Mercury Isotope Variability in Pyrenean Lake Sediments during the Late Holocene: Sources, Deposition, and...

Area of Science:

• Environmental Science
• Geochemistry
• Paleoclimatology

Background:

• Atmospheric mercury (Hg) emissions pose a global environmental and health risk.
• Stable Hg isotopes are crucial for tracing pollution sources and deposition in natural archives.
• Understanding historical Hg dynamics requires multi-archive approaches.

Purpose of the Study:

• To reconstruct a 4000-year Hg isotopic composition history from Pyrenean lake sediments and a peatland.
• To differentiate between regional atmospheric signals and local depositional processes.
• To assess the potential of Hg isotopes as paleoclimatic proxies.

Main Methods:

• Analysis of Hg isotopic composition in sediment cores from two Pyrenean lakes (Marboré and Estanya) and one peatland (Estibere mire).
• Reconstruction of Hg accumulation rates and isotopic variations over 4000 years.
• Comparison of Hg isotopic signatures across different altitudes and ecosystem types.

Main Results:

• Hg accumulation rates and isotopic values increased significantly since the 16th century, indicating intensified anthropogenic emissions.
• Lake Estanya showed a localized Hg signal influenced by land-use changes, while Lake Marboré reflected a broader regional atmospheric imprint.
• Similar temporal trends but distinct offsets in Δ¹⁹⁹Hg between Lake Marboré and Estibere mire suggest shared regional sources modulated by ecosystem processes.
• Variations in Δ²⁰⁰Hg in the alpine lake correlate with past climate phases.

Conclusions:

• Integrating multiple ecosystem archives is essential for disentangling Hg source signatures from postdepositional transformations.
• Hg isotopes provide valuable insights into historical atmospheric Hg pollution and regional deposition patterns.
• Hg isotopes, particularly Δ²⁰⁰Hg, show promise as paleoclimatic proxies.