Radiocarbon dating of Quaternary 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 Xiongan 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.