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

Fate of Mercury in the Arctic 101
sampling valves froze, and their data is not further considered. It was therefore necessary to
reposition the sampling valves, into a shipping box, buried in the snow for insulation. The third run
also showed sampling which favoured the down channel. One expects a micrometeorological
system to equally sample turbulence, as seen by similar number of counts in the up and down
channel. One channel being preferred over another is a sign that either the wind flow is being forced
in one direction of another, or that the instrumentation is not properly set up. Even though the
results indicated preferential sampling, the decision was made not to adjust the sonic. It was not
certain that any adjustments would make the system any more level, and the first three
measurements were consistent, so mass adjustments could be reasonably applied. Stopping the
system each hour to read the data caused the tilt function to reset. This could also be a source of
bias. In the new generation system, it is no longer necessary to stop the system to monitor and
download the data.
The total concentration is taken to be the sum of the up, down and mid masses multiplied by
total sampling time and the flow rate. The concentrations compare sometimes very well with the
RGM monitor, and other times not as well. There does not seem to be any general trend, except that
the REA system total is generally less RGM than the 1130 concentration, Figure 22., page 102.