 0.288 ± 0.118, 0.234 ± 0.025, and 0.368 ± 0.027 mm/month, respectively. DEMs based on LiDAR data suggested that south and southwest coasts are a risk of future sea-level inundation (height = 0.1–0.2 m during next 50 years and about 0.7 m in height during next 200 years, and distance = about 3.5–15.0 m from the present sea-level towards the inland). Consequently, it is important to consider future sea-level changes in disaster management and mitigation activities along the south and southwest coasts of Sri Lanka.
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Structures of water column and sediment sub-bottom in the Tangalle Bay, Sri Lanka
Weththasinghe, SM; Ratnayake, AS; Dushyantha, N; Ratnayake, NP; Samaradivakara, GVI; Vijitha, AVP; Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Water quality parameters and local morphology are important for monitoring aquatic life, and for planning any coastal development project. So far, few studies have been carried out in Sri Lanka for identifying water column structure and subbottom lithology in coastal zones. Tangalle Bay is situated in lowlands in the intermediate zone of southern Sri Lanka. Tangalle Bay replenish freshwater by minor tributaries (e.g., Kirama Oya) and Rekawa Lagoon. Field excursion in Tangalle Bay was carried out during the northeastern monsoon which is relatively less influenced by high wave-energy compared to the southwest monsoon. In this study, water quality parameters were measured using Valeport Midas CTD instrument. In addition, sub-bottom morphology was identified using Bathy 2010PCTM CHIRP sub-bottom profiler. Pre-decided systematic sampling locations were identified for covering three cross-shore and six long-shore survey lines. Water quality parameters of cross-shore and long-shore survey lines are represented separately. In cross-shore survey lines, temperature variations show warm pool in shallow water (depth < 3 m), up to a distance of 4 km from the shore. In addition, temperature variations in deep and distance (> 4 km) water can probably indicate well-mixed nature, perhaps due to upwelling. Less dense water can be observed in shallow water (depth < 3 m). Density variations also indicate upwelling of dense water at a distance of 4 km. The lowest salinity was detected close to the nearshore area due to freshwater supply by tributaries. Salinity variations also indicate possible vertical zonation of upwelling beyond 4 km distance from the shore. Dissolved oxygen values are high up to a 3 km distance in surface and bottom water, due to well mixing in the nearshore area. However, dissolved oxygen values are decreased in bottom water at distance of 3-4 km from the shore. In long-shore survey lines, temperature and density variations show strong stratifications same as that of cross-shore survey lines. High salinity on the bottom and low salinity on the surface water in the nearshore area can probably indicate freshwater supply from terrestrial margins. Sub-bottom profile data indicate the attached coral reef on the bed rock. This attached coral reef creates two depositional features such as layered sedimentary features on the landward side and homogeneous sediments on the seaward side of the bay.
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Unlocking the blue economy: financing a sustainable ocean future
(University of Moratuwa, 2023) Niluka, G; Dushyantha, N
The world’s oceans are integral to the livelihoods, food security, and economic well-be- ing of billions of people around the world. More than three billion people, roughly 40% of the global population, reside in coastal areas and rely on the ocean as a fundamental source of their livelihoods [1]. Meanwhile, industries such as tourism, fisheries, marine transportation and petroleum-related to the ocean economy play a key role in global economic expansion and climate action [2], [3]. Despite the immense value of the ocean, marine ecosystems face many threats, including climate change with rising sea levels and ocean acidification, pollution from natural and anthropogenic sources, unsustain- able fishing practices depleting fish stocks, and coastal development [4], [5]. For exam- ple, in the Sri Lankan context, the X-Press Pearl ship accident has caused enduring dam- age to the local coastal and marine ecosystem. The contamination of these ecosystems with hazardous materials and plastic pellets has led to a sustained decline in fish stocks, adversely impacting the fishing industry. The Sri Lankan eco-tourism has also experi- enced long-term declines in tourism revenue. The lasting health risks associated with pollutants threaten both marine life and communities dependent on the ocean