Nanoscale lignin particles as iron chelators in the ocean
Abstract
Iron is essential for the growth and metabolism of all marine organisms. Yet at the high dissolved oxygen concentration found in the open ocean, iron exists primarily as Fe(III) which is highly reactive with respect to hydrolysis and adsorption. Due to the low solubility of iron(III)hydroxide combined with sedimentation of iron-rich particles, iron concentrations in the open ocean are extremely low and could even reach a point too low to sustain life. Fortunately, iron solubility is enhanced by organic ligands which keep the iron in solution and prevent precipitation and sedimentation of iron oxide minerals. The low concentrations of these ligands make them difficult to detect, and only a few marine Fe ligands have been structurally characterized so far. It has been shown that the activities of plankton have a profound influence through the release of different classes of important chelating ligands like siderophores, porphyrins, or exopolymeric substances. The present project focuses on humic nanoparticles, a yet unidentified class of iron chelators in the ocean. These substances are released by wetland ecosystems and transported into the sea by rivers. The main goal of the proposed project is to prove that a fraction of the dissolved Fe found in the surface ocean waters is associated with the dissolved lignins found in these ocean waters (at the typical oceanic iron and lignin concentrations). The corroboration of this hypothesis affords highly sensitive and selective methods for accurate quantification of iron and iron bearing compounds in seawater at naturally occurring concentration levels. Aiming at the discovery and investigation of low to ultralow concentrations of organic iron-complexes, we decided to combine elemental and molecular mass spectrometry orthogonally. We will apply the concept of general unknown screening via pre-separation followed by on-line enrichment and accurate mass spectrometry (LC-TOF-MS). Concomitantly, X-ray absorption fine structure (EXAFS) spectroscopy will be used to determine the binding mode and oxidation state of iron in the iron-binding lignin fractions.
Publikationen
Project staff
Stephan Hann
Univ.Prof. Dr. Stephan Hann
stephan.hann@boku.ac.at
Tel: +43 1 47654-77001, 77191
Project Leader
01.08.2013 - 31.07.2016
BOKU partners
External partners
University of Wienna, Institute of Anorganic Chemistry
Ao. Univ.Prof. Dr. Regina Krachler
coordinator