Quantifying soil accumulation of atmospheric mercury using fallout radionuclide chronometry

Area of Science:

• Environmental Science
• Geochemistry
• Atmospheric Chemistry

Background:

• Soils are major global reservoirs for mercury (Hg), a neurotoxic pollutant.
• Anthropogenic emissions lead to Hg accumulation in terrestrial ecosystems.
• Uncertainty exists regarding the fate of soil Hg, especially re-emission as gaseous elemental mercury (GEM).

Purpose of the Study:

• To directly measure Hg accumulation rates in diverse soil types.
• To assess the quantitative efficiency of Hg retention in soils.
• To evaluate the potential for GEM re-emission from soils and challenge existing global models.

Main Methods:

• Utilized fallout radionuclide (FRN) chronometry to determine Hg accumulation rates.
• Employed a mass balance approach comparing accumulation rates with atmospheric Hg fluxes.
• Analyzed soils from Arctic, boreal, temperate, and tropical regions.

Main Results:

• Soils across various biomes demonstrate high efficiency in retaining anthropogenic Hg.
• Significant GEM re-emission potential is primarily restricted to a subset of coniferous soils.
• Findings contradict global models that assume substantial legacy Hg re-emission from soils.

Conclusions:

• Most soils are effective sinks for atmospheric mercury, limiting widespread GEM re-emission.
• FRN chronometry is a powerful technique for reconstructing terrestrial Hg accumulation at broad scales.
• Further research is needed to understand Hg mobilization susceptibility across different soil environments.