Comparative Foliar Atmospheric Mercury Accumulation across Functional Types in Temperate Trees

Area of Science:

• Environmental Chemistry
• Plant Ecology
• Atmospheric Science

Background:

• Vegetation's uptake of gaseous elemental mercury (GEM) is a major pathway for mercury deposition in terrestrial ecosystems.
• Understanding how different plant types accumulate mercury is crucial for ecological and environmental health assessments.

Purpose of the Study:

• To investigate mercury (Hg) accumulation mechanisms in deciduous broadleaves versus evergreen needles.
• To determine how ecophysiological strategies influence Hg accumulation in different tree functional types.
• To develop an empirical model for foliar Hg accumulation.

Main Methods:

• Comparison of total Hg (THg) concentrations and accumulation rates (THg_rate) between deciduous and evergreen species.
• Analysis of ecophysiological indicators: δ¹³C, δ¹⁸O, leaf mass per area, and leaf dry matter content.
• Statistical analysis of meteorological factors, air pollutants (PM_2.5, NO₂), and their correlation with THg_rate.

Main Results:

• Deciduous leaves showed significantly higher THg concentrations and THg_rate compared to evergreen needles.
• Distinct ecophysiological strategies were observed: deciduous trees exhibit dynamic stomatal control, while evergreens show stable control, influencing Hg uptake.
• Precipitation and wind speed negatively affected foliar THg_rate, while PM_2.5 and NO₂ showed synergistic effects with Hg accumulation in evergreens.

Conclusions:

• Tree functional type and species-specific ecophysiological strategies significantly mediate GEM accumulation.
• Deciduous trees play a key role in controlling THg_rate through rapid stomatal adjustment.
• The developed empirical model enhances the understanding and prediction of foliar Hg accumulation in diverse ecosystems.