Abstract

There exists observational evidence that gaseous elemental mercury (GEM) can be readily removed from the atmosphere via chemical oxidation followed by deposition in the polar and sub-polar regions, free troposphere, lower stratosphere, and marine boundary layer under specific environmental conditions. Here we report GEM depletions in a temperate mixed forest at Mt. Changbai, Northeast China. The strong depletions occurred predominantly at night during the leaf-growing season and in the absence of gaseous oxidized mercury (GOM) enrichment (GOM < 3 pg m(-3)). Vertical gradients of decreasing GEM concentrations from layers above to under forest canopy suggest in situ loss of GEM to forest canopy at Mt. Changbai. Foliar GEM flux measurements showed that the foliage of two predominant tree species is a net sink of GEM at night, with a mean flux of -1.8 +/- 0.3 ng m(2) h(-1) over Fraxinus mandshurica (deciduous tree species) and -0.1 +/- 0.2 ng m(2) h(-1) over Pinus Koraiensis (evergreen tree species). Daily integrated GEM delta Hg-202, Delta Hg-199, and Delta Hg-200 at Mt. Changbai during 8-18 July 2013 ranged from -0.34 to -0.91 parts per thousand, from -0.11 to -0.04 parts per thousand and from -0.06 to 0.01 parts per thousand, respectively. A large positive shift in GEM delta Hg-202 occurred during the strong GEM depletion events, whereas Delta Hg-199 and Delta Hg-200 remained essentially unchanged. The observational findings and box model results show that uptake of GEM by forest canopy plays a predominant role in the GEM depletion at Mt. Changbai forest. Such depletion events of GEM are likely to be a widespread phenomenon, suggesting that the forest ecosystem represents one of the largest sinks (similar to 1930 Mg) of atmospheric Hg on a global scale.

Published in

Atmospheric Chemistry and Physics
2016, Volume: 16, number: 20, pages: 12861-12873
Publisher: COPERNICUS GESELLSCHAFT MBH

UKÄ Subject classification

Environmental Sciences
Meteorology and Atmospheric Sciences


Publication identifier

DOI: https://doi.org/10.5194/acp-16-12861-2016

Permanent link to this page (URI)

https://res.slu.se/id/publ/86085