The installation of tall 
smokestacks at power plants, 
beginning in the 1950s, allowed 
emitted sulfur oxides to spread 
more widely before being deposited, 
providing time for greater 
portions to be converted into 
sulfuric acid. Such airborne 
acid can fall as acid rain 
hundreds of miles from the 
source of pollution. 
sometimes a dirty gray. And not just 
in industrial towns, but in areas such 
as south-central Norway, many hun- 
dreds of miles from the sources of 
the pollutants. Snow cores taken from 
that region of Norway contain gray 
bands corresponding to specific snow- 
storms that carried fly ash and other 
contaminants east and northward from 
the industrial regions of Great Britain 
and the rest of Europe. I have not 
yet seen this kind of banding in the 
snows of the Adirondack Mountains, 
probably because of the relatively 
stringent rules concerning airborne 
emissions of particulate pollutants in 
the United States. Some American 
snow, however, like the snow in Nor- 
way, is contaminated with acids. 
When rainwater freezes to form 
sleet, the ice crystals created in the 
process tend to exclude molecules of 
all substances other than water. A 
water droplet containing sulfuric acid 
will thus become a small clump of 
ice covered with the droplet’s total 
amount of acid. The acid on the out- 
side of the tiny clump is accordingly 
in a more concentrated form. Further- 
more, ice and snow crystals serve as 
attachment sites for sulfur and nitro- 
gen oxides, where the adhering oxides 
can react with other pollutants and 
water. When the sleet or snow falls 
to the ground, the pollutants stay 
bound to the outside of the crystals. 
As the snow pack ages, a slight melting 
and recrystallization take place, in- 
creasing the size of the ice particles. 
Since pollutants continue to be ex- 
cluded from the crystals, they become 
even more concentrated on the outside 
of the ice particles. If the partial melt- 
ing occurs above a layer of solid ice 
in the snow pack or on a lake, one 
or more bands of concentrated pol- 
lutants may be formed within the snow 
pack. 
As soon as enough melting takes 
Lenny Newman. Brookhaven National Laboratory 
place to allow water to move freely 
through the snow, the first meltwater 
will remove a large portion of all of 
the soluble pollutants. Researchers at 
the Norwegian Institute for Water Re- 
search have shown that this mech- 
anism typically removes 50 to 80 
percent of the pollutants in the first 
30 percent of the meltwater. The sud- 
den release of acids and other pol- 
lutants from snow that has collected 
for weeks or months can cause drastic 
acidification in lakes and streams. An 
example of this process can be found 
in Panther Lake in the western Ad- 
irondack Mountains of New York 
State. The lake usually has a pH of 
slightly above 7, almost neutral. But 
when the snow melted in the spring 
of 1979, the pH dropped to about 
5, an increase in ionized hydrogen of 
about a hundredfold. 
The cause and effect relationship 
between acid rain and the disappear- 
ance of fish was first suggested by 
a Norwegian fisheries inspector in 
1959. It was publicized in Norway 
in 1966 and has subsequently been 
well documented. Concern about acid 
rain was not felt anywhere until Scan- 
dinavian scientists began to notice that 
many lakes and streams in southern 
Norway and on the west coast of Swe- 
den were losing their populations of 
fish. The decline in the salmon catch 
in major rivers of southern Norway 
is most striking. The Tovdal River 
salmon catch began an unprecedented 
decline in the late 1920s. Periodic fish 
kills, which may have been caused 
by drops in the springtime levels of 
pH, possibly combined with simulta- 
neous increases in the concentration 
of aluminum, gradually reduced the 
stock of Atlantic salmon in the river 
(although other factors such as over- 
fishing might also have played a role 
and cannot be completely disre- 
garded). The scientific documentation 
for this period is poor, since few pH 
measurements in streams were made. 
We do know, however, that in the 
past two decades the entire Tovdal 
River, with pH values in the range 
of 4.6 to 5.2 in 1975, has become 
so acidic that throughout most of the 
year Atlantic salmon cannot survive 
in its waters. These low pH values 
are in marked contrast to those in 
Norwegian rivers beyond the reach 
of airborne acid. 
In 1975, Carl Schofield, a fisheries 
biologist at Cornell University, con- 
ducted a survey of 217 Adirondack 
62 
