Microbial Quality in Coastal Waters of Dardanelles in Relation to the Pollution Sources and Transport Pathways

The coastal water quality of Çanakkale Dardanelles (Turkey) was assessed based on bacteriological data and physical–chemical parameters. Total coliform (TC), fecal coliform (FC), and enterococci (ENT) bacteria along with physicochemical parameters were measured monthly up to a year at 12 different sampling sites located through both coastal lines of the strait. The fecal bacteria were abounded at several sampling sites such as B1, B3, G3, and G4 due to direct wastewater discharges and septic leakages or overloading. Storm water runoff and sediment resuspension were important pathways for the transport of coliform and ENT bacteria to the Dardanelles, as the region receives high precipitation and strong winds for most part of the year. The values of pH, temperature, and salinity were in typical ranges for the studied area. The microbiological and physicochemical data were correlated individually and in combination. The best fit correlations for bacterial data were attained between TC and FC or TC and ENT (R = 0.67 or ?0.68), while those for the combined data were obtained for TC with temperature (R = 0.94) and TC with salinity (R = ? 0.70).     

Delineation of shallow resistivity structure in the city of Burdur,SW Turkey by vertical electrical sounding measurements

The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and 2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface. The study area is characterized by low resistivity distribution (<150 Ωm) originating from high fluid content in the subsurface. Lower resistivity (3–30 Ωm) is associated with the Quaternary and the Tertiary lacustrine sediments while relatively high resistivity (40–150 Ωm) is related to the Quaternary alluvial cone deposits. This study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area was characterized by high liquefaction hazard risk.     

Residual and Fully Softened Strength Evaluation of Soils using Artificial Neural Networks

A backpropagation artificial neural network (ANN) model is developed to predict the secant friction angle of residual and fully softened soils, using data reported by Stark et al. (J Geotech Geoenviron Eng ASCE 131:575–588, 2005). In the ANN model, index properties such as liquid limit, plastic limit, activity, clay fraction and effective normal stress are used as input variables while secant residual friction angle is used as output variable. The model is verified using data that were not used for model training and testing. The results also indicate that the secant residual friction angle of cohesive soils can be predicted quite accurately using liquid limit, clay fraction and effective normal stress as input variables with R ² = 0.93. The sensitivity analysis results indicate that plastic limit and activity have no appreciable effect on ANN predicted secant friction angles. The secant friction angle predictions of the ANN model were also compared with those of Stark’s et al. (2005) curves and the empirical formulas suggested for the same data sets by Wright (Evaluation of soil shear strengths for slope and retaining wall stability with emphasis on high plasticity clays, 2005). The comparison shows that the ANN model predictions are very close to those suggested by the Stark et al. (2005) curves but much better than the prediction of Wright’s (2005) empirical equations. The results also show that ANN is an alternative powerful tool to predict the secant friction angle of soils.     

Comparison of Planimetric and Thematic Accuracy of OrbView-3 and IKONOS Images

Spatial mapping from space using high-resolution satellite sensor data instead of conventional data collection techniques widely gained popularity. This study aims to analyze the planimetric and thematic accuracy of high-resolution OrbView-3 and IKONOS orthoimages. OrbView-3 and IKONOS images of a test area were acquired and these images were geometrically corrected using rational polynomial functions to conduct accuracy assessment. 40 Ground Control Points (GCPs) generated from static Global Positioning System (GPS) survey were used in the orthorectification procedure. 182 Test Points (TPs) produced from terrestrial surveying technique were used to analyze the accuracy of orthorectifications. Root Mean Square Error (RMSE) values obtained for GCPs and TPs were used to determine the planimetric accuracy of these images. Thematic accuracy analyses were conducted in radiometric and spatial base. Transects, lines and polygons were created to analyze the radiometric quality of data sets and to determine minimum distinguishable distance and distinguishable area. Both planimetric and thematic accuracy analyses illustrated that OrbView-3 and IKONOS images could be used to create 1:10000 scale map of the concerned region with appropriate planimetric and thematic quality.     

Modeling of occurrence frequencies of ion conics as a function of altitude and conic angle

The occurrence frequencies of dayside ion conics with various conic angles are obtained as a function of altitude from Exos-D (Akebono) observations. We made a model calculation of ion conic evolution to match the observation results. The observed occurrence frequencies of ion conics with 80° to 90° conic angle are used as an input to the model and the occurrence frequencies of ion conics with smaller conic angles are numerically calculated at higher altitudes. The calculated occurrence frequencies are compared with the observed ones of ion conics with smaller conic angles. We take into account conic angle variation with altitude in both adiabatic and non-adiabatic cases, horizontal extension of ion conics due to E × B drift, and evolution to elevated conics and ion beams in the model. In the adiabatic case, the conic angle decreases with increasing altitude much faster than was observed. The occurrence frequency of small-angle conics is much larger than the observed value without E × B drift and evolution to the other UFIs. An agreement is obtained by assuming non-adiabatic variation of conic angles with altitude and an ion E × B drift to gyro velocity ratio of 0.08 to 0.6, depending on geomagnetic activities.     

Direct interpretation of magnetotelluric sounding data based on the frequency-normalized impedance function

An important aspect of any non-linear inversion method is the generation of a suitable or good initial model as this controls the rate of convergence and accuracy of the result. To overcome the problem, a numerical method is presented for direct interpretation of magnetotelluric sounding data based on the frequency-normalized impedance (FNI) function. The expressions used to calculate the parameters are developed, first for a two-layer case under the assumption that deeper layers do not contribute to the early part of the FNI curve, and they are then generalized for an n -layer situation. The parameters of the first layer are computed by using successive sample values and the final estimate is obtained from the arithmetic mean of selected values by excluding unacceptable results in the logarithmic space. The top layer is then removed using a reduction equation. The repetition of the procedure on successive branches of the FNI function gives successive layer parameters, the resistivity of the substratum being obtained at the final step, when the reduction equation becomes equal to the square root of that resistivity.   The proposed method can be used as a complementary method for iterative inversion as it creates an initial guess which is close to the optimal solution. The solution produced by the direct interpretation may also be modified by the interpreter to incorporate prior geological information before being input to iterative interpretation schemes.     

Investigation of groundwater contamination using electric and electromagnetic methods at an open waste-disposal site: a case study from Isparta, Turkey

 Geophysical methods, when integrated with soil chemical and hydrogeological methods, can be used to investigate groundwater contamination. Direct current (DC) resistivity geo-electrical sounding and very-low-frequency electromagnetic (VLF-EM) data were collected at an open waste site used by the municipality of the city of Isparta, Turkey. The groundwater at shallow depths in alluvium, which is composed of gravel, sand and clay, were expected to be hazardously contaminated under and around the open waste-disposal site, in which both household and industrial wastes are known to be disposed of improperly. In this study, we mapped the spread of groundwater contamination using a VLF-EM method, which allows fast and inexpensive data collection. The method complements the results of geo-electrical sounding. There is a good correlation between the results of the VLF-EM and the DC-resistivity methods employed for the investigation of subsurface structure of the site, where soil chemical and previous hydrogeological surveys have indicated high levels of chemical concentrations. Received: 17 January 2000 · Accepted: 12 August 2000     

The Geoelectrical Structure of Northwestern Anatolia,Turkey

The magnetotelluric method has been employed to generate a geoelectrical model that will reveal the rich geological pattern and dynamic character of western and northwestern Anatolia, Turkey. Magnetotelluric data were collected from 53 sites along a profile of 290 km from the Dardanelles to the Ala?ehir Graben. Magnetotelluric data were in the range of 0.00055 Hz to 320 Hz. The models were obtained through 2-D joint inversion of transverse electric and transverse magnetic modes. Lateral changes in geoelectrical models are verified by using gravity and magnetic data. In addition, some of the seismological data presented here agree with proposed models that suggest a brittle-ductile structure boundary at a depth of 20 km. Generally speaking, a regional extensional regime caused reduction in the thickness of the crust and consequent uplift towards the south. The constructed model delineates the western part of the North Anatolian Fault Zone along the Biga Peninsula. The current patterns of volcanic activity on the Biga Peninsula and at Kula are related to conductive spots presented in the models. The border of the Gördes Basin, located between the Izmir - Ankara suture zone and the Menderes Massif, is also well delineated. The North Anatolian Fault Zone presents a pattern in which density and susceptibility anomalies attain relatively high values. Fillings covering most of the surface have lower density and susceptibility values than those of underlying structures.