The influence of a heavily polluted urban river on the adjacent aquifer systems

 Ankara Creek is often subjected to overflowing of sewage caused by rainfall or direct discharge of raw sewage. Alluvial aquifers adjacent to Ankara Creek and its tributaries have considerable groundwater potential. The present status of groundwater quality is far from drinking water standards. Groundwater contamination in Ankara is suspected to be caused by Ankara Creek which is heavily polluted by raw sewage discharge, surface runoff and other common sources. In order to investigate the influence of heavily polluted Ankara Creek on the groundwater contamination in the adjacent alluvial aquifers, five sampling stations on Ankara Creek and 25 water wells were monitored during 1996. At five different sampling periods, water samples were collected from both surface water and groundwater. Chemical analyses of basic ions, pollution parameters and heavy metals in natural waters were carried out. The organic pollution prevails in Ankara Creek whereas total dissolved solids (TDS) and heavy metal concentrations are considerably low. Starting from the idea that Ankara Creek somewhat influences the groundwater quality and the contaminants in groundwater should attenuate with respect to distance, a series of water wells in a certain area, each having different distance from the creek, were examined using four pollution parameters. It is concluded that Ankara Creek barely influences the aquifer systems in connection. This is attributed to two reasons: rapid attenuation of contaminants due to dilution in groundwater and a blanket of very fine sized materials covering the bottom of Ankara Creek. Received: 28. April 1997 · Accepted: 23. February 1998     

Comparison of the QBO and F10.7 Solar Flux Effects on Total Mass Density

Geomagnetism and Aeronomy - The comparison of the Quasi Biennial Oscillation (QBO) and F10.7 solar flux effects on Total Mass Density (TMD) obtained from NRLMSIS-00 model for 90 km altitude of...     

The investigation of soil–structure resonance of historical buildings using seismic refraction and ambient vibrations HVSR measurements: a case study from Trabzon in Turkey

In this study, two different historical structures built in Trabzon have been processed by ambient vibrations and seismic refraction measurements. One of the investigated historical structures is the Atatürk Pavilion built in the nineteenth century, and the other one is Hagia Sophia which was built in the thirteenth century. These two buildings are among the most important historical buildings in Trabzon and are very important for the tourism of the city. In order to determine peak/s frequency and amplitude from the horizontal-to-vertical spectral ratios (HVSRs), we have performed several measurements of ambient vibrations both inside (at different floors) and outside (on the ground) of structures. We have also conducted seismic prospecting to evaluate the vertical 1D and 2D profile of longitudinal and shear seismic waves, V_p and V_s, respectively. To this purpose, we have performed seismic refraction tomography and MASW. Ambient vibrations and seismic measurements were compared with each other. The results show that average predominant frequencies and HVSR amplitudes of inside and outside of Atatürk Pavilion are 4.0 Hz, 7.8 Hz and 2.6, 2.3, respectively. The V_p values vary from 300 to 2070 m/s, and the V_s for maximum effective depth is up to 790 m/s in Atatürk Pavilion. On the other hand, average predominant frequencies and HVSR amplitudes of inside and outside of Hagia Sophia and its tower are 4.7, 4.4 and 2.4 Hz and 1.6, 1.8 and 6.9, respectively. V_p values range from 450 to 2200 m/s, and V_s for maximum effective depth is also up to 1000 m/s in Hagia Sophia. The frequency values (F₀?=?V_s/4 h) calculated from the velocities up to the maximum effective depth for Atatürk Pavilion are in good agreement with the predominant frequency values determined from ambient vibrations. Atatürk Pavilion and Hagia Sophia soils have been classed according to Eurocode 8 by using V_S30 values. The class was defined as “B.” Moreover, the bedrock in studied area is basalt. The high V_p and V_s values are also compatible with the lithology. The HVSR curves measured at the Hagia Sophia show the presence of clear peaks when compared to the Atatürk Pavilion. At the same time, there are marked velocity changes in the V_s sections calculated in both areas. As a result, in both areas there are significant impedance contrasts in the subsoil. However, this impedance contrast is more evident in Hagia Sophia. This could be also compatible with a lithological transition. The possible soil–structure interaction was investigated by using all the results and evaluated in terms of resonance risk. It is thought that the probability of resonance risk at Atatürk Pavilion is low according to the ambient vibrations measurements. However, resonance risk should be taken into consideration at Hagia Sophia site since the predominant frequency values are very close to each other. Finally, this site should be investigated in detail and necessary precautions should be taken against the risk of resonance.     

Influence of matric suction on shear strength behavior of a residual clayey soil

In this paper, the shear strength with respect to the matric suction of unsaturated soils was studied. For this purpose, unsaturated triaxial testing procedures were applied to the undisturbed residual soil specimens. An apparatus for performing triaxial tests was designed and constructed. In the tests, matric suction was controlled by using the axis translation technique, and pore water volume changes were measured by means of a volume change transducer with 10⁻⁸ m³ sensitivity. The test results indicated that the matric suction contributes to the shear strength of unsaturated soil specimens, and this contribution called suction strength varies non-linearly with respect to the matric suction. The logarithmic model needing to know the air-entry value and the internal friction angle of a soil specimen for prediction of the suction strength were presented and compared with the test results. It was found that suction strength values predicted from the proposed model were in satisfactory agreement with the experimental results.     

A field application for lime stabilization

This study presents the improvements achieved as a result of the lime stabilization application conducted by the joint effort of the Turkish Association of Lime Industrialists and the General Directorate of Rural Services on the 200 m long section of the Ankara Province Yukar? Yurtçu Village road where green and brown clays are dominant. The study also numerically demonstrates the impacts of these improvements on the road section based on the results of various laboratory and field tests. The lime stabilization in field conditions was performed with 5% lime for both clays and was applied as a 30 cm thick single layer. In the soaked California bearing-ratio (CBR) tests conducted in the laboratory, increases that reach up from 16 and 21 times compared to initial soaked CBR values were observed in green and brown clays, respectively, at the end of 28 days. The high increases observed in soaked CBR values would reduce the upper layer thickness of the roads. The similar improvements are also achieved in unconfined compression and plate loading tests. The comparisons performed with the plate loading tests clearly demonstrated the behavior of the surface to lime and its cure impact.     

The impact of water resources development projects on water vapor pressure trends in a semi-arid region, Turkey

The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP observation series of each station was rearranged on seasonal basis. Sequential Mann–Kendall trend test, Sen’s slope estimator, and Spearman’s rank–order correlation tests were employed for detection of likely trends, and Kruskall–Wallis test was used to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change phenomenon.     

Removal of cyanide from aqueous solutions by plain and metal-impregnated granular activated carbons

In this study, the removal of free cyanide from aqueous solutions by activated carbon was investigated. Effects of metal impregnation (Cu and Ag), aeration, and concentrations of adsorbent and cyanide on the rate and extent of the removal of cyanide were studied. The results have shown that the capacity of activated carbon for the removal of cyanide can be significantly improved (up to 6.3-fold) via impregnation of activated carbon with metals such as copper and silver. Silver-impregnated activated carbon was found to be the most effective at the reduction of cyanide level in solution. This appeared to be coupled with its comparatively high metal content after impregnation process where silver (5.07%) could be more readily loaded on activated carbon than copper (0.43%). Kinetics and equilibrium data for cyanide removal by plain and metal-impregnated activated carbons were determined to be consistent with the pseudo second-order kinetics and the Langmuir adsorption isotherms, respectively. Aeration (0.27 l/min) was found to exert a profound effect on the process leading to a 5.5–49.1% enhancement in the performances of plain and metal-impregnated activated carbons. This enhancement could be attributed to the increase in the availability of active sites on activated carbon for adsorption and the catalytic oxidising activity of activated carbon in the presence of oxygen. Practical limiting capacity of plain, copper- and silver-impregnated activated carbons for the removal of cyanide were experimentally determined to be 19.7, 22.4 and 29.6 mg/g, respectively.     

Neotethyan Evolution of the Ankara Mélange,Turkey: An Intraoceanic Subduction-Accretion System

<正>We report here new geochemical and geochronological data from mafic-ultramafic rock suites in the Ankara Mélange in north-central Turkey,and present a new tectonic model for its origin.Considered as one of most important relics of the Neotethyan realm in the region,the Ankara Mélange occurs between the Sakarya Continent     

Late Pleistocene–Holocene evolution of the southern Marmara shelf and sub-basins: middle strand of the North Anatolian fault,southern Marmara Sea,Turkey

Although there are many research studies on the northern and southern branches of the North Anatolian fault, cutting through the deep basins of the Sea of Marmara in the north and creating a series of pull-apart basins on the southern mainland, little data is available about the geometrical and kinematical characteristics of the middle strand of the North Anatolian fault. The first detailed geometry of the middle strand of the North Anatolian fault along the southern Marmara shelf, including the Gemlik and Band?rma Bay, will be given in this study, by a combined interpretation of different seismic data sets. The characteristic features of its segments and their importance on the paleogeographic evolution of the southern shelf sub-basins were defined. The longest one of these faults, the Armutlu-Band?rma segment, is a 75-km long dextral strike-slip fault which connects the W–E trending Gençali segment in the east and NE–SW trending Kap?da?-Edincik segment in the west. In this context, the Gemlik Bay opened as a pull-apart basin under the control of the middle strand whilst a new fault segment developed during the late Pleistocene, cutting through the eastern rim of the bay. In this region, a delta front forming the paleoshoreline of the Gemlik paleolake was cut and shifted approximately 60 ± 5 m by the new segment. The same offset on this fault was also measured on a natural scarp of acoustic basement to the west and integrated with this paleoshoreline forming the slightly descending topset–foreset reflections of the delta front. Therefore the new segment is believed to be active at least for the last 30,000 years. The annual lateral slip rate representing this period of time will be 2 mm, which is quite consistent with modern GPS measurements. Towards the west, the Band?rma Bay is a rectangular transpressional basin whilst the Erdek Bay is a passive basin under the control of NW–SE trending faults. When the water level of the paleo-Marmara lake dropped down to ?90 m, the water levels of the suspended paleolakes of Band?rma and Gemlik on the southern shelf were ?50.3 (?3.3 Global Isostatic Adjustment—GIA) and ?60.5 (?3.3 GIA) m below the present mean sea level, respectively. As of today a similar example can be seen between the Sea of Marmara and the shallow freshwater lakes of Manyas and Uluabat. Similarly, the paleolakes of Gemlik and Bandirma were affected by the water level fluctuations at different time periods, even though both lakes were isolated from the Sea of Marmara during the glacial periods.     

An application of the autoregressive extrapolation technique to enhance deconvolution results: a 2D marine data example

Interpreting a post‐stack seismic section is difficult due to the band‐limited nature of the seismic data even post deconvolution. Deconvolution is a process that is universally applied to extend the bandwidth of seismic data. However, deconvolution falls short of this task as low and high frequencies of the deconvolved data are either still missing or contaminated by noise. In this paper we use the autoregressive extrapolation technique to recover these missing frequencies, using the high signal‐to‐noise ratio (S/N) portions of the spectrum of deconvolved data. I introduce here an algorithm to extend the bandwidth of deconvolved data. This is achieved via an autoregressive extrapolation technique, which has been widely used to replace missing or corrupted samples of data in signal processing. This method is performed in the spectral domain. The spectral band to be extrapolated using autoregressive prediction filters is first selected from the part of the spectrum that has a high signal‐to‐noise ratio (S/N) and is then extended. As there can be more than one zone of good S/N in the spectrum, the results of prediction filter design and extrapolation from three different bands are averaged. When the spectrum of deconvolved data is extended in this way, the results show higher vertical resolution to a degree that the final seismic data closely resemble what is considered to be a reflectivity sequence of the layered medium. This helps to obtain acoustic impedance with inversion by stable integration. The results show that autoregressive spectral extrapolation highly increases vertical resolution and improves horizon tracking to determine continuities and faults. This increase in coherence ultimately yields a more interpretable seismic section.