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Van Gölü'nün sedimentolojik-stratigrafik evrimi ve göl seviyesi değişimleri
Van Gölü konumu gereği iklime duyarlı bir bölgede, Doğu Anadolu yüksek platosu, üzerinde yer almaktadır. Arap plakasının Avrasya levhasıyla çarpışması sonucunda platonun yükselmesi yaklaşık 12 Myıl'da başlamıştır. Göl; batıda ve kuzeyde Kuvaterner volkanları, güneyde Paleozoyik Bitlis Masifi ile çevrilidir. Doğuda ise yığışım karmaşığına ait birimler ve Plio-Kuvaterner çökelleri yer almaktadır. Ayrıca bölge, Kuzey Atlantik, Sibirya yüksek basınç ve orta enlem subtropikal yüksek basınç sistemlerinin kesiştiği bir noktada, Doğu Anadolu ve Akdeniz arasındaki iklime hassas bir bölgede yer almaktadır. Bulunduğu bu konum itibari ile iklim çalışmaları açısından önem arz etmesinin yanında gölün varvlı çökelleri ile paleoiklim, tektonik ve volkanoloji çalışamaları bakımından da bulunduğu bölgenin karmaşık yapısına ışık tutması açısından ilgi odağı olmuştur. Van Gölü Havzası, doğu-batı uzanımlı Muş depresyonunda Arap, Avrasya levhalarının çarpışması ile şekillenmiştir. Paleotektonik olarak sınıflandırılan bu birimlerin üzerine Miyosen-Kuvaterner yaşlı Neotektonik döneme ait birimler gelmektedir. Alt Miyosen-Pliyosen'de denizin çekilmesi ile bölge aşınma etkisinde kalmış ve bu dönemde genç volkanizma ürünleri bölge yüzeyini kaplamaya başlamıştır. Temelde yer alan birimlerin üzerine, göl içerisinde uyumsuzlukla gelen Pleyistosen-Kuvaterner çökelleri gelmektedir. Bu birimler içerisinde ise, Kuvaterner'de aktif olan Nemrut, Süphan ve İncekaya volkanlarına ait tefra birimleri yer almaktadır. Gölün oluşum yaşı volkanizma ve jeolojik çalışmaların yanı sıra ICDP PALEOVAN projesi kapsamında yapılan çalışmalar ile GÖ 600 kyıl olduğu ve Nemrut Volkanının faaliyete geçmesi ile volkanik bir set gölü olarak oluştuğu anlaşılmaktadır. Yapılan çalışmalarda, KB-GD sıkışma rejimi altında doğrultu atımlı fayların da etkisiyle şekillenen, başlangıçta Muş Havzası ile bağlantısı olan göl, ilk önce tatlı su gölü olarak oluşmuş, daha sonra Nemrut Volkanı'nın faaliyetleri sonucu gölün dışarı akışı kesilerek, volkanizma, kayaç ayrışması ve buharlaşmanın etkisi ile bugünkü kapalı, acı-alkali göl halini almıştır. Van Gölü, 607 km3 hacim, 3570 km2'lik alan ve 450 metrelere varan derinliği ile Türkiye'nin en büyük gölüdür. Van Gölü, 450 m derinliğindeki Tatvan Havzası, 260 m derinliğinde Kuzey Havzası (NB), batıda kuzeydoğudaki kuzey-kuzeydoğu yönünde yönelim gösteren Ahlat (AR) ve Kuzey Sırtı, kuzeydeki Erciş Körfezi ve Erek Fanı, doğuda Doğu Şelfi ve Doğu Fanı gibi birkaç morfolojik bölgeden oluşmaktadır. Bu tez çalışmasında, gölün sedimanter, tektonik ve paleoiklimsel evrimini anlamak için, göl içerisinde piston karot ve karotlu sondaj çalışmaları yanında sismik yansıma ve batimetri verileri toplanmış ve yorumlanmıştır. Tez çalışması kapsamında değerlendirilen 4-5 m uzunluğundaki piston karotlar Van İlinin batısında Doğu şelfi olarak adlandırılan bölgeden alınmıştır. Sondaj karotları ise ICDP PALEOVAN projesi kapsamında gölün kuzeybatısında yer alan NB olarak adlandırılan bölgede 245m su derinliğinden ve AR olarak adlandırılan bölgede 375m su derinliğinden alınmıştır. Göl tabanı çökellerinden alınan NB ve AR karotların uzunluğu göl tabanından itibaren sırası ile 145 m ve 220 m'dir. Alınan bu çökel karotlarda, çok sensörlü karot tarayıcı (Multi Sensor Core Logger – MSCL) ile yapılan ölçümlerden, karot boyunca p-dalgası hızı, manyetik geçirgenlik, gama yoğunluk ve özdirenç gibi fiziksel özellikleri hesaplanmıştır. P-dalga hızları ve gama yoğunlukları kullanılarak üretilen yapay sismogramlar yardımıyla çökel karotları ile sismik kesitler deneştirilmiş ve gölün sedimentolojik ve tektonik evrimi ile ilişkilendirilmeye çalışılmıştır. μ-X-Ray Florescene (XRF) tarayıcı ile çökel karotların derinlik boyunca element analizleri yapılarak Ca/Fe, Ca/Ti gibi iklimden etkilenen element oranları ile göl su seviyesi ve iklim değişimleri ile ilişkisi çalışılmıştır. Bunun yanı sıra K, Zr, Na, gibi elementlerin gama yoğunluk ve manyetik geçirgenlik verilerinin birlikte değerlendirilmesi ile çökel istifteki volkanizma ürünü çökelimlerin tespitine yönelik çalışmalar yapılmıştır. XRF tarayıcıdan elde edilen radyografi görüntülerinden tez çalışması kapsamında MATLAB yazılımı kullanılarak geliştirilen algoritma ile mevsimsel değişimlere bağlı olarak çökelen laminaların sayımı yapılarak, yıllık çökelimi oluşturan varvların kalınlığı hesaplanmış ve karot boyunca, yine karot çökelleri içerisinden alınan bitki parçası örneklerinden yaptırılan radyokarbon ve tefra örneklerinden alınan 40Ar/39Ar tarihlendirme analizleri ile, karot istiflerininin kronolojisi oluşturulmuştur. Bu kronoloji Grönland buzul karotları (NGRIP, intGRIP) ve denizel izotop dönemleri (MIS) ile desteklenmiştir. Kronolojiye bağlı jeokimyasal-sedimentolojik verilerin spektral sinyal analizi yapılarak, buradan iklime ait döngüsellikler belirlenmiş ve geçmiş iklim modellemesi yapılmıştır. Spektral analizin yanı sıra değişik periyotlarda çökel kalınlıkları grafiklenerek çökelim hızındaki farklılıklardan kurak/soğuk ve nemli/ılıman iklim dönemlerinin belirlenmesine çalışılmıştır. Oluşturulan bu iklim modelinin, tez çalışması kapsamında değerlendirilen diğer verilerden elde edilen bulgular ile karşılaştırılması yapılarak, göl su seviyesi değişimleri ve bu değişimin üzerinde iklimin etkisi tartışılmıştır. Verilerin değerlendirilmesi sonucu oluşturulan iklim modeli ve göl su seviyesi değişimleri, Van Gölü'ndeki ve literatürdeki diğer çalışmaların sonuçları ile karşılaştırılmıştır. Toplanan sismik yansıma ve batimetri verilerinden gölün batimetri haritası oluşturulmuş. Sismik yansıma verilerinin yorumlanması ile göl çökellerinin GÖ 600 kyıl'dan bu yana Tatvan Havzası'nda ve yaklaşık GÖ 90 kyıl'dan bu yana Kuzey Havzası'nda süreklilik gösterdiği sonucuna ulaşılmıştır. Çok kanallı sismik yansıma kesitleri ile oluşturulan yaş modeli korelasyonu ile günümüz göl su seviyesinin yaklaşık 200 m altında D1 deltasının GÖ 20-17 kyıl, 105m altında D1a deltasının G.Ö 65-60 kyıl, 150m altında D2 deltasının GÖ 115-106 kyıl, 225 m altında D3 deltasının GÖ 166-142 kyıl, 300 m altında D4 deltasının GÖ 195-169 kyıl, 375m altında D5 deltasının GÖ 270-234 kyıl ve 450m altında D6 deltasının 400-350 kyıl aralığında çökeldikleri belirlenmiştir. Yüksek çözünürlükte sismiklerde ise, günümüz göl su seviyesinin 60 m altında GÖ 4-3 kyıl göl seviyesine ait klinoform ile, 30 m, 20 m ve 15 m altında tarihlendirilemeyen; ancak GÖ 3 kyıl'dan sonrasında, olasılıkla Yunan Karanlık veya Demir Çağı Soğuk Dönemi, Avrupa Karanlık Çağı ve Küçük Buzul Çağı dönemine ait olan düşük göl seviyesine ait delta ve kıyı düzlükleri (taraçalar) tanımlanmıştır. Van Gölü içerisinde sualtı kanal sistemleri, Doğu Şelfi'nde ve Erciş Boğazı'nda oldukça gelişmiş bir yapı göstermektedir. Kara üzerinde yer alan akarsu drenaj sistemi ile bağlantılı olarak göl içerisinde 100 m'den daha fazla su derinliklerine kadar uzanırlar. Genel olarak kanallar 50 m kadar derin ve 500 m genişliğindedir. Şelf üzerinde ve eğimli alanlarındaki sualtı kanal sistemleri, Van Gölü su seviyesinin günümüze kıyasla, G.Ö 15 kyıl'da 200m ve Younger Dryas (YD) döneminde 70m gibi göl su seviyesinin daha düşük olduğu dönemlerde gelişmiştir. Varv kalınlıklarından yıllık çökelim hızları hesaplanmıştır. Kuzey Havzada göl çökelleri türbidit ve tefra ardalanmalı şekilde çökelmiştir. Burada tefra ve kütle akması birimleri hesaba katılmadan elde edilen Holosen ve en geç Pleyistosen dönemindeki çökelme hızları; 5,8-12,65 kyıl arasında 0,43 mm/yıl ile en düşük, 12,65-13,89 kyıl arasında 3,72 mm/yıl ile en yüksek çökelme hızlarına sahip dönemlerdir. Holosen'deki ortalama çökelim hızı ise 1,54 mm/yıl'dır. Kuzey Havzası'ndaki çökelim hızı, Tatvan Havzasındaki ve Doğu Deltasındaki çökelimden kabaca iki kat daha hızlıdır. Gerek AR sondajından gerekse kısa karotlardan elde edilen çökelim hızları yaklaşık 0,4-0,7 mm/yıl arasındadır. Varv kalınlıklarının spektral dekompozisyonu ile iklimsel periyodların belirlenmesi ve bu periyodlar ile oluşturulan geçmiş iklim modellerinin literatürde yer alan Bond, Heinrich (H), Dansgaard-Oeschger (DO), güneş aktivitesi minimumları ve tarihsel olaylar ile uyumu Van Gölü'ndeki çökelimin iklimsel dinamikler ile uyumlu olduğunu göstermektedir. Aynı zamanda bu uyum, birim zamanda çökel istifin kalınlığının bilinmesi ile geçmiş iklim modelinin oluşturulabileceğini göstermiştir. İklim modelinden elde edilen sonuçlara göre; GÖ 82-81 kyıl, GÖ 71-69 kyıl, GÖ 62-60 kyıl, GÖ 58-GÖ 55 kyıl, GÖ 38-35kyıl, GÖ 18-16 kyıl, GÖ 5-4,8 kyıl, 4,4-4,2 kyıl, GÖ 2,7-2,6 kyıl, GÖ 1,6-1,2 kyıl (MS 450-800), 0,7-0,45 kyıl (MS 1300-1550), MS 1790-1840 ve MS 1880-1950 göreceli en soğuk dönemler; GÖ 87-82 kyıl, GÖ 65-62 kyıl, GÖ 47-43 kyıl, GÖ 32-30 kyıl, GÖ 22-21 kyıl, GÖ 8-5 kyıl, GÖ 4,8-4,4 kyıl, GÖ 3,2-3,15 kyıl, GÖ 2,6-2,5 kyıl, GÖ 1,8-1,65 kyıl (MS 200-450), GÖ 1,2-0,95 kyıl (MS 800-1050), MS 1550-1790, MS 1840-1880 ve MS 1950'den günümüze göreceli sıcak dönemler olarak iklim modelinden elde edilmiştir. Tektonik rejimin sürekliliği bölgede sıkışan havzaların daralarak D-B ve KB-GD doğrultulu kıvrımlanmasına ve volkanizma ile beraber havzaların bölünmesine sebep olmuştur. Van Gölü içerisinde yer alan Kuzey Sınır Fayı (KSF) boyunca oluşan AR ve Kuzey Sırt (KS), gölün kuzeyinde yer alan havza ile Tatvan Havzası'nı birbirinden ayırmaktadır. Muş Havzası ile Van Gölü Havzası'nı ise, Üst Miyosen'de Avrasya Levhasının altına dalan okyanus kabuğunun kopması ile açılan pencereden giren magma sonucu Kuvaterner başlarında geliştiği öne sürülen Nemrut Volkanı ayırmaktadır. Havzayı güneyden sınırlayan Güney Sınır Fayı (GSF) boyunca benzer özellikteki volkanik kraterlerin yer alması, magmanın yüzeye ulaşmasında bu fayın etkisinin olduğunu göstermektedir. KB-GD yönlü sıkışma rejimi altında, genel olarak KB-GD yönlü normal fay sistemi gelişmiştir. Bu fay sistemi boyunca karbonat kayaç birimlerinin yer aldığı Adilcevaz ve Tatvan açıklarında bikarbonatça zengin yer altı suyu ile beslenerek, sismik kesit ve batimetri verilerinde de açık bir şekilde gözlemlenen, boyları 30 m'ye varan mikrobiyolitler oluşmuştur. Gölün güney şelfinde, sismik ve batimetri verilerinden KB-GD doğrultulu düşey bileşene sahip sol yanal atımlı bir fay belirlenmiştir. Bu fay büyük olasılıkla 9 Kasım 2011'de meydana gelen Mw= 5,7 büyüklüğündeki Edremit depreminin kırığıdır. Ayrıca Erciş Boğazı'ndan güneye yönelen kanal sistemlerinin de fay kontrollü geliştiği anlaşılmıştır. Erciş Boğazı'nda yer alan sismik kesitte gözlenen fayın düşey atım hızı 0,43 mm/yıl olarak hesaplanmıştır.
Modeling spatial distribution of oriental beech (fagus orientalis): Past, present and future
Climate change affects forest biomes more severely than ever, even with the ~1°C temperature warming so far. Geographical distributions of these biomes are linked to warming temperatures and decreasing precipitation. Species try to adapt to this change by changing these geographical barriers. Recent warming not only impacted the survival rates of most tree species, also increased risks in handling extreme events. Fagus orientalis is a temperate, deciduous, broad-leaved species, which covers a wide area from the eastern Balkans through Turkey, Caucasia, Crimea and northern Iran, including the Amanos Mountains in the south, with a large elevational distribution from sea level to 2100 m. Beech has an important role in terms of dominating forests and creating new ecosystems, also it is used by many industries. Several research indicate that these species are disturbed by changing the climate in terms of increasing temperature and decreasing precipitation. Because of its importance in forestry, industry and ecosystem Fagus sp. were the focus of interest in this study. We conducted species distribution model simulations with five different algorithms embedded in biomod2 R package – BIOCLIM, GAM, GLM, RF, MaxEnt – and with environmental data from the climate of the present, past, and future from Wordclim version 1.4, as well as digital elevation model for altitude from NASA. Our simulations covered an area in Eurasia where Fagus sp. is seen, exact coordinates of 18 – 62 East and 33 – 51 North. We verified our model with present-day classifications, which fitted well the distributional data obtained from General Directorate of Forestry and EUFORGEN project. These models were used to 'predict' distributions through climate changes spanning Last Glacial Maximum (21,000 bp), Mid-Holocene (6,000 bp), 2050 and 2070 obtained from two global climate models, MIROC-ESM and CCSM4. We observed that F. orientalis distribution is toward the northeast from its present distribution, where mountainous regions are intense, colder and wetter climates are available according to future conditions. These results led us to verify that drier climate and higher temperatures are considered as limitations to these species. Additionally, we could identify refugia areas for this particular species in the past which might lead to new studies. We believe that the outcomes of this study would help improving management and conservation plans for Fagus orientalis in order to protect it from severe effects of climate change.
Çavuşbaşı Granodiyoriti'nin yaşı ve petrojenezi
ÇAVUŞBAŞI GRANODİYORİTİ'NİN YAŞI VE PETROJENEZİ ÖZET Çavuşbaşı Granodiyoriti, İstanbul Boğazı'nın doğusunda, Batı Pontidlerde İstanbul Zonu içerisinde bulunur. Üst Kretase yaşlı magmatik sokulum kayası (plüton), İstanbul Zonu'nun paleozoyik birimlerini yer yer kesmektedir. Alt Ordovisiyen yaşlı kumtaşı ve şeyllerin içine sokulum yapar. Etrafında yaklaşık olarak 300-500 m civarında bir dokanak başkalaşım halesi vardır. Bu çalışmanın amacı, bu sokulumun petrojenezini ve yaşını sınırlandırmaktır. Çavuşbaşı granodiyoriti yaklaşık olarak 25 km2'lik bir alanı kaplamaktadır. Çavuşbaşı plütonu, çapı yaklaşık olarak 4,5 - 5,6 km arasında değişen dairesel bir granodiyorit sokulumudur. Yüzeysel aşınma nedeniyle tamamen arenalaşmış bir topoğrafya gözlenmesine rağmen dere yataklarında, inşaat ve yol için açılan bölgelerdeki mostralardan alınan numunelerin mikroskobik ve arazi gözlemleriyle jeolojik birimler ayırtlanmıştır. Dalma-batma ile kıtasal levha kenarına yerleşmiş bu granitik plüton, kalkalkalen özellikte, hornblend içerikli, magmatik bileşimli I-tipi granittir. Sokulum genel itibarıyla granodiyoritten oluşmakta ve yer yer küçük ölçekte kuvarsdiyorit porfirlere geçiş yapmaktadır. Ana kayayı granodiyorit ve kuvarsdiyorit oluşturmaktadır. Granodiyoritin başlıca bileşenleri plajioklas, kuvars, K-feldspat, hornblend ve biyotittir. Kuvarsdiyorit ise aynı minerallerden oluşmakta olup, yalnızca porfirik dokusu ile granodiyoritlerden ayrılmaktadır. Çavuşbaşı Granodiyoriti ayrıca aplit ve pegmatit damarları, mafik magmatik anklavlar ve dayklar içermektedir. Aplitler beyaz renkli, ince taneli, feldspat ve kuvars içerikli granit kökenli damar kayaçlarıdır. Aplit damarları mm boyutunda tanelerden oluşmakta ve genişlikleri 0,5 - 40 cm arasında değişmektedir. Pegmatitler pembe renkli, iri taneli, aplit ile aynı bileşime sahip damar kayaçlarıdır. Pegmatit damarları cm boyutunda tanelerden oluşmakta ve genişlikleri 3 - 8 cm arasında değişir. Aplit ve pegmatit damarları yatay olarak ayrışmış granodiyoritler içerisinde metrelerce izlenebilmektedir. İnceleme alanında bulunan aplitler Karanlıkdere'de yoğunlaşırken, pegmatitler Çiflik mahallesinde yoğunlaşmaktadır. Aplit ve pegmatitler granit magmatizmasının son evre ürünleridir. Mafik magmatik anklavlar, ince taneli, koyu renkli ve kesin dokanaklıdır. 0,5 - 30 cm arasında değişen boyutlarda, yer yer yuvarlak, yer yer köşeli, yer yer de elips biçimindedir. Anklav mikrogranüler dokulu olup, ince taneli matriksin (plajioklas, kuvars, hornblend, biyotit) içinde, 2 mm'ye varan hornblend ve plajioklas minerallerinden oluşur. Farklı magma bileşenlerinin magma mingling ile oluşturduğu akma bantları görülmektedir. Dayklar kırıklı ve çatlaklı; hornblend ve biyotit içeren dasit ve andezit; bazen de koyu yeşil renkli lamprofirler halindedir. Ortaç bileşimli dayklarda ince taneli feldspat grubu matriksin içinde, 6 mm'ye kadar honblend, ortoklas ve plajioklas mineralleri görülmektedir. Daykların boyutları 20 cm'den 3,50 m'ye kadar değişmektedir. Ortaç bileşimli daykların çok az bir kısmında, ana kayayı kesen kenarlarında kısmen soğuma kenarları oluşmuştur; bunlar bazı yerlerde ince dilimlenmeler, bazı yerlerde ise erime şeklinde gözlenmektedir. Ana kaya da ısı transferinden etkilenmiş, bu nedenle oluşan pişme dokanağı, soğuma kenarları boyunca görülen renk değişimi ile farkedilmektedir. Adakitik kayaçlar kalkalkalendir, dalma batma ile ilişkilidirler. SiO2 ≥ %56; Al2O3 ≥ %15; MgO < %3; %3,5 ≤ Na2O ≤ %7,5 Sr > 300 ppm; Y < 15 ppm; Sr/Y oranı > 20; Yb ≤ 1,9 ppm ve (La/Yb)kn > 10'dur. K2O/Na2O oranları düşüktür (~0,42); Mg numarası 51'dir. Zr ve Ti anomalisi çok küçük veya belirgin değildir. Negatif Nb anomalisi vardır. Eu anomalisi yoktur; pozitif Sr anomalisi yani Sr içeriğinin yüksek olması adakitik magmanın tipik özelliğidir. Jeokimyasal olarak Çavuşbaşı granodiyoriti (ana kaya) dar alanda değişen bir bileşim sunar. Orta K-lu kalkalen niteliklidir. Aluminyum doygunluk indeksi 0,90 ile 1,04 arasında değişmekte olup, bu kayanın metalumin-peralumin nitelikte olduğuna işaret eder. Çavuşbaşı Granodiyoriti kalkalkalen, SiO2 ≥ %56 (64,91 – 68,26), Al2O3 ≥ %15 (16,13 – 16,84), MgO < %3 (1,52 – 2,04), %3,5 ≤ Na2O ≤ %7,5 (4,80 – 5,20), Sr > 300 ppm (578,10 – 900,70 ppm), Y < 15 ppm (5,30 – 10,20 ppm), Sr/Y > 20 (70,2 – 112,49), Yb ≤ 1,9 ppm (0,56 – 0,95) ppm ve (La/Yb)kn > 10 (12,64 – 19,98 ppm) 'dir. Adakitik kayaçların aksine K2O/Na2O oranı 0,42'den küçüktür (0,25 – 0,41); Mg numarası 51'den büyüktür (52,99 - 61,68); pozitif Zr anomalisi and negatif Ti anomalisine sahip olmasına rağmen negatif Nb anomalisi, Eu anomalisinin yok ya da çok az belirgin olması ve belirgin Sr anomalisi ile Çavuşbaşı Granodiyoriti dalma-batma ile oluşmuş, adakitik nitelikli kayaçlara benzemektedir. Aplitler yüksek K-lu kalkalen niteliklidir. Alüminyum doygunluk indeksi 1,02 olup, metalumin-peralumin nitelikte olduğuna işaret eder. Düşük Na2O (%3,26), düşük Sr/Y oranı (7,04), düşük Sr değeri (72,6 ppm) ve negatif Eu anomalisi (Eu/Eu*= 0,50) ile adakitik kayaçlardan ayrılmaktadır. Magmanın son evresinde oluşan aplitler, granitik bileşimiyle inceleme alanındaki en yüksek SiO2 (%77,69) ve en yüksek K2O (%5,18), en düşük Fe2O3 (%0,44), en düşük MgO (%0,04) ve en düşük CaO (%0,56) değerlerine sahip olması ile üst kabuktan türemiş magmalara benzemektedir. Anklavlar orta K-lu kalkalen niteliklidir. Alüminyum Doygunluk İndeksi 0,84 olup, metalümin karakterlidir. Anklav numunesi, SiO2 (%55,45) oranıyla inceleme alanındaki en mafik üyedir. Ağır nadir toprak elementleri adakitlere göre daha yüksektir: Yb değeri 2,48 ppm; Y değeri 25,7 ppm'dir. Sr/Y oranı (27,99) adakitlere göre düşüktür ve negatif Eu anomalisi (Eu/Eu*=0,62) ile adakitik kayaçlardan ayrılmaktadır. Fe2O3 (%6,75); MgO (%3,57) ve CaO (%6,06) açısından granodiyorit, kuvarsdiyorit ve aplitlerden yüksek olması ile mantodan türemiş mafik magmalara benzemektedir. Bir granodiyorit örneğinden ayırtlanan zirkonlar üzerinde Lazer Ablasyon ICP-MS cihazıyla yapılan U/Pb yaş tayiniyle 68,32 ± 0,66 My (2σ) bulunmuştur. Buna göre Çavuşbaşı granodiyoriti Maastrihtiyen döneminde sokulum yapmıştır ve Üst Kretase'de kuzeye dalan Neo-Tetis okyanus litosferinin yitimiyle ilgilidir. Oluşumu muhtemelen ya İntrapontid ya da İzmir-Ankara- Erzincan Kenedi boyunca okyanusal litosferin kuzeye doğru dalımı ile ilişkilidir.
Trajectories of cyclones affecting Turkey: NCEP 2 versus ERA-Interim
Cyclones are low pressure atmospheric systems that control weather conditions every day in many places of mid-latitudes. Any systematic change in the density, frequency or location of cyclones has a wide range of influence on the local climate. When they arise it takes time to evolve and become a mature cyclone and fade away after a cyclone exists. So, lifetime of a cyclone is about a week or so. As it is known from the polar front theory, this strong horizontal temperature gradient results from the cold air from the Polar cell and the warm air from Ferrel cell moving towards each other and this movement develops a transition zone. If there is a convenient environment in the upper atmosphere, the pressure begins to drop, developing a low center at the surface, so cyclogenesis starts. The cold air moves to south and starts to rotate around warm air, forming a cold front, and the warm air moves north into the cold air, developing a warm front. While the system moves to the east, the central pressure keeps reducing and the cold front approaches to the warm front. Ultimately, the cold front cuts off the connection between the warm front and surface and goes under the cooler air ahead of the warm front, thus occluded front forms. This mature system covers a large area and vigorous weather events generally occur in the occlusion stage. The huge warm sea surface of the Mediterranean Basin immensely triggers cyclogenesis and evolutions of the cyclones. These cyclones can bring rain and snow in the form of flooding, snow storms and severe thunderstorm with hail. For instance, a long-running snowstorm hit Turkey on January 22nd, 2004 and it lasted until January 25nd. There were a lot of accidents, the power outage, and one of the rope of Bosphorus Bridge was broken. Shortly, life stopped in ˙ Istanbul and nearby cities for a few days. Purpose of this thesis is to identify the trajectories of cyclones affecting Turkey from two different reanalysis data sets. Detection of cyclone is achieved by The University of Melbourne automatic cyclone tracking scheme (CTS) using 6 hourly NCEP Reanalysis 2 and ERA-Interim mean sea level pressure field respectively at 2.5 x 2.5 and 1.0 x 1.0 spatial resolution for a region between 15◦W - 60◦E and 20◦N - 60◦N for 38 years (1979 - 2016). The first step is to transform latitude and longitude data into 101 x 101 polar stereographic (PS) array via bicubic spline interpolation. Smoothing is applied to ERA-Interim pressure field, however it is not preferred for NCEP 2 data because of its low spatial resolution. The local maxima of relative cyclonic geostrophic vorticity (x) value via the Laplacian of pressure is sought through comparing each grid point with surrounding eight grid points. If there is no closed depression reasonable distance (diflt1), scanning for minimum pressure gradient begins to find an open depression in closest allowable space (diflt2). There is no need to integrate the diflt1 parameter to ERA-Interim case after smoothing. Each cyclone is followed from the first moment of its formation to its perish. This procedure involves three steps. First one is estimating the subsequent positions of the centres. Second is looking for probability of a relations between the estimated position and the current position. The subsequent positions are predicted via prediction velocity (upred). Positions were estimated using upred. Final step is choosing most probable candidate for matching. Thus, this study shows that the most of the cyclones affecting Turkey are generally westerly and they follow a southerly trajectory in winter, however their trajectory shifts northward towards summer. Cyclones affecting Turkey generally originate in Gulf of Genoa, northern Italy, and the Black Sea, but there are other regions such as the Aegean Sea, Cyprus, and Sahara. However, some changes are seen season to season. Gulf of Genoa and northern Italy regions play major role for all seasons. In winter seasons, Turkey is also affected by southern Italy, the Aegean Sea and the Black Sea cyclones other than Gulf of Genoa and northern Italy cyclones. Sahara, Cyprus, the Aegean Sea, and the Black Sea are cyclogenesis regions in spring seasons. While winter cyclones traverse, summer cyclones are more stationary. Cyclones of Cyprus and the Black Sea have high intensity in summer season. In autumn seasons, cyclones of Sahara, Cyprus, and the Black Sea become pronounced. The results of NCEP2 and ERA-Interim are generally similar, however there are several differences between them. There are approximately 31% more tracks in the result of NCEP2 than ERA-Interim. In all seasons, there are more tracks in North Africa in ERA-Interim results than NCEP2. While there is a few tracks around Syria, Iraq, and Persian Gulf in ERA-Interim results, NCEP2 results has more tracks than ERA-Interim in these regions in the spring, summer, and autumn seasons. The average central pressure of cyclones is around 1010 hPa for ERA-Interim and 1009 hPa for NCEP2. While the mean cyclone intesity is 0.68 hPa(◦lat)−2 for ERA-Interim, it is obtained to be 0.53 hPa(◦lat)−2 for NCEP2. Also, the mean radius of the cyclones is around 4.10 ◦lat for ERA-Interim and it is found to be 4.08 ◦lat for NCEP2.
A study of the changes in the forest phenology in Turkey through MODIS satellite data
The Start of Growing Season (SGS) marks the time of year where a type of plant starts its growing season; therefore, forming green leaves. The End of Growing Season (EGS) is the opposite, where plants end their growing seasons and start defoliation. The difference in green leaf changes are much more dramatic in deciduous forests than coniferous forests, all plants show annual differences after SGS and EGS. As all plants undergo SGS and EGS, they look for environmental cues in order to keep up with their annual cycles. To detect variations in SGS and EGS, MODIS imagery was used. MODIS satellites have a polar orbit and capture images in 7 spectral bands daily. To detect the SGS and EGS from MODIS satellite data by comparing the surface reflectance in red versus green through the GRVI index was used. The threshold for the detection of SGS and EGS is set to GRVI = 0. If GRVI > 0, then it is currently the growing season; if GRVI < 0 then it is the senescence season. Yearly GRVI estimates are analyzed to detect the SGS and EGS by catching GRVI zero crossing. We tried to detect the yearly shifts of SGS and EGS using this GRVI estimates. For these measurements, daily MODIS Terra MOD09GA V006 products were downloaded for the period 2007-2017, then analyzed through an R script using RASTER package. Noise reduction was applied on the results using Exponential Moving Average and the GRVI=0 crossings were detected. Later, the refined data were compared annually and among regions with different vegetation to look for SGS and EGS shifts over time. Although in all plots there were obvious peaks during Growing Season, in some cases of mountain ranges and coniferous forests, GRVI method was unable to detect SGS or EGS; as there was no 0 crossing. In the regions where GRVI was successful, SGS shifted to an earlier DOY and EGS shifted to a later DOY on a scale of 11 years. Overall, the GRVI has been successful in showing seasonal patterns in a given region.
Statistical challenges in paleoclimatology: independent component analysis of lake hazar and Lake Van data, and a bayesian test for 4.2 ka bp event
There are numerous statistical and numerical methodological problems of paleoclimate studies. In this study, I offer solutions for two problems of paleoclimatology in three different studies. It is a well known fact that, each geochemical measurement and especially each micro-X-ray fluorescence (μ-XRF) measurement through a sediment core is a reflection of different independent processes, i.e. an indirect indicator of paleoenvironments. That's why most studies present μ-XRF measurements as elemental ratios, in order to eliminate a possible dependence upon a single profile. Some studies use second order statistical methods, such as principal component analysis, to eliminate dependence, however there are systematic problems of second order statistical methods as is used in these studies. In order to overcome this issue, we offer an almost well-defined signal processing technique, independent component analysis of geochemistry data gathered from paleoclimate archives. Accordingly, we propose data based models of paleo-precipitation and paleo-temperature for the studied regions. In the first study (Chapter 2), a 3.5 m long piston core (Hz11-P03) has been recovered from Lake Hazar and it is used for multiproxy measurements. μ-XRF, magnetic susceptibility (MS) and stable isotope (δ 18 O and δ 13 C) measurements have been carried out for 3 mm, 1 cm and 3 cm resolutions, respectively. A Bayesian age-depth model according to six radiocarbon dates shows that Hz11-P03 represents the last 17.3 ka BP. We apply independent component analysis on Lake Hazar μ-XRF data (namely, Ca, Fe, K, Mn, Sr and Ti counts). By the measure of distance correlation of resulting independent components with the analyzed data and other regional well-defined paleorecords, we select two independent components as proxies of temperature (Hz-ic5) and precipitation (Hz-ic4) of the region. According to the results, the region was wet/cold during 17.3 ka BP and 14.8 ka BP and wet/warm during the Bølling-Allerød period. According to the age model, there is a hiatus at the Younger Dryas period. At the start of the Holocene, temperatures rose gradually and reached the Holocene "normals" around 8 ka BP. During that period, it was wet. Between 8 ka BP and 5 ka BP, it was warm but exceptionally dry. Between 5 ka BP and 3.5 ka BP, it was warm/wet. After 3.5 ka BP within the oscillations there are abrupt cold/dry phases around 3.5 ka BP, 2.8 ka BP and 1.8 ka BP. In the second study (Chapter 3), ICA method is applied to previously published data from Lake Van, which span the last 250 ka BP. The data used through ICA were element concentrations of Ca, Fe, K, Mn, Si from XRF measurement, TOC and CaCO 3 content and B* (color reflectance) of the Ahlat Ridge sediment record. The analysis is based on applying the algorithm several times by changing the initial random unit vector and clustering the possible independent components through average–link agglomeration, which make it different and innovative than Lake Hazar study. Appropriate components are selected by mutual information method. Accordingly, we claim that Van-IC8 is a proxy for temperature variability for the region, by its similarity with Greenland δ 18 O data and (Van-IC7) is a proxy for precipitation variability for the region, by its similarity with B* (Van-IC7) data. The results reveal that, temperature of the region follows the Northern Hemisphere records, i.e. warm during interglacials, cold during stadials with abrupt warming episodes. On the other hand, precipitation record shows that, it was not dry, or at least as much wet as today, during the LGM and at the end of penultimate glacial as previous studies claim. It was previously proposed that an abrupt climatic change around 4.2 ka BP was the cause of the collapse of the Akkadian Empire. Afterwards, many geological studies arose, which claim to support the climatic deterioration hypothesis. In the third study (Chapter 4), we apply a Bayesian test on the records from Eastern Mediterranean and Arabian Peninsula which claim to show an abrupt climatic change around 4.2 ka BP. To do this, time series are reconstructed using "unaffected" ones in a fully Bayesian framework by the Bayesian structural time series method and then a Bayesian hypothesis test is applied on the results. Our results show that some studies which have previously been cited to support the abrupt 4.2 ka BP event hypothesis hold true, we also show that in a number of other studies, there is no statistically significant abrupt climatic change effect.
Understanding the sources and the extend of atmospheric particulate matter problem over Turkey using mesoscale chemical transport model
Turkey, with a population climbing to 80 million, has its own challenging air pollution issues, especially particulate matter pollution. Local emission sources are generally the main contributors of particulate matter levels due to their nature. Among these local emission sources, residential heating is one of the emission sectors that contribute to emissions of harmful air pollutants in highly populated urban areas. As the capital of Turkey's industry, megacity Istanbul has been experiencing air pollution problems that has reached to significant levels since 1980's, in which the pollutant concentrations have exceeded the air quality standards for several times. In Istanbul, local anthropogenic sources comprise nearly 60% of particulate matter levels. According to the air quality monitoring report of the Ministry of Environment and Urbanization, the daily mean particulate matter (<10 μg, PM10) concentrations exceeded the limit with more than 100 μg/m3 at several provinces in winter of 2015 in Istanbul. Representation of major emission sources such as road transportation and residential heating are crucial for the air quality modeling and policy making. Modeling concentrations of particulate matter have a number of important roles, some of which are complementary to measurement. These roles include assessing concentrations at locations without monitors and answering questions such as how will particulate matter levels change in the future. Results of modeling studies can be directly compared to the appropriate ambient air quality standards because all relevant sources of pollution in the modeling domain are included in this type of model. The US EPA Community Multiscale Air Quality (CMAQ v5.2) model, a three-dimensional Eulerian atmospheric chemistry and transport model, was used to evaluate the air quality of Turkey, focusing on Marmara Region and Istanbul for the winter of 2015 using three-level nested domains with an up to date spatially distributed high-resolution emissions inventory based on local activity data. Emissions is one of the two main inputs of CMAQ model. In order to process the high-resolution emissions inventory used in this thesis, a regional emission model, called DUMANpy, similar to Sparse Matrix Operator Kernel Emissions (SMOKE) Modeling System of the US EPA was adapted and customized to create temporally and spatially distributed emission for Turkey. One of the main purpose of DUMANpy is to convert the resolution of the emission inventory data to the resolution needed by an air quality model. Other main input of CMAQ model is the meteorology input because sophisticated air quality models require meteorological fields and incorporate complex chemical reaction schemes. The meteorological modeling inputs are important due to complications caused by complex terrain conditions, where measurement is not an option. The meteorological inputs for air quality modeling were generated using the Weather Research and Forecasting (WRF v3.8.1) model. CMAQ model results showed that using high-resolution emissions for the residential heating sector significantly improve the spatial distribution and concentration of air pollutants (SO2, PM10, PM2.5) for Istanbul. Air quality model simulations with our high-resolution emissions underestimated PM10 concentrations throughout the study episode on average by only 4.16% with a mean bias of 2.23 μg/m3 while base inventory underestimated PM10 concentrations on average by 35.1% with a mean bias of 18.91 μg/m3. Results show that our spatially distributed high-resolution emissions inventory produces more realistic results for Istanbul during wintertime when residential heating has the most influence on local air pollution. These results show the necessity and importance of high-resolution local emissions for anthropogenic emissions sectors for urban areas which in turn would help improve our understanding and extend of the air pollution problem in Turkey.
Analysis of air pollution over Izmir via atmospheric modeling
Besides being Turkey's third largest city with a population exceeding 4 million, İzmir is among the metropolitans that have major economic improvements. Economic growths of big cities inevitably bring some social and environmental issues as well. Among these, air pollution is the most serious and common one that both developed and developing countries are encountered. Air quality problem is affected from a lot of parameters especially in big cities. These include meteorology, topography, population, altitude, industrialization and social-economical developments. Exposure to pollution increases with the increasing human population living in developing urban areas. United Nations announced in 2000 that approximately half of the world population (48%) live in cities and every 3 years 2% growth is expected in the city populations. According to a research in 2013, twenty-three cities in the world have populations higher than 10 million. Air pollution is the existence of the foreign substances suspended in different phases of the atmosphere in varying amount, density and duration that damage human health, living organisms, and ecological balance. Therefore being exposed to air pollution became one of the inevitable results of urban life due to intense anthropogenic activities. Different researches are done on air pollution, which is a significant problem for both developed and developing countries. Especially air pollutants can threaten human health in various ways and levels. While there are high amounts of air pollutants, especially in urban areas, increase in mortality and morbidity rates has been discovered. Particularly lung diseases, neurobehavioral disorders and the effects of cardiovascular diseases are the main adverse effects of air pollution. Growing city population and industrialization level result in increasing energy demand. In densely populated areas, air pollution emission increases by rapid urbanization, transportation, energy production and industrial activities. Air quality management is one of the issues that need to be implemented urgently in the cities where strategical planning is limited or does not exist. Thus, developing emission inventories is one of the most important steps for air quality determination and improvement. These inventories are necessary tools for evaluating human and environmental risks, which are based on anthropogenic sources. Air quality control strategies are determined by air quality and emission standards defined by authorities in regional, national and global scales. Developing emission control strategies, determining applicability of control programs are required for creating reliable emission inventory. It is required to estimate the spatial and temporal density of emission sources in the best possible resolution for forming a healthy air quality control strategy and planning air pollution control reduction strategies. Having a reliable emission inventory is a primary requirement for qualified air quality management system. An emission inventory system supports pollution evaluation activities by data collection and scanning, storing, data organization. Also it creates databases for emission scenarios that will be prepared in the future. In this study, by improving existing emission inventory, activity data, which is more up-to-date and with reduced uncertainty, is compiled thus more reliable entries are provided for the air quality model. Via this model, which is run by the new inventory, temporal and spatial distribution of pollutants is investigated according to the sources. In the model, compiling of pollutants that are distributed according to the sources is set up based on sectoral distributions. Three types of source data is collected in the repository then are calculated depending on the calculation methods of source types. In the model, industry emissions are in SNAP-34 sector, traffic emissions exist in SNAP-7 sector. SNAP-7 also is divided into five based on source emissions. Regional sources named as domestic heating are calculated for SNAP-2 sector. While preparing emission inventory, for each sector required data is obtained from enterprises, calculations are done according to the related sector. Traffic emissions are calculated using COPERT 4 model, which is used in the transportation sector section of the İzmir's inventory. COPERT 4 traffic emission calculation model is commonly used for the calculation of vehicle emissions in several European countries. For industrial emissions, plants' direct emission measurements, which are provided by Izmir Provincial Directorate of Environment and Urban Planning, are calculated and used in the SNAP-34 sector of the study. For domestic heating emissions, which are provided by Izmır Provincial Directorate of Environment and Urban Planning by using the natural gas consumption and coal sales data, are calculated for SNAP-2 sector. In this study, WRF/CMAQ models included in EPA Models-3 system are used together. Meteorological and chemical transport models are run as two domains. Main domain includes whole Europe, North Africa and Eastern Asia, second domain covers whole Turkey and the resolutions are 30 km and 10 km respectively. WRF model is with 3 days spin-up timing is run for January 2010. For the result of the model, temperature and wind speed/direction data that is provided by İzmir Turkish State Meteorological Service is used and Gaziemir station performance analysis is done. When the temperature and station data are evaluated together, it is found that at temperatures in 2 m, for the trend and temperature values partially in line with the model estimations. For the evaluations of the wind speed and direction, at lower levels of wind speed, model estimates are compatible with station observations, although there are some deviations at certain days. There are some uncertainties in the model estimates regarding the wind direction and which is an expected situation. Following the evaluation of the changing model parameters' effects on emissions, air quality model is run to understand how these effects will be reflected into air quality. TNO/MACC-II inventory is used as a baseline scenario and run for 30 km and 10 km. Then CMAQ model is run once again for İzmir SNAP-2, SNAP-34 and SNAP-7 sectors with up-to-date emission data. For TNO inventory and new inventory that is created by new emission calculations, analyses are done by using different analysis methods and the affects of sectoral changes on the model results are investigated. For the emissions as TNO-OUR, total emission maps are created separately for each, the differences from each others are drawn as maps. In OUR emissions, for all pollutants changes are monitored according to the increases and decreases based on sectors. While PM10 emissions are decreased in SNAP-2, increased in SNAP-34 and SNAP-7, as a result overall PM10 emissions are increased. While CO is declined in SNAP-2 sector dramatically, it is increased sharply in SNAP-34 and SNAP-7 sectors. NOx is increased in the sectors except for SNAP-34. SO2 from pollutants is increased in all sectors. As a result of all these changes in emissions, different results are observed in the concentrations for each pollutant. In this study, distributions based on sectors takes into account for the spatial distribution of TNO inventory. Thus, the differences are considered based on the TNO spatial distribution. It is found that for all pollutant emissions and concentrations over İzmir, maximum changes are observed in city center. Through more detailed examinations, days and hours are determined where the maximum differences occur in concentrations and affects and results of these on emissions are investigated. Our findings indicate that the maximum impact of the CMAQ model's concentration results which are used by the newly developed emission inventory as an input, is observed in the İzmir city center where the most emission sources exist.
Quantification of residential heating emissions in Istanbul via CMAQ air quality model
Istanbul is the most populated city of Turkey as well as Europe. The population is over than 14 million. The city is economical center of the country. Labour and social opportunities makes the city attractive to live and this situation causes inevitable increasing on urbanization of the province. According to authorities, it is expected that the population will be over 16 million in 2030. Due to high population, house holding is also increasing. Distribution of buildings is expending over the city. Residential heating is the main requirement of the people in cold, winter season. By the high population and urbanization, residential heating emissions significantly affects air pollution over the city. Results of many epidemiological studies proves that air pollution causes negative impact on cardiovascular and respiratory system, serious diseases such as cancer and hearth attack. Especially for sensitive people such as elders, children, babies or pregnant the effects may be higher and vitally important. This study aims to examine residential heating impact over Istanbul city by atmospheric modelling. For this purpose WRF (Weather Research and Forecasting) meteorology model and CMAQ (Community Multiscale Air Quality) chemistry and transport model was applied. The first step was preparing emission inventory as input of the model. More complete and current emission inventory provides more trustable outputs. Residential heating emissions are generated with activity data and emission factor. The calculated emissions are also compared with TNO and EMEP emissions. Another purpose of this study was developing region specific emission factors of residential heating for Istanbul. The main fuels which are commonly used in the city are determined and combustion system is analysed. Residential heating is commonly supplied from natural gas and solid fuels such as coals and wood. The coals are classified as domestic and import coal. The fuels were burned in conventional stoves that is commonly used individual combustion system in Istanbul and pollutant concentrations are measured. The measurements for solid fuels were continuous and the concentration values of each pollutants are reported minutely. For natural gas, individual combustion system was combi and concentrations were measured instantaneously. Combustion systems, burning efficiency and calorific values of the fuels are essential for burning regime and pollutant concentrations. Moreover, fuel consumption per unit time is a critical parameter for emission factor calculation. By considering all these parameters and concentrations emission factors are calculated for each fuels and pollutants. The main pollutants of this source are SOx, NOx, CO, PM10. Moreover, uncertainties of region specific emission factors that are calculated with continuous measurements are evaluated for solid fuels. Statistical methods are used in order to quantify the factors. Both parametric and non-parametric bootstrapping techniques applied and many distribution fitting models and related diagnostics were applied in the study. The emissions via using calculated region specific emission factors and WRF meteorological model outputs were used as input of CMAQ. The study episode was three months that is from December 1, 2009 to February 30, 2010. As reference case CMAQ model is applied with TNO inventory and then the model is run for the same episode with new emission inventory that is updated with calculated residential emissions. The difference of concentrations between two model outputs provide to understand contribution of the revised residential emissions over the city. The days and hours that have maximum concentration differences are determined as giving the highest response to the new inventory.
The bacterial and archaeal biodiversity of Insuyu cave
Caves are one of the unique habitats to see interaction between rock and microbes. In the aspect of microbiological researches, caves are unique environments in order to not only the limitations on exposing to exterior environmental conditions but also the natural isolation for disturbants such as other living creatures. In these harsh environments, Proteobacteria, Actinobacteria, Chlorobi/Bacteriodetes, Chloroflexi, Deltaproteobacteria, Acidobacteria, Nitrospirae, Actinobacteria and Betaproteobacteria are the most common and diverse group of bacteria because of their adaptation ability. In this study, we conducted cultivation-independent 16S rDNA surveys on the bacterial and archaeal community of Insuyu Cave, Burdur, TURKEY. The complexity of microbial communities has been presented in samples through PCR amplification of the 16S ribosomal RNA (16S rRNA) gene sequence, high resolution melting curve (HRM) and next generation sequence (NGS) based on 16S rRNA metagenomics from a variety of cave samples to identify bacterial and archaeal community profile of Insuyu Cave. A total of nine known bacterial class were found within the context of this research (Figure 3.4). The most prevalent class is alphaproteobacteria with 89,23% of the total bacteria found grouping into four order, with the most abundant ones: rhizobiales (88,85%) and sphingomonadales (0,21%). The followings, ordered by abundancy, are actinobacteria (3,94%), bacilli (2,92%), gammaproteobacteria (1,69%) and betaproteobacteria (0,74%). Also, a total of fourteen genera from ten order were identified in this study (Figure 3.5). The most dominant is methylobacterium with 88,83%, from the class of rhizobiales (88,85%). The followings are propionibacterium (3,58%), dolosigranulum (1,69%), streptococcus (1,10%) and pseudomonas (1,13%). On the other hand, no Archaeal species has been detected at the result of NGS analysis while some archaeal nucleic acid had been marked as a result of PCR analysis. The reasons of this situation has been investigated in the section of discussion.
Kalkolitik ve Tunç çağlarında Göller bölgesindeki iklimsel değişiklikler ve bu değişikliklerin bölgedeki arkeolojik yerleşim sistemlerine etkisi
Bu çalışmanın amacı, Kalkolitik ve Tunç çağlarında (~G.Ö.8000-3000/~M.Ö. 6000-1000) Göller Bölgesi'nde meydana gelen iklimsel değişiklikleri bir paleoiklim modeli yardımıyla modelleyerek önemli iklimsel parametrelerin (yıllık ortalama yağış ve sıcaklık gibi) gösterdiği değişimlerin derece ve önemini kantitatif yöntemlerle çalışmaktır. Bu değişimlerin bölgede yapılan arkeolojik yayınlardan oluşturulan arkeolojik yerleşim sistemlerine etkisini araştırmaktır. Göller Bölgesi coğrafik ve kültürel açıdan bakıldığında Burdur, Isparta ve Antalya illeri ile temsil edilmektedir. Çalışma kapsamına Ege, Akdeniz ve İç Anadolu bölgeleri arasındaki ilişkileri anlamak adına Afyon ve Konya illeri de dâhil edilmiştir. Bu illerinden elde ettiğimiz iklimsel kayıtlar ve çalışma dönemini temsil eden 500'ü aşkın arkeolojik yerleşme kullanılmıştır. Bu çalışma kapsamında istatistiksel verilerin incelenmesi için R Studio kullanılmış, çalışılan bölgenin mekânsal verilerinin bilgisayar ortamında toplanması, coğrafi bilgi sistemine girilmesi, mekânsal analizlerin yapılması, görüntülenmesi ve uygun formatta çıktı alınabilmesi için ise açık kaynak kodlu GRASS CBS (Coğrafi Bilgi Sistemleri) kullanılmıştır. Yapılacak olan tüm analizlerin ve buna bağlı elde edilecek olan tüm verilerin, geçmişteki iklimsel değişiklilerin arkeolojik yerleşim sistemlerini ne derece etkilediğini anlamak için ise Makrofiziksel İklim Modeli (MİM) kullanılmıştır. Çalışmadan elde ettiğimiz ilk verilere göre, Kalkolitik Çağ'dan Erken Tunç Çağı sonuna kadar (~G.Ö. 8000-4000/~M.Ö. 6000-2000) arkeolojik yerleşmelerin sayısında artış görülmüştür. Bu süre içerisinde ise yaşayan Göller Bölgesi insanlarının yeryüzü şekilleri içerisinde düzlük alanlarda, suya yakın geçiş noktalarında (kanal) ve dağın bayır kısımlarında yaşamayı, zirve ve vadilere oranla daha fazla tercih etmişlerdir. Yağış ve sıcak verilerine bakıldığında ise, Geç Kalkolitik Çağ'dan Geç Tunç Çağı sonuna kadar (G.Ö. 5600-3000/M.Ö. 3600-1000) olan zaman diliminde yağışta ve sıcaklıkta azalmaların görüldüğü ve buna ek olarak her 2000 yıllık süreçte Göller Bölgesinde yerel ve bölgesel değişimlerin olduğu gözlenmiştir. Yine yağış ve sıcaklık verileri göz önünde bulundurulduğunda, 4.2 ka iklim olayının Göller Bölgesi için bölgesel bir kuraklığı işaret etmediği görülmektedir. Orta Holosen sürecindeki iklimsel değişikliklerin, bu dönemde yaşamış toplulukların sosyal, ekonomik ve siyasi sistemlerin değişmesinde payı olabileceği düşünülse bile, bu değişimin sadece yerel ölçekte gerçekleştiği ve küresel bir etkisi olamayacağını söylemek doğru olacaktır.
Üniversite öğrencilerinin biyoçeşitlilik algısı ve biyoçeşitlilikle ilgili tutumlarının analizi
Turkey has a very rich biodiversity yet this enourmous richness is seriously under threat. Lack of nature education leads conservation acts and campaigns to be under supported and even rejected by people. To have a sufficient nature education is very important for young population, who are scientists, engineers, decision makers, law makers...etc. of the future. In Turkey, nature education basically consists of biology courses. In this study, two hundred higher education students were asked to participate in a twelve item questionnaire about biodiversity. Their perception and attitudes towards biodiversity were investigated. Results show that although the students know what biodiversity is and they are sensitive about environmental issues they have many confusions, misconceptions and lack of knowledge. Results also underline that, a well planned, early starting nature education which families also will be a part of it is required and this education should be seperated from biology courses and be a life long learning process.
Bir Zebra Midyesi (Dreissena Polymorpha) istilasının mekansal ve zamansal örüntüleri
Biological invasions are an important dimension of global change and is an environmental problem which has a serious consequences. Awareness about this issue has increased, especially after the invasion of zebra mussels in Great Lakes of North America and environmental and economic results of this invasion. In this study, spatial and temporal patterns of the zebra mussel invasion in Great Lakes was studied, for a 20-year period by using individual based modelling method. The model was developed in NetLogo environment. Numerical experiments were also conducted in this environment. First of six experiment sets is reference case experiment. Effects of phytoplankton density on zebra mussel populations were investigated in P75 and P125 experiment sets. In T0.1 and T10 experiment sets, effects of transportation probability on zebra mussels were investigated. Last experiment set, SupD, was conducted to observe how environmental changes would affect a biological invasion, by applying Lake Huron conditions to Lake Superior. According to results, there is no linear relation between the change of phytoplankton amount and the increase of zebra mussel population and slight changes of phytoplankton amount cause significant increases in invasion strenght. Changes in transportation probability, affect invasion stages temporally and also have impact on population size. SupD experiment results show that probable climate changes have a strengthening effect on biological invasions. Results also show that, lake location in the waterbody network is also important beside the individual conditions of each lake and mussel populations constitute characteristic patterns depending on invasion strenght.
Hersiniyen Orojenik Sisteminin Doğu Avrupadaki Kısmının Geometrisi, Evrimi ve İskititlere Geçişi
The Hercynian Orogen, one of the best-known orogenic belts in the world, still hides many secrets concerning its evolution. This orogen formed through the collision between Laurussia and Gondwana-Land, which resulted in the supercontinent of Pangaea. Pangaea's formation began in the late Devonian with the onset of subduction and continued from the early-medial Carboniferous to the Permo-Triassic by means of collision. However, at the eastern part of this supercontinent, collision never happened and subduction continued in the Permo-Triassic. The coast of the Palaeo-Tethys known as Alpine-type Triassic succession was the scene of high mobility events in the core of the Pangaea in terms of Hercynian and Post-Hercynian stages. It is a fact that when the subduction process was still continuing, a rifting event began in the Permo Triassic at the eastern part of Pangaea by disrupting a magmatic arc. The results show a continuous arc goes from the Rhodope-Pontide Fragment in the north, through the Eastern Carpathians, Tisza Block, Western Carpathians, and Pelagonian Zone, to the Eastern Pontides in the south. Additionally, the lithostratigraphic charts of all the tectonic zones indicate the volcano sedimentary complexes, which show a rifting event as their most likely interpretation. As a consequence of this rifting, a marginal basin started to form beginning from the eastern part and tore westward by tracing the weak zones of the former arc. It began to take shape from the Karakaya Complex, goes through the Pelagonian zone and the Inner Western Carpathians namely Meliaticum into the Tisza Block in the Late Permian-Early Triassic. From the medial to the end of the late Triassic, the entire Hellenic-Dinaric System and Italy began to disintegrate, which started from the Pindos Zone in Hellenides and Sicily in Italy, and joined together into the Southern Alps by passing through all along the coast of the present Adriatic Sea. This presentation shows a reconstruction of the Mediterranean Tethysides at the time of the early Triassic. It was done by palinspastically restoring all the orogenic deformation for which data were to be had painstakingly and not just schematically. It is still incomplete, because it does not show the rift areas of the Sclafani-Imerese, Lagonegro and Pindos-Budva, except to show where they were. It also delineates the lie of the Karakaya and the Meliata rifts and shows that they were one and the same rift. Karakaya was later partly incorporated into the Vardar Ocean. Most of it closed during the earliest Jurassic, whereas the Meliata part was delayed until the late Jurassic. These closures are responses to two events: 1) Palaeo-Tethyan closure in case of Karakaya and 2) the opening of the South Atlantic in case of the Meliata. This paper addresses itself mainly to the solution of the Karakaya-Meliata problem.
Lavrasya'nın güney aktif kenarı boyunca çarpışma öcesi eklemlenme ve yüzeylenme, Orta Pontidler, Türkiye
The Central Pontides is an accretionary-type orogenic area within the Alpine-Himalayan orogenic belt characterized by pre-collisional tectonic continental growth. The region comprises Mesozoic subduction-accretionary complexes and an accreted intra-oceanic arc that are sandwiched between the Laurasian active continental margin and Gondwana-derived the Kırşehir Block. The subduction-accretion complexes mainly consist of an Albian-Turonian accretionary wedge representing the Laurasian active continental margin. To the north, the wedge consists of slate/phyllite and metasandstone intercalation with recrystallized limestone, Na-amphibole-bearing metabasite (PT= 7–12 kbar and 400 ± 70 ºC) and tectonic slices of serpentinite representing accreted distal part of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed. Raman spectra of carbonaceous material (RSCM) of the metapelitic rocks revealed that the metaflysch sequence consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330 °C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. The rest are phyllites that are characterized by slightly pronounced G band with D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 °C. The phyllites are associated with a strip of incipient blueschist facies metabasites which are found as slivers within the offscraped distal turbidites. They possibly represent underplated continental metasediments together with oceanic crustal basalt along the basal décollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge. 40Ar/39Ar phengite ages from the phyllites are ca. 100 Ma, indicating Albian subduction and regional HP metamorphism. The accreted continental metasediments are underlain by HP/LT metamorphic rocks of oceanic origin along an extensional shear zone. The oceanic metamorphic sequence mainly comprises tectonically thickened deep-seated eclogite to blueschist facies metabasites and micaschists. In the studied area, metabasites are epidote-blueschists locally with garnet (PT= 17 ± 1 kbar and 500 ± 40 °C). Lawsonite-blueschists are exposed as blocks along the extensional shear zone (PT= 14 ± 2 kbar and 370–440 °C). They are possibly associated with low shear stress regime of the initial stage of convergence. Close to the shear zone, the footwall micaschists consist of quartz, phengite, paragonite, chlorite, rutile with syn-kinematic albite porphyroblast formed by pervasive shearing during exhumation. These types of micaschists are tourmaline-bearing and their retrograde nature suggests high-fluid flux along shear zones. Peak metamorphic mineral assemblages are partly preserved in the chloritoid-micaschist farther away from the shear zone representing the zero strain domains during exhumation. Three peak metamorphic assemblages are identified and their PT conditions are constrained by pseudosections produced by Theriak-Domino and by Raman spectra of carbonaceous material: 1) garnet-chloritoid-glaucophane with lawsonite pseudomorphs (P= 17.5 ± 1 kbar, T: 390-450 °C) 2) chloritoid with glaucophane pseudomorphs (P= 16-18 kbar, T: 475 ± 40 °C) and 3) relatively high-Mg chloritoid (17%) with jadeite pseudomorphs (P= 22-25 kbar; T: 440 ± 30 °C) in addition to phengite, paragonite, quartz, chlorite, rutile and apatite. The last mineral assemblage is interpreted as transformation of the chloritoid + glaucophane assemblage to chloritoid + jadeite paragenesis with increasing pressure. Absence of tourmaline suggests that the chloritoid-micaschist did not interact with B-rich fluids during zero strain exhumation. 40Ar/39Ar phengite age of a pervasively sheared footwall micaschist is constrained to 100.6 ± 1.3 Ma and that of a chloritoid-micaschist is constrained to 91.8 ± 1.8 Ma suggesting exhumation during on-going subduction with a southward younging of the basal accretion and the regional metamorphism. To the south, accretionary wedge consists of blueschist and greenschist facies metabasite, marble and volcanogenic metasediment intercalation. 40Ar/39Ar phengite dating reveals that this part of the wedge is of Middle Jurassic age partly overprinted during the Albian. Emplacement of the Middle Jurassic subduction-accretion complexes is possibly associated with obliquity of the Albian convergence. Peak metamorphic assemblages and PT estimates of the deep-seated oceanic metamorphic sequence suggest tectonic stacking within wedge with different depths of burial. Coupling and exhumation of the distinct metamorphic slices are controlled by decompression of the wedge possibly along a retreating slab. Structurally, decompression of the wedge is evident by an extensional shear zone and the footwall micaschists with syn-kinematic albite porphyroblasts. Post-kinematic garnets with increasing grossular content and pseudomorphing minerals within the chloritoid-micaschists also support decompression model without an extra heating. Thickening of subduction-accretionary complexes is attributed to i) significant amount of clastic sediment supply from the overriding continental domain and ii) deep level basal underplating by propagation of the décollement along a retreating slab. Underplating by basal décollement propagation and subsequent exhumation of the deep-seated subduction-accretion complexes are connected and controlled by slab rollback creating a necessary space for progressive basal accretion along the plate interface and extension of the wedge above for exhumation of the tectonically thickened metamorphic sequences. This might be the most common mechanism of the tectonic thickening and subsequent exhumation of deep-seated HP/LT subduction-accretion complexes. To the south, the Albian-Turonian accretionary wedge structurally overlies a low-grade volcanic arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed north of the İzmir-Ankara-Erzincan suture (İAES), separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metavolcanic rocks are stratigraphically overlain by recrystallized micritic limestone with rare volcanogenic metaclastic rocks. Two groups can be identified based on trace and rare earth element characteristics. The first group consists of basaltic andesite/andesite (BA1) and rhyolite with abundant cognate gabbroic xenoliths. It is characterized by relative enrichment of LREE with respect to HREE. The rocks are enriched in fluid mobile LILE, and strongly depleted in Ti and P reflecting fractionation of Fe-Ti oxides and apatite, which are found in the mafic cognate xenoliths. Abundant cognate gabbroic xenoliths and identical trace and rare earth elements compositions suggest that rhyolites and basaltic andesites/andesites (BA1) are cogenetic and felsic rocks were derived from a common mafic parental magma by fractional crystallization and accumulation processes. The second group consists only of basaltic andesites (BA2) with flat REE pattern resembling island arc tholeiites. Although enriched in LILE, this group is not depleted in Ti or P. Geochemistry of the metavolcanic rocks indicates supra-subduction volcanism evidenced by depletion of HFSE and enrichment of LILE. The arc sequence is sandwiched between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic mélange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kösdağ Arc was intra-oceanic. This is in accordance with basaltic andesites (BA2) with island arc tholeiite REE pattern. Zircons from two metarhyolite samples give Late Cretaceous (93.8 ± 1.9 and 94.4 ± 1.9 Ma) U/Pb ages. Low-grade regional metamorphism of the intra-oceanic arc sequence is constrained 69.9 ± 0.4 Ma by 40Ar/39Ar dating on metamorphic muscovite from a metarhyolite indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. The youngest 40Ar/39Ar phengite age from the overlying subduction-accretion complexes is 92 Ma confirming southward younging of an accretionary-type orogenic belt. Hence, the arc sequence represents an intra-oceanic paleo-arc that formed above the sinking Tethyan slab and finally accreted to Laurasian active continental margin. Abrupt non-collisional termination of arc volcanism was possibly associated with southward migration of the arc volcanism similar to the Izu-Bonin-Mariana arc system. The intra-oceanic Kösdağ Arc is coeval with the obducted supra-subduction ophiolites in NW Turkey suggesting that it represents part of the presumed but missing incipient intra-oceanic arc associated with the generation of the regional supra-subduction ophiolites. Remnants of a Late Cretaceous intra-oceanic paleo-arc and supra-subduction ophiolites can be traced eastward within the Alp-Himalayan orogenic belt. This reveals that Late Cretaceous intra-oceanic subduction occurred as connected event above the sinking Tethyan slab. It resulted as arc accretion to Laurasian active margin and supra-subduction ophiolite obduction on Gondwana-derived terranes.
Van Gölü'nün geç holosen'deki yüksek çözünürlüklü iklim ve çevresel kayıtları
Doğu Anadolu Yüksek Platosu'nda yer alan Van Gölü, 607 km3 hacmi ve 3,570 km2 lik alanı ile dünyanın en büyük 4. kapalı gölü ve en büyük soda gölüdür. Derinliği 460 m ve su seviyesi deniz seviyesinden 1648 m yükseklikte olan gölün suları, yüksek pH değeri (9.8) ve %24'luk tuzluluk oranına sahiptir. Gölün yıllık lamina (varv) yapılı çökel istifi, bölgede yüksek çözünürlüklü iklim ve çevresel değişimlerin arşivini oluşturmaktadır. Bu tez kapsamında, Van Gölü'nde çökel karotlarında özellikle son 3500 yıldaki iklimsel ve çevresel değişim kayıtları incelenmiştir. Çalışmadan elde edilen iklim kayıtları; Anadolu, Yakın Doğu ve Avrupa'dan elde edilmiş kayıtlarla karşılaştırılarak tartışılmıştır. Tez çalışması, Van Gölü'nün farklı bölgelerinden alınan ve uzunlukları 0.75 ile 1.30 m arasında değişen toplam dört karotta değişik kimyasal ve fiziksel analizler ile yapılmıştır. Çok Sensörlü karot tarayıcısı (Multi Sensor Core Logger, MSCL) ile 5 mm çözünürlükte manyetik duyarlılık, yoğunluk ve porozite ölçümleri yapılmış, µ-XRF karot tarayıcısı ile 0.5 mm çözünürlükle 15 element taranmıştır. Sediment örnekleri 0.5-1 cm aralıklarla örneklenerek toplam inorganik (TIC) ve toplam organik karbon (TOC) analizleri yapılmıştır. 0.5-1 cm aralıkla sediment örnekleri 63 μm elek kullanılarak yıkanıp elenmiş elek-üstü malzemede binoküler mikroskop altında ostrakod tanımları yapılmıştır. En uzun çökel karotu boyunca sürekliliği olan ostrakod çeşidi ve sayıları belirlenerek kavkıları toplanmış ve kavkı ve çökel örneklerinin toplam (bulk) karbonat fraksiyonunda duraylı oksijen ve karbon analizleri yapılmıştır. Ayrıca karotun çökel örneklerinin organik madde fraksiyonunda elementel C ve N analizleri yapılmıştır. Van Gölü sediment karotlarının kronostratigrafisi için değişik yöntemler kullanılmıştır. Kronostratigrafinin ana yöntemleri 210Pb radyoizotopik tarihlendirme ve varve sayımı olmakla birlikte; bu iki yönteme ek olarak 137Cs tarihlendirme ve tefrakronoloji yöntemleri de kullanılmıştır. Ayrıca, yüksek TOC değerleri içeren seviyelerde organik karbondan elde edilen AMS radyokarbon yaşları, varve yaşları ile karşılaştırıldığında gölün 1.2 ile 3.8 bin yıl arasında değişen 14C rezervuar yaşına sahip olduğu saptanmıştır. 210Pb analizleri Sıvı Sintilasyon Sayım Sistemi kullanılarak Çift Enerji Pencere Yöntemi (Double Energetic Window Method) ile gerçekleştirilmiştir. Bu yöntem 210Pb izotopunun 17 keV'lik β enerjisini kullanmaktadır. Yöntemin en büyük avantajı örneklerin alınır alınmaz analiz edilebilmesidir. 210Pb tarihlendirme, 210Pb'un kız radyoizotopu olan 210Po'un 5.30 MeV'deki alfa enerjisinden yararlanılarak da yapılabilmektedir. Ancak bu çalışmada kullanılan yöntemden farklı olarak, çevreden gelen ve sediment örneklerinin içinde olması beklenen 210Po radyoizotoplarının 210Pb radyoizotopları ile dengeye gelmesi için en az 5 yarı ömür (yaklaşık 2 yıl) beklemek gerekmektedir. CRS (Constant Rate of Supply) modeli ile yapılan tarihlendirme sonuçlarına göre Van Gölü'nün sedimanlarının sedimantasyon hızı gölün değişik karotlarında 0.3 ile 0.7 mm.yıl-1 arasında, kütle birikim hızları ise 0.3-0.60 kg.m-2.yıl-1 değerleri arasında değişmektedir. Sedimantasyon ve kütle birikim hızlarındaki bu değişkenlik, gölün değişik noktalarındaki farklı sediment akılarına bağlıdır. Sediment akılarındaki bu farklılıklar, gölün topografyasındaki farklılıklara, göl yatağı litolojisine, farklı bölgelerdeki drenaj özelliklerine ve ayrıca bölgeye göre değişim gösteren antropojenik aktivitelere bağlı olarak açıklanabilmektedir. Bir fizyon ürünü olan 137Cs izotopunun çökel karotları boyunca aktivite dağılımları HpGe Gama Sayım Sistemi ile 671 keV'deki gama enerjisi kullanılarak incelenmiş ve 1950-1963 yıllarındaki nükleer silah denemeleri sonucunda ve 1986 yılında meydana gelen Çernobil Nükleer santral kazası sonucu çevreye yayılan 137Cs radyoizotopunun varlığı tespit edilmiştir. Van Gölü sediment karotlarının yaşlandırılması için kullanılan ana yöntemlerden biri olan varv sayımı, bir algoritma ile yıllık laminalı (varv) yapıdaki karotların sayısal X-ışını radyografi görüntülerinden yapılır. Bu çalışmada kullanılan varv sayım yöntemi ile elde edilen yaş verileri, karotların 7.5 cm lik üst kısımları için (100-150 yıl) radyoizotopik (210Pb ve 137Cs) tarihlendirme yöntemlerinden elde edilen yaş verileri ile büyük bir uyum içerisindedir. Bu uyum göz önüne alınarak karotların yaş-derinlik modelleri varv sayım yöntemi kullanılarak yapılmış ve böylece radyoizotopik yöntem ile 100-150 yıla kadar yaşlandırılabilen çökel karot istifleri uzunluklarına bağlı olarak 3500 yıla kadar yaşlandırılmıştır. Geç Holosen süresince, Van Gölü çökel istifinde karbonatlardaki düşük oksijen-izotop değerleri, kış yağışının (kar) etkisinin bir sonucu olarak değerlendirilmektedir. Dağlara doğru yönelen nemi engelleyen yerel yaz doğulu rüzgarlarının erken oluşması ile meydana gelen "klasik" Akdeniz ikliminin, bölgede artan kış yağışlarının sebebi olduğu düşünülmektedir. Ostrakod sayıları, C/N oranı, duraylı izotop değerleri, TOC-TIC değerleri ve Ti/Ca oranı gibi tüm çoklu belirteç (multi-proxy) verileri değerlendirilerek son 3500 yıldaki soğuk/kurak ve ılık/yağışlı dönemlerin değişimleri incelenmiştir. Tüm bu parametrelerin birlikte değerlendirilmesi sonucu söz konusu zaman aralığında 16 adet ardışık soğuk/kurak ve ılık/yağışlı dönem tespit edilmiş olup, bu dönemlerin uzunluğu 100 yıl ile 350 yıl arasında değişim göstermektedir. Günümüzden önce 3500-3300, 2900-2600, 2400-1800, 1600-1450, 1350-1050, 770-600, 500-350 ve 200-0 yılları arasında soğuk/kurak dönemlerin hakim olduğu öte yandan günümüzden önce 3300-2900, 2600-2400, 2300-2100, 1800-1600, 1400-1350, 1050-770, 600-500 ve 350-200 yılları arasında sıcak/yağışlı dönemlerin hüküm sürdüğü sonucuna varılmıştır. Bu çalışmada elde edilen veriler ışığında Van Gölü iklim kayıtlarının özellikle Kuzey Atlantik iklim sistemi ile uyumluluğunu doğrulayan Roma Ilık Dönemi (RWP), Karanlık Çağ Soğuk Dönemi (DACP), Ortaçağ Ilık Dönemi (MWP) ve Küçük Buz Çağı dönemlerini içeren son 1800 yıllık verilerinin Nar Gölü (Orta Anadolu) çökel ve Sofular Mağarası (Kuzeybatı Anadolu) stalagmit kayıtları ile uyumlu olduğu görülmüştür. Bölgesel ölçekte, Van Gölü kayıtları İran'da bulunan Zeribar ve Mirabad göllerine ait düşük çözünürlüklü sediment ve İsrail'de bulunan Soreq Mağarası kayıtları ile de uyumludur. Van Gölü çökel karotları boyunca elde edilen µ-XRF ağır metal profilleri 1960'lardan bu yana göle olan antropojenik girdileri göstermektedir. Van Gölü bölgesinde son 30-60 yılda Zn, Pb, Ni ve Co metallerinin önemli ölçüde arttığı saptanmıştır. Özellikle karotların üst kısımlarında çok belirgin olarak gözüken Zn ve Pb zenginleşmesi 1960 yıllarında başlayan önemli tarımsal ve endüstriyel kirlenmenin bir göstergesidir. µ-XRF sayım sonuçları göz önünde bulundurularak dört karottaki ağır metal konsantrasyonları karşılaştırıldığında Gölde Van Şehri'nin batısından alınan karotta en yüksek ağır metal değerleri karotun üst kısımlarında görülmüştür. Bu sonuç ağır metallerin ana kaynağının antropojenik kirlenme olduğunu güçlü bir şekilde göstermektedir. Son 60 yılı temsil eden, karotların üst kısımlarındaki metal birikimi Van'ın şehirleşme ve endüstrileşmesinin 1960'dan sonra daha hızlandığını doğrulamaktadır. Bu hızlanma Van Gölü kıyılarının her iki yakasınında kara yolu ulaşımına açılmasının bir sonucudur. 1960'lardan itibaren sulama, hasat gibi tarımsal işlemlerde kullanılan tarım makineleri ve trafikteki araç sayısı artmıştır. Bu da araçlarda kullanılan yakıtın içeriğinde bulunan Pb salınımını artırmıştır. Bu salınım artışının sonuçları çalışılan karotlarda belirgin Pb anomalisinin gözlenmesine neden olmuştur. 2000'li yıllarda kurşunsuz yakıtın kullanılmaya başlamasıyla bu anomali değişerek doğal seviyelere gelmiştir. Öte yandan tarımsal faaliyetlerde kullanılan gübrenin içeriğinde bulunan Zn, direkt olarak ya da nehirler aracılığıyla metal kirliliğine katkıda bulunmuştur. Ayrıca genel olarak yollarda artan trafik metal kirliliğinin önemli sebeplerindendir.
Marmara bölgesindeki atmosferik sirkülasyon paternleri ve yağış üzerine etkileri
The Marmara Region comprises the northwestern end of Anatolia and the southeastern end of the Balkans: two peninsulas separated by Dardaneles and Bosphorus straits, and the Sea of Marmara. Located on two continents, Asia and Europe, this unique area is the most industrialized, agriculturally developed and populated geographical division in Turkey with a population density of up to 2500 people per km2 in Istanbul, averaging 300 people per km2 regionally. Parallel to its economic development, the region continues to draw migration from other regions in Turkey. This leads to an ever increasing demand for water, while threatening the existing water resources in the form of new and uncontrolled building activity over water reservoirs. Thus, amount and variability of precipitation play a key role in the management of limited water supply. Large-scale circulation patterns and synoptic patterns play significant role in determining the precipitation climate of the region. For the first time, in order to reveal the synoptic properties of the Marmara, circulation types, their long-term mean occurrence frequencies and relationships with precipitation are investigated. Automated Lamb Weather Types classification method is applied on NCEP/NCAR daily mean sea level pressure data to determine circulation types. Northeasterly (NE) and easterly (E) types are found to be the most frequent both on the annual basis and during winter (DJF, the wettest season in the region). Circulation types with the highest rainfall potential, namely the cyclonic (C) and northerly (N), are among the least frequent; therefore they are not the dominant "rainfall modes". Instead, NE and E have the greatest contribution to the regionally averaged rainfall amount, although they do not have the highest potential to create precipitation. This shows that Marmara Region receives a substantial amount of precipitation from northerly and easterly maritime trajectories, implying a profound influence of the Black Sea on the rainfall regime in this area. However, rainfall at the stations that are far away or less affected by the Black Sea (especially at the ones in the west) occurs during types with a southerly component (S, SW and SE). In addition to the relationship between CTs and precipitation in Marmara, the significant roles of the teleconnection patterns (TPs) on CTs and precipitation mechanism were also investigated. For this purpose, five main TPs, namely North Atlantic Oscillation (NAO), Arctic Oscillation (AO), East Atlantic (EA), East Atlantic-West Russia (EAWR) and Scandinavian (SCA) patterns index values were used. EA/WR is the most influential pattern in the occurrence of CTs during winter, exhibiting positive significant (at 99% level) correlations with NE and NW; and negative ones with SW and C. the strongest association of EA/WR is with NE and NW; and negative ones with SW and C. The second most influential teleconnection pattern on the CTs of Marmara Region during DJF is the AO, whose relationship with the occurrence of NE, SW and C is in the same fashion with EA/WR. Surprisingly, the NAO, whose wintertime impact on Turkey is the most studied and documented among all teleconnection patterns; has generally weak and insignificant influence on the occurrence of CTs in Marmara Region in DJF. In water management strategies, the amount of precipitation in particular basin has a great importance. Therefore, which CTs quantitatively cause precipitation occurrence and intensity in the sub-basins of the Marmara were investigated. By applying Ward's hierarchical cluster analysis, Marmara were divided into five coherent zones, namely Black Sea-Marmara, Black Sea, Marmara, Thrace and Aegean sub-regions. Precipitation occurrence suggested that wet CTs (i.e. N, NE, NW, and C) offer a high chance of precipitation in all sub-regions. For the eastern (western) part of the region, the high probability of rainfall occurrence is shown under the influence of E (SE, S, SW) atmospheric CTs. In terms of precipitation intensity, N and C CTs had the highest positive gradients in all sub-basins of the Marmara. In addition, although Marmara and Black Sea sub-regions have the highest daily rainfall potential during NE types, high daily rainfall totals are recorded in all sub-regions except Black Sea during NW types.
Copert4 modeliyle hesaplanan karayolları emisyonlarının duyarlılığının İstanbul hava kalitesine etkisinin WRF/CMAQ model sistemiyle belirlenmesi
Istanbul, the study area and the economic capital of Turkey, is the most populated city all around Europe with a population well over 14 million. The city has faced with environmental problems due to rapid urbanization and industrialization for a couple of decades. Air pollution is one of the most challenging problems for Istanbul where studies publicized that air pollution, particulate matter pollution in specific, has various serious effects on public health. Although air pollution is caused by numerous sources ranging from industrial to biogenic activities, emissions from motor vehicles have the most adverse effects on public health as they are released at the locations with certain levels where human activity is the highest. Traffic related emissions were calculated by using COPERT 4 (COmputer Programme to calculate Emissions from Road Transport) which is vehicle emission computation software and supported by European Environment Agency (EEA). Model input data were obtained from Turkish Ministry of Environment and Urbanization, and TUVTURK, then the data were processed by R that is a software environment for statistical computing and graphics. Besides fleet distribution process based on EURO levels, engine volumes, and fuel type was done first time for Istanbul, COPERT 4 was also run with this high resolution data. High-resolution emission inventory for other sectors, which is prepared by Dr. Ulaş Im, were employed. It can be summarized from the results of this analysis that road transport itself is solely responsible for 32 percent of CO emissions, as well as playing a main role in NMVOC emissions with the contribution of 43 percent to the total NMVOC emissions inventory, and NOx emissions with the contribution of 40 percent to total NOx emissions inventory. Furthermore, overall CO, NOx and PM2.5 contributions by road transport are found as 51%, 42%, and 11%, respectively. It is also realized that impact of road transport on inventory is higher than other sources. Vehicle emissions in inventory with this vitality increase the importance of determining the sensitivity and the uncertainty of calculations. To investigate the sensitivity of COPERT 4, three scenarios are determined based on temperature and speed parameters with numerous values that are strongly affecting the calculations. Then, base case emission values were compared with obtained emission values of these three scenarios. For the each scenario COPERT model was run and emissions of road transport was obtained. Then, calculated vehicle emissions used as input for air quality model. As a result of emissions for each scenario, a conclusion can be drawn that the major pollutant is NOx and minor pollutant is PM2.5 in general, where the emissions are higher in rural areas than urban areas and than the highways When a general analysis is done on scenarios regarding to pollutants, it can be realized that there is a decrease in emissions of all kinds of pollutants except CO as speed increases, and increase in emissions of all kinds of pollutants except CO as speed decreases. On the other hand, an obvious decrease in emissions of pollutants except NMVOC is realized in the case of temperature decrease. After evaluating the effect of change in model parameters on emission rates, air quality model was run to determine how would the effect of variation on emission rates embody in air quality. Model was first run for base case, then it is tried to determine the impact on air quality by running the model for each case separately. PM2.5 is analyzed since it has a significant effect on public health although it is not one of the pollutants that are caused by vehicle emissions. The day and time was examined when the gap is at maximum between the concentrations that are calculated for fundamental cases and the concentrations that are calculated within each model cell for all scenarios. It has been realized that there is 1.5 μg/m3 (~5%) decrease in PM2.5 concentration Istanbul-wide when results from CMAQ is analyzed within Scenario-I where the speed increased by 20%. 1.5 μg/m3 rate might be considered insignificant when it is compared with other average concentrations; however, it plays a key role on public health. In Scenario-II, it was realized that there is an average 2μg/m3 decrease in PM2.5 concentration depending on decrease in speed. This study can be advanced by obtaining higher resolution data that are employed for emission calculations of vehicles such as truck, bus, etc., by preparing more detailed emission inventory, and by employing the data suiting more accurate boundary conditions for air quality model.
İstanbul'da MODELS-3/CMAQ model sistemi kullanarak düşük emisyon bölgesi çalışması
Istanbul is the most populated city of Turkey as well as one of the mega cities of the world. Due to growing population and economy, city has been experiencing the problems of air pollution. There are many studies about air pollution effects on human health in the literature. Road transport emissions are released in areas where people live intensively, therefore these emissions are important for public health. This thesis aims to identify and quantify the measures to be taken to prevent traffic-related air pollution by using WRF meteorology model and CMAQ chemistry and transport model. This study presents the first Low Emission Zone study in Istanbul by using modeling and highlights the requirements of Low Emission Zone establishment. Istanbul-specific inventory includes main anthropogenic sources on 2 km horizontal and hourly temporal resolution. Road transport emissions were obtained from COPERT emission model. Emission model results reveal that on-road traffic emissions are the main source for most of the pollutants such as CO, NMVOC and NOx, industrial combustion is responsible for high amount of SO2 emissions and solvent use and traffic are the main participants for NMVOC emissions. The spatial distribution of air pollutants has proved that the highest concentrations occur at the places where emission sources are located. But uncertainties may be occur due to the activity data, emission factors and temporal profiles used in this thesis. WRF model was run for a 11-day period, includes PM concentrations are mostly higher than EU limit value (50μg/m3), from November 2 to November 12, 2010. Model run results from the WRF simulation were compared with observations from Ataturk Airport and Goztepe air quality stations. According to statistical and time plot results WRF has captured surface temperature successfully. But this performance can be further improved by changing physical parameters of WRF. The results from the CMAQ model were compared with Aksaray air quality station based on PM10 concentrations. The statistical performance of model shows low correlation with the observations. Differences between model with measurement results can arise from many causes such as; uncertainty in the meteorological model and COPERT model, improper boundary conditions and temporal profiles and measurement errors. In order to limit traffic related air pollutants, methods and regions which have high density of population and work places were determined. Based on these criteria Historical Peninsula, Kadikoy and Maslak were selected as candidates. When transport sector emissions were reduced by 30% and given to DUMAN model, Historical Peninsula has demonstrated most significant response which is 10μg/m3 reduction in PM10 hourly concentration. Then, effect of each method on PM levels was examined by using literature studies and COPERT model. The most effective method was found as EURO 3 standard causes 85% reduction in PM10 emissions. In the case of only EURO 3, EURO 4, EUR0 5 and EURO 6 vehicles can enter the zone, hourly PM concentration differences between base situation and low emission case has reached up 35μg/m3. Overall, a low emission zone will be announced on the Historical Peninsula, will provide a significant improvement in regional air quality.
Knidos fay zonu'nun deprem geçmişini klor-36 yüzey yaş tayini yöntemiyle modelleme
Knidos is an ancient city, which is located in the south of Gulf of Gökova in Western Anatolia. The Knidos Fault Zone is situated in ancient settlement ruins on the Datça Peninsula. The recent geological and archaeological evidences point out that this ancient site has been affected by at least two crucial momentous seismic events. In the light of this information, we have carried out cosmogenic 36Cl dating in order to obtain information about the seismic history of the Knidos Fault Zone. Using cosmic-ray surface exposure dating of a well-preserved limestone fault scarp facilitates us to attain information, which reveals a seismic history of faulting events and identifies timing and recurrence interval of past major earthquakes, and slip rates of the Knidos Fault Zone. There are two distinct faults located in the study area; those are the Demeter Fault and the Mezarlık Fault. I have chosen to aim at the Mezarlık Fault on account of that it has well-preserved fault scarp. The concentration of cosmogenic 36Cl isotopes measured in 128 limestone samples from a ~15m high bedrock fault scarp helps us to reveal the fault displacement history of the Knidos fault, in the Western Turkey. Although this method can cause breakthrough to the recent studies in earth science, there are plenty of limitations and uncertainties to deal with. The important factors are latitude and air pressure (elevation) scaling factors for a constant geomagnetic field, shielding resulting from the specific geometry of active normal faults, effects of the chemical composition of the colluvial wedge, effects of denudation of the scarp surface and snow cover effects on scarp shielding. Through the modelling of the cosmogenic 36Cl nuclides, it can be understood that Mezarlık Fault might be post-glacial as a result of previous studies implied in the similar fault scarps in the Mediterranean. As oppose to all of these limitations, it has been tried to understand impacts of these factors on the target fault by using recent numerical models. I have set out to obtain accurate conclusion through correlate and compare the result with synthetic profiles and previous studies as much as possible. The slip histories modelled via concentrations of 36Cl indicate that at least three or more events occurred on the Mezarlık fault within the past 20 kyr; over 10 meters of displacement took place between early Holocene and late Pleistocene. This study was conducted with the Decision of the Council of Ministers with No. 2013/5387 on the date 30.09.2013 and was done with the permission of Knidos Presidency of excavation in accordance with the scope of Knidos Excavation and Research carried out on behalf of Selçuk University and Ministry of Culture and Tourism. This study was supported by the TÜBİTAK (Project No: 113Y436).