Adsorption of Dimethylmercury onto Natural Particles

Dimethylmercury (DMeHg), a highly toxic form of mercury (Hg), appears as a dissolved gas in marine waters as well as some terrestrial environments. Although DMeHg does not reach concentrations in natural environments that are of direct concern for human and wildlife health, it has been suggested that DMeHg could play a role in controlling the amount of monomethylmercury (MMeHg) available. As MMeHg bioaccumulates in aquatic food webs to concentrations of concern, it links the occurrence of DMeHg in marine systems with the negative consequences of Hg pollution for human and wildlife health. Our understanding of the biogeochemical cycle of DMeHg is however scant. The potential for adsorption of DMeHg onto natural particles has so far not been addressed. This, despite the fact that adsorption is recognised to be an important process controlling the distribution of other chemical forms of Hg in the environment, including ionic forms of inorganic divalent Hg and monomethylmercury as well as gaseous elemental Hg.  

Here, we will present the data from the first adsorption experiments with dimethylmercury using model compounds (including FeS-minerals) as well as natural sediments and soils. For FeS(s), DMeHg readily adsorbed onto the mineral surface reaching equilibrium within 1-2 h. Observed partitioning between the solid and aqueous phase for FeS were also close to observed partitioning of e.g. MMeHg. Preliminary data also suggests DMeHg to readily adsorb onto natural particles, including sediments and soils.