ICMGP - Abstract

Abstract Information :

Mercury (Hg) is a potent neurotoxin posing a health risk of global concern. The long residence time of Hg in the atmosphere of several months leads to long-range transport of anthropogenic emissions and deposition to the Earth surface far away from the emission sources. The relation between anthropogenic emission and atmospheric deposition and thus exposure is complex, as Hg can be re-emitted from the Earth surface and cycle in the environment. Global chemical transport models are a key tool to assess the response of the Earth system to changes in anthropogenic emissions and climate conditions. The global Hg Earth system models are constrained by observations, which are largely restricted to gaseous Hg measurements in the atmosphere and Hg wet deposition measurements to terrestrial surfaces. Other global fluxes like direct gasous Hg deposition remain largely unconstrained due to limited observations, resulting in large uncertainties in the global Hg Earth system models. In this contribution, I will present a the Hg stable isotope fingerprinting tool to constrain pathways of atmospheric mercury deposition. The photochemical redox transformations in the atmosphere result in distinct isotopic compositions of the elemental Hg(0) and oxidized Hg(II) species allowing to quantitatively trace the deposition pathways to the Earth surface. Hg stable isotope results from terrestrial vegetaion and soils reveal that 60 to 90 % of terrestrial Hg was deposited via direct Hg(0) deposition through the uptake by plants, rather than via the wet deposition pathway (Zhu et al., 2021). The first mesaurements of Hg stable isotopes in seawater suggest that Hg(0) deposition to the ocean is equally important to Hg(II) deposition (Jiskra et al., 2021). Hg stable isotope fingerprinting therefore have revealed that the direct deposition of gaseous elemental Hg both to terrestrial surfaces and the Ocean has previously been underestimates, which has implications for our understanding of global Hg cycling and ecosystem response to curbed Hg emissions and climate change.