Mercury sequestration in forests and peatlands: a review

Area of Science:

• Environmental Chemistry
• Biogeochemistry
• Ecosystem Science

Background:

• Atmospheric mercury (Hg) is the primary source for vegetation.
• Mercury distribution in terrestrial ecosystems is strongly linked to organic matter and sulfur content.
• Wetlands and peatlands exhibit higher mercury sequestration than uplands and mineral soils.

Purpose of the Study:

• To investigate the distribution and sequestration of mercury in forest and wetland ecosystems.
• To understand the relationship between mercury, organic matter, and sulfur in terrestrial systems.
• To assess the role of landscape conditions and climate change in mercury cycling.

Main Methods:

• Quantification of mercury mass in vegetation, forest floor, mineral soil, and peat.
• Analysis of mercury-organic matter and mercury-sulfur relationships.
• Comparison of mercury pools with annual anthropogenic emissions.

Main Results:

• Forest vegetation contains significantly less mercury (0.1 mg m(-2)) than forest floor (1 mg m(-2)) and mineral soil (10 mg m(-2)).
• Peatlands sequester substantial mercury (20 mg m(-2)), exceeding combined mineral soil and forest floor pools.
• Methylmercury (MeHg) constitutes a small fraction (<1.5%) of total mercury, but is produced in poorly drained soils and wetlands.

Conclusions:

• Mercury accumulation in terrestrial ecosystems is predominantly controlled by organic matter content and landscape characteristics.
• Peatlands act as critical mercury sinks, sequestering mercury far exceeding annual anthropogenic emissions.
• Climate change impacts on carbon storage will indirectly influence mercury sequestration and the global mercury cycle.