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

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.

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 (δ(18)O) and carbon (δ(13)C) records from Dim Cave (~36°N) in SW Turkey. The glacial-interglacial δ(18)O 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 δ(13)C are interpreted as reflecting soil organic matter composition and/or thickness. δ(13)C 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) < http://www.epa.gov/rpdweb00/docs/federal/402-r-99-001.pdf >] (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.

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

The Lamas Basin is an area covering approximately 4,400 km(2) 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 delta(18)O and delta(2)H compositions. The delta(18)O-altitude effect was determined as approximately-0.12 per thousand/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-HCO(3) water type changes to Na-HCO(3) 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.