Mercury Isotope Fractionation by Internal Demethylation and Biomineralization Reactions in Seabirds: Implications for Environmental Mercury Science

• DOI: 10.1021/acs.est.1c04388
• Publication Date: 2021-10-01T15:45:02Z
• Authors: Alain Manceau; Romain Brossier; Sarah E. Janssen; Tylor J. Rosera; David P. Krabbenhoft; Yves Cherel; Paco Bustamante; Brett A. Poulin
• Keywords: Mass-independent fractionation; Mercury; Methylmercury; Equilibrium fractionation; Isotopes of zinc

A prerequisite for environmental and toxicological applications of mercury (Hg) stable isotopes in wildlife humans is quantifying the isotopic fractionation biological reactions. Here, we measured Hg isotope values relevant tissues giant petrels (Macronectes spp.). Isotopic data were interpreted with published HR-XANES spectroscopic that document a stepwise transformation methylmercury (MeHg) to Hg-tetraselenolate (Hg(Sec)4) selenide (HgSe) (Sec = selenocysteine). By mathematical inversion data, identical δ202Hg MeHg (2.69 ± 0.04‰), Hg(Sec)4 (-1.37 0.06‰), HgSe (0.18 0.02‰) determined 23 eight birds from Kerguelen Islands Adélie Land (Antarctica). differences between (-4.1 0.1‰) reflect mass-dependent kinetic effect due → demethylation reaction. Surprisingly, differed isotopically (+1.6 mass-independent anomalies (i.e., changes Δ199Hg ≤0.3‰), consistent equilibrium effects nuclear volume biomineralization. The invariance species-specific across individual reflects lability Hg-ligand bonds tissue-specific redistribution inorganic Hg, likely as Hg(Sec)4. These observations provide fundamental information necessary improve interpretation provoke revisitation processes governing biota risk assessment wildlife.