Temporal and spatial trends in Hg deposition monitored by moss analysis

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Biomonitoring

Background:

• Atmospheric deposition of heavy metals, including mercury (Hg), is a significant environmental concern.
• Feather moss (Hylocomium splendens) is a reliable bioindicator for heavy metal deposition in Norway.
• Long-term monitoring data (1985-1995) established baseline Hg levels and deposition patterns.

Purpose of the Study:

• To present and compare Hg deposition results from a nationwide moss survey in Norway in 2000.
• To analyze trends in Hg concentration in Hylocomium splendens from 1985 to 2000.
• To investigate the factors influencing Hg deposition and concentration in Norwegian ecosystems.

Main Methods:

• Nationwide sampling of Hylocomium splendens at approximately 500 sites across Norway.
• Determination of Hg concentrations using Cold Vapor Atomic Absorption Spectrometry (AAS) and Atomic Fluorescence Spectrometry (AFS).
• Acid digestion (HNO3) of moss samples prior to Hg analysis.

Main Results:

• Hg concentration in moss showed no significant north-south gradient, unlike other heavy metals.
• Both dry deposition of Hg(0) and retention of Hg(2+) from wet deposition contribute to moss Hg levels.
• Cool summer climates in central and northern Norway may reduce Hg re-volatilization from moss.

Conclusions:

• The lack of a north-south gradient is attributed to combined dry and wet Hg deposition processes.
• Climate plays a role in Hg retention within the moss, influencing overall deposition patterns.
• A significant 30% decrease in Hg levels was observed in 2000, the cause of which requires further investigation.