The geology of Sri Lanka captures one of the longest and most complete records of Jurassic to Miocene tectonic evolutions from the mid-latitudes of the southern hemisphere to the equatorial northern ...hemisphere. Sedimentary basins in Sri Lanka provide a natural laboratory with which to reconstruct paleoclimate during the island’s northward voyage from Gondwana to Asia. Here, drill core cuttings were obtained from the Barracuda hydrocarbon exploration well in the offshore Mannar Basin, Sri Lanka. CHNS elemental analysis, gas chromatography-mass spectrometry, and stable C and N isotopic analyses were performed. The results suggest the deposition of organic carbon depleted (average total organic carbon (TOC) = 0.97%) sediments under the arid climate of the Early Campanian. Separation of the Laxmi Ridge-Seychelles and Seychelles from the Indian plate and sea-level regression may have enhanced the deposition of organic carbon–rich (average TOC = 1.34%) and terrestrial organic matter (OM)–rich (average C/N ratio = 20.36) sediments during the Late Campanian to Late Maastrichtian. CaCO
3
-rich (average = 32.5%) Upper Cretaceous sediments then show a period of high productivity under a warm climate. The Deccan-Reunion basalt likely acted as a major contributor to the mass extinction of coccolithophores/foraminifera at the Late Maastrichtian followed by a reduction of CaCO
3
and organic carbon content. The Early-Late Paleocene was characterized by the deposition of algal-derived OM with a terrestrial contribution (average C/N ratio = 15.75) under oxic depositional conditions (average C/S ratio = 16.21). However, the depositional environment changed drastically to one of oxygen-poor marine conditions (average C/S ratio = 6.83) during the Late Paleocene to the Early Oligocene due to weak oceanic circulation under a greenhouse climate. In contrast, the deposition of CaCO
3
-rich sediments since the Late Paleocene (average = 40.2%) is linked to the movement of the Indian plate into northern, warmer tropical latitudes. The Middle Oligocene to Miocene sedimentary succession was characterized by terrestrial OM-rich (average TOC = 2.51% and C/N = 23.45) sediments. The Middle-Upper Miocene sedimentary succession contains lamination and back carbon (charcoal fragments) suggesting the development of the present-day South Asian monsoon system. This record from Sri Lanka provides important new insights into Jurassic-Miocene geological and climatic evolution in this tropical part of the world for the first time.
Graphical abstract
The Upper Cretaceous to Eocene sedimentary succession of the Dorado North exploration well in the Mannar Basin has been studied for paleoenvironment (organic matter richness, its composition, and ...depositional environment) and petroleum source rock potential. In this study, drillcore cuttings (
n
= 142) were analyzed using CHNS elementary analyzer. Results indicated that Lower Campanian sediments were depleted by total organic carbon content (TOC = 0.45%), under arid climate. The Lower Campanian to Upper Maastrichtian sedimentary sequence contains organic carbon rich (TOC = 1.64%) terrestrial (C/N ratio = 27.13) sediments. Consequently, this sedimentary sequence can be identified as a good source rock for gas generation. The formation of organic matter rich terrestrial sediments has been linked to sea-level changes and tectonic activities during the Late Cretaceous. Carbonate carbon contents are rich in the Lower Campanian to Upper Maastrichtian sedimentary sequence that indicates diversification of microorganisms under warm climatic conditions. The Paleocene to Eocene sedimentary sequence indicates poor to fair source rocks for possibly oil generation. However, the depositional environment was drastically changed from oxic (Early-Late Paleocene) to anoxic (Late Paleocene-Late Eocene) conditions. Consequently, the Eocene epoch is characterized by weak oceanic circulation in the Indian Ocean under greenhouse climate. In contrast, the deposition of carbonate platforms since the Late Paleocene (CaCO
3
= 29.3%) can be related to the northward movement of the Indian plate into warmer tropical latitudes.
The tropical Bolgoda Lake is one of the largest lagoonal estuaries in Sri Lanka. Organic constituents in this lake were investigated using 28 surface sediments, three cores from the lake, and four ...short cores from mangrove mud. Elemental and molecular compositions of sediments and living organic matter (OM) were determined using CNS elemental analysis and gas chromatography–mass spectrometry, respectively. Chronology of events was determined using accelerated mass spectrometry (AMS) 14C data for bulk OMs, woods and mollusk shells. The history of Bolgoda Lake can be divided into two major chrono-stratigraphic divisions, namely a lower sedimentary succession (from ca. 7.0calkyB.P. to 2.5calkyB.P.) and an upper sedimentary succession (from ca. 2.5calkyB.P. to the Recent), according to the sapropelic depositional system. Concentrations of the mangrove biomarker taraxone increased significantly at ca. 7.0calkyB.P. The lower part of the sediment sequence had moderate productivity, and was mainly deposited under marine-terrestrial influence in oxygen-poor/anoxic conditions during mid-Holocene sea-level highstands. A drastic increase in total organic carbon (TOC) content, reaching 29%, was found in one of the Bolgoda cores. This increase occurred because of sea-level regression at about 2.5calkyB.P. This change was probably caused by development of a beach rock/sandbar, and the estuary system changed to a semi-closed lake due to the sea-level regression. As a result, aquatic vascular plants predominate in this depositional system. After ca. 2.5calkyB.P., TOC content decreased slightly, but relatively high TOC contents were maintained in the muddy sediments. In moderately-sized and shallow (1–2m) tropical estuaries/lagoons such as Bolgoda Lake, drastic changes in TOC contents may be the most sensitive indicator of sea-level variations. Increase in higher plant OM with higher n-C29/n-Call and n-C37/n-Call alkane ratios also suggest a climatic transition from wetter to somewhat drier after the middle Holocene. Accumulations of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in the modern sediments record anthropogenic activity after European settlement in the 15th century.
•Bolgoda sediments contain vascular plants and sapropels deposited at low rates.•Organic carbon contents increased dramatically at ca. 2.5calkyB.P.•This change was due to sea-level regression.•Reworked OMs and aquatic plants increased after ca. 2.5calkyB.P.•PAH contents rise from anthropogenic activity after European settlement in the 15th C.
IODP Expedition 357 used two seabed drills to core 17 shallow holes at 9 sites across Atlantis Massif ocean core complex (Mid-Atlantic Ridge 30°N). The goals of this expedition were to investigate ...serpentinization processes and microbial activity in the shallow subsurface of highly altered ultramafic and mafic sequences that have been uplifted to the seafloor along a major detachment fault zone. More than 57 m of core were recovered, with borehole penetration ranging from 1.3 to 16.4 meters below seafloor, and core recovery as high as 75% of total penetration in one borehole. The cores show highly heterogeneous rock types and alteration associated with changes in bulk rock chemistry that reflect multiple phases of magmatism, fluid-rock interaction and mass transfer within the detachment fault zone. Recovered ultramafic rocks are dominated by pervasively serpentinized harzburgite with intervals of serpentinized dunite and minor pyroxenite veins; gabbroic rocks occur as melt impregnations and veins. Dolerite intrusions and basaltic rocks represent the latest magmatic activity. The proportion of mafic rocks is volumetrically less than the amount of mafic rocks recovered previously by drilling the central dome of Atlantis Massif at IODP Site U1309. This suggests a different mode of melt accumulation in the mantle peridotites at the ridge-transform intersection and/or a tectonic transposition of rock types within a complex detachment fault zone. The cores revealed a high degree of serpentinization and metasomatic alteration dominated by talc-amphibole-chlorite overprinting. Metasomatism is most prevalent at contacts between ultramafic and mafic domains (gabbroic and/or doleritic intrusions) and points to channeled fluid flow and silica mobility during exhumation along the detachment fault. The presence of the mafic lenses within the serpentinites and their alteration to mechanically weak talc, serpentine and chlorite may also be critical in the development of the detachment fault zone and may aid in continued unroofing of the upper mantle peridotite/gabbro sequences.
New technologies were also developed for the seabed drills to enable biogeochemical and microbiological characterization of the environment. An in situ sensor package and water sampling system recorded real-time variations in dissolved methane, oxygen, pH, oxidation reduction potential (Eh), and temperature and during drilling and sampled bottom water after drilling. Systematic excursions in these parameters together with elevated hydrogen and methane concentrations in post-drilling fluids provide evidence for active serpentinization at all sites. In addition, chemical tracers were delivered into the drilling fluids for contamination testing, and a borehole plug system was successfully deployed at some sites for future fluid sampling. A major achievement of IODP Expedition 357 was to obtain microbiological samples along a west–east profile, which will provide a better understanding of how microbial communities evolve as ultramafic and mafic rocks are altered and emplaced on the seafloor. Strict sampling handling protocols allowed for very low limits of microbial cell detection, and our results show that the Atlantis Massif subsurface contains a relatively low density of microbial life.
•Seabed rock drills and real-time fluid monitoring for first time in ocean drilling•First time recovery of continuous sequences along oceanic detachment fault zone•Highly heterogeneous rock type and alteration in shallow detachment fault zone•High methane and hydrogen concentrations in Atlantis Massif shallow basement•Oceanic serpentinites potentially provide important niches for microbial life
The world of plastic waste: A review Nayanathara Thathsarani Pilapitiya, P.G.C.; Ratnayake, Amila Sandaruwan
Cleaner Materials,
March 2024, 2024-03-00, 2024-03-01, Letnik:
11
Journal Article
Recenzirano
Odprti dostop
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•We systematically reviewed up-to-date information on plastics and plastic waste.•It covers applications, benefits, production, consumption, and classifications of plastics.•We also ...discuss the major issues of plastic waste on the environment and human health.•This article includes process-oriented practices in plastic and plastic waste management.•It also covers legal frameworks and policies for sustainable environmental management.
People discover various materials from time to time that break the boundaries of traditional materials. Plastic is a revolutionized material, and is referred to as “a material with 1,000 uses”. This review summarized up-to-date research on plastic and its waste pollution. Plastic has a domain throughout human life with its versatile properties such as lightweight, high durability, flexibility, and low production cost. This article describes the applications, benefits, production, consumption, and classifications of plastics. Plastic commercialization began with the Second World War and grew all over the world within less than a century. The global annual production of plastic is more than 359 million tons. Despite all the benefits, plastics cause severe environmental and public health issues. Accordingly, this study addresses the major issues of plastic waste on the environment and human health. Plastics can degrade into micro to nano sizes, and those fine particles are more spreadable in air, water, and soil. Therefore, both terrestrial and aquatic animals go through various negative impacts such as ingestion, entangling, ulcers, low reproduction, and oxidative stress. Microplastics also degrade human health due to cardiovascular diseases, chronic kidney disease, birth defects, cancer, etc. The closing contains the developed end-of-life options (e.g., recycling and reprocessing, incineration with energy recovery, modification reuse, value addition, and landfilling) of biodegradable and non-biodegradable plastic wastes. Several international, regional/national level legislations and policies/concepts (e.g., plastic trade, 3R policy, and circular economy) are available to manage plastic and plastic waste generation. Plastic waste management is also discussed offering practical insights and real-world scenarios. Solutions and challenges in effective plastic waste management guide to create a more sustainable and environmentally responsible approach. Finally, this review article highlights the importance of judicious decisions and the involvement of all stakeholders to overcome the plastic waste crisis.
Global phosphorus scarcity will result in significant consequences for future food security with the depletion of current phosphate reserves. Therefore, exploration of new phosphorus sources is ...essential to address future phosphorus scarcity. The current study investigated the geochemical potential of lake sediment around the Eppawala Phosphate Deposit (EPD) in Sri Lanka to be used as a low-grade phosphorus source for agricultural purposes. Jaya-Ganga is a man-made water canal that drains through the EPD feeding three lakes, namely, upstream Ihalahalmilla Lake and Koon Lake, and downstream Kiralogama Lake with respect to the EPD. Three cores (cores A, B, and C) were collected from the above three lakes and major oxides and minerals distributions along the cores were analyzed. Notable high enrichment of phosphorus pentoxide (P2O5) content and high P2O5 solubility values were measured in the top 60 cm sediment layer in Core B and throughout the Core C compared to the Core A. This high enrichment of P2O5 content in the same sediment columns were confirmed by the comparison with the Upper Continental Crust (UCC) values and literature survey. According to the X-ray Diffraction (XRD) results, phosphate minerals, such as fluorapatite, crandallite, and millisite were abundantly found in the same sediment columns. Therefore, these phosphate minerals can be considered as pathfinding minerals for soluble phosphates in sediment cores. Thus, sediment with high P2O5 content and high solubility in downstream Kiralogama Lake showed the potential for application of these sediments as a direct phosphate source in agricultural purposes. Furthermore, the current study has introduced a new area of interest, i.e., soil and sediments around major phosphate deposits, for the exploration of new phosphate sources to meet future phosphorus demand.
•Core sediment in the study area is geochemically analyzed to prospect low-grade phosphate sources.•High enrichment of phosphorus pentoxide content and high solubility were determined in downstream Kiralogama lake.•Fluorapatite, crandallite, and millisite were abundantly found in downstream Kiralogama lake.•These minerals can be identified as pathfinding minerals for soluble phosphates in lake sediments.•Downstream lake sediment could be a reasonable substitute for low-grade phosphates.
Emerging clean energy transition technologies have expanded the range of nickel (Ni) applications, making it a critical metal in the metal industry. With the increasing demand, high-grade deposits ...are incapable of fulfilling continuous supply, and therefore, Ni recovery from low-grade deposits such as serpentine soils has gained wide attention. In this context, phytomining has been identified as a viable approach for Ni mining from low-grade serpentinite deposits due to the abundance of Ni hyperaccumulators. Ginigalpelessa serpentinite deposit in Sri Lanka has been recognized as a potential area for Ni phytomining as the soil contains a high concentration of Ni. The present study aimed to determine the Ni and other valuable metal distribution within the deposit and assess the Ni hyperaccumulation potential of native species for phytomining. Therefore, soil, rock, and plant samples from 31 sampling locations were analyzed using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The total Ni concentration in serpentine soil varied from 4005 to 17,352 mg/kg, where the bioavailable fraction was 1–4%. Among the six plant species considered in hyperaccumulation analysis,
Apluda mutica
(
A. mutica
) accumulated 2802 ± 1182 mg/kg of Ni in its shoot biomass, exceeding the hyperaccumulator threshold limits (1000 mg/kg). The bioconcentration factor (BCF) of Ni and Co for all the selected species was > 1, showing the highest value in
A. mutica
species (8.26). The translocation ability of Ni in
A. mutica
(3.06) also indicates the potential of Ni phytomining using the plant species. The findings of this study should be further developed to prospect the phytomining potential in the Ginigalpelessa serpentinite deposit.
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.
Background
Ilmenite and rutile are naturally occurring titanium-bearing heavy minerals. Sri Lanka consists of ilmenite and rutile in placer deposits mainly along the northeast coast. The commercial ...value of rutile is higher than ilmenite. Therefore, the current study focuses to upgrade Sri Lankan ilmenite ores using commercially available activated carbon as a reducing agent. Ilmenite fraction was initially separated from raw beach sand using an industrial-scale magnetic separator (Wet high-intensity magnetic separator: sixteen pole model). The mixtures of ilmenite and activated carbon (4 to 1 ratio by weight) were milled using a planetary ball mill for one to four hours at one-hour intervals.
Results
The milled samples were subsequently heated for two hours continuously at temperatures of 800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C, respectively. Initial and annealed samples were analysed using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and X-ray fluorescence (XRF) analyses. XRD pattern of the initial sample was characterized by less percentage of rutile (TiO
2
) peaks and low crystallinity. However, the number of rutile peaks and crystallinity were increased with respective milling hours and annealed temperature. Besides, XRD analysis indicates a higher number of sharp and intense rutile and elemental iron peaks in the samples annealed above 1000 °C. FTIR analysis of raw ilmenite indicates mainly stretching vibrations of Fe–O. However, vibrational spectral bands around 700 cm
−1
in samples annealed above 1000 °C are assigned to Ti–O–Ti stretching vibrations. High TiO
2
and TiO
2
+ Fe
2
O
3
(total) wt. (%) can also be observed in samples annealed above 1000 °C.
Conclusions
The optimum conditions for carbothermic reduction were obtained at 4 h of ball milling of ilmenite with activated carbon and continuously annealing at 1000 °C for 2 h. Carbothermic reduction is applicable to upgrade Sri Lankan ilmenite ores, and thus this method adds value to heavy mineral resources in Sri Lanka.
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