Environmental Engineering Reference
In-Depth Information
120
100
80
80
60
40
40
20
0
0
3
5
7
9
0
100
200
300
400
Maximum Cl (mg L
-1
)
Minimum pH
80
80
60
60
40
40
20
20
0
0
0
40 80 120 160 200
Maximum turbidity (mg L
-1
)
3 8 13
Minimum O
2
(mg L
-1
)
FIGURE 14.5
Number of invertebrate species as a function of pH, chloride, minimum O
2
,
and turbidity (data from Roback, 1974).
additional sources of acid contamination that are not specifically covered,
such as mine drainage (Gray, 1998) and natural acidic systems, but the gen-
eralities of the following discussion apply to pH effects regardless of source.
Sources and Geography of Acid Precipitation
Acid precipitation has vast effects on aquatic ecosystems in the vicin-
ity of dense human activity associated with burning hydrocarbons. Acid
rain has acidified lakes and streams in all industrialized regions of the
world. The U.S. Environmental Protection Agency surveyed more than
1000 lakes and 211,000 km of streams during the 1980s. About 75% of
the lakes and 8% of the streams surveyed were influenced by acid precip-
itation. The areas most impacted were the Adirondacks, the mid-
Appalachian highlands, the upper Midwest, and the high-elevation West.
In the worst case, 90% of the streams in the New Jersey Pine Barrens were
acidic. In mid-Appalachia, there were 1350 acidic streams. Furthermore,
the Canadian government estimates that 14,000 lakes in eastern Canada
are acidic. The Norwegian government sampled 1000 lakes and found that
52% of the lakes were endangered. In the southern part of Norway,
60-70% of the lakes had lost their fish (Henriksen
et al.,
1990).
The proximate cause of acid precipitation is sulfuric and nitric acids in
rain, snow, and fog. Combustion of coal and oil leads to formation of sul-
furic and nitric acids in clouds, ultimately reaching the ground. Acid pre-
cipitation is concentrated downwind from industrial and urban areas be-
cause they have maximal emissions from factories and automobile exhaust.
Acid deposition in the United States is greater in the heavily populated and
industrialized northeast. Acid deposition is correlated most closely with
sulfate deposition (Fig. 14.6).
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