ICMGP 2022 – On-Demand / Poster Presentation

Abstract Information :

The biogeochemical Hg cycle is a complex cascade of release, dispersal, transformation and bio-uptake processes that link Hg sources to Hg exposure. Climate change interacts with the Hg cycle by impacting the physical, biogeochemical and ecological factors that control these processes. If we want to understand climate change effects on Hg cycling, we first need to fully understand the global Hg cycle itself. Despite the tremendous progress made over the past decades, observations of some of the largest global fluxes such as Hg(0) uptake by vegetation and soils, and Hg(II) deposition and air-sea exchange over oceans, are technically difficult to make. In this presentation we will illustrate how Hg stable isotope analysis of atmospheric, terrestrial and marine reservoirs has recently provided a new perspective on these difficult to observe fluxes. The basis behind the isotope perspective, is that atmospheric Hg(0) and Hg(II) have contrasting isotopic (?) signatures, that can be traced into the receptor environment. Soil, and lake sediment Hg isotope signatures reflect 75% net Hg(0) and 25% Hg(II) deposition (1), and marine signatures 60% net Hg(0) and 40% Hg(II) deposition (2). These numbers are different from deposition estimates in global Hg models, where Hg(II) deposition dominates. We will discuss the implications of these findings for climate change effects on Hg cycling, via the concept of the biological Hg pump (3), and from the perspective of atmospheric Hg redox chemistry (4). 1. Enrico, M. et al. Environ. Sci. Technol. (2016) doi:10.1021/acs.est.5b06058 2. Jiskra, M. et al., Nature 597, 678?682 (2021) doi:s41586-021-03859-8 3. Jiskra, M. et al., Nat Geosci 11, 244 (2018) doi:s41561-018-0078-8 4. Saiz-Lopez, A. et al., PNAS. (2020) doi:10.1073/pnas.1922486117