soils as well as shallow ones can be 
transported. Nevertheless, whatever 
the source, the deeper the soil, the 
greater the possibility of contact with 
water passing through it. Therefore, 
even soils with little buffering capacity 
can, if they are deep enough, neu- 
tralize acidic precipitation. 
The topography of a region has an 
important influence on the suscepti- 
bility of its lakes and streams to acidi- 
fication. Mountainous areas, for in- 
stance, are likely to have shallower 
soils and more exposed bedrock than 
lowlands. Many mountain streams 
have little water and sometimes dry 
up. Close to the top of their watershed, 
these streams get relatively little 
ground water and, since they swell 
rapidly during small rainstorms, are 
in many cases vulnerable to the chemi- 
cal effects of rain. Studies conducted 
exposed bedrock. In these areas the 
chemical characteristics of the bed- 
rock determine the fate of the acids 
deposited from the atmosphere. Lime- 
stone terrain has a nearly infinite abil- 
ity to buffer H*, but hard crystalline 
rocks such as granites contain no min- 
erals that could contribute alkalinity, 
are slow to dissolve, and therefore have 
little ability to neutralize acids. 
The freshwater regions of North 
America where acidification is most 
severe are the Canadian Shield and 
the Adirondack Massif. In less sen- 
sitive regions the bedrock is more ex- 
tensively covered by soil, derived ei- 
ther from the local bedrock by means 
of erosion or transported into the area 
by water, winds, glaciers, or land- 
slides. A transported soil, in contrast 
to local soil, may be quite different 
from the bedrock under it, and deep 
last year in the Shenandoah National 
Forest by James Galloway of the Uni- 
versity of Virginia show this to be 
true for some streams in the Blue 
Ridge Mountains of the southeastern 
United States. Before these studies, 
this region was not known to have 
been affected by acidic precipitation. 
Another way in which topography 
influences lake and stream acidifica- 
tion is by increasing the amount of 
precipitation they receive. When bod- 
ies of air moving across lowlands en- 
counter a mountainous region they are 
forced to rise. As they rise, they en- 
counter diminishing atmospheric pres- 
sures, and the air expands to occupy 
a larger volume with the same mass. 
The heat contained in the rising air 
parcel is also distributed throughout 
a larger volume, so that the tempera- 
ture of the air decreases. This cooling 
process is what causes clouds to form 
and rain to fall more frequently over 
the mountains than over lowlands. The 
first rain that falls after a body of 
cooled air has passed through a moun- 
tainous region tends to remove more 
pollutants than subsequent rainfalls 
do, thereby causing the mountains 
nearest the source of the acidic air 
pollution to receive more acid than 
neighboring areas. 
In 1979 a computerized inventory 
of water chemistry data from the east- 
ern United States was set up at Brook- 
haven National Laboratory on Long 
Island. Known by the acronym ACID 
(for Acidification Chemistry Infor- 
mation Database), this inventory re- 
veals that waters with low alkalinities 
(that is, less than 100 ppb) are found 
in many areas of the eastern United 
States. A large number of such head- 
water streams have probably become 
at least temporarily acidified by rain 
or snow that is strongly acidic. 
Abundant snow is a feature common 
to the geographical regions most heav- 
ily affected by acidification. But much 
of the snow is no longer pure. Like 
the rain, it carries a burden of pol- 
lutants released by humans into the 
atmosphere. In fact, falling snow is 
The lakes and streams of southern 
Norway began to lose their fish 
populations decades ago. There 
are now thousands of lakes in this 
region from which fish have been 
completely eliminated. 
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