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

espectively (Naucke et al., 1993). There is an exceptional zone of elevated ash content in the
DK core at ca. 18cm (Fig. 2b), which may reflect the disturbance of the bog surface by peat
cutting during WWII. Bulk density values are generally higher in the GL core (Fig. 2a) compared
to DK core (Fig. 2b).
The Hg concentration profiles reveal elevated Hg concentrations in both the upper and
lower sections of the GL core (Fig. 2b), but only in the upper section of the DK core (Fig. 2b).
To take into account the large differences in bulk density within and between the two cores, the
Hg concentrations are also expressed on a volumetric basis (Fig. 2). The variation in volumetric
Hg concentrations above 30 cm show a remarkable similarity between the two cores, with a very
intense peak in volumetric Hg concentration in the GL core at 21 cm (Fig. 2a) and in the DK
core at 17 cm (Fig. 2b), respectively. The selected age dates shown in Fig. 2 indicate that the
zone of greatest Hg concentration in each core dates from the 1950`s. The very old radiocarbon
ages in the DK peat samples below 29 cm (which was dated at 2395 ± 45 14 C yr BP) is evidence
that some part of the original peat surface has been lost due to peat cutting. These old sections
of the DK profile will not be considered further.
Mercury concentrations in ombrotrophic (DK) versus minerotrophic (GL) peat profiles
The chronology of changes in volumetric Hg concentrations is remarkably similar at
the two sites (Fig. 2). The DK core is ombrotrophic, therefore Hg was supplied to this profile
exclusively by atmospheric deposition. The greatest Hg concentrations are found in samples
dating from the 1950`s. As there are no known natural geochemical processes which could have
led to this pronounced Hg enrichment, we assume that the elevated Hg concentrations in the
surface layers, compared to deeper, older peats, reflect increased rates of atmospheric Hg
deposition caused by industrial activities. Similarly, in the GL core the greatest Hg
concentrations are found in samples dating from the 1950`s. In contrast to the DK core, the GL
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