A Revised Iron Extraction Protocol for Environmental Samples Rich in Nitrite and Carbonate

Wet-chemical iron extraction is widely applied to quantify the mineral-bound ferriferous fraction of sediments and soils. As previously shown, this method is strongly affected by the composition of the soil/sediment. Samples enriched in mostly microbially produced nitrite require the removal of the nitrite-containing aqueous phase or the replacement of HCl with sulfamic acid (SA) as the extractant. In this study, we show that sedimentary carbonate buffers SA, inhibiting the stabilization of Fe(II) and effective extraction of iron. We therefore provide a revised extraction protocol which allows the preservation of low pH conditions, leading to efficient iron extraction in nitrite- and carbonate-enriched samples.