ABSTRACT
ABSTRACT: A study of the 14C age of groundwater was performed along a flow path in a Pleistocene sand and mudstone aquifer system containing a small amount of carbonate. Groundwater was sampled from artesian wells varying in depth from 120 to 420 m. CaHCO3 type water was detected in all samples, providing apparent 14C ages ranging from 1500 to 7600 years. Geochemical and hydrological analysis indicated that the dissolved inorganic carbon was mainly from dissolution of calcite, and addition of CO2 from the soil zone and organic matter in the aquifer. Based on these results, a quantitative reaction was calculated using the carbon and isotope balance method. The corrected 14C ages were obtained as 100 to 3400 years with 1.3 to 3.8 m/yr of average flow rate. Despite the small calcite content in the geologic layer, the effect of dissolution on 14C ages is quite significant.
Keywords: Corrected 14C age, isotope mass balance
