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

► Potential environmental impact of high arsenic from geothermal sources was identified. ► Geothermal waters from deep wells are characterized by Na-HCO3 type. ► Hot spring fluids are characterized by Ca-HCO3 type. ► As(III) is the dominant species in both deep wells and hot spring fluids. ► Mixing of geothermal waters containing As is responsible for environmental impact.