Waste disposal on karstic terrain: a case study from the ancient marble quarries in Iznik (Nicaea), Turkey

This study is conducted in Iznik, a city situated in the Marmara region of Turkey. There are number of ancient marble pits in the area, some of which are used as sewage and solid waste dump sites. This study is aimed at investigating the hydrogeological and hydrogeochemical properties of Iznik plain with special emphasis on these waste sites. In terms of geological features, Derekoy metamorphics are basement rocks that consist of graphite schist, muscovite-quartz schist and marble lenses. Since Iznik marble was used as a natural construction material in the area since in the Roman era, 20 ancient marble quarries in different sizes existed in and around the study area. Wastewater from the city of Iznik and surrounding residential areas was disposed in three of these ancient marble quarries. In terms of hydrogeological features, the Iznik marble and alluvium units constitute the main aquifer system in the study area. Because of the highly fractured structure of the Iznik marble, the wastewater in the quarries was able to move rapidly within the rock. Analyses of groundwater samples revealed that the wastewater flowing in the marble unit discharges eventually into the alluvial unit and thereby affecting groundwater quality around the antique quarries. Based on chemical analyses results, the wastewater was Na-Cl water type and contained high concentrations of Na (3260 mg/l), K (903 mg/l) and Cl (10396 mg/l). Samples from wells down gradient of the wastewater source had comparatively higher Na, K and Cl concentrations