Iron is an element of great interest due to its role in primary production and in oceanic carbon cycle regulation, such that past changes in iron deposition may have influenced oceanic sequestration of atmospheric CO 2 on millennial time scales. The behavior of iron in biological and environmental contexts depends strongly on its oxidation state. Solubility in water and the capacity to form complexes are just two important characteristics that are species dependent. Distinguishing between the two iron species, Fe(ii) and Fe(iii), is necessary to evaluate bioavailability, as Fe(ii) is more soluble and therefore more readily available for phytoplankton uptake and growth. Here, we present a novel analytical method for iron speciation analysis using Collision Reaction Cell-Inductively Coupled Plasma-Mass Spectrometry (CRC-ICP-MS) and apply it to ice core samples from Talos Dome, Antarctica. The method detection limit is 0.01 ng g -1. A chelating resin, Ni-NTA Superflow, was used to separate the Fe species. At pH 2 the resin is capable of retaining Fe 3+ with no retention of Fe 2+. After the initial separation, we oxidized the Fe 2+ using H 2O 2, and determined the Fe 2+ concentration as the difference between the two measurements. Our preliminary results demonstrate higher Fe 2+ concentrations during glacial periods than during interglacial periods. This elevated concentration of Fe 2+ suggests that more iron was available for phytoplankton growth during the Last Glacial Maximum, than would be expected from measurements of proxies such as dust mass or total Fe.
Determination of Fe 2+ and Fe 3+ species by FIA-CRC-ICP-MS in Antarctic ice samples
Spolaor;Gabrieli;Cozzi;
2012
Abstract
Iron is an element of great interest due to its role in primary production and in oceanic carbon cycle regulation, such that past changes in iron deposition may have influenced oceanic sequestration of atmospheric CO 2 on millennial time scales. The behavior of iron in biological and environmental contexts depends strongly on its oxidation state. Solubility in water and the capacity to form complexes are just two important characteristics that are species dependent. Distinguishing between the two iron species, Fe(ii) and Fe(iii), is necessary to evaluate bioavailability, as Fe(ii) is more soluble and therefore more readily available for phytoplankton uptake and growth. Here, we present a novel analytical method for iron speciation analysis using Collision Reaction Cell-Inductively Coupled Plasma-Mass Spectrometry (CRC-ICP-MS) and apply it to ice core samples from Talos Dome, Antarctica. The method detection limit is 0.01 ng g -1. A chelating resin, Ni-NTA Superflow, was used to separate the Fe species. At pH 2 the resin is capable of retaining Fe 3+ with no retention of Fe 2+. After the initial separation, we oxidized the Fe 2+ using H 2O 2, and determined the Fe 2+ concentration as the difference between the two measurements. Our preliminary results demonstrate higher Fe 2+ concentrations during glacial periods than during interglacial periods. This elevated concentration of Fe 2+ suggests that more iron was available for phytoplankton growth during the Last Glacial Maximum, than would be expected from measurements of proxies such as dust mass or total Fe.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
