A study on the curvilinear projection clibration of mixed 14C ages for groundwaters in Jianghan Plain
The distribution of 14C ages of groundwaters can indicate the direction and its change of groundwater seepage.The classical calibration models can eliminate the impact of 14C ages by changes of hydrochemical compositions of groundwaters,but hardly identify the mixing of groundwaters,resulting in that the obtained 14C ages represent mixed ages of groundwaters.In this paper,we have proposed a method for identifying the mixing of groundwaters and calibrating a14C values of groundwaters based on changes of hydrochemical compositions of groundwater samples along the flow path of groundwater,and have undertaken a case study of the groundwaters in the Jianghan Plain.The dissolution of sulfate minerals in groundwaters in the Jianghan Plain leads to the increase of SO42-contents in groundwaters.The relationship curve between SO42-contents and a14C values of groundwaters can be used to identify the mixing of groundwaters and to calibrate a14C values of groundwaters by using the curvilinear projection.Thus,we have proposed the mixed-IAEA model.The difference between the IAEA modelling age and the mixed-IAEA modelling age can be used to reveal the change of groundwater seepage.The mixing area of young aged groundwaters repersents the convergence direction of groundwaters in the Jianghan Plain,while the mixing area of old aged groundwaters represents the the convergence direction of the old aged groundwaters.Therefore,it is necessary to consider the influence on 14C dated ages of groundwaters by the mixing of grounderwaters for the groundwater flow system in large sedimentary plains(or basins).The calibrated 14C ages by using the mixed-IAEA model can be used to identify the change of groundwater seepage.
14C agethe calibration by using the mixed-IAEA modelhydrogeochemistrygroundwater flowJianghan Plain
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