Investigation on groundwater salinization has been carried out in the city of Pasuruan using environmental isotopes and hydrochemistry methods. Assessment on correlation of stable isotopes and major chemical elements of samples from precititation, shallow groundwater, deep graundwater and sea water was performed. This was done based on the properties of stable isotopes oxygen-18 and deuterium within the phenomena of hydrology cycle and also based on the chemical exchange taken place during the passage of groundwater through the rock formation. The result of the investigation showed that the increase of chloride content in groundwater at coastal area of Pasuruan was not due to sea water instrussion but due to the salt containing air born desolved precipitation. while salinization of the deep groundwater was due to aquifer leaching of coastal sediment formation.Wandowo, Zainal Abidin & Djijono
