Olof Regnell

affiliated with the university


My main research area is the biogeochemistry of mercury (Hg) in the aquatic environment. Biogeochemistry is a discipline concerned with the cycling and speciation (chemical form and physical state) of elements and compounds on Earth, and the role of biological, geological and chemical processes in the various cycles and speciation processes. I am interested mainly in processes leading to mobilisation and export of Hg from soils to surface waters, and in processes causing Hg methylation (production of highly toxic and bioavailable methyl mercury). Although intensely studied, the Hg methylation process is far from fully understood. Mercury is methylated by anaerobic bacteria, and sulfate reduction is the microbial process most often being associated with Hg methylation. Possibly, the limiting step in Hg methylation is the formation of inorganic Hg species that leads to uptake of Hg by microbial cells. A likely precursor of methyl mercury is the complex Hg(SH)2, which is formed as a result of sulfate reduction. Laboratory studies suggest that Hg is taken up by an active mechanism intended for uptake of essential metal ions. However, passive uptake may also occur, in which hydrophobic Hg-complexes, and possibly HgS nano particles, partition to microbial cells. As a result of methylation, Hg is released from microbial cells. This works fine in sulfidic water, because the hydrophilic complex CH3HgSH is formed.

The biogeochemistry of Hg is strongly dependent on organic matter cycling, because Hg has strong affinity for organic matter, and because organic matter fuels microbial activity that causes various conversions of Hg, including its methylation.

Although I started off doing laboratory work, my research now rests entirely on field studies. Rather than studying processes in isolation, field studies combine various observations, trying to constrain the number of possible mechanisms that could explain why a process of interest varies in intensity in time and space. In a recent study, we related temporal and spatial variation in sediment methyl Hg levels to organic matter cycling and to temporal and spatial variation of sediment nitrogen, phosphorus, sulfur and iron. Background knowledge of factors involved in Hg methylation and of factors involved in the retention/release of methyl Hg, enabled us to infer from the results what microbial processes were involved in Hg methylation. Interestingly, heterotrophic activity (organic matter decay) and chemoautotrophic activity (production of organic matter from carbon dioxide) both gave rise to Hg methylation.

Presently, I try to raise money to study mercury – selenium interaction in fish. Because of high methyl mercury levels (virtually all mercury in fish is methyl mercury), Swedish health authorities recommend pregnant women not to eat certain fish species such as pike, perch and sander. For obvious reasons fish eating birds and mammals may suffer at even lower fish Hg levels than humans. Fish populations themselves may suffer at present fish Hg levels. However, there is a growing body of evidence that selenium strongly modulates methyl mercury toxicity. In order to make more precise environmental and health risk assessments of fish Hg, it is my conviction that fish selenium must be determined, not just fish Hg.

Recent research outputs

Olof Regnell, 2016 Sep 6, In : Environmental Science and Technology. 50, 17, p. 9798-9799 2 p.

Research output: Contribution to journalLetter

Sara M. Ekström, Olof Regnell, Heather E. Reader, Anders Nilsson, Stefan Löfgren & Emma S. Kritzberg, 2016 Feb 1, In : Journal of Geophysical Research - Biogeosciences. 121, 2, p. 479-493 15 p.

Research output: Contribution to journalArticle

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