Acidification and Arctic Haze - The Changing Arctic Environment: The Arctic Messenger - page 85

during long winter periods of atmospheric inversions that trapped the industrial and do-
mestic heating smoke in the lowest few hundred metres of the atmosphere.
One of the abatement measures taken was to simply increase the height of
smokestacks.Itimprovedlocalairqualitybutalsoincreasedtheexportofpollutiontoother
areas. This leads us to another “unique” feature of the acid rain situation. The most im-
pacted areas showing ecosystem stress from acidification were generally (but not always)
hundreds of kilometres distant from potential sources. It was realized that two factors were
responsible for the observed pattern of acidification. The first is pretty obvious: It is the
direction of prevailing wind. Therefore, much of the cargo of acidifying substances gen-
erated, for example, in the industrial heartlands of the United Kingdom and Germany was
exported in the atmosphere by south-westerly winds towards the Nordic countries. The
second factor was less obvious but was easy to understand. Not all regional environments
are equally vulnerable to acid rain. For example, soils and lakes sitting on a bedrock that
is chemically basic (the opposite of acid) will buffer the incoming acid rain, resulting in
few ecosystem effects. However, if the bedrock is acidic (such as one of the many types
of granite, schist and gneiss), the overlying terrestrial and freshwater systems will already
be under a significant degree of natural acid stress. There will be little buffering capacity
to deal with anthropogenic acid rain. Consequently, the most acid-sensitive terrestrial and
freshwater ecosystems were generally those situated on the Precambrian shields in Fenno-
scandia, Scotland and north-eastern North America. The crystal clear waters of a loch in
Scotland are an artefact of their natural acidity and low nutrient concentrations (mainly ni-
trogen and phosphorus) that severely restrict plankton growth.
Arctic haze is the name given to a visibility-reducing dirty brown haze that has been
noticed by Inuit, whalers and Arctic explorers since the nineteenth century and since the
1950s by pilots flying polar routes. Known as Poo-jokt by the Inuit, the phenomenon is
mainly seasonal, occurring with a peak in late winter and spring. By the late 1960s and
early 1970s, atmospheric studies showed that Arctic haze is a visible manifestation of the
long-rangetransportintheatmosphere ofamixture ofanthropogenic pollutants. Thesepol-
lutants come from the mid-latitude industrial combustion of hydrocarbon-based fuels and