Hydrogeochemistry of surface and spring waters in the surroundings of the CO2 injection site at Hontomín-Huermeces (Burgos, Spain)

► A pilot plant to inject CO2 will shortly be installed at Hontomín-Huermeces (HH) (Burgos, Spain). ► First geochemical and isotopic data of the HH surface and ground waters. ► Low TDS and Ca(Mg)-HCO3 chemistry suggests shallow and rapid circulation. ► These data represent a geochemical background for intra- and post-injection monitoring programs. ► Carbon isotopes (CO2 and TDIC) in the Hontomín-Huermeces waters were modeled.