STREAM POLLUTION 
389 
stream. Again, the movement of the current facilitates the constant reaeration of 
stream waters with a tendency for these waters to lose carbon dioxide to the air as 
soon as the carbon-dioxide tension in the water exceeds that of the surrounding air, 
which is usually quite low (2 to 4 parts per 10,000). Both of these conditions, to- 
gether with the usual presence of calcium and magnesium salts in stream waters, 
tend to keep these flowing streams more alkaline than pond, lake, and bog waters, 
so that in many river waters the alkalinity is raised to a point where there is little or 
no uncombined carbon dioxide. 
Table 1 . — Characteristics of water at different depths in deep holes of flowing rivers, showing general 
uniformity of composition at any given station due to mixing action of current 
I. UPPER TENNESSEE RIVER, AT PAN EDDY, 18 MILES BELOW CHATTANOOGA, TENN., AUG. 21, 1931, AIR 
TEMPERATURE, 23° C. 
Depth in feet 
Water tem- 
perature, de- 
grees centi- 
grade 
pH 
Specific con- 
ductivity in 
mhoXlO -6 at 
25° C. 
Fixed carbon 
dioxide, cubic 
centimeters 
per liter 
Dissolved 
oxygen 
parts per 
million 
Light pene- 
tration, mil- 
lionth inten- 
sity depth in 
millimeters 
S> 
28.0 
7.3 
169 
15.4 
5. 6 
.544 
10 
28.0 
7.2 
169 
15.4 
5. 5 
561 
20 
27.9 
7.3 
169 
14.9 
5.7 
561 
30 _ 
27.9 
7.3 
169 
14. 9 
5.9 
561 
40 . 
27.8 
7.3 
169 
14. 9 
6. 0 
561 
50 
27.8 
7.3 
169 
14.9 
5.7 
561 
00 ___ 
27.8 
7.3 
109 
14.9 
5.2 
581 
70 ... 
27.8 
7.4 
169 
15. 2 
5.5 
552 
80 
27.8 
7.4 
169 
15.2 
5.7 
552 
90 
27.8 
7.4 
169 
15. 2 
5.5 
544 
100 
27.6 
7.4 
169 
15.4 
5.6 
538 
no . ... .. 
27. 7 
7.3 
168 
14. 9 
5.7 
528 
120 
27. 8 
7.3 
168 
14. 9 
6. 1 
521 
130 
27.8 
7.3 
167 
15. 1 
5.9 
513 
II. MISSISSIPPI RIVER, OFF TOWER ROCK, NEAR GRAND TOWER, ILL., SEPT. 8, 1931, AIR TEMPERATURE 
30.5° C. 
S > 
28.2 
7.5 
340 
26.4 
5.3 
129 
10 
26.0 
7.5 
341 
26.6 
5. 1 
125 
20 
25.8 
7.6 
339 
26.8 
5.3 
125 
30 
26.0 
7.5 
337 
26.4 
5.3 
122 
40 
26.0 
7.5 
338 
26.4 
5.3 
129 
50 
26.0 
7.5 
340 
26.4 
5.3 
120 
60 
26.0 
7.5 
331 
26. 6 
5.3 
122 
70 
20. 2 
7.4 
338 
26.7 
5.3 
122 
80 . . . 
26.0 
7.4 
342 
26. 7 
5.3 
125 
90 __ 
26.0 
7. 4 
339 
26.8 
5. 4 
122 
10(1 .. 
26.0 
7.4 
338 
26.8 
5.4 
119 
110 
•26.0 
7.4 
341 
26.8 
5.3 
124 
1 Surface, i. e., top 12 inches of water. 
The specific toxicity of carbon dioxide for aquatic organisms is well known and is 
discussed under acid wastes. From all of the field data and in view of the experimental 
findings presented, the determination of free carbon dioxide was found to be a valuable 
aid in pollution studies, and river and stream waters carrying more than 3 cubic centi- 
meters of free carbon dioxide per liter were checked carefully for some source of 
organic pollution. Values in excess of 3 cubic centimeters per liter usually were 
indicative of such pollution in our flowing inland streams. The relatively high free 
carbon dioxide as compared with the composite found in Hastings Pool in the upper 
Mississippi River and in the polluted portions of the Atlantic coast streams and other 
systems are evident from the graphs presented in figs. 18E and ISA’. 
