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

contemporary environmental interest.
Implications for the global atmospheric Hg cycle
A model of the global atmospheric Hg cycle has recently been published (Lamborg
et al., 2002) in which an annual pre-industrial annual flux of Hg to the continents of 4 Mmoles
was reported. If this value is taken to represent the continental land mass (total 147 x 10 6 km 2 ),
then an average, pre-industrial flux of 5.5 :g/m 2 /yr is implied. For comparison, the minimum
pre-industrial flux recorded by the GL core is only 0.3 :g/m 2 /yr; this is also the minimum Hg
accumulation rate recorded by the Swiss peat bog (Roos-Barraclough et al., 2002). In fact, the
value reported by Lamborg et al. (2002) is at the upper end of the range (0.3 to 8 :g/m 2 /yr)
reported for the Swiss bog (Roos-Barraclough et al., 2002), with the uppermost Swiss values
seen only during periods of volcanic activity. The modelled result is also outside of the pre-
industrial range reported here for GL (0.3 to 3 :g/m 2 /yr). Given that the deeper GL peats
containing elevated Hg accumulation rates are enriched in Cu, Se, and U, we assume that the
lowest Hg accumulation rates (0.3 to 0.5 :g/m 2 /yr from AD 550 to 975) are representative of the
pre-industrial, atmospheric Hg flux. The pre-industrial flux calculated by Lamborg et al. (2002),
therefore, may be too large by as much as one order of magnitude.
At this time, we cannot determine how much of the atmospheric Hg accumulation in
GL may have been due to long range atmospheric transport, and how much due to local sources.
Since our study began, we have learned that the U.S. military operated a secret base called
“Bluie West One”, across the fjord from the sampling site, from 1941 to 1958 (the former airfield
is now Narsarssuaq airport). This base is said to have housed up to 10,000 persons during its
zenith, and had its own kilns for manufacturing bricks: this may help to explain the magnitude
and chronology of the elevated Hg fluxes from this period. Additional studies of peat bogs from
other locations should help improve our understanding of local and long-range Hg transport, and
31