A peat core Hg stable isotope reconstruction of Holocene atmospheric Hg deposition at Amsterdam Island (37.8oS)

• Published in: Geochimica et cosmochimica acta 2023-01, Vol.341, p.62-74
• Main Authors: Li, Chuxian, Enrico, Maxime, Magand, Oliver, Araujo, Beatriz F., Le Roux, Gaël, Osterwalder, Stefan, Dommergue, Aurélien, Bertrand, Yann, Brioude, Jérôme, De Vleeschouwer, François, Sonke, Jeroen E.
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemical Sciences; Environmental Sciences; Hg deposition; Hg stable isotopes; Material chemistry; or physical chemistry; Peat; Polymers; Rain; Southern Hemisphere; Theoretical and
• ISSN: 0016-7037; 1872-9533
• DOI: 10.1016/j.gca.2022.11.024

Mercury (Hg) stable isotopes have been broadly used to investigate the sources, transformation and deposition of atmospheric Hg during the industrial era thanks to the multiple isotope signatures deriving from mass-dependent (represented by δ202Hg) and mass-independent fractionation (represented by ΔxxxHg) in the environment. Less is known about the impact of past climate change on atmospheric Hg deposition and cycling, and whether Hg isotopes covary with past climate. Here, we investigate Hg concentration and Hg isotope signatures in a 6600-year-old ombrotrophic peat record from Amsterdam Island (AMS, 37.8oS), and in modern AMS rainfall and gaseous elemental Hg (Hg0) samples. Results show that Holocene atmospheric Hg deposition and plant Hg uptake covary with dust deposition, and are both lower under a high humidity regime associated with enhanced Southern Westerly Winds. Modern AMS gaseous Hg0 and rainfall HgII isotope signatures are similar to those in the Northern Hemisphere (NH). Holocene peat Δ199Hg and Δ200Hg are significantly correlated (R2 = 0.67, P