Emissions of Fe(II) due to the undersea volcano of El Hierro and its kinetic of oxidation

Abstract

The eruptive process and the subsequent hydrothermal stage which took place in the undersea volcano at the southeast of the El Hierro Island, have increased the concentration of TDFe(II) (Total dissolvable iron(II), unfiltered) in the waters nearest to the main cone. Three cruises were carried out in October 2013, March 2014 and May 2015 in order to detect any variation in concentrations of TDFe(II) due to hydroothermal emissions, two years after the eruptive process. Flow injection chemiluminescence using luminol as the reagent was used to determine the concentrations of TDFe(II). The results confirm positive anomalies in TDFe(II) which coincide with negatives anomalies in pHT in a secondary cone during these cruises. Temporal studies in the stations located over the main cone and two secondary cones with positively anomalies in TDFee(II) concentrations and negative anomalies in pH values were carried out during hours to days. These showed an important variability in both pHT and TDFe(II) concentrations which indicated that the volcanic area was affected by intermittent events of hydrothermal fluid emissions. These anomalies were present in the volcanic cone three years after the eruptive phase had ceased. The increased TDFe(II) concentrations and the low associated pHT values may be triggering an important fertilization event in the seawater around the volcano at the Island of El Hiierro providing optimal conditions for the regeneration of the area.