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

control system (Metsupport, Denmark) coupled with a RGM manual sampling system utilizing
heated KCl coated annular denuders to capture RGM (Landis et al., 2002). This system uses heating
mantles specifically built for Arctic use.
2. Methods
2.1 Study Site
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Flux measurements were made in March – April, 2001 at the NOAA Climate Monitoring and
Diagnostic Laboratory (CMDL) in Barrow, AK. Barrow is geographically the northern-most point
in Alaska, located at 71°19’ N, 156°37’ W, and the CMDL is approximately 9 m above mean sea
level, providing a very flat fetch for micrometeorological measurements. The air sampled at the
station is characteristically part of the marine boundary layer during the sunlit hours. The Beaufort
Sea was frozen, with periodic leads opening during the campaign. The weather was very stable, as
expected for a high Arctic coastal area. A more detailed description of the study site is provided in
Lindberg et al., 2002.
2.2 RGM determination
RGM was measured and analysed by the method developed by Landis et al. (2002), employing
a KCl coated quartz annular denuder sampling chain heated to 50 0 C, to sample air. At the inlet,
there is an elutriator and an impactor, with impactor plate. The elutriator accelerates the flow, by
forcing it through an orifice onto a roughened, non-coated impactor plate. The cut-off diameter is
2.5 µm, so only the fine fraction of particles flows through the denuder. The flow rate is 10 litres
per minute and was controlled prior to and after sampling sampling with a “dry cal” flow meter
prior attached just before the denuder sampling train.
Denuders had a collocated precision of < 15.0 ± 9.3 % with 3x std. dev., in agreement with the
findings reported in Landis et. al., 2002.