Radiocarbon dating of groundwater in the North China Plain and its implication to ¹⁴C correction

¹⁴C is commonly used in groundwater dating. Due to the uncertainty of the initial ¹⁴C contents (A₀) and the complex geochemical processes in the subsurface, the ¹⁴C ages were corrected but remain largely uncertain. To determine the groundwater age for the Quaternary aquifer in the North China Plain, 27 new ¹⁴C samples were collected from the Xiong’an Area and its surroundings. Combined with 65 ¹⁴C samples from published references, the initial ¹⁴C content (A₀) was determined after analyzing the hydrochemical evolution and constructing a parameter model of the aquifer. A feasible method was proposed to evaluate the accuracy of ¹⁴C ages. The initial ¹⁴C content was expected to be 87.0 pMC, with the dissolution of dead carbon being neglected in the aquifer. Oxygen isotope in groundwater can be divided into three stages by two climatic anomalous of 4.2 ka and Younger Dryas (YD, approximately 12 ka). There is a significant divergence between ¹⁴C dating results and ⁴He/⁸¹Kr ages at the well depth of 300 m in the central and coastal plain, which indicates the arrival of the ¹⁴C dating limit. Therefore, the ¹⁴C ages can be evaluated by oxygen isotope in groundwater divided by two climatic anomalous of 4.2 ka and Younger Dryas. The ¹⁴C method should be used with caution in the deep aquifer.