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

Fate of Mercury in the Arctic 62
hemisphere (Goodsite et al., 2002) individual samples more recent than AD 1950 could be dated
directly with high time resolution, ± 2 years. Samples that stopped respiration between this period
and 1995 have elevated levels of carbon 14, since thermonuclear testing led to elevated 14 C levels in
the atmosphere. Using AMS, these levels can be directly measured and correlated with the curve,
not utilizing the conventional method of half-life decay of 14 C.
Selected samples from deeper layers, dating from before AD 1950, could not use this method
and were AMS 14 C dated by the usual tree-ring calibration method, with much larger uncertainties
to follow or by 210 Pb dating.
Pb-210 dating
1,5 grams of solid sample powders along with water content and dry bulk density information
were sent to Professor Peter G. Appleby, University of Liverpool, for age dating using the 210 Pb
constant rate of supply model (Appleby and Oldfield, 1978). This method results in a model
providing chronological information spanning the last approximately 200 years. Further details are
discussed in the papers where employed. Comparison of 210 Pb age dating with the Goodsite et al.,
2002 atmospheric bomb pulse method of the same set of peat samples, is found in the paper,
Appendix C.