Project

Photocatalyzed Fe acquisition from atmospheric dust in marine environments

Oceans have vast HNLC (High-Nutrient, Low-Chlorophyll) areas, where primary productivity is limited by iron (Fe) availability. In this way Fe bioavailability in the ocean affects the global carbon cycle by limiting how much carbon is captured from the atmosphere. In the photic zone of the ocean, where photosynthesis by microorganisms takes place, atmospheric mineral dust is an important source of Fe.

Background

Small soil particles (e.g Saharan dust) are picked up by the wind and transported over large distances (up to thousands of kilometres) until the dust enters into the ocean.

Before Fe can be taken up by marine microorganisms, it needs to dissolve from mineral dust particles. Certain microorganisms exude chelating ligands called siderophores that can dissolve Fe. Also, in the photic zone, sunlight can reduce Fe(III) to Fe(II). The latter is much more soluble, but rapidly re-oxidizes under oxic conditions to the poorly soluble Fe(III). Recently it was demonstrated that Fe mobilisation by siderophores in oxic soil suspensions can be enhanced when Fe is present in the (short-lived) reduced Fe(II) state. By analogy, in the photic zone of marine environments, the combination of siderophores and sunlight might bring about a synergistic enhancement of Fe mobilisation (i.e. Fe mobilisation in the presence of both siderophores and sunlight is larger than the summed mobilisation under conditions with only siderophores and only sunlight).

In this MSc thesis project hypothesis above will be tested in batch experiments with atmospheric dust suspended in artificial ocean water. Siderophores will be added to the suspension, which will be irradiated using a solar simulator. The influence of dust suspension density, photoreductants (compounds that give off electrons upon irradiation with light) and oxygen on the dissolution rate of Fe and other elements will be examined. Results from this study will improve our understanding of the mechanisms underlying marine Fe acquisition in the photic zone.

This project will be carried out in the framework of a collaboration between Wageningen University, the University of Vienna and the Hebrew University of Jerusalem. A substantial part of the experimental work will be carried out at the University of Vienna.

Used skills

  • Literature review;
  • proposal writing;
  • laboratory (kinetic batch experiments), data processing;
  • Thesis writing.

Requirements

  • Some laboratory experience is required;
  • The required courses for the MSc thesis Soil Chemistry and Chemical Soil Quality (SOC-81336), including:
    • Chemical Processes in Soil, Water and Atmosphere (SOC22306);
    • Preferably including Soil Quality (SOC21806).

Supervisor