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

Fate of Mercury in the Arctic 89
Discussion
It is important to have reliable RGM concentrations because the RGM levels represent the
amount of GEM oxidised and thereafter available for fast deposition from the Arctic troposphere
during mercury depletion events, with resultant wash out to the marine environment once the snow
melts. We are in need of reliable RGM observations in order to accurately measure flux, verify
atmospheric models e.g. DEHM on both a temporal and spatial scale. Experimental data from this
work confirms that whether deployed in the laboratory, or the Arctic, the annular denuder method is
one that when deployed in accordance with Landis et al., 2002, reproducibly measures the
operationally defined RGM with a 15% precision within 3 standard deviations.
RGM annular denuder tests
Annular denuders were tested under a variety of circumstances to determine how well the
denuders could reproduce the same measurement and if they were subject to any passive uptake.
The denuders are hand crafted, and are fragile, therefore the denuders are inspected and categorized
prior to use.
The RGM annular denuder tests performed in Oak Ridge at Station Nord taught many valuable
lessons about the operational measurement of reactive gaseous mercury and have raised questions
that should be addressed as this method improves.
The primary lesson is that RGM measurements are not trivial. In fact they are difficult to
perform. They require routine, and strict adherence to protocols to be able to compare them with
other data. The blanking, analysis and zeroing of a single denuder takes approximately 1 hour.
The results of this work show, that in the future, manual methods for measuring RGM should
be performed using triplicate co-located denuder measurements, and the automatic RGM analyser
should be deployed when a high-resolution time series is needed.