Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Orhan Gunduz is active.

Publication


Featured researches published by Orhan Gunduz.


Journal of Contaminant Hydrology | 2009

Groundwater contamination mechanism in a geothermal field: a case study of Balcova, Turkey.

Niyazi Aksoy; Celalettin Şimşek; Orhan Gunduz

The Balcova Geothermal Field (BGF) located in Izmir, Turkey is situated on an east-west directed graben plain within which the hot waters surface from a fault zone that cuts the Mesozoic aged Bornova Flysch. Due to the low permeability and porosity of the Bornova Flysch, the geothermal water cycles along the immediate vicinity of the Agamemnon fault and mixes with cold waters at different depths of this fractured zone. Within the scope of this study, the mixing patterns and the groundwater contamination mechanisms are analyzed by, hydrogeological and hydrogeochemical methods. Based on the results of this research, it has been found out that the hot geothermal water and the cold regional groundwater resources of the surficial aquifer mix within the fractured zone in Bornova Flysch and within the Quaternary alluvium aquifer due to natural and anthropogenic activities including (i) the natural upward movement of geothermal fluid along the fault line, (ii) the accelerated upward seepage of geothermal fluid from faulty constructed boreholes drilled in the area, (iii) the faulty reinjection applications; and, (iv) the uncontrolled discharge of waste geothermal fluid to the natural drainage network. As a result of these activities, the cold groundwater reserves of the alluvial aquifer are contaminated thermally and chemically in such a way that various toxic chemicals including arsenic, antimony and boron are introduced to the heavily used surficial aquifer waters hindering their use for human consumption and agricultural irrigation. Furthermore, the excessive pumping from the surficial aquifer as well as the reduced surface water inflow into BGF due to the dam constructed on Ilica Creek intensify the detrimental effects of this contamination. Based on the results of this study, it can be concluded that the groundwater pollution in BGF will expand and reach to the levels of no return unless a series of preventive measures is taken immediately.


Journal of Hazardous Materials | 2013

Naturally occurring arsenic in terrestrial geothermal systems of western Anatolia, Turkey: Potential role in contamination of freshwater resources

Jochen Bundschuh; Jyoti Prakash Maity; Bibhash Nath; Alper Baba; Orhan Gunduz; Thomas R. Kulp; Jiin-Shuh Jean; Sandeep Kar; Huai Jen Yang; Yu Jung Tseng; Prosun Bhattacharya; Chien-Yen Chen

Arsenic (As) contamination in terrestrial geothermal systems has been identified in many countries worldwide. Concentrations higher than 0.01 mg/L are detrimental to human health. We examined potential consequences for As contamination of freshwater resources based on hydrogeochemical investigations of geothermal waters in deep wells and hot springs collected from western Anatolia, Turkey. We analyzed samples for major ions and trace element concentrations. Temperature of geothermal waters in deep wells showed extreme ranges (40 and 230 °C), while, temperature of hot spring fluids was up to 90 °C. The Piper plot illustrated two dominant water types: Na-HCO3(-) type for geothermal waters in deep wells and Ca-HCO3(-) type for hot spring fluids. Arsenic concentration ranged from 0.03 to 1.5mg/L. Dominance of reduced As species, i.e., As(III), was observed in our samples. The Eh value ranged between -250 and 119 mV, which suggests diverse geochemical conditions. Some of the measured trace elements were found above the World Health Organization guidelines and Turkish national safe drinking water limits. The variation in pH (range: 6.4-9.3) and As in geothermal waters suggest mixing with groundwater. Mixing of geothermal waters is primarily responsible for contamination of freshwater resources and making them unsuitable for drinking or irrigation.


Archives of Environmental & Occupational Health | 2015

Statistical Analysis of Causes of Death (2005–2010) in Villages of Simav Plain, Turkey, With High Arsenic Levels in Drinking Water Supplies

Orhan Gunduz; Coskun Bakar; Celalettin Simsek; Alper Baba; Alper Elçi; Hakan Gurleyuk; Merdiye Mutlu; Ayse Cakir

The purpose of this research was to compare the causes of death in 5 villages situated in Simav Plain, Turkey, during 2005–2010 where different arsenic levels were detected in drinking water supplies. Since groundwater in Simav Plain had arsenic concentrations that ranged between 7.1 and 833.9 ppb, a two-phase research was formulated. In the first phase, public health surveys were conducted with 1,003 villagers to determine the distribution of diseases. In the second phase, verbal autopsy surveys and official death records were used to investigate the causes of death. In total, 402 death cases were found in the study area where cardiovascular system diseases (44%) and cancers (15.2%) were major causes. Cancers of lung (44.3%), prostate (9.8%), colon (9.8%), and stomach (8.2%) were comparably higher in villages with high arsenic levels in drinking water supplies. Furthermore, the majority of cases of liver, bladder, and stomach cancers were observed in villages with high arsenic levels.


WIT Transactions on Ecology and the Environment | 2003

Simultaneous Solution Of Coupled Surface Water/groundwater Flow Systems

Orhan Gunduz; Mustafa M. Aral

The use of coupled models of hydrologic analysis, which includes more than one component of the hydrologic cycle, is a common occurrence. Coupled models tend to be more complex and their solution may suffer numerical complications. In this study, we present a coupled hydrological model to simulate the interaction between stream flow and groundwater flow. A one-dimensional stream flow model using the complete form of the St Venant equation is coupled with a twodimensional vertically averaged groundwater flow equation in an unconfined aquifer. The governing equations of the two different hydrological domains are linked with the recharge term at the river bed. The resulting coupled mathematical model is solved simultaneously by linking the two hydrologic system matrices in a global matrix. The proposed simultaneous solution approach provides a more efficient solution for the coupled flow problem and is superior to the approximate solution obtained through an iterative approach.


Water Quality, Exposure and Health | 2015

Water Quality Perspectives in a Changing World

Orhan Gunduz

Water is a crucial part of human life. Ever-increasing population coupled with changing life styles is constantly increasing the demand for water. Today, populations require more water with higher quality standards than before, and it is becoming more difficult to satisfy these demands without altering the balance of nature. Anthropogenic stresses and natural phenomenon are playing critical roles during the supply of sufficient quantities of water with required quality. Consequently, previously unused resources are being considered for use; advanced treatment methods are being implemented to satisfy the quality requirements, and reuse of wastewaters is becoming a significant factor in many parts of the world. While trying to satisfy this supply–demand cycle, resource managers and decision makers are facing other challenges, which, in essence, are re-defining our whole understanding for water resources management. Health concerns related to water quality are being the primary issue all around the world, and the direction of research is now shifting towards understanding the complex interactions that water quality imposes on human health.


Water Air and Soil Pollution | 2016

The Impacts of Geothermal Fluid Discharge on Surface Water Quality with Emphasis on Arsenic

Reyhan Tugba Baysal; Orhan Gunduz

Geothermal energy is known to be a clean and renewable energy resource. However, geothermal fluid has significant impacts on surface water quality when disposed in an uncontrolled manner due to the high concentrations of numerous dissolved constituents and the elevated thermal content. The geothermal fluid in western Anatolia typically contains high concentrations of arsenic, boron, and lithium that are toxic to human and plant life. A river system in western Anatolia, Turkey, receives uncontrolled waste geothermal fluid discharge from three fields and is thermally and chemically contaminated. A one-dimensional water quality model is developed to assess the extent and strength of geothermal pollution in the river system. The calibrated and verified model results revealed that although both the point and nonpoint sources of contamination are influential in the water quality degradation, point discharges of waste geothermal fluid were responsible for dramatic increases in the contaminant concentrations and water temperature in the river. The model was later used to analyze the potential measures to improve the degraded water quality and compare the effectiveness of structural and non-structural mitigation scenarios.


Archive | 2006

Surface/subsurface interactions: coupling mechanisms and numerical solution procedures

Orhan Gunduz

The interaction sb e tween surface and subsurface waters have long been an important topic in hydrological research. In general, these interactions are considered to be one of the most difficult areas of the discipline, particularly for the modeler who intends to simulate the dynamic relations between these two major domains of the hydrological cycle. In essence, one major complexity is the spatial and temporal variations in the dynamically interacting system behavior. The proper simulation of these variations requires the need for providing an appropriate coupling mechanism between the two components of the system. This study discusses the fundamental differences between the numerous coupling techniques that the hydrologic modeler can use to couple these two components. The details associated with their numerical solution procedures as well as the selection criteria of the most suitable coupling technique are also presented with particular emphasis on the spatial and temporal scales of subprocesses, the accuracy of the output required, and the numerical and computational complexity allowed.


Exposure and Health | 2017

The Health Risk Associated with Chronic Diseases in Villages with High Arsenic Levels in Drinking Water Supplies

Orhan Gunduz; Coskun Bakar; Celalettin Simsek; Alper Baba; Alper Elçi; Hakan Gurleyuk; Merdiye Mutlu; Ayse Cakir

This study is intended to compare and assess the distribution and possible causes of current chronic diseases in villages with high arsenic levels in drinking water supplies. It is a cross-sectional epidemiological research that analyzes the frequency and underlying risk factors of chronic diseases in villages with varying levels of arsenic exposure through drinking water. Sample space of study included 1003 individuals, 614 of whom were from villages with high arsenic levels in drinking water and remaining 389 were from two control villages with below-limit arsenic levels in drinking water. While nutritional habits and living environments of two groups were similar, cigarette smoking and alcohol use were higher in villages with low arsenic levels. Mini mental state examination test results in 60+ age group were lower in villages with high arsenic levels. Although no statistically significant differences were detected in chronic disease occurrence between the groups, the number of cases was higher in villages with higher percentage of cigarette smoking and alcohol use. Moreover, cases of lung, colon, and stomach cancers were higher in villages with high arsenic levels in drinking water supplies.


Archive | 2011

Influence of Climate Change on Shallow Groundwater Resources: The Link Between Precipitation and Groundwater Levels in Alluvial Systems

Orhan Gunduz; Celalettin Simsek

Alluvial groundwater systems are extremely vulnerable to changes in precipitation amounts as they are typically recharged from above. Thus, any change in precipitation patterns due to climate change is likely to influence such systems first. Dynamic behavior of these systems is clearly seen from large fluctuations in the declining and rising curves of groundwater level time series graphs. An example of such a system is analyzed within the scope of this study that is located in Western Anatolia near Izmir, Turkey. Data collected from 21 monitoring wells were used to assess the long term general trend in the groundwater levels of Torbali-Bayindir plain, an alluvial system near Izmir city. The results demonstrated an average declining pattern of 0.75 m/year in groundwater levels where strong seasonal fluctuations in some wells could reach as high as 30 m. Considering this dynamic behavior, such systems, which are highly dependent on timing, persistence and total amounts of precipitation, are extremely vulnerable to changes in precipitation patterns, particularly in areas where climate change effects are towards increased temperature values and reduced precipitation totals.


Archive | 2006

ALTERNATIVE FORMULATIONS FOR THE REUSE OF TREATED WASTEWATER IN MENEMEN PLAIN IRRIGATION SCHEME

Orhan Gunduz; Ayşen Türkman; Deniz Ulas Doganlar

In this study, it is intended to investigate the possibility and technical viability of using the effluents of Izmir Wastewater Treatment Plant in Menemen plain irrigation. The research verified the fact that the influent of the plant generally demonstrates typical characteristics of domestic wastewater with the exception of elevated values of electrical conductivity and salinity. These high values are mainly attributed not only to salt water intrusion due to failing pipes and improper pipe connections of the interceptor canal but also to highly-concentrated pre-treated discharges of various industries within the city. It has also been observed that these high values are as well reflected in the plant effluent hindering its use in irrigation. Considering the strong demand for the treatment plant effluent by the farmers and irrigation unions, this study intends to find out possible solutions for high conductivity and salinity. The research involves the formulation of alternative techniques and methodologies such that the quality of treated effluents would satisfy the irrigation water quality criteria currently effective in Turkish legislation.

Collaboration


Dive into the Orhan Gunduz's collaboration.

Top Co-Authors

Avatar

Alper Baba

İzmir Institute of Technology

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Alper Elçi

Dokuz Eylül University

View shared research outputs
Top Co-Authors

Avatar

Mustafa M. Aral

Georgia Institute of Technology

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Ayse Cakir

Dokuz Eylül University

View shared research outputs
Top Co-Authors

Avatar

Coskun Bakar

Çanakkale Onsekiz Mart University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge