Environmental Engineering Reference
In-Depth Information
1.42
1.38
1.34
1.30
1.26
1.22
1.19
1.15
1.11
1.07
1.03
0.990
0.951
0.912
0.873
0.834
0.795
0.755
0.716
0.677
0.638
0.599
0.560
0.521
0.482
0.442
0.403
0.364
0.325
0.286
0.247
0.208
0.169
0.130
0.0905
0.0513
Ammonium at 09/30/1995 23:00
Distance (m)
50,000
40,000
30,000
20,000
10,000
0
0
0
5
5
10
10
15
15
20
20
25
25
30
30
35
35
40
40
9/30/1995
45
45
50,000
40,000
30,000
20,000
10,000
0
Distance (m)
Ammonium at 11/30/1995 23:00
Distance (m)
50,000
40,000
30,000
20,000
10,000
0
0
0
5
5
10
10
15
15
20
20
25
25
30
30
35
35
40
40
11/30/1995
45
45
50,000
40,000
30,000
20,000
10,000
0
(b)
Distance (m)
FIGURE 14.29
(Continued)
metal speciation, calcium solubility, and other chemical properties. Lake organisms may have only
a limited tolerance to pH changes, with the speciic degree of tolerance being a function of the life
stage.
Generally, the young of most species are least tolerant. Each state may have differing standards,
but the U.S. EPA's national recommended water quality criteria (USEPA 1986) is for a pH in the
range of 5-9. As of July 26, 2012, of the 71,577 listed causes of impairment of waters of the United
States (from 303(d) lists by the U.S. EPA of waters not meeting water quality standards), 4126 were
due to pH, acidity, or caustic conditions. Lake acidiication has been a major environmental problem
in the United States and Canada.
A number of chemical and biological processes impact the pH in lakes. One of the factors impact-
ing the pH is variations in carbon dioxide, such as those due to biological processes, gas exchange,
and external loads.
Biological processes produce or consume carbon dioxide. The addition of carbon dioxide to
water can produce a weak acid, carbonic acid:
CO HO HCO
2
+
(14.19)
2
2
3
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