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

Fate of Mercury in the Arctic 38
For all measurements a field blank was obtained by handling a denuder in the field. Hg Mass
from this field blank was subtracted from the measured Hg masses on the exposed denuders.
If there was any indication of Hg (0) adsorption, for example with sudden sharp increases in Hg
amounts then the denuder was cleaned and re-coated, since as pointed out by Sheu and Mason,
2001, just 1% of Hg (0) adsorption on a denuder is enough to compromise RGM measurements. It
is therefore very important to carefully follow the prescribed methods, especially since annular
denuders are used as part of the reactive gaseous mercury flux measurement system.
All accuracies with the denuders were found to be in good agreement with those reported by
Landis et al., 2002. In the Barrow 2001 campaign, the EPA manual denuders exhibited a precision
of 10%, based on co-located parallel measurements.
During sampling the denuders were kept constant at approximately 50 o C above ambient
temperatures with the initial heating caps, or at 50 o C, with the improved heating caps. Temperature
was verified by sliding a thermometer probe into the air surrounding the denuder between the outer
wall of the denuder and the heating mantel, and measuring the air temperature. It is assumed that
the denuder coating temperature is in equilibrium with the air temperature.