Variability in gaseous elemental mercury at Villum Research Station, Station Nord, in North Greenland from 1999 to 2017

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Mercury is ubiquitous in the atmosphere, and atmospheric
transport is an important source for this element
in the Arctic. Measurements of gaseous elemental mercury
(GEM) have been carried out at Villum Research Station
(Villum) at Station Nord, situated in northern Greenland. The
measurements cover the period 1999–2017, with a gap in the
data for the period 2003–2008 (for a total of 11 years). The
measurements were compared with model results from the
Danish Eulerian Hemispheric Model (DEHM) that describes
the contribution from direct anthropogenic transport, marine
emissions and general background concentration. The percentage
of time spent over different surfaces was calculated
by back-trajectory analysis, and the reaction kinetics were
determined by a comparison with ozone.
The GEM measurements were analysed for trends, both
seasonal and annual. The only significant trends found were
negative ones for the winter and autumn months. Comparison
of the measurements to simulations using the Danish Eulerian
Hemispheric Model (DEHM) indicated that direct transport
of anthropogenic emissions of mercury accounts for between
14% and 17% of the measured mercury. Analysis of
the kinetics of the observed atmospheric mercury depletion
events (AMDEs) confirms the results of a previous study at
Villum of the competing reactions of GEM and ozone with
Br, which suggests that the lifetime of GEM is about a month.
However, a GEM lifetime of 12 months gave the best agreement
between the model and measurements. The chemical
lifetime is shorter, and thus, the apparent lifetime appears
to be the result of deposition followed by reduction and reemission;
for this reason, the term “relaxation time” is preferred
to “lifetime” for GEM. The relaxation time for GEM
causes a delay between emission reductions and the effect on
actual concentrations.
No significant annual trend was found for the measured
concentrations of GEM over the measurement period, despite
emission reductions. This is interesting, and together
with low direct transport of GEM to Villum as found by the
DEHM model, it shows that the dynamics of GEM are very
complex. Therefore, in the coming years, intensive measurement
networks are needed to describe the global distribution
of mercury in the environment as the use of models to predict
future levels will still be highly uncertain. The situation is
increasingly complex due to global changes that most likely
will change the transport patterns of mercury, not only in the
atmosphere but also between matrixes.
OriginalsprogEngelsk
TidsskriftAtmospheric Chemistry and Physics
Vol/bind20
Nummer21
Sider (fra-til)13253-13266
Antal sider13
ISSN1680-7316
DOI
StatusUdgivet - 2020

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