Using Kr and isotopic tracers to characterise old groundwater in the Bangkok metropolitan and vicinity areas.

Krypton-81 was applied to investigate the age of groundwater in the aquifer system in the Bangkok metropolitan and vicinity areas. Stable (H, O and C) and radioactive (H, Kr and C) isotopes and noble gases were applied in parallel. Low levels of C and significant radiogenic He confirm that groundwater in the deep aquifers is older than 30 ka.