Transcript Diapositiva 1

Climate Change and Future Scenarios
in the Arctic Region
Venice International University,
Isola di San Servolo
11-12 December 2014
The Polar Mercury Cycle in a changing
climate
Ian M. Hedgecock1 and Nicola Pirrone2
[email protected]
1 CNR – Institute of Atmospheric Pollution Research, Rende, Italy
2 CNR – Institute of Atmospheric Pollution Research, Area della
Ricerca di Roma 1, Monterotondo, Rome, Italy
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
Recent Progress towards limiting
Mercury in the Environment
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
Hg Species in the Environment
Elemental Mercury, Hg0
Unreactive, not very soluble, transported long distances,
makes up most of the Hg in the atmosphere, and the major
part of anthropogenic and almost all natural emissions
Oxidised Inorganic Mercury, HgII
The major component in mercury deposition fluxes, soluble,
can be methylated in the water column, lasts a few days in the
atmosphere
Methyl Mercury, MeHgX
Deadly
Dimethyl Mercury Hg(CH3)2 – practically irrelevant
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
The impact of methylmercury on
health
The fox on the left
lives on the coast and
feeds on sea birds, and
sometimes seal carcasses.
The one on the right lives
Inland and eats rodents and
non-marine birds.
Bocharova et al.,
Correlation between
Feeding Ecology and
Mercury Levels in
Historical and Modern
Arctic Foxes (Vulpes
lagopus). PLoS ONE,
2013; 8 (5): e60879
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
The processes influencing Mercury
fluxes in the Arctic
• Atmospheric transport via the atmosphere of Hg0
• In-situ oxidation of Hg0 to HgII by Br, during the Bromine
explosion
• Deposition of HgII, but also subsequent reduction
followed by re-emission of Hg
• Methylation of HgII in (lakes, sediments, ocean)
• Uptake by biota and subsequent bio-magnification
through the food web
All of which are likely to influenced by climate change
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
The chemistry behind the Bromine
explosion is complex
Bromine is derived from
sea-salt present both in
sea-ice and because seasalt aerosol deposits on
the snow. Acidification of
the snow (nitrate), solar
radiation and wind
blowing through the
snow layers release Br
compounds to the
atmosphere.
Pratt et al.,
Photochemical
production of molecular
bromine in Arctic surface
snowpacks, Nature
Geoscience 6, 351–356
(2013)
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
Recent studies show that it isn’t that
simple
Cloud plumes from cracks of open water in the Arctic sea ice cover.
Image credit: University of Hamburg, Germany
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
The age and salinity of sea-ice
• The chemistry behind the Bromine explosion is influenced by, temperature,
solar radiation and salinity
• Perennial sea-ice is less saline and less prone to form leads than seasonal
sea-ice
• The boundary layer over ice is often low, hence the quantity of Hg available
to be oxidised is limited
• When leads form they produce significant convection and therefore act to
pump Hg down from higher in the troposphere than when they are not
present.
• The increased salinity of seasonal ice rather than perennial ice can lead to
increased Bromine production especially during cold spells
Nghiem, S. V., et al. (2012), Field and satellite observations of the formation and
distribution of Arctic atmospheric bromine above a rejuvenated sea ice cover, J.
Geophys. Res., 117, D00S05
Moore et al., (2014), Covective forcing if mercury and ozone in the Arctic boundary
layer induced by leads in sea ice, Nature, 506, 81–84
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
And Chlorine too
Scientists studying the
atmosphere above Barrow,
Alaska, have discovered
unprecedented levels of
molecular chlorine in the air, a
new study reports.
Researcher Jin Liao checks the instrumentation in Barrow,
Alaska, during a research trip to measure molecular
chlorine in the atmosphere. (Photo: Georgia Institute of
Technology)
Jin Liao et al., (2014) High levels of molecular chlorine in
the Arctic atmosphere, Nature Geoscience 7, 91–94
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
“We don’t really know the
mechanism. It’s a mystery to
us right now,” Huey said. “But
the sea ice is changing
dramatically, so we’re in a
time where we have
absolutely no predictive
power over what’s going to
happen to this chemistry.
We’re really in the dark about
the chlorine.”
Rivers
A recent study suggests that
riverine input of Hg to the Arctic is
significantly higher than once
thought, and that input from rivers
is twice that from the atmosphere.
Which rivers is a good question as
another study has shown that the
burbot fish in two Russian rivers,
the Lena and the Mezen, are safe to
eat.
Leandro et al., (2013), Low and
Declining Mercury in Arctic Russian
Rivers, ES&T, 48, 747-752
From Fisher et al., (2012), Riverine source of Arctic Ocean mercury
inferred from atmospheric observations, Nature Geoscience 5, 499–
504
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
And the less known unknowns
While the impact of changing sea ice age and coverage are being studied and
becoming better understood, the impact of riverine inputs is less well studied.
However as pointed out in a review by Stern et al., a number of consequences
of climate change really are unquantifiable:
Permafrost melting – mercury release, more microbial activity?
Ocean stratification – more oligotrophic waters increasing the rate of Hg
methylation in the ocean?
Animal behaviour and animal feeding habits are likely to change, will they be
more or less exposed to Hg contamination?
Stern et al., (2012), How does climate change influence arctic mercury? STOTEN, 414,
22–42
CNR – Institute of Atmospheric Pollution Research, Rende, Italy
http://www.iia.cnr.it
Further details
The Global Mercury Observation
System www.gmos.eu
http://www.cnrmerc.org/
National Reference Centre for
Mercury (CNRM)
Thank you