FATE OF MERCURY IN THE ARCTIC Michael Evan ... - COGCI

1. Introduction
Mercury in the atmosphere, is approximately 95% in the gaseous elemental form (Slemr et al.,
1985, Schroeder and Munthe, 1998). Its characteristics, such as low aqueous solubility, mean that it
is relatively non reactive and stable and therefore has a long atmospheric residence time, enabling
global transport.
In 1998 Schroeder et al., reported on their 1995 discovery of the springtime depletion of
tropospheric gaseous mercury in the high Canadian Arctic. This perennial phenomenon is since
dubbed atmospheric mercury depletion episodes, AMDEs and has since been shown to be a polar
and sub-polar phenomenon (Schroeder et al., 2003 and references therein). The mercury depleted
from the atmosphere is oxidized to divalent gaseous mercury and exists during AMDEs in
concentrations up to 900 pg m -3 (Lindberg et al., 2002, Skov et al. 2003). The divalent gaseous
mercury species are operationally defined as reactive gaseous mercury, RGM, since the analytical
methods, in this case, thermally desorbed KCL coated annular denuders (Landis et al., 2002) only
allow quantification after reduction to gaseous elemental mercury. Therefore, any speciation
information is lost.
It is necessary to quantify the flux of RGM in Arctic areas and determine the depositional
velocity in order to better understand the temporal, and spatial patterns of mercury deposition and
accumulation in the Arctic, and gain an understanding of the chemical and dry depositional
processes so that they might be applied to parameterization of atmospheric transport and deposition
models and eventually policy decisions.
The conditional sampling, or relaxed eddy accumulation technique (Businger and Oncley,
1989) has been used to determine the flux of elemental gaseous mercury (Cobos et al., 2002). Their
work thoroughly discusses the advantages of using a micrometeorological technique over other flux
measurement methods. In this paper, RGM flux is determined with a relaxed eddy accumulation
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