The salinization process was investigated with hydrogeochemical tools to evaluate the origin of salinity in the Selçuk Plain. Na/Cl and Cl/Br molar ratios of coastal zone that covers an alluvial aquifer, karstic discharges, and a wetland are similar to the local seawater ratio. According to mixing ratios, seawater addition can reach 9-18% in both seasons at the coastal zone especially in karstic springs that are a kind of seawater-freshwater mixing points. A thematic map of the Salinization zone was constructed for the Selçuk Plain using geographical information system tools with different parameters such as major ion ratios, EC values, mixing ratios, and sodium adsorption ratio values. High correlation between Cl and Br, B, Li and Sr explains the salinization process that comes from marine intrusion. The δ 18 O and δD composition of water samples varies between −6.7‰ and −2.9‰; −37‰ and −20‰, respectively. The coastal zone waters are plotted on the mixing line due to the effects of the salinization process in the plain.

Izmir Bird Paradise is one of the most valuable wetlands in Turkey, but this area is now being threatened by the drying out of marshes and water pollution. This wetland consists of two ecosystems: fresh-and saltwater. The recharge of marshes is from rainfall, the Gediz River and groundwater from Can Suyu Pond. The water type of the river is Ca-Mg-Na-HCO 3 -SO 4 , whereas the groundwater is a Na-Cl water type. The reasons for the drying are long-term drought (evapotranspiration at 894 mm is >> rainfall at 546 mm), and excessive pumping of groundwater and seawater intrusion into Menemen Plain. Therefore, an additional freshwater resource is necessary. This water can be supplied from the limestone levels of Neogene sedimentary rocks in and around Izmir Bird Paradise that have a Ca-HCO 3 water type. Water pollution levels were also analysed. In the freshwater ecosystem Cd, Cr, Fe, Mn, Ni, Pb, Sb and Zn values, in the open channel in Izmir Bird Paradise Sb, Fe, Ni and Cd values, and in the river Fe, Pb and Sb values exceed the TSE 266 and EPA 2000 standards probably due to agricultural and industrial sources.

A baseline hydrogeochemical investigation was carried out as a contribution to the inventory of wetlands in Büyük Menderes River (BMR) coastal wetland which is the most important wetland in Turkey that is protected as "Natural Park" by government. In addition to the wetland values, agricultural activities are also important at this delta. From inland to coastal zone, the groundwater type is changed from Ca-HCO 3 to Na-Cl. Perfect correlation of Cl with Na and SO 4 indicated the mixing process between saline and fresh water. The seawater intrusion and "winter-leaching" is the main causes of salinization. Minor ions as B, Br, and Li versus Cl relationship also showed the marine influence at the BMR coastal wetland. The δ 18 O and δD composition of the waters are range between −8.11‰ and −1.65‰ and −49.2‰ and 8.1‰, respectively. Isotope values show the seawater mixing line and also dissolution of salts in the BMR coastal wetland. Weathering of aluminosilicates in the Paleozoic schist and clays resulted in the release of silica to the water. Due to the organic activity, iron concentrations reached to the tolerance limits. On the other hand, the use of phosphate fertilizers increases the phosphorus content in the water. The high value of As (from 0.6 to 134 μg/l) can be resulted as an evaporation process in the study area.

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The study area is located in the center of the Karaburun Peninsula, Turkey, where several karstic springs discharge near the coast 0-2 m above the sea level. The most important discharge points are the Ildırı and Gerence springs. Groundwater obtained from Ildırı springs and several drill wells provide water to the region during the summer periods. The electrical conductivity values are between 1900 and 3900 lS/cm. Springs are slightly salty and are not used directly as drinking water. Salinity was observed in the spring waters under natural flow conditions. The salinity values of the drillings and springs were measured in dry and wet seasons. Spring waters have conductivity values between 3000 and 4000 lS/cm. Preliminary surveys reveal that seawater contribution to Ildırı springs is 6.5 % maximum. Gerence spring waters discharge to the surface from a region very close to the sea. The dominant cation is Na, and the dominant anion is Cl. Conductivity values were between 7000 and 13,000 lS/ cm. Gerence spring waters discharge to the sea with seawater contributions ratios between 8.5 and 20.3 % depending on the seasonal changes. While some spring waters discharge 0.5-1.0 m above sea level, the rest of them discharge directly into the sea. Salinization of Gerence spring water is higher than the other springs.