Browsing by Subject "Pollution"

Now showing 1 - 13 of 13

Open Access
Bacteria encapsulated electrospun nanofibrous webs for remediation of methylene blue dye in water
(Elsevier, 2017-04) Sarioglu O.F.; Keskin, N. O. S.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials that were produced by encapsulation of bacterial cells within electrospun nanofibrous webs are described. A commercial strain of Pseudomonas aeruginosa which has methylene blue (MB) dye remediation capability was selected for encapsulation, and polyvinyl alcohol (PVA) and polyethylene oxide (PEO) were selected as the polymer matrices for the electrospinning of bacteria encapsulated nanofibrous webs. Encapsulation of bacterial cells was monitored by scanning electron microscopy (SEM) and fluorescence microscopy, and the viability of encapsulated bacteria was checked by live/dead staining and viable cell counting assay. Both bacteria/PVA and bacteria/PEO webs have shown a great potential for remediation of MB, yet bacteria/PEO web has shown higher removal performances than bacteria/PVA web, which was probably due to the differences in the initial viable bacterial cells for those two samples. The bacteria encapsulated electrospun nanofibrous webs were stored at 4 °C for three months and they were found as potentially storable for keeping encapsulated bacterial cells alive. Overall, the results suggest that electrospun nanofibrous webs are suitable platforms for preservation of living bacterial cells and they can be used directly as a starting inoculum for bioremediation of water systems.
Open Access
Bacteria immobilized electrospun polycaprolactone and polylactic acid fibrous webs for remediation of textile dyes in water
(Elsevier, 2017-10) Sarioglu O.F.; S. Keskin, N. O.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials for textile dye removal which are produced by immobilization of specific bacteria onto electrospun nanofibrous webs are presented. A textile dye remediating bacterial isolate, Clavibacter michiganensis, was selected for bacterial immobilization, a commercial reactive textile dye, Setazol Blue BRF-X, was selected as the target contaminant, and electrospun polycaprolactone (PCL) and polylactic acid (PLA) nanofibrous polymeric webs were selected for bacterial integration. Bacterial adhesion onto nanofibrous webs was monitored by scanning electron microscopy (SEM) imaging and optical density (OD) measurements were performed for the detached bacteria. After achieving sufficient amounts of immobilized bacteria on electrospun nanofibrous webs, equivalent web samples were utilized for testing the dye removal capabilities. Both bacteria/PCL and bacteria/PLA webs have shown efficient remediation of Setazol Blue BRF-X dye within 48 h at each tested concentration (50, 100 and 200 mg/L), and their removal performances were very similar to the free-bacteria cells. The bacteria immobilized webs were then tested for five times of reuse at an initial dye concentration of 100 mg/L, and found as potentially reusable with higher bacterial immobilization and faster dye removal capacities at the end of the test. Overall, these findings suggest that electrospun nanofibrous webs are available platforms for bacterial integration and the bacteria immobilized webs can be used as starting inocula for use in remediation of textile dyes in wastewater systems.
Open Access
Economic growth, trade and environmental quality in a two-region world economy
(Wiley-Blackwell Publishing Ltd., 2006) Sirakaya, S.; Turnovsky, S.; Alemdar, N. M.
This paper examines the linkages between international trade, environmental degradation, and economic growth, in a dynamic North-South trade game. The North produces manufactured goods by employing capital, labor, and a natural resource that it imports from the South, using a neoclassical production function subject to an endogenously improving technology. The South extracts the resource using raw labor, in the process generating local pollution. Genetic algorithms (GA) are used to search for optimal policies in the presence of local pollution and technology spillovers from North to South. In the GA search for optimal regional policies, both noncooperative and cooperative modes of trade are considered. Noncooperative trade results in inefficiencies stemming from externalities. Though cooperative trade policies are efficient, they lack credibility. A joint maximization of the global welfare shows that transfer of technology is a viable route to improve world welfare.
Open Access
Environmental efficiency in carbon dioxide emissions in the OECD: a non-parametric approach
(Academic Press, 2000) Zaim, O.; Taskin, F.
The role of the environment is an important issue in the policy-making and hence, the accurate assessment of the environmental conditions is vital. In this paper, an environmental efficiency index is developed for the OECD countries using non-parametric techniques. The approach adopted is based on the assumption that there is just one production process behind the production of both goods and pollution emissions. The index derived in this work measures the extent of the required output sacrifice, due to the transformation of the production process, from one where all outputs are strongly disposable to the one which is characterized by weak disposability of pollutants. Using this index, we first conduct cross-section comparisons on the state of each country's production process in its treatment of pollution emissions. We then trace each country's modification of their production processes overtime. The results indicate that if the disposability for CO2 emissions were strictly restricted as the result of an environmental regulation, the total value of output loss to the OECD countries as a whole would correspond to 3.7, 4.8 and 3.5% of the total OECD GDP for 1980, 1985 and 1990, respectively. © 2000 Academic Press.
Open Access
Evaluation of contact time and fiber morphology on bacterial immobilization for development of novel surfactant degrading nanofibrous webs
(Royal Society of Chemistry, 2015) Sarioglu O.F.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
Novel electrospun fibrous biocomposites were developed by immobilizing two different sodium dodecyl sulfate (SDS) biodegrading bacterial strains, Serratia proteamaculans STB3 and Achromobacter xylosoxidans STB4 on electrospun non-porous cellulose acetate (nCA) and porous cellulose acetate (pCA) webs. The required contact time for bacterial immobilization was determined by SEM imaging and viable cell counting of the immobilized bacteria, and bacterial attachment was ended at day 25 based on these results. SDS biodegradation capabilities of bacteria immobilized webs were evaluated at different concentrations of SDS, and found to be highly efficient at concentrations up to 100 mg L-1. It was observed that SDS remediation capabilities of bacteria immobilized webs were primarily based on the bacterial existence and very similar to the free-bacterial cells. A reusability test was applied on the two most efficient webs (STB3/pCA and STB4/pCA) at 100 mg L-1 SDS, and the results suggest that the webs are potentially reusable and improvable for SDS remediation in water. SEM images of bacteria immobilized webs after the reusability test demonstrate strong bacterial adhesion onto the fibrous surfaces, which was also supported by the viable cell counting results. Our results are highly promising and suggest that bacteria immobilized electrospun fibrous webs have the potential to be used effectively and continually for remediation of SDS from aqueous environments.
Open Access
Evaluation of fiber diameter and morphology differences for electrospun fibers on bacterial immobilization and bioremediation performance
(Elsevier, 2017-05) Sarioglu O.F.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this report, morphology and fiber diameter differences of electrospun polysulfone (PSU) fibers on bacterial immobilization and bioremediation performance were evaluated. PSU fibers were produced with aligned or randomly oriented morphologies, and PSU fibers with thinner and thicker diameters were also produced. PSU fibers were utilized as carrier matrices for bacterial integration and the sample showing highest bacterial immobilization was tested for bioremediation of ammonium and methylene blue dye in water. It was found that randomly oriented and thinner PSU fibers are the optimal system for bacterial immobilization, hence bioremediation studies were performed with this sample. The results demonstrated that bacteria immobilized PSU fibers are promising candidates for simultaneous removal of ammonium and methylene blue dye, and they have a potential to be used in remediation of water systems.
Open Access
The formation and characterization of cyclodextrin functionalized polystyrene nanofibers produced by electrospinning
(2009) Uyar, Tamer; Havelund, R.; Hacaloglu J.; Zhou X.; Besenbacher F.; Kingshott P.
Polystyrene (PS) nanofibers containing the inclusion complex forming beta-cyclodextrin (β-CD) were successfully produced by electrospinning aimed at developing functional fibrous nanowebs. By optimization of the electrospinning parameters, which included varying the relative concentration of PS and β-CD in the solutions, bead-free fibers were produced. Homogeneous solutions of β-CD and PS in dimethylformamide (DMF) were used with concentrations of PS varying from 10% to 25% (w/v, with respect to DMF), and β-CD concentrations of 1% to 50% (w/w, with respect to PS). The presence of β-CD facilitated the production of bead-free PS fibers even from lower polymer concentrations as a result of the higher conductivity of the PS/CD solutions. The morphology and the production of bead-free PS/CD fibers were highly dependent on the β-CD contents. Transmission electron microscope (TEM) and atomic force microscope (AFM) images showed that incorporation of β-CD yielded PS fibers with rougher surfaces. Thermogravimetric analysis (TGA) and direct insertion probe pyrolysis mass spectroscopy (DP-MS) results confirmed the presence of β-CD in the PS fibers. X-ray diffraction (XRD) spectra of the fibers indicated that the β-CD molecules are distributed within the PS matrix without any phase separated crystalline aggregates up to 40% (w/w) β-CD loading. Furthermore, chemical analyses by Fourier transform infrared (FTIR) spectroscopy studies confirm that β-CD molecules are located within the PS fiber matrix. Finally, preliminary investigations using x-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectrometry (ToF-static-SIMS) show the presence of the cyclodextrin molecules in the outer molecular layers of the fiber surfaces. The XPS and ToF-SIMS findings indicate that cyclodextrin functionalized PS webs would have the potential to be used as molecular filters and/or nanofilters for the purposes of filtration/purification/separation owing to surface associated β-CD molecules which have inclusion complexation capability. © 2009 IOP Publishing Ltd.
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Geçmişten günümüze İncesu Deresi
(Bilkent University, 2023) Şen,Emre; Yemenici,Ahmet Oğuz; Eser,Eylül; Ustaer,Ulaş; Öztürk,Yılmaz Kaan
İncesu Deresi, Ankara’nın imarı sırasında 1930’larda yer yer kapatılmaya başlandı ve 1950’lerden sonra Ankara’nın diğer dereleriyle birlikte ıslah çalışmaları sonucunda büyük çoğunluğuyla yol altında kaldı. İncesu’nun asfalt yol altına alınması kanalizasyon olarak kullanılmasına da olanak tanıdı. Bu müdahaleler sonucunda, eskiden şehrin içerisinden geçen ve başkentin sosyal hayatında yeri olan İncesu deresi bugün ölmeye yüz tutan bir dere hâline geldi. Bu makale, İncesu Deresinin Cumhuriyet sonrasındaki tarihini, kapatılmasının toplum sağlığı ve şehir imarı açısından nedenlerini, toplum hayatına etkilerini ve üstünün geri açılması için yapılan çalışmaları inceliyor.
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Limits to growth through functional specialization in a closed system
(1978) Fung, K. K.
Open Access
Multifunctional ZnO nanorod-reduced graphene oxide hybrids nanocomposites for effective water remediation: effective sunlight driven degradation of organic dyes and rapid heavy metal adsorption
(Elsevier, 2017-10) Ranjith, K. S.; Manivel, P.; Rajendrakumar, R. T.; Uyar, Tamer
We demonstrate the multi-functionality engineering on nanocomposite by combining one dimensional (1D) ZnO nanorod (NR) and two dimensional (2D) reduced graphene oxide (rGO) for efficient water remediation. Nano-engineered ZnO NR-rGO nanocomposites show efficient water remediation in terms of degradation of organic dyes and removal of heavy metal ions. Herein, we report on the fabrication of ZnO NR-rGO nanocomposite via a facile template-free hydrothermal route with an aim to improve the visible photocatalytic efficiency of the ZnO NR based nanocomposites. The structural and morphological features reveal that the rGO sheets are attached on the ZnO NRs and form a hybrid composite assembly. The surface enabled ZnO NR-rGO nanocomposites were used to degrade organic dye molecules (methylene blue (MB), methyl orange (MO) and rhodamine B (RhB)) under visible irradiation and adsorb Cu (II) and Co (II) ions from water through an adsorption process. The nanocomposite containing 7.5 wt% rGO and ZnO NRs shows a 4-fold enhancement in the visible photocatalytic activity and effective removal of Cu (II) and Co (II) ions from aqueous solution respectively. The photocatalytic performance is discussed in detail with respect to interaction between ZnO NRs and rGO sheets, light-harvesting properties of the nanocomposites. The effective experimental adsorption data also fit very well with the pseudo-second-order model which reveals the surface adsorption of metal ions. The results provide insight into a new method utilize for both visible photo degradation and adsorption for the removal of various wastewater pollutants. Construction of hybrid form of nanostructures delivers the effective catalytic properties with tunable functionalities for the water remediation.
Open Access
Phytoremediation of Cu, Cr and Pb mixtures by lemna minor
(2013) Üçüncü, E.; Tunca, E.; Fikirdeşici, S.; Özkan, A.D.; Altindaǧ, A.
The present study reports the capacity of the aquatic macrophyte Lemna minor to remediate combinations of Cu(II), Pb(II) and Cr(III) from a simulated natural environment. The effect of these metal mixtures on the growth of L. minor was also investigated using growth rate and biomass inhibition calculations. L. minor was successful in removing Cr and Pb from the water, and it remained an effective remediation agent when both metals were present in the environment. However, a relatively low absorption capacity was observed for Cu, increasing concentrations of which were associated with significant decreases in growth rate. No statistically significant difference was found between the 24 h and 7 days absorption rates of Cu, Pb and Cr, suggesting that, at the concentrations tested, equilibrium occurs within 24 h of metal exposure. © 2013 Springer Science+Business Media New York.
Open Access
Radiochronological methods as tools to study environmental pollution
(Springer, 2011) Erten, Hasan N.
The study of the environmental impact of natural and anthropogenic events forms the essence of environmental pollution considerations. The nature of the polluting species as well as their time distributions are of primary importance with respect to identifying the polluting sources. Sediments are the most frequently used materials in such studies. Sediments act as the ecological memories of the environments of their formation. Besides classical chronological methods, radiochronological methods developed recently gave a big impetus to environmental pollution studies. One of the key radioisotopic technique is to utilize 210Pb, a product of the 235U radioactive series to date the last 200 years of the sediments. A number of supporting indicators are also utilized. One of them being anthropogenic 137Cs which is used as a time-marker. Large amounts of 137Cs radioactivity was released to the environment during 1954-1963, in time of the most intense atmospheric nuclear arms testing and again in 1986 during the Chernobyl nuclear accident. These intense 137s activities form time-markers throughout sediment cores corresponding to their release years. During our studies extending over several years we have used radiochronological methods in dating several sediment cores from Zurich and Constance Lakes in Switzerland from east coast of Spain, Sea of Marmara, from the Black Sea region, Southern coast of Turkey and from North Cyprus. The distribution of several elemental concentrations of importance in pollution considerations along sediment cores were also determined. These studies allowes proposing time frames to pollution events and help inqueries in tracing possible sources of pollution.
Open Access
Radiochronology of sediments from the Mediterranean sea using natural 210Pb and fallout 137Cs
(Kluwer Academic Publishers, 1994) Tadjiki, S.; Erten, H. N.
The210Pb and137Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct γ-ray spectroscopy. Sedimentation rates were derived for all locations using the210Pb data. The rates range from 1.39±0.12 cm · y-1 (0.50±0.04 g · cm-2 · y-1) to 0.08±0.01 cm · y-1 (0.039±0.003 g · cm-2 · y-1). Except for one core, the137Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of210Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported210Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm-2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean. © 1994 Akadémiai Kiadó.