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

Fate of Mercury in the Arctic 113
This method can be applied where standard-dating methods cannot be, for example in peat
disturbed by digging or cutting. The limitation of this method is that it only covers the last half of
the 20 th century. The primary gain is that the chronology is an order of magnitude better than
standard chronological dating methods.
Figure 16., page 80, shows high resolution dating is applied successfully for the first time in
Denmark and Greenland. In Denmark, due to peat digging during WWII, the Pb-210 dating method
could only be applied with error an order of magnitude higher than that provided by the bomb-pulse
method. In Greenland application of the method allowed for the first coastal high time resolution
investigation of trace metal accumulation in an environmental archive in the Arctic.
In Figure 17a. and b., page 83; 18a. and 18b., page 84; 19., page 85; and 20., page 86, it is seen
that in the minerotrophic southern Greenland, and the blanket bog on the Faroe Islands, that the
chronology of Hg accumulation is similar to that of the ombrotrophic bog in Denmark, during the
last 50 years. This suggests that in remote areas, Hg is supplied to the wetlands primarily via
atmospheric deposition, demonstrating that given the proper conditions, minerotrophic sediments
provide a history of atmospheric deposition as consistent as one provided by a raised bog. It is also
seen that dry bulk density is very variable, most likely the result of sampling and determination
methods.
Hg fluxes in the Greenland core (0.3 to 0.5 µg m -2 yr -1 ) were found in peats dating from AD
550 to AD 975, compared to the maximum of 164 µg m -2 yr -1 in 1953. Atmospheric Hg
accumulation rates have since declined with the value for 1995, 14 µg m -2 yr -1 comparable to
published 1995 values from the Danish Eulerian Hemispheric Model (Christensen et al., 2002, also
found in Skov et al., 2003, Appendix C), of 12 µg m -2 yr -1 for southern Greenland.
In Denmark, the greatest rate of atmospheric Hg accumulation is found in 1953, 184 µg m -2 yr -
1 , comparable to that of Greenland with the flux going into sharp decline, with an accumulation rate