First discrete iron(II) records from Dome C (Antarctica) and the Holtedahlfonna glacier (Svalbard)

Fe(II) is more soluble and bioavailable than Fe(III) species, therefore the investigation of their relative abundance and redox processes is relevant to better assess the supply of bioavailable iron to the ocean and its impact on marine productivity. In this context, we present a discrete chemiluminescence-based method for the determination of Fe(II) in firn matrices. The method was applied on discrete samples from a snow pit collected at Dome C (DC, Antarctica) and on a shallow firn core from the Holtedahlfonna glacier (HDF, Svalbard), providing the first Fe(II) record from both Antarctica and Svalbard. The method showed low detection limits (0.006 ng g(-1) for DC and 0.003 ng g(-1) for the HDF) and a precision ranging from 3% to 20% RSD. Fe(II) concentrations ranged between the LoD and 0.077 ng g(-1) and between the LoD and 0.300 ng g(-1) for the Antarctic and Arctic samples, respectively. The Fe(II) contribution with respect to the total dissolved Fe was comparable in both sites accounting, on average, for 5% and 3%, respectively. We found that Fe(II) correctly identified the Pinatubo/Cerro Hudson eruption in the DC record, demonstrating its reliability as volcanic tracer, while, on the HDF core, we provided the first preliminary insight on the processes that might influence Fe speciation in firn matrices (i.e. organic ligands and pH influences). (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Fe(II) is more soluble and bioavailable than Fe(III), and a chemiluminescence-based method was used to determine Fe(II) concentrations in firn matrices from Antarctica and Svalbard. The method showed low detection limits and good precision, with Fe(II) contributing 5% and 3% to total dissolved Fe in Antarctica and the Arctic, respectively. Fe(II) was able to accurately identify volcanic eruptions and provide insights into Fe speciation in firn matrices.