Dissolved Fe(II) from the southbound leg of the US GEOTRACES Arctic cruise (HLY1502) on USCGC Healy from August to October 2015

Dissolved Fe(II) concentrations were determined using an automated flow injection analysis system (FeLume II Waterville Analytical) employing a luminol chemiluminescence based detection system as described in King et al. (1995) and Heller et al. (2017).

From published and ongoing work in the Peru and Chile oxygen minimum zones an optimized methodology for Fe(II) detection by luminol has been described in Croot et al. (2019). This work details some of the challenges and limitations of using luminol for dFe(II) detection. It should be noted that as Fe(II) is a transient redox species with a short half life in oxygenated seawater that is dependent on dissolved oxygen and pH, it is not possible to archive (preserve) samples for later analysis. Intercalibrations for Fe(II) have yet to be conducted in the context of GEOTRACES studies and should be pursued where logistically possible.