Study of the effect of fossil organic carbon on (super 14) C in groundwater from Hvinningdal, Denmark.

Abstract

The carbonate hydrochemistry of groundwater from the Hvinningdal aquifer (Denmark) was studied by radiocarbon (accelerator mass spectrometry (AMS)) and delta (super 13) C measurements as a preliminary step towards (super 14) C groundwater dating. The (super 14) C concentrations varied between 30 and 100 percent modern carbon (pMC) in apparent contradiction with tritium ( (super 3) H) data, which in most cases indicate a post-bomb date. The dilution of (super 14) C can be explained as being due to the combined effect of dissolution of old soil carbonate and oxidation of old organic carbon. The last effect proved to be essential. To calculate this correction the dissolved oxygen concentration was used together with the delta (super 13) C values. The combined corrections bring the (super 14) C concentrations up to post-bomb levels in better agreement with the (super 3) H data.