248
T
he effects of acid rain on
stone were noticed as long
ago as the 17th century
in England, and in Norway in the
19th century. However, it was not
until American ecologist Gene
Likens carried out in-depth studies
in an area of rural New Hampshire
that the phenomenon came to be
properly understood.
From 1963 onward, freshwater
ecologist Likens and his team
studied the relationship betweenwater quality and life forms in the
Hubbard Brook drainage basin in
New Hampshire. They discovered
that the rainfall there was unusually
acidic. Acidity, as expressed by pH
(potential of hydrogen), ranges from
0 (most acidic) through 7 (neutral),
to 14 (least acidic). Most fish and
other aquatic animals fare best in
water with pH values of 6–8, but
Likens found values of 4—too acid
for fish, frogs, and the insects they
eat to survive. He set up monitoring
stations around New England,
which showed that acid rain and
snowfall were widespread in the
densely populated and heavily
industrialized northeastern states.
Likens’s systematic work persuaded
the US government to introduce
laws to control emissions of the
chemicals responsible for acid rain.Effects of acid rain
When fossil fuels are burned in
power stations and factories, sulfur
dioxide (SO 2 ) and nitrogen oxides
spew out of their chimneys.Acid rain had been wearing away
stonework—such as this statue in the
churchyard of St. Peter and St. Paul,
Krakow, Poland—for hundreds of years
before the phenomenon was understood.IN CONTEXT
KEY FIGURE
Gene Likens (1935 –)BEFORE
1667 The corrosive effect of
polluted city air on limestone
and marble is noted by the
English diarist John Evelyn.1852 British chemist Robert
Angus Smith argues that
industrial pollution causes the
acidic rainfall that damages
buildings. He is the first person
to call it “acid rain.”AFTER
1980 The US Congress
passes the Acid Deposition
Act, undertaking an extensive
18-year research program into
acid rain.1990 An amendment to the
US Clean Air Act (passed
originally in 1963) establishes
a system that is designed
to effectively control
emissions of sulfur dioxide
and nitrogen oxides.A LONG JOURNEY
FROM DISCOVERY
TO POLITICAL ACTION
ACID RAIN
US_248-249_Acid_Rain.indd 248 12/11/18 6:25 PM