Environmental Engineering Reference
In-Depth Information
ice at mid- and polar latitudes that could be the source of secondary emissions. In addition,
a warmer world will most probably increase the demand for pesticide use in mid-latitudes.
At the same time, the trophic structure of Arctic ecosystems and their biomagnification po-
tential can also be expected to change, but these are difficult elements to quantify. My own
interpretation of the present computer modelling is that it further emphasizes the need for
vigilance in the approval of chemicals with properties of POPs in a warming world. It also
helps to focus attention on the key properties of substances that could be expected to un-
dergo enhanced transport and polar deposition under given climate-warming scenarios.
The impact of climate change on mercury has been less well studied, but the potential
impacts and uncertainties of these aspects were reviewed by Gary Stern and colleagues
in 2012 based on the 2011 AMAP mercury assessment noted earlier. You will recall that
the cycling of mercury in the environment is very much linked to the cycling of organic
carbon, especially with respect to those parts of the cycle involving the biologically avail-
able and toxic methylmercury. The basic picture contains two fundamental climate-sensit-
iveelements.First,thetransformationofmercuryinthecyclefromoneformtoanotherand
those elements concerned with the movement of mercury into and out of the atmosphere
that are temperature dependent. This includes those strange atmospheric mercury depletion
events (AMDEs) that are strongly linked to ice-related processes. Second, a disproportion-
ately large slice of the environmental reservoir of mercury resulting from human activities
has built up in the Arctic cryosphere (ice sheets, ice caps, glaciers and frozen sediments
and tundra soils).
From a biological perspective, a key issue concerning climate warming relates to
methylmercury.Warmer and longer summers will increase conditions in low-oxygen envir-
onments (including thawing tundra permafrost) that are favourable for the microbiological
formation of methylmercury from inorganic mercury. Thawing permafrost alone has been
estimated to be able to release 200 micrograms of mercury per square kilometre each year.
To put this into perspective, it is an amount that is greater than that deposited annually from
the atmosphere. At the same time, the release of nutrients from frozen soils and sediments
will likely increase primary production at the base of the Arctic trophic system. We can
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