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Biogeochemical Cycling of Mercury in Marine and Polar Environments

2019-12-03 133

Title:Biogeochemical Cycling of Mercury in Marine and Polar Environments



SpeakerSofi Jonsson, Assistant Professor, Stockholm University

Biography of speaker:

Prof. Jonsson is a chemist and her research focuses on understanding the biogeochemical cycle of Mercury (Hg) and other toxic trace metals in aquatic environments. She received her PhD at Umea University, Sweden, with the thesis entitled "Unraveling the importance of solid and adsorbed phase mercury speciation for methylmercury formation, evasion and bioaccumulation" in 2013. From 2014 to 2017, she worked as a postdoctoral researcher in Robert Mason’s lab at the University of Connecticut in the US where she redirected her focus from estuaries to the marine environment. Since 2018, she have been an assistant professor at the department of Environmental Science and Analytical Chemistry at Stockholm University, Sweden. Her group is currently involved in projects focusing on e.g. i) marine cycling of Hg, with a particular interest for the role of dimethylmercury, ii) reactivity of toxic metals during transport from land to sea, and iii) mercury cycling in polar region with special interest for arctic coastal systems and thawing permafrost soils. In common, these project aims to better understand the link between sources of toxic metals to their environmental risk, as well as to understand how these cycles can be perturbed in the future by e.g. altered land use or a warmer climate.


Mercury (Hg) is mobilized from the Earth’s crust and accumulates as monomethylmercury (CH3Hg-X, where X is e.g. Cl- or R-S-) in aquatic food webs, thereby posing a threat to human and wildlife health. This has motivated over 50 years of research on Hg biogeochemistry. Still, our understanding of the processes controlling the amount of monomethylmercury available for bioaccumulation remains limited. In the first part of this talk, I will discuss our understanding of Hg biogeochemistry in coastal and marine systems and the role of dimethylmercury. The understanding of Hg cycling in marine environments is particularly incomplete even though marine harvested food is the primary monomethylmercury exposure route for most human populations. A unique feature of marine systems compared to freshwater systems is that ~30-80% of the total methylated Hg pool occurs as dimethylmercury ((CH3)2Hg). The vertical and geographical distribution of mono- and dimethylmercury have been documented in many coastal and oceanographic systems since the 90′s. More recent work has also quantified in situ transformation rates between chemical Hg forms (e.g. methylation and demethylation rates of monomethylmercury). However, what role in situ methylation and demethylation of mono- and dimethylmercury plays for the amount of monomethylmercury available for bioaccumulation is unknown. Secondly, I will talk about the biogeochemical cycling of Hg in polar environments. Widespread accelerated permafrost thawing is predicted for this century and beyond. This threatens to remobilize the enormous amount of Hg currently ‘locked’ in Arctic permafrost soils and thus potentially lead to severe consequences for human and wildlife health. The future risks of Arctic Hg in a warmer climate are, however, poorly understood. The talk will include both presentation of key research questions, as well as, ongoing research projects relating to above described research areas.