Galip Yuce

An 80 kyr-long continuous speleothem record from Dim Cave, SW Turkey with paleoclimatic implications for the Eastern Mediterranean

Speleothem-based stable isotope records are valuable in sub-humid and semi-arid settings where many other terrestrial climate proxies are fragmentary. The Eastern Mediterranean is one such region. Here we present an 80-kyr-long precisely-dated (by U-series) and high-resolution oxygen (δ18O) and carbon (δ13C) records from Dim Cave (~36°N) in SW Turkey. The glacial-interglacial δ18O variations in the Dim Cave speleothem are best explained in terms of changes in the trajectories of winter westerly air masses. These are along a northerly (European) track (isotopically less depleted) during the early last glaciation but are gradually depressed southward closer to the modern westerly track along the North African coast (more depleted) after c.50 kyr and remain in the southern track through the Last Glacial Maximum. The southward displacement of the westerly track reflects growth of the Fennoscandian ice sheet and its impact on westerly wind fields. Changes in δ13C are interpreted as reflecting soil organic matter composition and/or thickness. δ13C values are significantly more negative in interglacials reflecting active carbonic acid production in the soil and less negative in glacial times reflecting carbonate rock values. Several Heinrich events are recorded in the Dim record indicating intensification of westerly flow across this part of the EM.

Preliminary risk assessment of radon in groundwater: a case study from Eskisehir, Turkey

The aim of this study was to determine the radon concentrations in the water supplies of a residential area of central west Anatolia, Turkey. This research provides a preliminary risk assessment for inhabitants in the study area which can be applied for other regions. In 14 out of the 19 water supplies analysed, radon concentrations exceeded the maximum contaminant level (11.1 Bq l−1). The total annual effective doses of 10 for the wet season and 14 for the dry season out of the 19 water supplies are greater than the values recommended by EPA [Cancer Risk Coefficients for Environmental Exposure to Radionuclides, Federal Guidance Report No. 13 (US Environmental Protection Agency, Washington, DC, 1999) ] (0.1 mSv a−1). The elevated radon concentrations in water resources are most probably linked with geological origin which contains significant amounts of radioactive minerals.

Hydrochemical and Isotopic Composition of Tuzla Geothermal Field (Canakkale-Turkey) and its Environmental Impacts

Tuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. Geothermal brine, deriving from this area, contains an abundance of NaCl and a water temperature of 173°C (T1 well at 814 m depth) is typically encountered. The aim of this study was to determine the hydrogeochemical properties of the geothermal brine using both chemical and isotopic data, and to investigate the origin of the geothermal brine in the Tuzla area and the environmental impacts of Tuzla Geothermal Field (TGF). Both geothermal brine and shallow groundwater in the area are of meteoric origin. Isotope results indicate that the hot saline waters (brine) in the Tuzla geothermal field originate from connate water along faults. As the saline water rises to the surface, it mixes with shallow groundwaters in various ratios. In addition, the high sodium (Na) and chloride (Cl) content in the Tuzla Stream, fed from the Tuzla geothermal brine during the dry season, cause an increase in sodium and chloride concentrations in the shallow groundwaters by infiltration into the aquifer. Moreover, salt accumulation on the surface is observed due to the uncontrolled artesian flow of geothermal brine, which adversely affects the salinity of shallow groundwater.

Determination of the recharge area and salinization degree of karst springs in the Lamas Basin (Turkey)

The Lamas Basin is an area covering ∼4400 km2 situated on the eastern Mediterranean coast of Turkey covered with highly karstified limestone and dolomitic limestone from the Miocene and Mesozoic age, respectively. Owing to the area’s low karstification basement, groundwater in the karst aquifer circulates deep from the surface towards the springs along the coast as well as to the submarine springs. This study aims working out the salinization level and recharge characteristics of the Lamas Basin using environmental isotopes techniques. In the study, the data collected previously to discover, in general terms, the groundwater characteristics within the area are reanalyzed to fulfil the purpose of the study. In conclusion, it is found that the down gradient karst springs discharging along the Mediterranean coast mostly contain groundwater contributions from higher altitudes with depleted δ18O and δ2H compositions. The δ18O-altitude effect was determined as approximately−0.12 ‰/100 m which may indicate sea-spray intrusion towards inland. As a result, the salinization level of coastal springs changes ranging between 1.2 % and 17.0 %. Owing to the seawater encroachment, Ca–HCO3 water type changes to Na–HCO3 or Na-Cl water by the cation exchange during the dry period. As the unique freshwater potential extends along the coastal area, the groundwater production should be exploited in a way that seawater encroachment is kept at minimum.

Observation of excess heavy metal concentrations in water resources to infer surface water influences on shallow groundwater: a typical example of the Porsuk River (Eskisehir-Turkey)

The Eskisehir province is well-known due to its industrial and agricultural activities, which are a threat for the aquatic environment. Hence, monitoring of water quality in the area is of vital importance because of an excess heavy metal contents, especially As. The Porsuk River is heavily polluted by industrial activities from Kutahya city. It discharges into the Porsuk Dam and from there it flows relatively clean to Eskisehir city center, but beyond this point it increasingly deteriorates due to the negative impact of industrial and agricultural activities up to the junction point of Porsuk and Sakarya rivers. Heavy metal concentrations and As contents in surface and ground waters were selected as pollution indicators to examine pollution level and compare an interaction between river and groundwater. For this purpose, water samples taken between 2008 and 2010 from the Porsuk River along the section from the west of Kutahya to the discharge point into the Sakarya River, as well as groundwater samples from the wells located close to or far of the Porsuk River, were evaluated. Based on the obtained results, we found that the Porsuk River, especially at the locations close to the Sakarya River, and groundwater are polluted in terms of heavy metals and As compounds. In conclusion, the heavy metal and As pollution is also observed in the wells close to the locations in which groundwater is fed by the Porsuk River since it acts as an influent river. Thus, surface water is considered as a polluting source of groundwater.

The Ancient Gates to Hell and Their Relevance to Geogenic CO 2

In Greek mythology the netherworld is guarded by the three-headed hellhound Kerberos. For persons who have passed away, it is rather easy to find the way down to the realms of the shadows. Yet, there is no escape from the world of Hades. The gates to hell were used by the souls of the deceased but also by diseased people seeking cures or prophecies. In ancient times, these gates to the abyss were always connected to unexplainable geo-biological phenomena. These were regions of vapors, deadly gases, darkness, bubbling springs, and color changing creeks. Additionally, places where animals showed strange behavior or plant growth was irregular were selected for sanctuaries, oracles, or gates to the Hadean. Often but not always, carbon dioxide played a decisive role at these entrances, as it is colorless, tasteless, and kills all aerobic life quite quickly in higher concentrations.

Spatial distribution of groundwater pollution in the Porsuk River Basin (PRB), Turkey

The groundwater in the alluvium aquifer of the Eskisehir Plain (EP) is polluted by wastewaters transported through Porsuk River, agricultural-industrial activities, river-groundwater interactions and unsanitary landfill. Porsuk River flows throughout the alluvium aquifer in the EP. In this study, the effects of anthropogenic activities on groundwater quality in the EP were investigated. Since the sewage system has been operated from 1998, the ammonia content of the groundwater has decreased, but the groundwater and Porsuk River water have high contents of nitrite, ammonium, phenol, phosphorus, AOX, sulphide, and heavy metals. Thus, groundwater in the EP is in a poor quality both for drinking and domestic purposes.

Deadly CO2 gases in the Plutonium of Hierapolis (Denizli, Turkey)

Using a portable gas analyzer system, the geogenic gas regime below and around an ancient gate to hell at Hierapolis/Phrygia was characterized. The site was first described by Strabo and Plinius as a gate to the underworld. During centuries, it attracted even ancient tourists. In a grotto below the temple of Pluto, CO2 was found to be at deadly concentrations of up to 91%. Astonishingly, these vapors are still emitted in concentrations that nowadays kill insects, birds, and mammals. The concentrations of CO2 escaping from the mouth of the grotto to the outside atmosphere are still in the range of 4–53% CO2 depending on the height above ground level. They reach concentrations during the night that would easily kill even a human being within a minute. These emissions are thought to reflect the Hadean breath and/or the breath of the hellhound Kerberos guarding the entrance to hell. The origin of the geogenic CO2 is the still active seismic structure that crosses the old town of ancient Hierapolis as part of the Babadag fracture zone. Our measurements confirm the presence of geogenic CO2 in concentrations that explain ancient stories of killed bulls, rams, and songbirds during religious ceremonies. They also strongly corroborate that at least in the case of Hierapolis, ancient writers like Strabo or Plinius described a mystic phenomenon very exactly without much exaggeration. Two thousand years ago, only supernatural forces could explain these phenomena from Hadean depths whereas nowadays, modern techniques hint to the well-known phenomenon of geogenic CO2 degassing having mantle components with relatively higher helium and radon concentrations.

Assessment of the origin and geothermal potential of the thermal waters by hydro-isotope geochemistry: Eskisehir province, Turkey

ABSTRACT The thermal fluids vented over Eskisehir province have been investigated for their origin and to estimate the geothermal potential of the area. Thermal waters as well as bubbling and dissolved gases were collected and analysed for their chemical and isotopic features. Their isotopic composition varies in the range from −11.5 to −7.7 ‰ for δ18O, −84 and −57 ‰ for δ2H, and 0–7.2 TU for tritium. The gases (bubbling and dissolved) are mostly N2-dominated with a significant amount of CO2. The helium isotopic ratios are in the range of 0.2–0.66 R/Rac, indicate remarkable mantle-He contribution ranging between 2 and 10 % in the whole study area. Considering the estimated geothermal gradient about three times higher than the normal gradient, and the reservoir temperatures estimated to be between 50 and 100 °C using quartz and chalcedony geothermometers, a circulation model was built where possible mixing with shallow waters cool down the uprising geothermal fluids.