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

Fate of Mercury in the Arctic 34
sampling chain heated to 50 0 C, to sample air, Figure 2., page 33, and is described in detail as cited
so the sampling system and method will therefore only be briefly reviewed.
At the inlet, there is an elutriator and an impactor, with impactor plate. The elutriator is coated
in cross linked teflon. The elutriator straightens the flow and accelerates it, by forcing it through an
orifice onto a roughened impactor plate with no coating applied. The cut-off diameter is 2.5 µm, so
only the fine fraction of particles flows past the active area of the denuder. The sample flow is 10
litres per minute. The flow is controlled just prior to the denuder chain with a “dry cal” flow meter
prior to and after sampling.
Immediately following the impactor, there is a dead space prior to the annulus. This allows for
expansion of air, from ambient to 50 o C, since KCl optimally collects RGM at this temperature
(Landis et. al, 2002); as well as proper development of laminar flow, which is a necessary condition
for proper functioning of denuders.
9 annular denuders were available: 6 new, belonging to NERI and 3 approximately 1 year old,
belonging to ORNL; however, there were only 4 complete sampling systems as depicted in Figure
2., page 33.
Measurements made in Barrow were therefore with US EPA denuders and sampling systems,
to include the annular denuder system employed in the reactive gaseous mercury flux system.
The denuders were characterized in the laboratory of Dr. Lindberg at Oak Ridge National lab
prior to field deployment.
Upon receipt, denuders were physically inspected. The physical inspection is an important
aspect of quality control prior to using the denuders and includes checking for cracks, and ensuring
that the threads produce a tight seal. Each new denuder was then numbered 1 – 6, by carefully
etching with a diamond pen. The 3 older denuders were numbered X1 – X3.