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

Mercury (Hg) stable isotopes have been broadly used to investigate the sources, transformation and deposition of atmospheric Hg during industrial era thanks multiple isotope signatures deriving from mass-dependent (represented by δ202Hg) mass-independent fractionation ΔxxxHg) in environment. Less is known about impact past climate change on cycling, whether covary with climate. Here, we concentration a 6600-year-old ombrotrophic peat record Amsterdam Island (AMS, 37.8oS), modern AMS rainfall gaseous elemental (Hg0) samples. Results show that Holocene plant uptake dust deposition, are both lower under high humidity regime associated enhanced Southern Westerly Winds. Modern Hg0 HgII similar those Northern Hemisphere (NH). Δ199Hg Δ200Hg significantly correlated (R2 = 0.67, P < 0.001, n 58), consistently oscillating between end-members. Peat provide evidence as dominant pathway peatland, some exceptions humid periods. In contrast NH archives generally documenting increase Δ199Hg, recent layers (post-1900CE) lowest profile (−0.42 ± 0.27 ‰, 1σ, 8). This likely reflects significant post-depositional process deposited anthropogenic 20th century (i.e. dark abiotic reduction), enabling more negative be observed peat. We further find oscillations consistent established variability proxies. suggest records might valid indicator.