Application of chlorine-36 technique in determining the age of modern groundwater in the Al-Zulfi province, Saudi Arabia

The present study aims to estimate the residence time of groundwater based on bomb-produced Cl-36. Cl-36/Cl ratios in the water samples are determined by inductively coupled plasma mass spectrometry and liquid scintillation counting. Cl-36/Cl ratios in the groundwater were estimated to be 1.0-2.0x10(-12). Estimates of residence time were obtained by comparing the measured bomb-derived Cl-36 concentrations in groundwater with the background reference. Dating based on a Cl-36 bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s. The above Cl-36 background concentration was deduced by determining the background-corrected Dye-3 ice core data from the frozen Arctic data, according to the estimated total Cl-36 resources. The residence time of 7.81x10(4) y is obtained from extrapolated groundwater flow velocity. Cl-36 concentration in groundwater does not reflect the input of bomb pulse Cl-36, and it belongs to the era before 1950.