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

estimating for Alert an average springtime dry-deposition flux for mercury of 2.5 ± 0.5 ng m -2 h -1
based on their measurements of TGM. Comparing the flux with the average meteorological
conditions in Table 2., gives no direct correlations. One would expect that emissions would increase
as a function of the rising temperatures, but this can not said to be readily apparent. What seems to
be apparent is that following a large depositional event; there is a small re-emission. This is
probably the snow pack regaining equilibrium with the atmosphere.
As seen in Fig. 1., the depositional velocities noted for depositional events are fast, around 2
cm s -1 this is what would be expected for a very reactive gaseous species such as HNO3. On
average, the depositional velocity is approximately 1 cm s -1 . Comparing with measured dry
deposition velocities over snow for HNO3, reviewed in Karlson and Nyholm, 1998, show that the
measured dry depositional velocities for RGM may be an order of magnitude higher than that for
HNO3, given the snow surface temperature of < 2 0 C.
3.2 Comparison of RGM flux with RGM ambient concentrations
Fig. 2, are the monitored results RGM concentrations during the Barrow 2001flux measurement
campaign. Comparing with Fig. 1., show that when there is a deposition recorded by the REA
machine, there are correspondingly low RGM ambient values. The air has been apparently depleted
of RGM due to deposition. Trends of RGM rising in the air on the 8 th , 9 th and 12 th of April are
recorded by the REA system as reemission, perhaps indicating that RGM can be re-volatized from
the snow surface.
3.3 Drawbacks and other possible accumulators
Stable weather conditions are the greatest drawback to deploying the RGM system in the Arctic
for investigating mercury depletion events. Lu et al., 2001, summarize that the environmental
conditions favouring mercury depletion events at high latitudes are: 1, marine/maritime location; 2,
calm weather, low wind speeds, non-turbulent air flow; 3, the existence of a temperature inversion;
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