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

Fate of Mercury in the Arctic 112
northern hemisphere, 20-90 0 N latitude. None of the so far published records from tree rings, as
seen in the figure, covered the whole second half of the 20 th century, Therefore, tree ring and
cottonseed data from Arizona as well as data from Denmark was added to complete the curve.
Previously unpublished Atmospheric measurements provided by I. Levin, University of Heidelberg,
consisting of the annually averaged atmospheric 14 CO2 curve for the northernmost northern
hemisphere is plotted and recommended for use as the general bomb-pulse calibration curve for the
northern hemisphere for 4 reasons: 1) the data from Arizona closely follow the curve but do not
provide annual resolution, this is the limitation of any of the data from particular points or terrestrial
sources; 2) the curve provides consistent, carefully checked atmospheric data covering the whole
pulse until the present, 3) The portion of this data set up through 1997, is published and widely used
(Levin et al., 1997); differences for the other curves results in calibrated age differences of only 1-2
years from the data provided by Levin.
As then seen in Figure 15., page 79, for the northernmost northern hemisphere it is most
appropriate to use the Levin data as a calibration tool in General, though depending on location,
there are local features, e.g. testing around China that this curve now provides a ready reference to.
For more detail discussion, see Goodsite et al., 2002, Appendix C. this work is the first time that
bomb-pulse dating was successfully applied to peat. This was primarily a function of having the
appropriate calibration curve, and sampling and handling the peat appropriately, as discussed in the
paper.
The successful development of this method means that now, when it is able to be applied and
used, the greatest source of error in determining a chronological series of a trace metal in peat no
longer comes from the date determination, but rather comes from sampling and handling. With
especially the mundane determination of bulk density in peat now providing the greatest source of
error, when calculating accumulation rates.