Son 20 000 yılda Karadeniz ve Marmara Denizi'nde oluşan paleo-çevresel değişimler

The connection of Marmara Sea and Black Sea with global ocean and between themselves are established via the Çanakkale and Istanbul straits. Because of the shallow sill depths of these straits, these connections were interrupted in during the late glacial period (LGM). As a result of these important paleoceanographic events, Marmara and Black Seas experienced significant sedimentological, biological and chemical changes. Despite the high scientific interest and large number of previous studies, the timing and nature of the interruptions and reconnections of the two basins with each other and with the world ocean are still matters of debate. This debate has stemmed from mainly the following shortcomings of the previous studies: a) confinement of the study in one basin, b) selection of unsuitable core locations, and/or c) use of inadequate sampling resolution and proxies. To overcome these difficulties, we analyzed organic (Corg) and inorganic carbon (total carbonate:Tkarb) and determined sedimentation rates for the different climatic stages in four chronostratigraphically well dated cores (two each) from the Black Sea and Sea of Marmara. As identified by the previous studies, three units are present in the Black Sea Cores GC-19 and SL-12 covering the period from the LGM to present. The uppermost unit is the Coccolith Unit that consists of microlaminated gray green mud containing alternations of coccolith-rich and clay-organic matter rich lamina. The unit started depositing when coccolithophore Emiliania huxleyi invaded the basin at 2720 a (calib.) BP and the present-day oceanographic conditions were established. The underlying unit is Sapropel Unit that consists of laminated dark gray mud with high (up to 21 wt %) Corg. The Lutit Unit deposited under lacustrine conditions that consists of gray clayey mud. The lake /marine transition is characterized by high total carbonate content (up to 80 wt %) in the Black Sea (C1 carbonate) and dated 9.3 ka (calib.) BP. The Sea of Marmara cores contain two lithostratigraphic units deposited in the last 20 ka. The upper unit (Unit 1) is a green marine mud that includes a dark olive green Sapropel with more than 1.5 % Corg. The lower unit (Unit 2) is banded gray mud that was deposited under lacustrine conditions. The lacustrine / marine transition occurred 14.7 ka BP. Unit 2 includes a rhyodacitic ash layer that is defined as the Y-2 ash-layer of Santorini origin, dated 22 ka (calib.) BP. Sedimentological and geochemical (Corg and Tkarb) analysis, together with the changes in the sedimentation rates in the cores show that the Black Sea and Sea of Marmara were disconnected to each other during the LGM but connected during the post-glacial Heinrich 1 (H1, 17.9-16.5 ka BP), Red Clay Layer (RL; 16.2-14.8 ka BP) and Younger Dryas (YD, 12.9-11.9 ka BP) cold periods when large inputs of freshwater and sediment occurred to the Black Sea and Marmara basins by the west and northwest European rivers, leading to one-way connection between the two basins. In between the post-glacial cold periods during the early Holocene (11.9-9.3 ka BP) and Bølling-Allerød (14.8-12.9 ka BP), carbonate-rich C2 and C3 units, predominantly of calcite composition, were deposited with low sedimentation rates respectively. During these carbonate depositional periods relatively warm and dry conditions with low water levels prevailed in the Black Sea and the Sea of Marmara, and no connection existed between the two basins. Another carbonate depositional event, this time predominantly of aragonite composition, took place in the Sea of Marmara and the Black Sea as during the lake/marine transition. The carbonate beds are dated 14.5-12.9 ka BP in the Sea of Marmara and 8.6-7.6 ka BP in Black Sea (C1); the event in the Sea of Marmara partly overlapping with the Bolling/Allerod (B/A). The carbonate deposition in both the basins took place as a result of mixing of lacustrine and marine waters leading to carbonate overstaturation. Sapropels were deposited in the Black Sea and in the Sea of Marmara Sea during 11.5-7.0 and 7.8-2.7 ka BP, respectively, when the Mediterranean waters poured sequentially into the lacustrine Sea of Marmara and Black Sea. Arrival of marine waters pushed up the nutrient rich deep waters up into the photic zone, thereby initiating high primary productivity and lead to water stratification, preconditioning the basins for the sapropel formation. The sapropel deposition was interrupted in the Sea of Marmara during YD and 8.2 ka BP cold periods as a result of increased deep water ventilation. Keywords: Black Sea, Sea of Marmara, Paleoceanography, Paleoclimatology, Sapropel.Karadeniz ve Marmara Denizi’nde yapılan sedimentolojik ve jeokimyasal çalışmalar son 20 bin yıl boyunca her iki denizde önemli iklimsel ve oşinografik değişimlere işaret etmektedir. Çökelme oranı ve çökel jeokimyası (organik ve inorganik karbon) buzul çağında iki deniz arasında bağlantı olmadığını; buzul çağı sonrası H1 (Heinrich 1), RL (kırmızı kil) ve YD (Younger Dryas) soğuk dönemlerinde ise bağlantı sağlandığını desteklemektedir. H1, RL ve YD Avrupa nehirleri ile Karadeniz ve Marmara Denizi’ne bol miktarda kırıntı girdisinin olduğu dönemlerdir. Bu soğuk dönemler arasında Karadeniz’de erken Holosen (C2) ve Bølling-Allerød (C3) dönemlerinde düşük çökelme oranları ve yüksek toplam karbonat değerleri izlenmektedir. Bu dönemlerdeki yüksek toplam karbonat değerleri ve düşük çökelme oranları havzada kurak ve ılıman bir iklimin hakim olduğunu ve her iki deniz arasında bağlantının kesik olduğunu göstermektedir. Marmara Denizi’nde G.Ö. 11.5-7.0 ve Karadeniz’de G.Ö. 7.8-2.72 bin yılları arasında yüksek organik karbon (Corg) ve düşük çökelme oranları ile temsil edilen Sapropel birimleri, göl ortamına deniz suyunun girmesi, su tabakalanması oluşması ile bunların biyojeokimyasal döngülerde değişimler oluşturması ile çökelmeye başlamıştır. Özellikle tuzlu ve yoğun Akdeniz sularının bu havzalardaki besin elementlerince zengin derin suları üste, fotik zona itmesi ile organik üretimi artırması sapropel çökelimini tetikleyen en önemli etken olmuştur. Akdeniz sularının Marmara Denizi’ne girmesi ile başlayan organik maddece zengin çökellerin depolanması YD ve 8.2 bin yıl soğuk dönemlerinde su dolaşımındaki hızlanma nedeni ile kesintiye uğramıştır.  Anahtar Kelimeler: Karadeniz, Marmara Denizi, Paleoşinografi, Paleoiklim, Sapropel

Reappraisal of properties soils encountered in the Golden Horn

Haliç üstünde inşa edilen ve edilmekte olan Haliç Köprüsü, Yeni Galata Köprüsü, Haliç Metro Geçiş Köprüsü sondajlarından ve yapım sırasında elde edilen bilgiler, bu bölgedeki zeminlerin özellikleri hakkında ayrıntılı bilgiler elde edilmesini sağlamaktadır. Membadan mansaba doğru bu köprüler Haliç Köprüsü, Haliç Metro Geçiş Köprüsü, Yeni Galata Köprüsü olarak sıralanmaktadır. Yeni Galata Köprüsü kazıklarının girdiği çakıl tabakası, yaklaşık 80 m derinliktedir. Haliç Metro Metro Geçiş Köprüsü ekseninde kaya tabakasının derinliği, Azapkapı tarafında 55 metreden, Unkapanı tarafında 80 metreye alçalmaktadır. Yeni Galata Köprüsü kazıklarının oturduğu çakıl tabakası, Haliç Metro Geçiş Köprüsü yerindeki kaya tabakasına göre yatay olarak kabul edilebilir. Buna karşılık, Haliç Metro Geçiş Köprüsü’nün Unkapanı tarafında taban kayasında derin bir çukur bulunmaktadır. Böyle bir çukurun varlığı, Haliç’te kaya yüzeyinin enine ve boyuna doğrultudaki genel eğimlerine uymayan bir durum oluşturmaktadır. Kaya tabakaları çok yumuşak, kalın kil/silt tabakaları ile örtülüdür. Kıyılarda kalın şehir dolgusu bulunmaktadır. Yumuşak tabakaların üst yüzü hemen hemen yataydır ve bu durum zeminin yüksek su muhtevasını yansıtmaktadır. Likit limit kıvamında tabakalar, bir çanak şeklindeki taban kayasını doldurmaktadır. Haliç’in büyük ekseni boyunca kaya tabakasının derinliği, Haliç’in ağız kısmına doğru büyük bir eğimle alçalmakta ve 80 m kadar derinliğe ulaşmaktadır. Anahtar Kelimeler: Haliç (Golden Horn), yumuşak killi zeminler, çatlaklı ayrışmış kayalar.The Golden Horn is a seven and half kilometres long natural inlet of Boğaziçi Strait. It has a maximum width of about 700 m near its entrance. At its deepest part its  depth is 40 m. The Golden Horn divides historical part of the city from the rest. The geology of the Istanbul area has been studied by many investigators. Penck was first to recognize the shales and graywackes as the oldest of the formations encountered in the area. He named them as the Thrace series. Subsequent investigations indicated the existence of various lithological and paleontological zones in Thrace series, and it is concluded that they belonged to the Early Carboniferous Period of the same era. Over centuries, the detritus brought by Alibey, Kâğıthane, and other creeks, heavy industrial and domestic wastes, and uncontrolled fills have changed drastically almost the entire cross section of the Golden Horn. Along the shores, many valleys have been levelled off by generally uncontrolled fills, and comparatively large areas have been reclaimed.The thickness of the man-made fill is over 40 m along the south shore and over 30 m along the north shore on the axis of the New Galata Bridge. The thickness of the fill decreases with increasing distance from the shore. Man-made fill is underlain by sedimentary deposits consisting of sand, silt and clay in varying proportions. In general it is described as grey-dark organic silty clay of marine origin. On the Eminönü (South) site of the New Galata Bridge, the soft layers are underlain by a few meters thick weathered shale. Over the deeper part of the waterway and towards the Karaköy side soft layers is underlain by cobbly gravel. The design of new bridges over the Golden Horn was subject to severe constraints. The New Galata Bridge is founded on large diameter tubular steel piles. Piles were driven into limestone, diabase and sandstone origined gravel which is encountered between the depths of 76 m and 88 m. Most of the piles of the New Galata Bridge were driven into the shuttered rock bottom. The adoption of a closed end pile having a diameter as large as 2000 mm is well suited to the soil conditions and the design requirements – the damage of the pile tip is prevented, settlement criteria are satisfied. The piles of the New Galata Bridge were designed to carry high working loads (up to 12 000 kN) in end bearing and to comply with severe restrictions on allowable settlement.  A box girder  bridge carried on temporary  supports was constructed over the test pile and was loaded by ingots. Four hydraulic jacks were placed on the head of the test pile to obtain a total reaction of 2000 tonnes. The composite piles of the Metro Crossing Bridge extended to depths over 100 m. They were designed to carry even higher loads (up to 47 000 kN). Osterberg type of loading tests was made on Metro Crossing Bridge. In general dynamic measurements are not considered as a reliable substitute to static pile loading test. On the Metro Crossing Bridge site, dynamic analysis (PDA) is carried out and dynamic response during pile driving is also recorded. Results are found consistent with  the exploration data. Depth of water on the axis of Metro Crossing Bridge is about 34 m. Soil profile is overlain by very soft, almost at liquid consistency, silt clay layer. The thickness of clay layer varied between 30 m and 50 m. Very soft silty clay layer is underlain by sandstone, siltstone and mudstone layers. Depth of rock is 55 m at Azapkapı (North) and 80 m at Unkapanı (South) side of the Bridge. Sea bottom at Golden Horn Bridge site is very shallow. Depth of rock is more than 70 m and is overlain by a gravel layer. The depth of exploration at Metro Crossing Bridge site was well over 100 m. Special attention was given to ascertain the level and characteristics of a suitable stratum. Form the initial data indicated existence of weathered rocks and alternating strong and weak rock formations. Soil investigations and pile driving provided ample information about the rock bottom of the Golden Horn. Rock levels at the site of Golden Horn Bridge and at the site of New Galata Bridge are almost flat in comparison with that of the Metro Crossing Bridge. Furthermore transversal profile of the rock bottom at Metro Crossing Bridge contains a deeper section near Unkapanı (South). Existence of such depression is not confirming with the general slopes of the rock strata. Keywords: Golden Horn, soft clayey soils, soft rocks

Alüminyum yüzey işleme endüstrisi proses atıksularından elektrokoagülasyon yöntemiyle florür giderimi

Fluoride concentration higher than 4 mg/L creates several dental problems and decompositions in the skeletal structure. Daily intake of 6 mg fluoride may cause articulation diseases, weight losses and bone breakages. Therefore, fluoride concentration in drinking water has been strictly regulated as a maximum value of 1.5 mg/L by Turkish Standards Institute (TSE), World Health Organization (WHO) and European Commission (EC). Owing to its high toxicity, legal authorities have established the discharges standards for fluoride from wastewater treatment plants. Therefore, the increasing demand for the control of fluoride being released from industrial activities has led to the search of more effective treatment methods for fluoride bearing effluents. Although, several physico-chemical treatment methods such as adsorption using different types of adsorbents such as activated alumina, activated carbon, fly ash etc., coagulation with alum, chemical precipitation with lime, and electrocoagulation using aluminum electrodes have been addressed for removal of fluoride from the samples bearing moderately low amount of fluoride in the related literature. Among these treatment processes, electrocoagulation (EC) is deemed a promising one in removing fluoride from industrial effluents. The target of the present study is to examine the treatability of an aluminum surface treatment effluent bearing high amount of fluoride by EC with aluminum electrodes and to explore the effect of varying operating parameters such as the applied current density, initial pH, and electrolyte (NaCl) concentration on fluoride abatement as well as organic matter removal and aluminum reduction. In order to assess the effects of the operation parameters on process performance and to determine the optimum operation conditions in terms of removal efficiencies, a detailed experimental study was performed using composite samples taken from an aluminum surface treatment process. An aluminum surface treatment effluent bearing high amount of fluoride (3180-6490 mg/L) and aluminum (2695-4690 mg/L) together with organic matter (485-750 mg/L) was used in the experimental study. NaCl was selected as an electrolyte because of high efficiency on EC. The electrocoagulator consisted of a 10 L-capacity polyethylene reactor equipped with 4 pairs of anodes and cathodes made of aluminum. The process performence was followed by COD, fluoride, and aluminum. In order to determine the effect of the applied current density on EC process performance a wide range of the applied current density varying between 3.7 and 18.6 mA/cm2 was applied at an electrolyte concentration of 500 mg NaCl/L and at original pH of sample (2.52). The results indicated that increasing the applied current density improved fluoride removal efficiencies. Nevertheless, this improvement in fluoride removal was observed after 30 minutes of operation time. In these experiments commenced at an initial pH of 2.52, solution pH gradually increased and reached to ~6.0. The lowest remaining aluminum concentration was obtained at the end of EC process performed at the highest applied current density. The results obtained at EC applications run at an initial pH of 2.54, a high NaCl concentration of 1500 mg/L, and at a wide range of applied current density varying between 3.7 and 29.8 mA/cm2 indicated that increasing the applied current density increased fluoride and aluminum abatement efficiencies and shortened the reaction time. Similar to EC runs conducted at 500 mg NaCl/L solution pHs gradually increased up to 6.0 during these EC applications. Up to 40% COD removal efficiencies were obtained at the end of these EC applications. The effect of electrolyte concentration and initial pH on process performance was investigated at an applied current density of 18.6 mA/cm2 for an NaCl concentrations of 1500 and  3000 mg/L  and at initial pHs of 2.52 and 3.8. EC performed at initial pH of 3.8 yielded better fluoride abatements and aluminum reductions than EC run at original pH of 2.52.While an increase in electrolyte (NaCl) concentration from 1500 to 3000 mg/L slightly enhanced removal efficiencies at the beginning of EC operation, almost the same fluoride abatements as well as COD and aluminum reductions were obtained at the end of 180 minute EC operation. In the present study, the electrocoagulation using aluminum electrodes proved to be a promising treatment method for fluoride removal as well as aluminum and organic matter reductions from an aluminum surface treatment effluent bearing high amount of fluoride and aluminum. Keywords: Aluminum, aluminum surface process, aluminum electrode, electrocoagulation, fluoride.Bu çalışmada, yüksek florür içeriğine sahip atıksuları temsil etmek üzere, alüminyum yüzey işleme endüstrisinden alınan numuneler üzerinde, elektrokoagülasyon (E.K.) prosesi ile florür ve diğer kirleticilerin giderimi ile ilgili deneysel çalışmalar yürütülmüştür. Alüminyum yüzey işleme endüstrisi proseslerinden alüminyum yüzey temizleme ve durulama banyosundan alınan atıksu numuneleri hacimsel olarak 1:1 oranında homojen bir şekilde karıştırılarak kompozit numuneler hazırlanmıştır. Alüminyum yüzey temizleme banyosunda sırasıyla %19, %8.5 oranında hidroflorik asit ve fosforik asit ile birlikte tensit (noniyonik) kullanımından dolayı, pH’sı düşük, florür, alüminyum ve KOİ konsantrasyonu yüksek atıksular meydana gelmektedir. Bu atıksuların arıtımı gerek florür gerekse alüminyum ve KOİ değerlerinin alıcı ortam deşarj standartlarını sağlayabilmesi açısından önem kazanmaktadır. Deneysel çalışmalarda E.K. uygulamalarında işletme parametrelerinin proses performansı üzerine etkileri incelenmiştir. İşletme parametreleri olarak, akım yoğunluğu, elektrolit olarak kullanılan NaCl konsantrasyonu ve pH ele alınmıştır. Ham kompozit numuneler üzerinde uygulanan E.K. denemelerinde artan akım yoğunluğu ve zamana bağlı olarak florür için yaklaşık %97 giderim verimi elde edildiği, artan akım yoğunluğu ve NaCl konsantrasyonuna bağlı olarak alüminyum gideriminde yüksek giderim verimlerine ulaşılabildiği ancak organik maddeyi temsil eden KOİ gideriminin ise %40 civarında kaldığı tespit edilmiştir. Deneysel çalışmaların sonucu olarak ham numunelerin E.K. prosesi ile gideriminde florür, alüminyum ve KOİ parametreleri için alıcı ortam deşarj standartlarının sağlanamadığı tespit edilmiştir. Anahtar Kelimeler: Alüminyum, alüminyum yüzey işleme, alüminyum elektrod, elektrokoagülasyon florür

Zemin mekaniğinin temelleri

Research on shear strength of soils always had, and perhaps still has, an important part in the development of soil mechanics. Some of the work carried out on the shear strength of cohesive soils is discussed here. Karl Terzaghi came to Istanbul Technical University in 1916 and stayed in Istanbul till 1922. During his stay in Istanbul, he had the opportunity to re-evaluate and reconsider his engineering experiences of the past from the perspective of present. He later wrote, “I was sitting in a mood of depression at an old rustic coffee house overlooking Golden Horn. I suddenly visualised what was needed to obtain a rational approach to the problem involved in earthwork and foundation engineering.” He carried out a series of experiments and made observations. He recognized that the addition of an increment of external pressure to a clay sample resulted in a temporary increment of water pressure of equal magnitude and soil’s intergrain contacts would feel no increment of force until the pore pressure began to dissipate. He defined “the pressure acting in the solid phase of the clay” which is now known as “the effective stress”.  At the time  Karl Terzaghi stated one of the fundamental principles of soil mechanics (Terzaghi, 1936) “… All measurable effects of a change of the shearing resistance are exclusively due to the changes in the effective stresses….” The principle of effective stress is extremely important concept in soil mechanics. A number of corollaries can be deduced from that principle. The engineering behaviour of soils with similar structure and mineralogy will be the same if they have the same effective stress. If the soil loaded or unloaded without change of volume and without any distortion there will be no change of effective stress. By raising or lowering pore water pressure it is possible to change the volume of the soil. Coulomb studied the stability of earth masses by considering the frictional resistance of a sliding block and published his famous paper in 1776. After Coulomb and many attempts have been made to redefine c and f to improve the equation in view of the new findings. Besides field observations and physical simulation by means of tests and monitoring our understanding of soil behaviour is improved. The Mohr theory of strength has been very useful in predicting stress conditions at failure from triaxial and other shear test results. The theory is based on the assumption that the shear stress on a failure plane is a unique function of the normal stress acting on that plane without particular reference to the associated strains. M. Juul Hvorslev carried out a series of tests on remoulded consolidated clay samples in the soils laboratory of Terzaghi in Wien Technische Hochschule. Hvorslev was aware that a cohesive soil undergoes either decrease or increase in the void ratio depending on its state of consolidation and also this change in the void ratio is simultaneous with the increase or decrease of pore water pressure. The classical work of Peynircioğlu (1939) on the shear strength of remoulded saturated cohesive soils is the earliest verification of Hvorslev’s findings. Roscoe, Schofield, Wroth (1958) in their prominent work define shear strength in three dimensional form by taking deviator stress (q), mean principal effective stress (p) and void ratio (v) as axes. They showed that failure points of clay samples which were initially isotropically consolidated and then loaded in drained and undrained triaxial compression tests fall on the same line in that space. They coined that line as the Critical State Line. The projection of the critical state line onto the q – p plane may be described by  q = M p where M is its gradient. Remoulded, reconsolidated samples, such as used by Hvorslev, Peynircioğlu, and stress in their tests may fall into the class of normally and lightly overconsolidated soils. The exact boundaries of the failure surface defined by them are continuously improved and discussed by the introduction of new experimental evidence. Yet the work carried out in the late thirties constituted a major progress still to be challenged. We owe the development of Soil Mechanics and Foundation Engineering in Turkey to Professor A. Peynircioğlu (1908 – 1982). He worked in Istanbul Technical University where he was appointed as full professor in 1943. His lectures was always well prepared and inspiring. As an experienced engineer he was always consulted for constructions with difficult ground conditions.  He established Soil Mechanics Research Institute of Istanbul Technical University, and Geotechnical Laboratory, lead and chaired the group constituted Turkish National Committee of Soil Mechanics and Foundation Engineering. Keywords: Soil mechanics, geotechnical engineering, Istanbul Teknik Üniversitesi, Robert College.İstanbul, Zemin Mekaniği’nin bilimsel bir disiplin olarak kurulduğu yerdir. Hikaye, Karl Terzaghi’nin İstanbul Teknik Üniversitesi’nde, o zamanki adı ile Yüksek Mühendis Mektebi’nde 1916 yılında görev alması ile başlamaktadır. Terzaghi’nin 1918’e kadar Yüksek Mühendis Mektebi’nde, daha sonra 1922’ye kadar Robert College’de çalıştığı yıllarda, yapmış olduğu deneyler, geliştirmiş olduğu kavramlar inşaat mühendisliğinde yeni ufuklar açmıştır. Ortaya attığı “efektif gerilme” kavramı, zemin davranışı ile ilgili o zamana kadar karanlıkta kalan bir çok konunun anlaşılmasını sağladığı gibi yeni araştırmaları teşvik etmiş, yeni bulgulara yol açmıştır. Türkiye’de zemin mekaniğinin inşaat mühendisliğinin bir dalı olarak yerleşmesi ve gelişmesi, daha sonraki yıllarda, Ahmet Hamdi Peynircioğlu’nun çalışmaları ve uzak görüşlülüğü sayesinde gerçekleşmiştir. A. H. Peynircioğlu, Türkiye’de ilk kez, “zemin mekaniği ve temel inşaatı” bilim dalını ve kürsüsünü kurdu, birçok öğrenci yetiştirdi. Şimdi kendi adını taşıyan İTÜ Zemin Mekaniği Laboratuvarı’nı kurdu. İnşaat mühendisi olarak çeşitli zemin koşullarında zarif, ders niteliğinde çözümler meydana getirdi. Yurdumuzda yapılan çalışmaların duyurulması ve uluslararası toplantılara sunulması amacıyla 1947 yılında “İTÜ Zemin Mekaniği Araştırma Kurumu”nu kurdu, gelişen üniversiteler ortamını da dikkate alarak, 1974’te “Zemin Mekaniği ve Temel Mühendisliği Türk Milli Komitesi”nin kurulmasını sağladı. Bugün, üniversitelerde ve araştırma kurumlarındada görev alan, projelerde sorumluluk yüklenen birçok geoteknik mühendisi, Ahmet Hamdi Peynircioğlu’nun araştırıcı, öğretim üyesi ve insan olarak verdiği örneği hatırlamaktadır.  Anahtar Kelimeler: Zemin mekanği, geoteknik mühendisliği, İstanbul Teknik Üniversitesi, Robert College

Donatılı kil zemin üzerine oturan yüzeysel şerit temellerin taşıma kapasitesi

Many researchers investigated the behavior of surface foundations constructed on reinforced sand (Omar et al. 1993; Khing et al. 1993; Yetimoglu et al. 1994; Das ve Omar 1994; Adams & Collin 1997). However most of the problematic foundation soils are of cohesive nature. Therefore in this study the effect of reinforcing cohesive foundation soils was investigated. Normally the cohesive soil excavated would be replaced by a granular fill. This means that improvement will be obtained due to the geosynthetic reinforcement but also because of the soil exchange. In order to see the effect of geosynthetic reinforcement alone, in this study the backfill was considered to have the same properties as the natural cohesive soil. The foundation behavior is assessed using limit equilibrium and finite element method (FEM). In this study the finite element code, Plaxis was used. A parametric study was conducted. Safety factors were calculated by using the "Phi-c reduction" method in the finite element analyses. In the "Phi-c reduction" approach the shear strength parameters tan  and c of the soil are successively reduced until failure occurs. The soil was modeled as Mohr-Coulomb model and the reinforcement as a linear elastic material. In the analyses, no specific interaction model between soil and reinforcement was used. The analyses presented in this study involve strip foundations on clay soil. The problem was analyzed under plane strain condition. The material properties were chosen in accordance with those in the literature to represent a clay soil. The soil parameters adopted were:  = 15 kN/m3; E = 25000 kPa (500 * c);  = 0.30;  = 0o;  = 0oand c = 100, 75, 50, 37.5, 25, 12.5 kN/m2. Footing thickness was chosen as 0.143 m and was placed directly on the surface without any embedment. Geosynthetic axial stiffness per unit width was selected as J=2000kN/m to represent a typical geogrid (Deb et. al. 2007). For the finite element analyses, vertical boundary was chosen to have only horizontal fixity and bottom boundary has both horizontal and vertical fixity. The size of the finite element mesh used was the same for all the analyses. It was chosen to be large enough to reduce the boundary effects to a negligible level. Factor of Safety (GS) for bearing capacities of unreinforced soil were calculated first by Limit Equilibrium analysis and then by FEM. The footing width (B=2.5, 5, 10 and 20 m), cohesion of the foundation soil (c=50 and 100 kPa), and surcharge load on footing (100 and 200 kPa) were varied to assess their influence on the safety factor of the shallow foundation. A good agreement was achieved between bearing capacity calculated using limit equilibrium approaches and finite element solutions. The finite element analysis gave factor of safety values directly proportional to cohesion of the clay soil as expected. In order to investigate the influence of the reinforcement on the factor of safety, a parametric study was conducted using different reinforcement configurations. Number of reinforcement layers, depth of the first reinforcement, vertical spacing of reinforcement layers, width of reinforcements and cohesion values of soil were chosen as variables in the analyses. Results obtained are summarized below: As the number of reinforcement layer increases (from one to six), the safety factor increases as well. Regardless of total number of reinforcement layers, the foundation width did not have a significant effect on the bearing capacity. The depth of the first reinforcement varied between 0.05B and 0.7B. The most efficient initial reinforcement depth was found as 0.4B. The vertical spacing between horizontal reinforcement layers (H) were taken as 0.025B, 0.05B and 0.1B. When six reinforcement layers were used, increase in the factor of safety values were calculated as: 7.5%, 12% and 17% for H/B values of 0.025, 0.05 and 0.1 respectively. The reinforcement lengths analyzed were L=B; L=2B; L=3B; L=4B and L=5B. The increase in bearing capacity after a length of L=3B was negligible. BCR and effective reinforcement depth were not affected when cohesion of the soil changed. Keywords: Strip footing, bearing capacity, Finite Element method, clay soil.Geosentetikler zeminin taşıma gücünü arttırmakta donatı olarak kullanılmaktadır. Bu çalışmada kohezyonlu zeminlerde geosentetik donatıların etkilerini daha iyi anlayabilmek için donatılı kil zemine oturan yüzeysel şerit temellerin taşıma kapasiteleri analiz edilmiştir. Hesaplamalarda sonlu elemanlar kodu Plaxis kullanılmıştır. Temel zemini Mohr Coulomb ve donatı lineer elastik malzeme olarak modellenmiştir. Analizlerde Phi-c azaltma metoduyla güvenlik sayıları bulunarak taşıma kapasiteleri hesaplanmıştır. İlk olarak donatısız kil zeminde temel genişliği, sürşarj yükü ve zemin kohezyonunun etkileri incelenmiştir. Nihai taşıma kapasiteleri hesaplanarak literatürdeki limit analiz sonuçlarıyla karşılaştırılmıştır. Daha sonra, donatının etkisini araştırmak amacıyla parametrik bir çalışma yapılmıştır. Donatı sayısı, etkin ilk donatı derinliği, donatılar arası düşey mesafe, donatı genişliği ve zemin kohezyonu parametre olarak seçilmiştir. Analizler sonucunda donatı sayısı arttıkça taşıma kapasitesinin 6 donatı için %17’ye kadar arttığı, etkin ilk donatı derinliğinin 0.4B (B=Temel genişliği) olduğu görülmüştür. Kohezyonlu zeminde donatının çalışmasının zemin kohezyonundan etkilendiği, donatı sayısı 6 iken taşıma kapasitesini kohezyon cinsinden 0.9c kadar arttırdığı görülmüştür. Donatılar arası düşey mesafe arttıkça taşıma kapasitesindeki değişimi gösteren eğrinin eğiminin dikleştiği ve taşıma kapasitesinin büyüdüğü görülmüştür. Donatı genişliğinin temel genişliğinin 3 katından büyük olduğu durumlarda taşıma kapasitesi sabit kalmıştır. Taşıma kapasitesi oranları (BCR) ve etkin donatı derinliği zemin kohezyonundan bağımsız çıkmıştır. Anahtar Kelimeler: Şerit temel, taşıma kapasitesi, Sonlu Elemanlar metodu, kil zemin

Mevsimsel nüfus değişiklikleri ve atıksu yönetimi üzerine bir inceleme

One of the most critical issues in terms of management of touristic areas is the variability of population throughout the year. The population increase during the peak season due to tourism imposes a stress on water resources and leads to pollution risks in the coastal areas. Coastal tourism is widely regarded as one of the fastest growing areas of the world?s tourism industry. All over the world, coastal areas are developing rapidly and are attracting more and more tourists each year. The Mediterranean is the main tourist destination in the world. The main problems of Mediterranean destinations are the seasonal and coastal concentration of tourism activities. Every year more than 250 millions of people flock to the Mediterranean coasts. Additionally, second housing increases the population during the peak season.  This increase in population brings about a peak in water demand for domestic use. Tourism activity peaks in summer, coinciding with the time when natural water availability is at its lowest. According to European Environmental Agency (EEA, 2000), tourists consume up to 300 litres (up to 880 litres for luxury tourism) and as apposed to a use of 150-250 litres of water per person per day by a regular user. Extensive landscaping, water parks, swimming pools and golf courses are typical tourist facilities that require water during the dry season. Taking the example of Bodrum, a touristic summer town in the Eastern Mediterranean region, the top reasons for preference were reported to be the sea, the sun, the beaches, its natural beauty and cultural heritage. In this case study, the resident population of the Bodrum peninsula is 118237 and this is regularly and officially recorded. However vast increases in population are observed during the peak season due to national and international tourists and second housing in the area in addition to the busy pleasure craft traffic. No doubt, knowing the correct number people in town throughout the year is one of the prerequisites of water and wastewater management. However no information about second housing and tourism population seems to be officially recorded. This work focuses mainly on the prediction of the variations in the total population of Bodrum throughout the year. Predictions were based on an investigation to quantify the monthly percentages of resident, second housing, touristic and pleasure craft populations, based on currently available data to lead to a relevant wastewater management approach and an evaluation of its implications on wastewater management. The predictions have indicated that dominated by the tourists and second housing in July and August, the population is more than fourfold of that of February. As a result of the vast seasonal variations in population together with the topographical conditions of the peninsula, wastewater disposal of in Bodrum consists of central facilities and a large number of individual biological treatment systems serving second housing sites, hotels and marinas. Treated effluent is reused for irrigation of gardens in these areas. Holding tanks, which are widely used throughout the peninsula, also provide an alternative to individual biological treatment plants. Despite the quality of reclaimed domestic wastewaters is judged by the fecal coliform standard in the Turkish environmental legislation and international guidelines (WHO 89/2006 and USEPA2004), at this time, regulatory agencies allow the use of reclaimed domestic wastewater that has been treated to essentially secondary level followed by disinfection, for landscape purposes, park and golf course irrigation. The reclaimed effluent is monitored for BOI5, COD, pH and SS. but not for pathogenic microorganisms, which may lead to health concerns.The allocation of revenues of the general budget which is determined according to residential population, is the most significant financial source for municipalities. However this allocation does not seem fair for touristic summer towns like Bodrum as the population increase during the peak season is almost four times that of resident population. Environmental protection and pollution prevention is obviously one of the main factors in the sustainability of Bodrum peninsula as a popular and preferred touristic town, as well as other towns of similar character. A thorough recording of its demographical status and a serious well-planned monitoring and control strategy regarding wastewater management and water quality will provide powerful tools towards sustainability of the area. Keywords: Seasonal population, tourism, second housing, wastewater management, Bodrum.Turizm; yerleşimlerin nüfusunu arttıran ve yıl içinde mevsimsel nüfus hareketliliklerine neden olan bir aktivite olup, özellikle Akdeniz kıyılarındaki birçok yerleşimin ekonomisinde belirleyici olmaktadır. Mevsimsel nüfus hareketlilikleri de daha çok kıyı turizmi yapılan bölgelerde görülmekte, yerleşik nüfusla birlikte ikinci konut nüfusu, turizm nüfusu ve günübirlik nüfusun toplamından oluşan yaz nüfusu, kış nüfusunun birkaç katına çıkmaktadır. Turizmin neden olduğu mevsimsel nüfus hareketlilikleri özellikle atıksu yönetimi açısından önemli problemler oluşturmaktadır. Yerleşik nüfus göz önüne alınarak yapılan tesisler yaz aylarında yetersiz kalmaktadır. Bodrum Yarımadası son 30 yılda dünyanın önemli turizm merkezlerinden biri haline gelmiştir. Yarımada da yerleşik nüfus ile ilgili kayıtlı verilere ulaşılabilmekte ancak, ikinci konut ve turizm nüfusuna yönelik sınıflandırılmış veri bulunmamaktadır. Bu çalışmada yapılan kestirimlerde yarımada genelinde toplam nüfusun yerleşik nüfusun 4, ortalama nüfusun da 2 katına çıktığı hesaplanmıştır. Bodrum’da topoğrafik yapı ve mevsimsel nüfus değişiklikleri nedenleriyle merkezi ve bireysel arıtma tesisleri ile foseptikler bir arada kullanılmaktadır. Özellikle bireysel arıtma tesisleri çıkışları sulama amaçlı kullanılmakta olup denize deşarj edilmelerine izin verilmemektedir. Bodrum yarımadasındaki 397 arıtma tesisinin 387’si bireysel arıtma tesisi olup bunların işlevlerini yerine getirdiklerinin dikkatle planlanmış bir izleme denetim mekanizmasıyla takibi halk sağlığı ve sürdürülebilirlik açısından önemlidir. Mevsimsel nüfus hareketliliklerinin belirgin olduğu turizm yörelerinde teknik bakımdan pik nüfusun, finansal bakımdan ortalama nüfusun dikkate alınması uygun görülmektedir.  Anahtar Kelimeler: Mevsimsel nüfus hareketliliği, turizm, ikinci konut, atıksu yönetimi, Bodrum

Benzo[a]anthracene'nin aktif çamur üzerine kronik etkisinin respirometrik incelenmesi

In this study, activated sludge taken from İstanbul ISKI Paşaköy Biological Treatment Plant, acclimated to synthetic peptone mixture for 6 months. Benzo[a]anthracene (B[a]A) was selected as model xenobiotic and the effect of B[a]A to the acclimated activated sludge was investigated. B[a]A is a toxic and carcinogen polycyclic aromatic hydrocarbon (PAH) and generated via cigarette smoke, diesel exhaust, commercial solvents etc. B[a]A is also listed in Environmental Protection Agency (EPA) priority pollutant list. In this study, 0.011 g/L B[a]A was added to the sequencing batch reactor (SBR). The chronic effect of B[a]A to activated sludge, were performed and monitored through respirometric studies as well as conventional parameters. The activated sludge operated 10 sludge ages for chronic effects. The chronic effect was estimated by using a multi-component model. 0.011 g/L B[a]A addition has no effect on COD removal. While biodegradation of peptone mixture, the B[a]A addition effects hydrolysis rate and PHA storage mechanism. The amount of B[a]A in activated sludge and supernatant monitored through high performance liquid chromatography (HPLC). PAHs, which are a class of xenobiotic, are unique contaminants in the environment because they are generated continuously by the inadvertently incomplete combustion of organic matter. PAHs include 70 natural and anthropogenic organic compounds constituted by aromatic rings, ranging between two and seven, and mainly derived from petroleum activities. In the 20th century there was a great increase of anthropogenic production of PAHs by combustion of fossil fuel. Beside of predominating anthropogenic sources e.g. road traffic and combustion of fossil fuels, there are also natural sources, e.g. volcanic eruptions and forest fires. PAHs consist of fused benzene rings in linear, angular or clustered arrangements and contain by definition only carbon and hydrogen atoms. However, nitrogen, sulfur and oxygen atoms may readily substitute in the benzene rings to form heterocyclic aromatic compounds, which are commonly grouped with the PAHs. Due to their toxicity, 16 PAHs were listed by U.S. Environmental Protection Agency (USEPA) as priority pollutants, which should be monitored in aquatic and terrestrial ecosystems. The increase in the hydrophobicity and electrochemical stability is associated with an increase in the number of benzene rings and angularity of a PAH molecule. The high molecular weight (HMW) PAHs are more persistent and recalcitrant than the low molecular weight (LMW) PAHs. The stability and distribution of the PAHs in the natural environment is influenced by the configuration of the aromatic rings, physico-chemical properties. PAHs are considered as important environmental pollutants since many of the compounds in this group are of major concern to environmental agencies and researchers worldwide due to their mutagenic, toxic, genotoxic and carcinogenic properties depending upon the number and configuration of the benzene rings and the presence and position of their substituents. Microorganisms, such as bacteria and fungi, may transform the PAHs to other organic compounds or to inorganic end products such as carbon dioxide and water. The latter process has been referred to as mineralization. Some PAH-degrading microorganisms, primarily bacteria, are capable to use the PAHs as a carbon and energy source, and may thus transform the contaminants into molecules that can enter the organisms’ central metabolic pathways. Other microorganisms have the capacity to degrade PAHs, while living on a widely available substrate. Such co-metabolism does not always result in growth of the microorganism, and sometime the cosubstrate, i.e. the PAH, is only transformed into another compound without any apparent benefit for the organism. Keywords: Xenobiotic, PAH, activated sludge, Benzo[a]anthracene, modeling, respirometer.Benzo[a]anthracene (B[a]A), toksik ve karsinojen bir polisiklik aromatik hidrokarbon (PAH) olup sigara dumanında, dizel araçların egzoz dumanında, yangın sonucu çıkan dumanlarda, ticari solventlerde vb. bulunmaktadır. B[a]A, Amerika’daki Çevresel Koruma Ajansı (Environmental Protection Agency - EPA) tarafından öncelikli kirleticiler listesinde yer alan 16 PAH’tan biridir. Bu çalışmada, benzo[a]anthracene (B[a]A), model zenobiyotik olarak seçilmiş ve B[a]A’nın sentetik pepton karışımına alışmış aktif çamur üzerindeki kronik etkisi incelenmiştir. Aklimasyon çalışmaları İSKİ Paşaköy İleri Biyolojik Atıksu Arıtma Tesisi’nden alınan biyokütle ile başlatılmış, hidrolik bekletme süresi 1 gün olan doldur-boşalt reaktörler çamur yaşı 10 gün olarak işletilmiştir. Kronik deneylere başlamadan önce sistem 3 ay süre ile organik madde olarak evsel atıksuyu en iyi temsil ettiği düşünülen sentetik pepton karışımı (600 mg KOİ/L) ile beslenmiştir. Kronik etkinin belirlenmesi için günde iki çevrim ile çalıştırılan çamur yaşı 10 gün olan bir ardışık kesikli reaktör (AKR) sistemi kullanılmıştır. Sadece sentetik pepton karışımı ile beslenen AKR sistemi, kronik etkinin belirlenmesi için 21 gün boyunca sabit miktarda B[a]A (0.011 g/L) eklenerek izlenmiştir. B[a]A’nın aktif çamur üzerine olan kronik etkisi, respirometrik yöntemin yanı sıra konvansiyonel parametreler ile de incelenmiştir. 0.011 g/L B[a]A eklemesinin KOİ giderimi açısından AKR sistemi üzerine bir etkisi olmadığı anlaşılmıştır. Yürütülen modelleme çalışması, respirometrik testler aracılığıyla Modifiye Edilmiş Aktif Çamur Modeli No. 3’teki kinetikler hakkında deneysel veri desteği ve bilgi sağlamıştır. Pepton karışımının biyolojik parçalanmasında B[a]A ilavesi hidroliz hızında bir artışa neden olmuştur. Bunun yanısıra sistemin depolama mekanizması üzerinde de bir etkisi olduğu görülmüştür.  Anahtar Kelimeler: Zenobiyotik, PAH, aktif çamur, Benzo[a]anthracene, modelleme, respirometre

Zemin büyütmesi ve yerel koşulların spektral ivmeye etkisi

One of the most commonly encountered problems in geotechnical earthquake engineering is the evaluation of soil amplification. Soil amplification can be defined as the increase in the amplitudes of the earthquake waves. Soil amplification is mostly affected by the local soil conditions such as bedrock depth, the thickness and dynamic characteristics of the soil layers, the limited width of the soil layers and the topographical properties. The variation of ground motion is denoted as an amplification or de-amplification of amplitudes at all frequencies, which is dependent on many parameters. Some of them are inherent of the dynamic soil behavior and its physical properties such as shearing modulus, damping ratio, shear wave velocity, plasticity index etc., and others are related to the characteristics and the intensity of the incoming wave-field, geometrical features like surface/bedrock topography, lateral geological discontinuities etc. Site effects play an important role in the variation of ground motion intensity distribution during earthquakes and therefore they have to be evaluated correctly for the design of earthquake resistant buildings. In this study, in order to investigate the effects of the local soil conditions to the soil amplification, an idealized simple model consisting of a crest and basin geometry was selected. One (1D) and two-dimensional (2D) dynamic analyses were performed for the two different cases of the top basin layer as high plasticity clay and silty sand, and the obtained results were compared. Six bedrock acceleration records with different frequency content were used in the dynamic analyses. Within the scope of this study, EERA and Flushplus softwares were used in the 1D and 2D dynamic nonlinear dynamic analyses, respectively. Flushplus is a finite element dynamic analysis software that is based on equivalent linear method and it works in the frequency domain. Viscous dashpots that were calculated proportional to the shear and pressure waves of the relevant layers were set at the boundaries of vertical and horizontal layers in the 2D model. The variations of the soil amplifications with the surface geometry were investigated by the 1D and 2D dynamic analyses. The 2D/1D spectral acceleration ratios were calculated for different period values at the lowland and highland regions of the 2D model in order to understand the difference between 1D and 2D dynamic behaviors. It was understood that the peak acceleration value of the bedrock ground motion was amplified by twice in case the top basin layer was selected as silty sand and the soil amplification value reached to 4.5 for the case of top basin layer as high plasticity clay. When the top soil layer was high plasticity clay, the 2D/1D spectral acceleration ratios reached their maximum values for high frequencies at the basin edge section where X/D is between 0.5 and 0.75, while X indicates the horizontal distance and D is the depth. As approaching to the mid part of the basin, 2D/1D spectral acceleration ratios reached their maximum values at lower frequencies because of the wave transformations that occur at basin edges.  The difference between the results of 1D and 2D dynamic analyses decreased for higher frequencies with the increasing distance from the edge of the basin. When the top layer was selected as sand, the 2D/1D spectral acceleration ratios showed similar behavior for the lower frequencies, but an increase in the 2D/1D values was noticed at higher frequencies mainly for the sections 0.75Because of the limited width of the soil layers in basin and vertical boundary conditions, the 2D predominant period of the model took a lower value when compared with the results of 1D dynamic analysis. As a result the spectral acceleration values obtained by the 2D dynamic analyses were different from the spectral acceleration values calculated by 1D dynamic analysis especially at higher frequencies. The peak surface acceleration values that were calculated by the 2D analyses approached to each other regardless of the basin geometry when the non-linear behavior became dominant at the top layers. Topographical effects were negligible for very low frequencies, while the effects became significant for high frequencies or low wavelengths comparable to the geometric characteristics of the model. The intensity of the bedrock acceleration and the variation of dynamic properties with soil type play an important role in the development of non-linear dynamic behavior. Keywords: Soil amplification, local conditions, 2D dynamic analysis, spectral acceleration ratio.Bir sahada yerel koşullara bağlı olarak oluşabilecek zemin büyütmesinin belirlenmesi, geoteknik deprem mühendisliğinin önemli konularından birini oluşturmaktadır.  Anakaya seviyesinde bir kaynaktan açığa çıkan enerjinin oluşturduğu sismik dalgalar yayılımları sırasında, içinden geçtikleri ortamların özelliklerinden etkilenmekte; süre, frekans ve genliklerinde değişimler olabilmektedir. Deprem dalgalarının yüzeye yakın zemin tabakaları içinden geçerken genliklerinde meydana gelen artış zemin büyütmesi olarak tanımlanmaktadır. Zemin büyütmesi anakaya derinliği, zemin tabakalarının kalınlığı, cinsi ve dinamik özellikleri, tabakaların yanal süreksizliği ve topografik özellikler gibi yerel koşullardan etkilenmektedir. Bu çalışmada, yerel koşulların zemin büyütmesine etkisini incelemek amacıyla tepe ve ovadan oluşan bir model seçilmiş, ova bölgesinde zemin kesitinin en üstünde yüksek plastisiteli kil ve siltli kum tabakasının olması durumu için, altı anakaya depremi kullanılarak bir (1D) ve iki boyutlu(2D) dinamik analizler yapılmıştır.  Yüzeyde 19 farklı noktada farklı depremler için elde edilmiş ivme zaman geçmişleri ve ivme spektrumlarının mesafeye bağlı değişimleri incelenmiştir. Anakaya ivmelerinin, üst tabakanın kum olması durumunda zemin yüzeyinde ortalama iki kat, üst tabakanın kil olması durumunda ise daha fazla arttığı belirlenmiştir. Üst tabakanın kil olması hali için özellikle anakaya dalımının ova tabanına ulaştığı bölgenin izdüşümünde yer alan kesimlerde, spektral ivme oranlarının yüksek frekanslarda en büyük değerini aldığı, ova ortasına doğru 1D ve 2D analiz sonuçları arasındaki farkın azaldığı belirlenmiştir. 1D analizlerde sonlu farklar yöntemine dayanan, eşdeğer lineer malzeme modeli ile çalışan EERA yazılımı, 2D analizlerde ise frekans ortamında çalışan Flushplus sonlu elemanlar programı kullanılmıştır. Anahtar Kelimeler: Zemin büyütmesi, zemin koşulları, 2D dinamik analiz, spektral ivme oranı

Küçükçekmece Lagünü'nde (İstanbul) "Küçük Buzul Çağı" ve "Orta Çağ Ilık Dönemi" çökel kayıtları

This study focuses on the sedimentary records of climatic changes in the Küçükçekmece Lagoon over the last 1300 a. The main objective of the study is to investigate the envirenmental conditions in Istanbul during the Little Ice Age (LIA, 600-100 a BP) and Medieval Warm Period (MWP, 1000-600 a BP), which occurred in Europe during the last millenia. The Küçükçekmece Lagoon is situated on the northern shoreline of the Sea of Marmara, west of İstanbul. It has a surface area of 15 km2, maximum depth of 20 m and water volume of 145x106m3. The lagoon is connected to Sea of Marmara via a 2 km long natural narrow channel. The main freshwater input is mainly from small sterams and groundwater springs (Altun el al., 2009). The Little Ice Age was a period of mountain glacier expansion during 16th–mid 19th century period during which European climate was strongly impacted (Bradley and Jones, 1993; Jones et al., 1998; Mann et al., 1998, 1999; Mann, 2002). This period begins with a trend towards enhanced glacial conditions in Europe following the warm conditions of the so-called MWP. The LIA terminated with a dramatic retreat of the Alpine glaciers during the 20th century. During this period the temperature was 0.5-0.7ºC lower than 1950’s avarage. The previous Holocene climate studies in Turkey are rare and mostly confined to the Black Sea and Central Anatolia regions (e.g., Jones et al. 2006; Fleitmann et al, 2009; Kuzucuoğlu et al, 2011). In view of the variability of the present-day climate of Turkey mainly because of its geographic location and topography, and scarcity of data in NW Turkey, the recovery of late Holocene climate records from Küçükçekmece Lagoon (İstanbul) is very important. For this prupose we collected one short interface core (0.6 m) and one 4.5 m long piston core from the Küçükçekmece lagoon. The cores were analyzed for physical properties (magnetic susceptibilty: MS, gamma density, and resistivity) at 5 mm resolution using Multi Sensor Core Logger (MSCL), and multi-elemental analyis at 0.2 mm resolution using XRF (X-Ray Fluoresance) core scanner. The cores were then sampled at 50 mm intervals for total inorganic carbon (TIC), total organic carbon (TOC), and micropaleontological (ostracoda and benthic foraminifera) analysis. The micropaleontological analysis was made in the sand size fraction under binocular microscope. The ostracoda and benthic foraminifera individuals are identified. Suitable species of ostracoda (Loxoconcha sp.) and benthic foraminifera (Ammonia sp.) were picked and analyzed for the stable oxygen and carbon isotope analysis. Four samples were dated using AMS 14C analysis. The ages were calibrated to calendar year by CALIB 6.0 software using INTCAL 9.0 and MARINE 9.0 options. The short and long cores were correlated using the MS profiles and a continuous composite section was constituted. The lithology of the composite core section in general consists of homogenous olive green mud that rarely includes layers of plant remains and laminated intervals. The benthic foraminifera and ostracoda distribution suggests that the lagoon has been brackish over the last 1300 a. The age model was obtained from the calibrated AMS C-14 datings of two total bulk organic carbon and two plant remain layers. The multiproxy data were used to analyze the evaporation/precipitation changes in sediment cores. Increasing MS (SI), Ti (cps) values and decreasing of d18O-d13C (‰ VPDB), Ca/Ti, Sr/Ca ratio and TOC (%wt) values were interpreted to show wet conditions. We also modified the Leng and Marshall’s (2004) d18O-d13C model for the Küçükçekmece Lagoon. The multi-proxy physical properties, geochemical and stable O- and C-isotope data in Küçükçekmece Lagoon show that wet conditions prevailed during ca 220-70 a BP, 1300-750 a BP and dry conditions during ca 70- 0 a BP, 750-220 a BP. The late (250-100 a BP) and early episodes (600- 250 a BP) of the Little Ice Age period was wet and and dry, respectively. During the the Medieval Warm Period (1000-600 a BP) wet conditions occurred in the region. The climate records also show that decadal-scale wet periods occurred during 340-270 a BP and 680-610 a BP, and dry periods during ca 1050 – 1000 a BP, 1130-1080 a BP and 1260-1210 a BP. Climatic records of Küçükçekmece Lagoon shows similarity with European records in Little Ice Age and Medieval Warm Period. Keywords: Küçükçekmece Lagoon (İstanbul), Little Ice Age, Medieval Warm Period.Küçükçekmece Lagünü çökellerinde Günümüzden Önce (GÖ) 1300 yıldaki iklim değişimleri ile Avrupa’da soğuk dönem olan Küçük Buz Çağı (GÖ 600-100) ve öncesinde yaşanan Orta Çağ Ilık Dönemi’in (GÖ 1000-600) İstanbul’daki koşulların karşılaştırmasını amaçlamaktadır. Bu nedenle Küçükçekmece Lagünü’nden uzunlukları 0.6 ve 4.5 m olan iki çökel karotunda; 5 mm çözünürlükle Çok Sensörlü Karot Logu Alıcısı (Multi Sensor Core Logger, MSCL) ile manyetik duyarlılık, P-Dalga hızı, yoğunluk ve öz direnç; 0.2 mm çözünürlükle XRF (X -Ray Fluorescence) tarayıcısı ile 25 elementin analizi ve 50 mm çözünürlükle toplam inorganik (TIC)–organik (TOC) karbon analizleri yapılmıştır. Ayrıca 50 mm aralıkla örnekler yıkanıp elenerek elde edilen çökeller içinden belirlenen ostrakod (Loxoconcha sp.) ve bentik foraminifer (Ammoniasp.) türleri toplanarak duraylı oksijen ve karbon analizleri yapılmıştır. Karotlar AMS 14C yöntemleri ile yaşlandırılmıştır. Elde edilen sonuçlara göre Küçük Buz Çağı’nın (GÖ 600-100) GÖ 250-100 yılları arasındaki son bölümünde yağışlı; ilk bölümünde (GÖ 600-250 yılları arası) ise bölgede kurak koşulların egemen olduğu anlaşılmıştır. Buna göre, Ortaçağ Ilık Dönemi (GÖ 1000-600 yılları) ve Karanlık Çağ Soğuk Dönemi’nin (GÖ 1500-1000 yılları) son evresini içeren GÖ 1200-600 yılları arasında yağışlı ve GÖ 1300-1200 yılları arasında ise kuraktır. Anahtar Kelimeler: Küçükçekmece Lagünü (İstanbul), Küçük Buz Çağı, Ortaçağ Ilık Dönemi

Karışık karbon kaynağı ortamının nişasta giderim performansı ve bakteriyel kompozisyon üzerine etkisi

The microbial processes have been extensively investigated for the efficiently design and operation of the activated sludge systems. The experimental studies have often focused on the single representative carbon source, although, microorganisms have to remove wastewater which is the mixture of several different type carbon sources. Under such conditions, bacteria often utilize one carbon source preferentially and other carbon sources are consumed only, when the preferred one is exhausted. The carbon source providing the best growth rate and/or growth yield is preferred, and the successive utilization of the substrates is often represented (Monod, 1942). In the environmental engineering point of view, it is important to understand the interaction between the removal mechanisms of different carbon sources which have a different degree of complexity. Although, recent studies have mainly focused on the biodegradation kinetics of the industrially produced starch as the only pollutant in wastewater, the simultaneous use of multiple substrates, such as the co-treatment of the industrially produced wastewater with the domestic wastewater produced in the facility, can lead to differences in biodegradation kinetics of any individual organic constituent as well as in the bacterial community. The researches with bacteria and higher organisms have revealed that selective carbon source utilization is common and that glucose is the preferred carbon source by many organisms. Moreover, the presence of glucose often prevents the use of other, secondary, carbon sources (Gorke and Stülke, 2008). In a study carried out under aerobic conditions with a mixture of similar type substrates (i.e. a mixture of acetic, lactic and propionic acid), a strong decrease in the removal rates of acetic and lactic acid was observed when treated in the presence of another substrate (Dionisi et al., 2004). This strong interaction among different substrates was explained with the interconnected pathways utilized by microorganisms for the removal of these substrates. Less clear evidences are available when dealing with mixtures of different type substrates, like volatile fatty acids and carbohydrates. Carta et al. (2001) reported that there were no differences in the uptake rate of acetate and glucose under mixed substrate environment compared to single substrate environment. In addition to the substrate uptake rates, the degradation kinetics and rates of the storage compounds were also reported as the same. In another study, when starch and acetate were treated together, slightly lower rates were observed in terms of individual carbon removal of acetate and starch, as well as respective storage of PHA and glycogen compared to treatment of substrate alone (Karahan et al., 2008). The fate of slowly biodegradable carbon source was evaluated in a SBR acclimated to starch as the sole carbon source and mixture of starch and acetate. The SBRs were operated with the same organic loading rate at two different sludge ages. Acetate, which is the one of the volatile fatty acid, was used as secondary pollutant as the volatile fatty acids have been reported as the main constituents of the domestic wastewaters. Although, the carbon source was fed to the SBRs in continuous mode throughout the cycle, the production of the storage polymer, namely glycogen, was observed in all SBRs. The relatively constant storage ratios were observed in SBRs fed with different carbon sources. The COD removal efficiency of the SBRs operated at the sludge ages of 8 days was significantly affected from the presence of acetate in the environment, although the COD removal efficiencies were constant at the sludge ages of 2 days independently from the presence of the secondary substrate. The bacterial characterization studies performed with fluorescent in situ hybridization (FISH) showed the decrease in the Actinobacteria phylum which was reported as the main starch consumer when the starch removal was performed in the multiple substrate environments at the sludge ages of 8 days. On the other hand, the detection of different groups at different sludge ages indicated the importance of the sludge age for evaluating treatment performance in activated sludge systems.  Keywords: Starch; dual substrate; substrate removal kinetic; FISH, activated sludge system. Evsel atıksuların arıtımında yaygın olarak kullanılan aktif çamur sistemlerinin başlıca kirletici parametre olan karbon kaynağının giderim performansı açısından değerlendirilmesi, sistemin en uygun tasarım kriterlerinin belirlenmesi açısından büyük önem taşımaktadır. Bu konuda yürütülen çalışmalarda, evsel atıksuların içeriğini yansıtacak şekilde seçilen tek bir karbon kaynağı model substrat olarak kullanılmaktadır. Fakat farklı karbon kaynaklarının bir arada veya ayrı ayrı arıtılmaları mikrobiyal dinamikler doğrultusunda farklı giderim performansları elde edilmesine neden olabilmektedir. Bu kapsamda, çalışmanın amacı evsel atıksuların karbonhidrat içeriğini yansıtan ve hedef karbon kaynağı olarak ele alınan nişastanın, başka bir karbon kaynağı ile beraber aktif çamur sisteminde arıtılması durumunda, giderim veriminde ve bakteriyel komposizyonda oluşabilecek farklılıkların tespit edilmesidir. 2 farklı çamur yaşında işletilen sistemde, ikincil karbon kaynağı olarak evsel atıksu kompozisyonun büyük bir kısmını oluşturan uçucu yağ asitlerini temsilen asetat seçilmiş ve bu sayede farklı giderim mekanizmaları ile giderilen farklı yapıdaki karbon kaynaklarının birbirlerine etkileri araştırılmıştır. Elde edilen veriler, 8 gün çamur yaşında nişasta giderim performansının, ortamda asetatın bulunmasından etkilendiğini ancak, 2 gün çamur yaşında karışık karbon kaynağı ortamının nişasta giderim performansı bakımında önemli bir etkisi olmadığını göstermiştir. Farklı koşullarda işletilen reaktörlerde bulunan baskın türlerin Flüoresanlı yerinde hibritleşme tekniği (FISH) yöntemi ile analizi sonucunda, 8 gün çamur yaşında karışık karbon kaynağı ortamının sadece mikrobiyal aktivite üzerinde değil aynı zamanda mikrobiyal seleksiyon üzerinde de etkisi olduğunu göstermiştir. Ayrıca, deneysel sonuçlar, çamur yaşının sistem performansı ve bakteriyel kompozisyon üzerinde etkili bir parametre olduğunu ve bu nedenle aktif çamur tesislerinin tasarımında öncelikli olarak ele alınması gerektiğini ortaya koymuştur.  Anahtar Kelimeler: Nişasta; karışık karbon kaynağı; karbon kaynağı giderim kinetiği; FISH; Aktif Çamur Sistemi.&nbsp