Seasonal and Spatial Variations of Metals in Melen Watershed Groundwater, Turkey

Effective groundwater monitoring and status assessment is vital in the management and protection of groundwater systems according to e.g., the European Groundwater Directive. This study determined metal concentrations in groundwater in the Melen watershed close to Istanbul and assessed land use effects on groundwater status. In the monitoring period (2010-2011), elevated metal concentrations were observed in regions close to industrial zones and seasonally in agricultural fields. The highest values of metals (As, Mn, Zn, V, Cu, Na and Ba) concentrations were found in autumn and winter, when groundwater recharge occurs. Detectable levels of dissolved metals, such as Cr and Cd, were only found close to industrial zones. The aquifer can be considered to be in good qualitative status regarding some metals. However, As, Mn and Zn are present in concentrations higher than approved by international standards and pose a risk to human health. Therefore, measures to prevent metal contamination close to potential sources and good watershed management are needed