Van Geen et al. (1994, GCA 58, 2073) determined sorption of carbonate on goethite as function of pH. They concludeds that the reactive surface sites of metal oxides in natural waters may be predominantly covered by carbonate species. The lower availability of sorption sites affects sorption of trace metals such as Cd, Cu, Ni and As, and thus influences the mobility of these heavy metals in the natural environment. The de facto standard database of Dzombak and Morel (1990) for sorption of heavy metals on hydrous ferric oxide (HFO) does not contain data on CO2 species, Applications of geochemical models such as MINTEQ and PHREEQC which use this database may be in serious error when sorption of a major ion is neglected.
The carbonate sorption data obtained by Zachara et al. (1987, EST 21, 589) for ferrihydrite were optimized to the Dzombak and Morel database by Appelo, Van der Weiden, Tournassat and Charlet (2002); 98 kB pdf.

Appelo et al. showed that HCO3- is important for displacing As from surface sorption sites, and may explain the high concentrations found in Bangladesh groundwater.