Jiskra M., Guédron Stéphane, Tolu J., Fritz S. C., Baker P. A., Sonke J. E. (2022). Climatic controls on a Holocene mercury stable isotope sediment record of Lake Titicaca. ACS Earth and Space Chemistry, [Early access], p. [12 p.]. ISSN 2472-3452.
Titre du document
Climatic controls on a Holocene mercury stable isotope sediment record of Lake Titicaca
Jiskra M., Guédron Stéphane, Tolu J., Fritz S. C., Baker P. A., Sonke J. E.
Source
ACS Earth and Space Chemistry, 2022,
[Early access], p. [12 p.] ISSN 2472-3452
Mercury (Hg) records in sediment archives inform past patterns of Hg deposition and the anthropogenic contribution to global Hg cycling. Natural climate variations complicate the interpretation of past Hg accumulation rates (HgARs), warranting additional research. Here, we investigated Hg stable isotopes in a ca. 8k year-long sediment core of Lake Titicaca and combined isotopic data with organic biomarkers and biogeochemical measurements. A wet period in the early Holocene (8000-7300 BP) induced strong watershed erosion, leading to a high HgAR (20.2 +/- 6.9 mu g m(-2) year(-1)), which exceeded the 20th century HgAR (8.4 +/- 1.0 mu g m(-2) year(-1)). Geogenic Hg input dominated during the early Holocene (f(geog) = 79%) and played a minor role during the mid- to late Holocene (4500 BP to present; f(geog) = 20%) when atmospheric Hg deposition dominated. Sediment Delta Hg-200 values and the absence of terrestrial lignin biomarkers suggest that direct lake uptake of atmospheric Hg(0), and subsequent algal scavenging of lake Hg, represented an important atmospheric deposition pathway (42%) during the mid- to late Holocene. During wet episodes of the late Holocene (2400 BP to present), atmospheric Hg(II) deposition was the dominant source of lake sediment Hg (up to 82%). Sediment Delta Hg-199 values suggest that photochemical reduction and re-emission of Hg(0) occurred from the lake surface. Hg stable isotopes show promise as proxies for understanding the history of Hg sources and transformations and help to disentangle anthropogenic and climate factors influencing HgAR observed in sediment archives.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
;
Géologie et formations superficielles [064]
