Groundwater dating using Radioisotopes of 3H and 14C in Kashan Plain Aquifer

Radioisotopes, as a new achievement in the environmental sciences, have found significant development in water resources management, especially in dating, aquifer recharge management, and the role of contaminants in water resources pollution. Due to the quantitative and qualitative critical condition of groundwater resources in Kashan plain, having accurate isotopic data from water resources can be effective in proper management of water resources in this region. In this paper, while present the groundwater sampling, preparation and analysis methods for measuring 3H and 14C, we have investigated the age of groundwater resources in Kashan plain. For this aim, 11 groundwater samples for tritium by enrichment method and 3 samples for carbon-14 were analyzed. The results showed that the amount of tritium in the groundwater resources of Kashan plain is less than 0.08 TU which indicates that the water resources are old. Also, carbon-14 results showed that the age of groundwater resources in Kashan plain varies between 10,000 and 21,000 years. The results showed that by moving toward the northeast of the aquifer (aquifer’s outlet), the age of the water resources decreased, which indicating that the paleo deep-waters were mixed with the freshwater waters. In general, by mowing toward the southwest and west of the aquifer to northeast of the aquifer, groundwater age decreases.