Origin of 14C in Icelandic Groundwater

We report the first attempt to date Icelandic groundwater by the radiocarbon dating technique. We propose that boron concentrations of the water samples can be taken as a measure of the amount of dead CO2 in the groundwater leached from rock. By assuming that the ratio of boron to CO2 is the same in the rock and groundwater it is possible to correct the 14C concentration for the contribution of rock-derived carbon in the groundwater and thus calculate the initial (undiluted) 14C concentration. When this correction is applied, the values for the cold and warm waters lie in the range 60 to 110 pMC, which is in accordance with the estimated residence time for the groundwater. We have also calculated the fractions of atmospheric and organic carbon in the water, based on the δ13C measurements, and the results agree well with the general hydrology and vegetational cover of the areas. Results from geothermal systems indicate that it is possible to use 14C to estimate relative age differences of the water in a particular geothermal area.

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