The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe

11 pages, 7 figures, 1 table, supplementary data https://doi.org/10.1016/j.watres.2018.06.064

Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06–2.78 ng L−1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8–159 pg L−1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems

This research was partially funded the Generalitat de Catalunya (Beatriu de Pinos BP-00385-2016) grants to AGB. DNK would like to acknowledge the Swedish National Science Foundation, Vetenskapsrådet (VR), for a starting grant. [...] We also thank the seven national freshwater societies financing this project, namely the Iberian Association of Limnology (AIL; Spain and Portugal), Deutsche Gesellschaft für Limnologie e.V. (DGL; Germany), Swiss Society for Hydrology and Limnology (SGHL; Switzerland), Italian Association of Oceanography and Limnology (Italy), Freshwater Biological Association (FBA; United Kingdom), French Limnological Association (AFL; France), Austrian Limnological Society (SIL-Austria), as well as the Leibniz-Institute of Freshwater Ecology and Inland Fisheries for additional funds. CML was funded by the French Agency for Biodiversity (ONEMA-AFB, Action 13, “Colmatage, échange snappe-rivière et processus biogéochimiques). NC held a “Juan de la Cierva” postdoctoral grant (FJCI-2014-23064)

Peer reviewed