Fróðskaparrit - 01.07.2004, Síða 88

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MERCURY IN THE FAROE ISLANDS — A REVIEW OF AVAILABLE DATA
Introduction
Mercury, Hg, is a metal and thus is a natur-
al component of our environment. We are
familiar with mercury from our every-day
life through our dental “silver” fdlings,
which are in fact amalgams, where the term
amalgam means a mixture of mercury and
other metals. This property to blend with
other metals at ambient temperature is a
special feature of mercury and is the basis
for the use of mercury in gold extraction in
some areas, an application that leads to at
least locally significant pollution. Due to
suitable electrochemical and electronic
characteristics mercury has also been used
in electric equipment and in chlor-alkali
production, applications which are now
highly restricted in the developed parts of
the world. The toxicity of mercury is high-
ly dependent on the physiochemical form it
occurs in, i.e. the actual species. Pure,
metallic mercury for example is more poi-
sonous than mercury bound in amalgams,
and methylated mercury is more poisonous
that mercury in inorganic species. The
species are however not static and transi-
tion between most chemical forms occur
depending on the environment. In the pre-
sent review, only inorganic, divalent mer-
cury and occasionally methylated mercury
or gaseous elemental mercury species are
discussed.
There are many different mercury
sources in the environment but the most im-
portant ones are burning of fossil fuels and
waste (Pacyna and Keeler, 1995), where
stationary combustion' in 1995 of mainly
coal accounted for 3A of the global emission
(Pacyna and Pacyna, 2000). In addition to
this, a large quantity comes from the earth
itself as evaporation from the crust and veg-
etation and from volcanic activities. Inven-
tories indicate that approximately 60% of
the mercury entering the atmosphere every
year is anthropogenic (AMAP, 1998),
where anthropogenic or man-made in this
case of a naturally occurring substance sim-
ply means that the metal is released to the
biosphere through mans activities. Invento-
ries based on 1990 and 1995 emission data
indicate that there were no major changes
in global emission in this period (Pacyna
and Pacyna, 2000). There have however,
been a decrease estimated to 45% in emis-
sions in Europe and North America during
this time, but globally this decrease is offset
by an almost doubling in the contribution
from the Asian sources where the emission
which stems from stationary combustion of
fossil fuel have increased markedly (Pacy-
na and Pacyna, 2000; Pacyna et al., 2001).
In the eighties, Nriagu and Pacyna (1988)
estimated the amount of mercury being
emitted to the atmosphere from anthro-
pogenic activities to be equal to that being
directly discharged to the sea and approxi-
mately half the amount that is deposited on
land (Pacyna and Keeler, 1995), implying
thus that the other half of the mercury de-
posited were stemming from natural pro-
cesses.
For areas with limited local emission, it
is mainly the emissions to air of elemental
gaseous mercury which is the most inter-
esting part of the overall mercury release,
because mercury has a long residence time
in the atmosphere and can be transported
over long distances until it is eventually de-