Fróðskaparrit - 01.07.2004, Side 90

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MERCURY IN THE FAROE ISLANDS — A REVIEW OF AVAILABLE DATA
compounds in gaseous state or in aerosols,
and embraced a series of metals and acid
rain components, but not mercury. The re-
sults are however, very likely of value in in-
terpreting subsequent analyses on the air
medium in the Faroes and are thus men-
tioned here.
From May 2000 to March 2001 NERI
has in cooperation with the Faroese Food-
and Environmental Agency investigated
mercury Hg° in the air on the Faroe Islands
using a Tekran Model 2537A Mercury
Vapour Analyser (Skov et al., 2003). The
purpose of this investigation was to deter-
mine the concentration of mercury in the
air on the Faroes. Also, part of this study
was to examine possible anthropogenic, lo-
cal mercury sources and to find the origin
of the airborne mercury.
The study revealed that the measured
quantities of mercury in air were very vari-
able. During some time intervals the mea-
sured values were as high as 2,8 ng/m3 and
at others it was as low as 0,5 ng/m3, which
is lower than the global background value
for mercury at 1,7 ng/m3. The mean value
for the entire period was 1,33 ng/m3.
Possible mercury sources on the Faroes
were presumed to be: The incineration
plants, the hospital, the shipyard and den-
tists. After questioning the staff in these
places it was concluded that the mercury
source of most significance was the incin-
eration plants. The last couple of years the
mercury emissions from the incineration
plants have been generally lower than the
max. allowed value in those years of 100
p,g/m3. Furthermore it was concluded that
smoke from the incineration plants in Tór-
shavn and Leirvík would probably not
reach the location of the air sampling and
measurements.
Also, if the incineration plants were to
blame for the high values measured, one
would expect a large variation in the mea-
sured mercury concentration and high val-
ues to be measured from time to time
throughout the year, but this was not the
case. Instead, the work was concentrated on
wind direction during measurements of
high and low values. However, due to the
high air humidity, and the sensitivity of the
equipment towards this, there was a degree
of uncertainty in the measured values.
It was concluded that the sources of the
high air mercury levels were not to be
found on the Faroes but rather that the mer-
cury was transported to the Faroe Islands
via long-range atmospheric transport.
In the summer months of 2002 from June
through September, passive mercury vapo-
ur samplers were placed at 5 study stations
around the Eysturoy and Streymoy islands
as part of a Ms.Sc. study on the extent of
uptake of mercury in grass under the influ-
ence of factors as dry and wet deposition
(Daugaard, 2003). The passive samplers
consisted of gold-nets in glass-tubes invert-
ed so as not to be wetted by rain. The ap-
plication of the passive samplers was part
of pioneer work on these and the efficiency
of the samplers was not fully known at the
beginning of the study. It turned out how-
ever, that the measured overall mean con-
centration of air mercury in the study peri-
od was close to 1,24 ng/m3 (Daugaard,
2004) and thus within the range found us-
ing the Tekran analyser (Skov et al., 2003).