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

Fate of Mercury in the Arctic 31
Arctic station, Alert, and distributed to other Arctic mercury research teams for standardization, as
broadly as possible (Steffen and Schroeder, 1999).
NERI adopted this SOP to the situation and resources that were available to us for our
measurement campaigns. The major changes were the type of heated sampling line and quality
control procedures. As we were not on site for the entire campaign period, we did not conduct a
daily manual calibration of the machine, relying instead upon on the permeation tube as a secondary
standard.
By directly sampling the air, the machine measures total gaseous mercury, TGM, utilizing two
channels. One channel is being sampled while the other is being thermally desorbed and then the
function switches, allowing continuous sampling.
Through introduction of a soda lime trap into the sampling chain, as well as a 45 mm diameter
Teflon filter, to protect from the introduction of particulate matter, only the gaseous elemental
mercury fraction is measured.
Measuring GEM can also be achieved by introducing a KCl coated denuder into the sampling
train, Figure 2., page 33, which captures only reactive gaseous mercury, as described below.
Although it is the method utilized by Tekran for their automated mercury speciation unit, Model
1130, it was not utilized as part of the present study’s mercury sampling chain, except by the
American teams at Barrow, when reporting GEM.
The principle of the Tekran 2537A instrument is cold vapour atomic fluorescence spectroscopy
(CVAFS) and is described as follows: A measured volume of sample air is drawn through a gold
trap that retains elemental mercury. The collected mercury is desorbed by heat and is transferred by
argon into the detection chamber where the amount of mercury is detected by CVAFS.