Çevre Bilimleri

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16S rDNA analysis of microbial communities in a highly polluted region of the Marmara Sea
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2007., 2007.) Türker, Gökhan.; İnce, Bahar Kasapgil.
The Marmara Sea is a small (size 70 x 250 km) intercontinental basin connecting Black Sea and Mediterranean Sea. The population of Marmara region reaches to 25 million and therefore there is large number of domestic and industrial wastewater discharges to the Marmara Sea from different points. Also large quantities of Central Asian oil and gas are transported to the west through the Marmara Sea. Combining effect of pollution sources create a chronic pollution at the Marmara Sea and formed several anoxic sediments in highly polluted sites. One of the areas is Küçükçekmece region. The region is populated by both residential and industrial sites and takes domestic and industrial effluent of more than 3 million people. Industrial sites mainly composed of metal industry, textile and leather industry, medicine industry, paper industry, chemical industry, rubber and plastic industry. Also in 1999 due to tanker accident at Küçükçekmece beach, the region was polluted with more than 3000 tones of petroleum. Sediment is a carbon and nutrient pool for aquatic environments. The presence of hydrocarbon compounds creates a suitable environment for the growth of anaerobic bacteria. Anaerobic biodegradation processes are slower than aerobic biodegradation. However, anaerobic processes can be a significant factor in removal of organic contaminants owing to the abundance of anaerobic electron acceptors relative to dissolved xygen; therefore promising a stable and long term removal of contaminants. It has been estimated that less than 1% of the total microbial population in the land environment and even less in the marine environment have been successfully isolated in pure culture. Marmara Sea has great importance not only because of geological position but also its composition of microbial life which still remains in darkness. The microbial diversity in this unique ecosystem has not been studied using culture-independent molecular techniques yet. Microbial community analyses together with chemical analyses of the sediments will undoubtly form a base to develop bioremediation strategies to overcome chronic pollution at the Küçükçekmece coast. Main aim of this study is to find a suitable microbial community in anoxic sediments taken from Marmara Sea for a bioremediation strategy depending on anaerobic biodegradation. The microbial diversity and community structure were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rDNA Clone Library method. The results were evaluated with sediment quality parameters along the sampling point. Established results will be used with other information from the literature to analyze the suitability of any of the community in the anoxic sediments from the Küçükçekmeçe coast for bioremediation purposes. Suitable communities will be marked and used as a cornerstone for a bioremediation strategy based on anaerobic biodegradation. DGGE results indicate presence of 34 different bands for bacterial community and 15 different bands for archaeal community with each band representing a different organism. Clone library results are parallel to results of DGGE. In bacterial clone library there are 23 different clones and 26 different clones for September 05 and December 06 respectively. In archaeal 16S rDNA clone library, 19 different clones and 20 different clones were found in September 05 and December 06 respectively. The result of sequencing of bacterial dominant clones indicate presence of Trichococcus pasteurii, Clostridium glycolicum in September 05 and Elbe River snow isolate Iso26, Xanthomonas sp. CC-FH5, and Gallicola barnesae in December 06. Archaeal dominant clones are Methanoplanus petrolearius, Methanoplanus limicola, Methanogenium organophilum in September 05 and Methanogenium frigidum and Methanosaeta sp. in December 06. Results of clone library generation show that syntrophic relations are running in both times. In September 05, fermentation and hydrogenotrophic methanogenesis dominated pathway. In December 06, anaerobic respiration and fermentation coupled with acetoclastic and hydrogenotrophic methanogenesis dominated the pathway.
16S rDNA analysis of microbial communities in anoxic marine sediments of the Marmara Sea
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2007., 2007.) Sezgin, Aslı.; İnce, Bahar Kasapgil.
The sediments of the Marmara Sea are of importance since they are believed to have been a rather sensitive recorder of climatic, biological and chemical changes and water-mass movements in the region. In this study, overall microbial community of coastal sediments from the Marmara Sea was characterized by cloning and sequencing of 16S rRNA genes. Denaturing Gradient Gel Electrophoresis was used to investigate the seasonal distribution of the microbial communities in coastal sediments from Tuzla and Moda. The sequencing of clone libraries revealed a higher microbial diversity in anoxic sediment samples of Tuzla than that of derived from Moda. and served to understand the potential dominant metabolic processes prevailing under anoxic conditions. Methylotrophic methanogenesis and denitrification were found as the potential dominant metabolic processes in Tuzla sediments, whereas hydrogenotrophic methanogenesis and fermentation appeared to be the potential dominant metabolic processes in Moda sediments. DGGE data revealed a more significant seasonal change in microbial community structure of Tuzla sediments.|Keywords: Marmara Sea, Anoxic Marine Sediments, 16S rDNA, Microbial Diversity, Clone Library
A dynamic simulation approach to soil salinity and sodicity in Konya plain of Turkey
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2021., 2021.) Tunca, Mehmet Can.; Saysel, Ali Kerem.
Soil salinity and sodicity are twin problems potentially affecting soil fertility, farmers’ livelihoods and food security. Management and control of these problems, particularly on irrigated farmlands require knowledge and expertise crafted through appropriate models and experiments. The accumulation of salts on the soil profiles may occur through natural processes as well as by human actions, that are mostly related to poor agricultural and irrigation practices. Accumulation of salt in soil water impedes crop evapotranspiration, sodicity threatens the soil structure and degrades its hydraulic qualities. These problems are more pervasive in arid and semi-arid regions. Therefore, irrigation and agricultural practices are crucial in controlling these problems to avoid their undesired consequences. In this research, a dynamic simulation model is built to represent salinization and sodification in soil layers so as to test the long-term impact of alternative irrigation practices with respect to water quality, quantity and schedule, on soil fertility and farm yields. The model is developed based on the system dynamics methodology. Model parameter values are selected as representative of the field conditions of Konya Plain in Turkey, which is a semi-arid region partially experiencing soil salinization problems. This study is completed as a part of the TÜBİTAK-funded research project entitled, “Soil Salinity and Sodicity Management by Sustainable Irrigation Practices in Konya Plain”. Based on the scenario analyses performed in the research, irrigation water quality, irrigation method as well as crop rotations found to be important factors on soil salinization and sodification process in soil.
A life cycle perspective for hydrometallurgical and biohydrometallurgical metal recovery from weee
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Karal, Engin.; Copty, Nadim.
Rare earth elements (REEs) are being employed in an increasing number of critical or widely popular consumer/ industrial products leading to increase in their demand particularly in the last few decades. Since almost all of REEs are produced in China, the European Commission and US energy department have identified REEs as critical elements and have directed special efforts to obtain sustainable resources of REE. End of life consumer electrical products contain significant amounts of metals and plastics. Thus the aim of this study is focused on recycling metals from waste electric and electronic equipment (WEEE). WEEE contains high amounts of base metals, precious metals and REEs. The concentration of metals in waste streams is higher than that of natural ores. Current recycling methods consume high amounts of energy and chemicals. Economically feasible industrial facilities (waste incineration) perform poorly for environment. In this study life cycle assessment (LCA) of two metal recovery systems were examined: biohydrometallurgical recovery of copper and hydrometallurgical recovery of neodymium from WEEE. Biohydrometallurgical methods are identified as environmentally friendly and low cost operation methods. An ex-ante scaled-up life cycle assessment (LCA) model was created for copper metal recovery. Results show that recovering only copper metal from WEEE is neither economically feasible nor environmentally friendly. The feasibility and environmental performance of neodymium metal recycling experiment model was investigated with a LCA scenario of neodymium iron boron magnet production model. It was found that neodymium metal recycling economically and environmentally performed better than virgin magnet production.
A numerical model for the Marmara sea
(Thesis (M.S.)- Bogazici University. Institute of Environmental Sciences, 1987., 1987.) Albek, Erdem Ahmet.; İnel, Yüksel.
In this study, a numerical model has been developed to predict currents and water levels prevailing in the Marmara Sea. The model is a depth averaged two-layer transient model to adequately simulate stratified flow conditions in the sea. The nonlinear partial differential equations of the model have been solved by using an explicit finite difference scheme and employing a local integral method to reduce truncation and round-off errors and to improve accuracy. Special emphasis has been laid on the prediction of currents and water levels under strong winds.
A QSAR study on the mutagenic activity of azo dyes and aromatic amine derivatives
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Küçükali, Müge.; Saçan, Melek Türker.
In the present study, the mutagenic activity of diverse structure of azo dyes and aromatic amine derivatives on TA98 Salmonella typhimurium bacterial strain with S9 activation was used to generate a quantitative structure – activity relationship (QSAR) model. The descriptors required for the model development were obtained by SPARTAN (v.10), DRAGON (v.7.0) software packages. The selection of descriptors was carried out by the tools implemented in QSARINS (v.2.2.3) software. Many division trials were performed on the dataset as training and test sets which comprise the 80% and 20% of the whole set, respectively. 6 descriptors (CIC2, Chi_D/Dt, L/Bw, TDB09p, Mor28s and piPC08) constitute the final model. The applicability domain (AD) of the generated QSAR model was defined by both the ranges of response and descriptors. The predictive ability of the final model was tested using an external dataset consisting of currently used 33 anionic water soluble textile dyes (eight anthraquinone and 25 azo dyes) with no experimental mutagenicity data. The proposed QSAR model had 70% structural coverage for the external set chemicals. The mutagenic activities of 22 current textile dyes belonging anthraquinone and azo dyes fell within the applicability domain of the proposed QSAR model which means that they were well predicted by the model. The order of 6 anthraquinone dyes which are mainly used for cotton, fiber dyeing and leather shading with the most mutagenic activity is: Acid Blue 62>Acid Blue 40>Acid Blue 45>Acid Blue 80>Acid Blue 230>Acid Blue 344. The least mutagenic azo dye is Direct Orange 34 which is mainly used for cotton, silk, wool and their blended fabric dyeing and printing, also can be used for leather and paper shading.
A social-ecological systems analysis of water supply governance on Samothraki, Greece
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2021., 2021.) Beaucamp, Anna.; Saysel, Ali Kerem.
The island of Samothraki in the North Aegean Sea features astonishing water resources of pris tine quality and high quantity. Contrary to what the condition of the water resources would suggest, the residents of Samothraki suffer from water shortages and incidents of contamination, as well as unsteady water provision to economic activities. Meanwhile, the natural water resource system starts showing signs of degradation. The situation is associated with inappropriate municipal water man agement within the frame of a collective action problem. The local municipality’s inability to provide sufficient network coverage and quality control is facing resource-intense and hard-to-control surface water abstractions by individuals for agricultural purposes. Without a coherent understanding of the structures, dynamics and interdependencies underlying management decisions, the situation is likely to continue and cause social conflict as well as ecological harm . Through the application of the Social-Ecological Systems Framework (McGinnis and Ostrom 2014), I first map out a wide range of variables connected to water management and analyse them according to their their relevance and interdependence. The results show that water mismanagement on the island is a much more complex issue than suggested until now, with strong symbiotic links between current informal and official, collective, individual and municipal institutions. I thus argue that the water supply on Samothraki is best understood as a complex social-ecological system. In a second step I draw on insights from adaptive and decentralized governance approaches to eval uate the potentials of sustainable resource management inherent in current practices on Samothraki. I find that informal networks currently contribute most to the social-ecological system’s sustainability and resilience, and embody the incubators of new approaches of sustainable governance.
A study of shipping industry and assessment of environmental impacts in Turkey
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 1998., 1998.) Tuzcu, M. Fikret.; Kocasoy, Günay.
In recent years, the importance of the environmental concerns at shipping and the related standards/safety measures have become subject to clear understanding and acceptance of each country at international platforms. The aim of this study was to evaluatelinvestigate the reflections of the international standardization developments at Turkey and the ways for reaching the very strict and internationally requested standards at her shipping industry at once. For this purpose; general evaluation of the prospective Turkish Shipping Industry, its development during the recent years, its current performance in the terms of conforming with the international standards and ways for reaching these standards with a better conformance have been investigated. The necessary steps that Turkey should immediately take during this period have been evaluated by specifically studying the problems of the Turkish Ports that can be defined as evident indicators of the economic power of a country. The results were expressed by analyzing the economic, commercial and technological means of overcoming the sub standardization at Turkish ShippingIPorts. Moreover, 'Pipe-Line' alternative has been suggested instead of 'Straits' alternative with social cost/benefit analysis of marine pollution and other environmental effects that have been studied by evaluating the effects of tanker accidents on environment and human nature.
Absorbance spectroscopy based evaluation of humic acid under non-oxidative and oxidative conditions
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2011., 2011.) Paçal, Müge.; Bekbölet, Miray.
The aim of this study was to examine the mathematical relationships between humic acid concentration and UV-vis spectroscopic parameters under oxidative and non-oxidative conditions. Humic acid concentration was represented by dissolved organic carbon contents (DOC). UV-vis spectroscopic parameters were presented by absorbance measurements at wavelength λ = 436 nm as Color436, λ= 365 nm as UV365, λ=280 nm as UV280, and λ= 254 nm as UV254. Humic acids were selected as representing terrestrial humic acids (FHA, AHA and RHA) and aquatic humic acid (NHA). As a lot of different humic molecules in very diverse physical associations are mixed together in natural environments, it is difficult to determine their exact concentrations (units of ppm, mg L-1 or mol L-1) and allocate them to a certain class of organic molecules. Since direct determination of humic acid concentraton is not possible to the unspecified chemical structure,various methods have been developed to express the humic acid contents of the aqueous humic solutions. Due to the fact that humic acid does not have a well identified structure, the researchers applied some methods to represent the humic acid concentration as a function of DOC concentration and/or UV-vis parameters (UV254, UV280, UV365 and Color436).This study includes evaluation of the experimental work performed on the UV-vis parameters in relation to the humic acid “prepared” concentration and DOC contents. The mathematical relationships between i. DOC concentration and HA “prepared” concentration, ii. DOC concentration and UV-vis parameters (UV254, UV280, UV365 and Color436) and iii. HA “prepared” concentration and UV-vis parameters (UV254, UV280, UV365 and Color436) were investigated for NHA, FHA, AHA and RHA under the non-oxidative conditions. DOC concentrations, corresponding to HA concentration (NHA, FHA, AHA, and RHA), were correlated with UV-vis parameters (UV254, UV280, UV365 and Color436) under the non-treatment condition and HA concentrations (NHA, FHA, AHA, and RHA) were correlated with UV-vis parameters (UV254, UV280, UV365 and Color436) with high regression coefficient under the non-treatment condition. Furthermore, the overall humic acids (NHA, FHA, AHA, and RHA) and also DOC concentrations of the overall humic acids were correlated with UV-vis parameters. The same steps were done under the oxidative treatment conditions where photocatalytic treatment was applied. In general, photocatalytic oxidation can be considered as an example of innovative technologies collectively known as ‘‘Advanced Oxidation Processes’’ that rely on the generation of very reactive oxygen radicals. Those reactive species are subsequently used to degrade non selectively organic compounds. The known concentrations of NHA and AHA was treated by photocatalytic treatment. The removal of DOC concentration of NHA and AHA were determined by using TOC analyzer and the removal of UV-vis parameter (UV254, UV280, UV365 and Color436) was determined by using UV-vis spectrophotometer after the photocatalytic treatment.The mathematical relationships between DOC concentration of NHA and AHA, and UV-vis parameters (UV254, UV280, UV365 and Color436) were investigated after the photocatalytic treatment. DOC concentrations of NHA (in the presence of 0.25 mg mL-1 TiO2) and AHA (in the presence of 0.10, 0.25 and 1.00 mg mL-1 TiO2) were correlated with UV-vis parameters under the treatment condition (the photocatalytic treatment). Some researchers represented the removal of HA as a function of UV-vis parameter under the photocatalytic treatment. Moreover, DOC ‘DOCcalc’ was calculated as a function of UV254, UV280, UV365 and Color436 parameter of the removed HA concentration, by using the non-treatment Equations of NHA and AHA. The mathematical relationship between DOCobs and DOCcalc was evaluated..
Activated carbon production from pretreated and fermented agricultural residues
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2016., 2016.) Yıldırım, Hacer.; Cılız, Nilgün.
All forms of lignocellulosic biomass consist of three major chemical components: cellulose, hemicellulose and lignin. The remaining lignin from bioethanol production can be utilized as a feedstock for green chemicals. The purpose of this study was to produce activated carbon from pretreated and fermented agricultural residues and to investigate the influence of different process conditions such as feedstock type, impregnation ratio, and carbonization temperature on the pore structure of the products. This is the first study that investigated the production of activated carbon as a high value-added product from lignin-rich residues generated from bioethanol processes. The first step in the experimental path of the study was the recovery of lignin-rich biomass samples. Four samples were prepared from ethanol production wastes; the first one was from the pretreatment of corn stover, the second one was from pretreatment of wheat straw, the third one was from fermentation of corn stover, and the fourth one was from fermentation of wheat straw. The second step was the chemical characterization of feedstocks. In the third step, feedstocks were impregnated with 30%, 40% and 50% (w/w) H3PO4 and then carbonized with a rate of 20ºC/min to carbonization temperatures of 400ºC, 500ºC, 600ºC and 700ºC. The N2 adsorption/desorption capacities of products were compared according to their specific surface area and pore volume by applying the Brunauer-Emmett-Teller (BET) equation. The results demonstrated that the best way to produce activated carbon from lignin-rich residue was using pretreated wheat-based lignin, which was impregnated with 40% H3PO4 concentration and carbonized at 700ºC. In addition, both pretreated corn and fermented wheat-based products, which were impregnated with 50% H3PO4 and carbonized at 500ºC, had quite well developed specific surface area. Interestingly, mesoporous structures dominate in H3PO4-impregnated lignocellulosic material-based activated carbon. Therefore, these carbons are ideal for the adsorption of large molecules and decolorization.
Aerobic biodegradation of dominant micropollutants in the Ergene river by river microcosms and pure cultures of bacteria
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Karakaya, Emre.; Tezel, Ulaş.
The Ergene River is the most polluted surface water in Turkey. A great number of micropollutants, which have potential toxic and endocrine-disruptive effects and play a role in antibiotic resistance, are identified in the Ergene River. Once discharged into the environment, micropollutants are exposed to various natural attenuation processes such as dilution, sorption onto solids and sediments, photolysis, hydrolysis, and biodegradation. However, biodegradation is considered the most important process for the removal of most micropollutants. In this study, aerobic biodegradation of forty-three micropollutants belonging to different chemical groups such as industrial chemicals i.e. plasticizers, UV blockers, surfactants etc., antibiotics, pesticides and personal care products i.e. fragrances, pharmaceuticals etc. were investigated in river water samples taken in August 2017, November 2017, February 2018, and May 2018. Analysis of the micropollutants was performed using ultra-high-performance liquid chromatography and tandem mass spectrometry (UHPLC-MSn). At the end of the study, most compounds such as acetaminophen, celestolide, piperonyl butoxide, oxybenzone, and 3-chloraniline were degraded via river microcosms at different rates whereas diuron, N-Ethyl-p-toluenesulfonamide, benzo[a]pyrene, benzanthrone, terbutryn, prochloraz, and omethoate were not removed in any samples. Aerobic biodegradability of hexa(methoxymethyl)melamine, the most abundant target micropollutant in the river was also investigated using different bacterial strains previously isolated at BIOMIG Lab. A strain named Pseudomonas sp. BIOMIG1 transformed almost all hexa(methoxymethyl)melamine into melamine in 45 days. With this study, aerobic biodegradability of various micropollutants in the Ergene River and the biotransformation of hexa(methoxymethyl)melamine have been first revealed.
Agricultural decision-making in Turkey from climate change perspective :|a new road map for the period of 2021-2050
(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2020., 2020.) An, Nazan.; Yenigün, Orhan.; Kurnaz, M. Levent.
The expectation that it can affect basic life resources and particularly food security on a global, regional, and local scale with its impact on the ecosystem has made climate change one of the most urgent issues on the global agenda. Extreme weather events due to climate change may degrade food quality, affect access to food and raise food prices, markedly affecting agricultural productivity. Many countries have already been faced the global impacts of climate change, therefore studies on the effects that may occur on ecosystems are of great importance. As one of the regions that may be most affected by climate change, the Mediterranean Basin is at risk in terms of agricultural production due to temperature increases and precipitation regime changes, and what’s more the increase in the frequency and severity of extreme weather events due to climate change. As a country located in the Mediterranean Basin, Turkey may also suffer from climate change. This situation poses a risk in terms of crop production value and export income, particularly for products with high commercial value grown in Turkey. Therefore, the study has focused two crops of the country i.e., hazelnut and grape with the high commercial value. In the first stage, the climate data for different phenological periods and different variables for each crop was obtained from the regional climate model, RegCM4.4 with the MPI-ESM-MR global climate model under the RCP8.5 pessimistic scenario for the baseline of 1991-2012 and the future period of 2021-2050. In the second stage, the change in hazelnut yield was analyzed by statistical approach, panel data method, and the change in grape yield was analyzed using the crop growth simulation model, STICS. At the last stage, how the climate conditions of hazelnut (88 locations) and grapes (96 locations) will change in the future has been examined by using membership function. However, considering the crop production values of these two crops and export revenue contribution to the national economy, the possibility of new locations where these crops may grow in the future has been analyzed in 923 locations throughout Turkey. Accordingly, at this stage of the thesis, climate suitability index was calculated for hazelnut and grape, and climatic suitability conditions were determined according to 5 classification ranges. In brief, it has been observed that climate change may have a negative impact on both hazelnut and grape yields in the future and it is predicted that there may be significant reductions in climatic suitability conditions in the locations where these two crops grow.
An assessment of soil erosion using rusle model :|a case study from the Marmara region
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Ezer, Alkor.; Güven, Başak.; Kurnaz, M. Levent.
Soil is a vital resource for life. Soil erosion is one of the most serious natural problem caused by degrading land, agricultural and other human induced activities. The aim of this study is to predict the soil loss in the Marmara Region as a result of climate change. To achieve this, the Revised Universal Soil Loss Equation (RUSLE) is used and soil loss maps of the region are produced by the the help of remote sensing and geographic information systems techniques. While soil loss maps are produced between the years 1989 and 2017, future projections of soil erosion are also investigated for the period between years 2020 and 2049. For climate projections two scenarios of the Regional Climate Model are used: RCP 4.5 and RCP 8.5. The results showed that, when compared to the historical data, soil erosion risk in the future will increase in the Marmara Region. The soil loss results for the time interval 2020-2049 of the scenario RCP 8.5 is 61% higher than the results of the scenario RCP 4.5. Also, the results based on the historical data of the Regional Climate Model showed that the soil loss ranged from 0 to 24.298 Mg. ha-1. year-1 during the time interval 1989 -2017 in the Marmara Region, and the average soil loss is estimated as 12.2 Mg. ha-1. year-1.
An fmri based method for characterizing superficial layer contamination in fnirs signals
(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2014., 2014.) Erdoğan, Sinem Burcu.; Akın, Ata.
Functional near infrared spectroscopy (fNIRS) is a method for monitoring cerebral hemodynamics with a wide range of clinical applications. fNIRS signals are contaminated with systemic physiological interferences from both the brain and superficial tissues, resulting in a poor estimation of the task related neuronal activation. In this study, we introduce an extended superficial signal regression (ESSR) method for cancelling physiology-based systemic interference in fNIRS signals. We apply and validate our method on the optically weighted BOLD signals, which are obtained by projecting the fMRI image onto optical measurement space by use of the optical forward problem. The performance of ESSR method in removing physiological artifacts is compared to i) a global signal regression (GSR) method and ii) a superficial signal regression (SSR) method. The retrieved signals from each method are compared with the neural signals that represent the "ground truth" brain activation cleaned from cerebral systemic fluctuations. We report significant improvements in the recovery of task induced neural activation with the ESSR method when compared to the other two methods with higher spatial localization, lower inter-trial variability, and higher contrast-to-noise (CNR) improvement. Our findings suggest that, during a cognitive task i) superficial scalp contribution to fNIRS signals varies significantly among different regions on the forehead and ii) using an average scalp measurement together with a local measure of superficial hemodynamics better accounts for the total systemic interference. We conclude that maximizing the overlap between the optical pathlength of superficial and deeper penetration measurements is of crucial importance for accurate recovery of the evoked hemodynamic response in fNIRS recordings.|Keywords : Hemodynamic response, systemic interference, functional near infrared spectroscopy, magnetic resonance imaging, physiological artifact removal.
An in silico approach for estimating the activity of vector control chemicals targeting Aedes aegypti and their aquatic toxicity
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Yılmaz, Zeynep.; Türker, Melek.
The mosquito Aedes aegypti is known as the main vector that transmits the viruses cause dengue, yellow fever, chikungunya epidemic arthritis, and Zika. Control of the vector is an important strategy to avoid disease propagation. However, vector control is threatened by the increasing resistance of mosquitoes to insecticides. On the other hand, environmental impacts of the intense use of these insecticides is of great concern. In the present study, the larvicidal activity of plant-derived compounds was subjected to a quantitative structure-activity relationship (QSAR) analysis. A valid QSAR model which fulfill the criteria set by the Organization for Economic Co-operation and Development (OECD) was generated using QSARINS 2.2.2 software. The generated QSAR model was validated both internally and externally. The external predictivity of model was tested with chemicals with no experimental larvicidal data and it has 95.3% structural coverage. The most toxic and the least toxic plant-based larvicides were determined. Piperidine derivatives were found highly effective on Aedes aegypti larvae. Also, the fruit Piper nigrum was highlighted as a plant-based larvicide source. Additionally, in order to propose a safe larvicide the toxicity of larvicides to nontarget organism living in aquatic systems was evaluated by using previously generated acute toxicity and cytotoxicity models towards three representative aquatic species (algae, fish, and planarian) by Institute of Environmental Sciences, Ecotoxicology and Chemometrics Lab group and the most toxic larvicides are detected for these aquatic species.
An integrated land use-hydrological model for the Bartın spring watershed
(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2009., 2009.) Öztürk, Melih.; Copty, Nadim.; Saysel, Ali Kerem.
The Bartın spring watershed located in northwestern Turkey supplies the water needs of the Bartın, Amasra and nkumu city centers. Although the water is presently adequate for the spring, autumn and winter seasons, the city centers suffer water scarcity in summer seasons. It is widely recognized that land use changes have a significant impact on the water budget of a watershed. The purpose of this study is to model the land use and hydrological processes within the Bartın spring watershed and simulate the water yield under different future land use scenarios. For this purpose, a coupled land use-hydrodynamics model was developed. The land use dynamic simulation model was built using STELLA dynamic simulation platform while the MIKE SHE computer program was used to simulate the hydrodynamics of the watershed. The link between the two models is through the Leaf Area Index (LAI) and Root Depth (RD) parameters which are generated in the land use model and supplied to the hydrodynamics model. The dynamic land use model represents several forest stand groups and land use categories with their respective acreages and their conversions. The model was structurally validated and analyzed through a series of sensitivity tests. It was calibrated with respect to the historical geographical data and the calibration results are quite satisfactory. The calibration target for the hydrodynamics model was the river discharge at the downstream end of the watershed, while the calibration parameters were the saturated hydraulic conductivity of the deeper soil, the threshold melting temperature values and the RD value. The optimal simulation produced correlation coefficients, R=0.72 and R2=0.52 with a mean error of 0.01 m3/s. Sensitivity analyses of the hydrodynamics model indicate that it is quite sensitive to the land use type; complete agricultural cover would yield 25- 33% higher discharge compared to a completely forested watershed. The hydrodynamics model is also sensitive to the LAI up to a value of 3 and becomes insensitive for higher values. The model however, is not strongly sensitive to hydraulic conductivity of the saturated zone.
An interdisciplinary educational program on population growth using drama as a tool
(Thesis (M.S.)-Bogazici University. Institute Environmental Sciences, 2005., 2005.) Alibeyoğlu, Meltem Ceylan.; Bekbölet, Miray.
After the Industrial Revolution in eighteenth century, the gap between human and nature became more visible than the past. Unfortunately, technological and economical developments do not seem as right tools in solving social and environmental problems the world is facing such as racism, poverty, AIDS, climate change, endangered species, wars, atomic and nuclear bombs, loosing cultural diversity, globalisation. In that sense, environmental education has moved to the countries' agenda as a solution in order to have a more livable environment. Whether population growth is one of the results or reasons of the problems that the earth is facing now, it is obvious that it has a direct relation with social, political and environmental issues. Environmental education programs, which are learner oriented and based on interdisciplinary approaches, guide for effective teaching and learning environments for the future of the earth, since they emphasize the importance of awareness, knowledge, skills, attitudes, participation and promote a multi perpective look. The aim of this study is to develop an interdisciplinary environmental education program for 12-14 years old students using process drama technique in order to create an awareness about the factors of population dynamics as well as social, economical and ecological effects of population growth.
An investigation on direct free cooling potential of climate in key cities of Turkey
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Tunç, C. Mutlu.; Yenigün, Orhan.
Data centers operating throughout the globe demanded up to 2% of world's electricity generation in the last decade, and they were responsible for the associated emissions and resources. There exists a potential of climate for times weather parameters comply with the environmental needs of our state of the art IT equipment, when the energy demand for cooling is offloaded to ambient air and both energy savings and reduction in emissions are realized, in so called Direct Free Cooling (DFC) mode of operation. In this research, the direct free cooling potential of climate is investigated for the top socioeconomically developed cities of Turkey, namely Istanbul, Ankara, and Izmir along with the city of Konya that is planned to almost double the data center whitespace area of Turkey, and Erzurum as the representative of a city with year-round cold ambient air temperatures and high elevation, in two different periods of time, a control period in the past and a subject period in future. The DFC potentials calculated for both periods of each city are compared within and between cities. The findings reported in this research should affect policy and investment making processes due to changing climate. The aim is to establish sustainable and efficient data center operations in harmony with the climate of Turkey's key cities, leading to lesser green house gas emissions and more development.
An investigation on intertidal zone amphipod crustaceans on the coasts of the south shetland islands and antarctic peninsula west coast islands using DNA barcoding method
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2023., 2023) Gencer, Fadime.; Bilgin, Raşit.
After Gondwana's breakup, Antarctica got isolated as a continent resulting in the endemicity of the organisms, well-adapted to their extreme habitats. Antarctic Peninsula is vulnerable to climate change and environmental stressors, including tourism and fisheries, among others. Species that might not adapt to such environmental changes can face extinction. Studies indicate that invertebrates comprise 97% of animal species and are the most vulnerable. They need to be represented more since most studies focused on charismatic species like sea birds, mammals, and fishes. Species identification and distribution are crucial for conservation initiatives. Since traditional taxonomy requires time and expertise, barcoding is utilized to identify species and estimate the species diversity of cryptic and error-prone groups. We precisely utilized the COI barcode for the "reverse taxonomy" approach to identify and estimate phylogeographic relationships of Antarctic amphipods collected during Turkish Antarctic expeditions in 2017, 2018, and 2019. We observed Bovallia gigantea, Vibilia antarctica, Eurymera monticulosa, Gondogeneia antarctica, Cheirimedon femoratus, Hippomedon kergueleni, Prostebbingia brevicornis, Orchomenella rotundifrons, and Paramoera walkeri. A non-target sequence was amplified and found to be related to Shewanella. An individual was assigned to the Paraceradocus genus based on morphology. We could not identify four OTUs at the species level through DNA barcoding. The next step of this study is to collaborate with Antarctic amphipod taxonomists to determine if these morphotypes are new species or belong to species that have already been defined. Despite ongoing taxonomic research on Antarctic amphipods, more barcodes still need to be uploaded to BOLD and GenBank.
An investigation on the evolution and conservation of the harbor porpoise, phocoena phocoena in Turkey
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2015., 2015.) Yazıcı, Özge.; Bilgin, Raşit.
In 2008, the species Phocoena phocoena was categorized as “least concern” and Phocoena phocoena ssp. relicta, as “endangered,” on the IUCN Red List. In the last five decades, the number of harbor porpoises in the Black Sea declined significantly, especially due to mass killings associated with commercial fisheries. Tissue samples of 71 individuals of the Phocoena phocoena were collected from 33 locations in Turkey: the western Black Sea (n = 44), the eastern Black Sea (n = 11), the Marmara Sea (n = 14), and the Aegean Sea (n = 2). Samples were either stranded or by-catch from fisheries. Consistent with other studies, none of the haplotypes we found clustered with Atlantic populations. The most common haplotype in the study was found in 49 individuals. The study uncovered five total unique haplotypes from the Black Sea samples. All of them were found in the western Black Sea region. The idea that harbor porpoises from the Aegean Sea first came from the Black Sea through the Istanbul and Dardanelles Straits is supported by our findings. Our data also supports the possibility that there is an isolated population in the Sea of Marmara because four of the individuals we observed shared a unique haplotype with previously studied individuals in the same region. As a result of these findings, it was concluded that the Phocoena phocoena population in the Sea of Marmara should be treated of as a management unit (MU) for conservation purposes.

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