Erik Björn

Bio

2009 Associate Professor, Umeå University, Sweden
2002 PhD Umeå University, Sweden

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Research

We study how the chemical structure of metal compounds control mechanisms and kinetics for reactions which are central for the cycling of metals in the environment.

Chemical and biological processes of trace metals – from molecule to ecosystem

The research is focused on studies of chemical and biological processes of metal compounds in ecosystems, biological systems and industrial processes. We develop new powerful analytical techniques and experimental strategies to study chemical form (speciation) and reaction mechanisms and rates of trace metal compounds. An important area of focus is the study biogeochemical processes of mercury (Hg) in aquatic and terrestrial ecosystems. The research program aims to both understand such processes at the molecular level and to establish their importance in natural environmental systems.

To achieve these challenging objectives we develop analytical methods and experimental strategies to determine; molecular structure of Hg compounds, concentrations and thermodynamic stability constants of compounds and rate constants for their formation and degradation. We carry out experimental studies on both controlled model systems of varying complexity and on natural systems at realistic conditions. The developed methods and approaches are generally applicable to studies on trace metals, but the research program is well-focused on studies of how the chemical speciation of Hg controls its methylation and redox transformation reactions and bioaccumulation processes.


Principal analytical techniques and research methodologies:

  • Chromatography – mass spectrometry coupled techniques, in particular GC- and LC-ICPMS. These are used for selective determination of trace metal compounds at low concentrations, and often in combination with the use of isotopically enriched tracers.
  • X-ray absorption spectroscopy, in particular synchrotron-based techniques, to further characterize chemical structures of trace metal compounds.
  • Various thermodynamic and kinetic modeling approaches, to determine chemical speciation and the rate of transformation reactions.
  • Characterization of microbial communities and aquatic food webs in close collaborations with molecular biology and ecology partners.
  • Incorporating mechanistic process understanding in regional and global scale biogeochemical and food web models for Hg in collaborations with partners.

Our current research program is largely focused on three projects:

Adapted from Sofi Jonsson 2009

1. Chemical structure of Hg(II) and its availability for microbial methylation

The microbial formation of neurotoxic methylmercury (MeHg) is a key step in transferring Hg from the abiotic to the biotic environmental compartments since MeHg accumulates in the aquatic food web. We study how the chemical speciation of Hg(II) in both solid/adsorbed and dissolved phases control the availability of Hg(II) to methylating microbes.

2. Activity of Hg(II)-methylating microbes

The methylation of Hg(II) is mediated by anaerobe microorganisms. The community composition and metabolic activity of such organisms are controlled by redox potential and availability of metabolic electron donors and acceptors. We study how the molecular composition of natural organic matter can control MeHg formation by supplying electron donors to Hg(II)-methylating microbes.

3. Incorporation and magnification of methylmercury in the aquatic food web

We study how the chemical speciation of MeHg control its cellular uptake from water by phytoplankton, and how the structure of the pelagic food web control its further biomagnification.

 

All publications, see here

Publications in DIVA, see here.