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Atmosphere-Land Dynamics of Mercury in a Forest
Landscape
of the Adirondack Region of New York
Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY
Hyun-Deok Choi, Thomas M. Holsen
Department of Civil and Environmental Engineering, Clarkson University, Postdam,
NY
| Atmosphere-land dynamics of mercury were investigated
at the Huntington Forest in the central Adirondack region of New York.
Measurements of mercury were made in air, wet deposition, throughfall,
foliage, litter, and streamwater, and soil mercury evasion was characterized.
Measurements show a slight enrichment of mercury in throughfall (6.83
µg/m2-yr) compared to wet deposition (5.79 µg/m2-yr) in this
northern hardwood watershed. Large increases in concentrations of mercury
were evident in foliage of the dominant hardwoods over the growing season,
with accumulation of mercury in American beech significantly higher than
in sugar maple or yellow birch. Concentrations of mercury in understory
foliage were significantly greater than overstory foliage. Concentrations
of mercury in hardwood litter were consistent with values observed in
foliage. Litter flux of mercury (17.2 µg/m2-yr) greatly exceeded
throughfall and was the major pathway of mercury deposited to the forest
floor (24.0 µg/m2-yr). Soil evasion of mercury was highly variable
across diurnal cycles and the annual cycle, and was highly dependent on
environmental conditions (e.g., temperature, radiation). Our best estimate
of mercury evasion from upland soil (10.4 µg/m2-yr) suggests that
this flux exceeded throughfall, but is less than total mercury deposition.
Stream fluxes (2.3 µg/m2-yr) indicated that most of the mercury
deposited to the watershed is evaded back to the atmosphere or retained
in soil. However, stream losses are a critical pathway of mercury supply
to aquatic ecosystems and ultimately human and wildlife exposure. Stream
mercury species flux increased greatly during storm events, driven by
the increase in runoff. Source areas of mercury varied within events,
with recently deposited mercury readily mobilized on the rising limb of
the hydrograph before shifting to mercury derived from soil water as the
hydrograph peaked. The form and source of mercury may have important implications
for the bioavailability in downstream Arbutus Lake.
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