Our paper introducing a new sampling method for 14C-dating of groundwater is in press for the journal Radiocarbon [CO2-14C_RY_ReRev].
New 81Kr data from Negev desert revealed that the estimated recharge period based on radiocarbon was by far underestimate. This can partly be attributed to the modern carbon contamination during sampling. We measured radiocarbon in CO2 gas from groundwater using a device originally developed for studies of noble gas radionuclides. Carbon is collected in the gas phase, eliminating the possibility of fostering microbial activities and aqueous chemical reactions during sample storage, although samples are still subject to further adjustment for water-rock interaction and subsurface geochemical processes prior to sampling.
Most of them showed lower CO2–14C activity than that of DIC-14C, presumably due to the absence of atmospheric contamination. These field data serve as confirmations for the reliability of the newly presented sample collection and CO2–14C method, as well as for the outstanding roles of radiokrypton isotopes in characterizing old groundwater.