3.4. Sources of metal dust dispersion in Maarmorilik and comparison
with previous estimates
The reason for the relative high dispersion of Pb, Zn and Cd in
Maarmorilik long after mine closure is mainly considered due to
a continuous generation of dust particles (although not as high
as during the mining period) and a climate dominated by moderate
to strong winds and little precipitation. A continuous generation ofdust particles containing relative high concentrations of Pb, Zn and
Cd is expected from the waste rocks left on the mountain sides in
Maarmorilik, especially from the remains of the major waste rock
dump near Site T12SW (Fig. 1A) due to chemical and physical
weathering processes breaking the rocks down. In addition, remains
of ore-material and concentrate in the Maarmorilik mining
town, especially near the former ball mill, is still considered an
important source. The dry climate and scarce vegetation cover favours
an effective mobilisation of dust particles by the wind and
moderate to strong easterly winds coming from the inland ice
sheet in the bottom of Qaamarujuk fiord dominate in Maarmorilik.
Steep, roughly 1000 m high mountain sides surround the narrow
fiord near Maarmorilik, which compresses the wind flow and increases
the wind speed, thus making the dust dispersion very
effective.
During the mining period in 1973–1990, some rough estimates
of the annual Pb downfall near Maarmorilik were made (Grønlands
Miljøundersøgelser, 1988). According to these estimates, 1300 to
6400 kg of Pb were dispersed and deposited annually within the
period 1979 to 1987. Thus, the 770 kg Pb estimated to disperse
and deposit during the 2010–2011 snow-free period, 20 years after
mine closure, represents a significant fraction of the downfall
when the mine operated.