STREAM POLLUTION 
387 
In general, it was found that the fixed carbonates vary with the character of the 
country drained, mountain streams in regions where igneous rocks dominate being 
very low in fixed carbonates and streams traversing limestone country or alkaline 
soil being relatively high. However, it must be added that excepting the headwater 
streams in mountainous regions the fixed carbonate load of flowing stream water was 
rarely less than 5 cubic centimeters per liter. 
A. COMPOSITE 
LOCALITIES WITH GOOD 
PERCENT FISH FAUNA 
B. ATLANTIC COAST STREAMS 
61 STATIONS 
109 DETERMINATIONS 
C. MISSISSIPPI 
GOOD FISH FAUNA 
108 STATIONS 
494 DETERMINATIONS 
D. MISSISSIPPI 
MEDIUM, POOR, OR NO 
FISH FAUNA 
87 STA., 284 OETERMIN 
HASTINGS POOL C MINN. ) 
8 STATIONS 
112 DETERMINATIONS 
F. MISSISSIPPI, IMPOUNDED WATER 
LAKE OAVENPORT AND 
G. MISSISSIPPI, IMPOUNDED WATER 
LAKE PEPIN ( MINN. , Wl S .) 
22 STATIONS 
H. MISSISSIPPI, IMPOUNDED WATER 
LAKE KEOKUK CIOWA, ILL.) 
25 STATIONS 
Figure 16. — Fixed carbon dioxide values (as cubic centimeters of carbon dioxide per liter, bottom line) for the waters of various 
river units. Stippled and black graphs composed as explained under figure 6. 
In pollution studies, although fixed carbonates may not be important in defining 
particular water as suitable or unsuitable for good fish faunae, the fixed carbon dioxide 
is of large importance in evaluating the extent of certain types of pollution and in 
determining the amount of dilution required to render certain effluents relatively 
harmless to aquatic life. The fixed carbon dioxide of the stream water is the major 
buffer against which both acid and alkali pollutants act, and the fixed carbonate 
must be taken into consideration, therefore, when the maximal nontoxic dilution of 
any effluent is to be determined. Tiffs problem is discussed more fully under acid 
wastes, but it may be pointed out here that the toxicity to fishes and other aquatic 
life of many of the common acids is much greater in distilled water or water carrying 
very little fixed carbon dioxide than in water carrying 20 to 60 cubic centimeters per 
liter of fixed carbon dioxide. The reason is obvious because of the buffer and 
99773° — 37 4 
