The global flux of carbon dioxide into groundwater

The global flux of dissolved inorganic carbon (DIC) downward into groundwater is estimated to be ∼0.2 GtC/y. The flux is mapped over the earth's land surface by combining existing global maps of groundwater recharge, soil water pH and average temperature with a global map of soil vapor PCO 2 estimated from evapotranspiration. The estimated total flux of DIC into groundwater is significantly increased if larger, but reasonable, estimates of groundwater recharge are used, and the flux could potentially be much larger for higher soil moisture pH. The residence time of DIC in groundwater is at least as long as the residence time of groundwater, which may be on the order of hundreds to thousands of years.