Type and Origin of Springs and Hotsprings at Surrounding Ridges of Bandung Basin, Related with its Potential Natural Contamination

Type and origin of groundwater is important to understand potential natural contamination. Bandung Basin in West Java Indonesia as anintra montan basin was chosen for this study. In some places, groundwater chemistry could be related to volcanic and thermal activities and may lead as the source of natural contamination to the water resources. In this research, seven water samples from southern and northern ridgesof Bandung Basin were taken and analyzed. In order to determine the type, origin of the water and potential natural contamination, hydrogeochemistry and stable isotopes H2 and O18 were used in this research. The methods were used to interprate the mixing mechanism between thermal water and shallowgroundwater with minerals in the aquifer. The thermal water from Walini in southern ridge and Maribaya in northern ridge can be distinguished to be related with deep geothermal activities as mixing of upflowing thermal fluid with shallow groundwater. Thermal water from Kamojang site is related with meteoric water and not related or mixed with deep thermal water. One cool spring waternear Kamojang hot spring shows it could be influenced by deeper water/fluids. Two other samples from springs around a hydrothermal mineralization showthat Arsenic and other metal ions concentration in mineralized aquiferis present at a very low concentration.