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

to recover ca. 2 cm 3 plugs from every cm down to 40 cm, and every 2 nd cm below 40 cm; these
were air-dried overnight at room temperature in a Class 100 laminar flow clean air cabinet.
Mercury concentrations were measured in these plugs using solid sample atomic absorption
spectroscopy (Salvato and Pirola, 1996) with a LECO AMA 254 as described in detail elsewhere
(Roos-Barraclough et al., 2002). The instrument was calibrated using liquid Hg working
standards prepared from a Merck 1000 mg/l Hg standard solution. Every 12th measurement was
a certified reference material, either NIST 1515 (Apple Leaves) or NIST 1547 (Peach Leaves).
The average measured values were 45.0 ± 0.7 ng/g (n=11) for NIST 1515 (certified value 44 ±
4 ng/g) and 32.1 ± 1.4 ng/g (n=15) for NIST 1547 (certified value 31 ± 7 ng/g). The Hg
concentration profiles presented here (analyst: F. R-B.) are in excellent agreement with those
reported previously (analyst: M.E.G.) for selected samples from the same cores (Goodsite, 2000).
As an independent check on the data which are presented here, Hg concentrations were
also measured in a complete set of subsamples at the Department of Arctic Environment, Danish
National Environmental Research Institute (analyst: G.A.). Approximately 1 g fresh sample and
4 ml concentrated Merck Suprapur nitric acid were added to Teflon bombs with stainless steel
caps, which were then heated for 12 hours at 150/C. After cooling the dissolved samples were
left uncovered until the majority of the nitrous oxides had evaporated. Before analysing for Hg,
potassium permanganate solution was added until a permanent pink colour was obtained in order
to maintain an oxidising environment and to prevent loss of Hg. The samples were then diluted
with 18 MS water to approximately 25 g in polyethylene bottles. Mercury concentrations were
determined following reduction with sodium borohydride in a flow injection AAS system
(Perkin Elmer FIMS). The data set obtained using this procedure is in good agreement with the
data which is presented in this paper, obtained using the LECO AMA 254 (on average, within
15%, r 2 = 0.727, n=65).
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