FIG. 2 Supersaturation generator system where air and water 

 are mixed under pressure to produce required percentage of 

 total gas supersaturation. 



pressure, and mixed with compressed air (Fig. 3). 

 Water and any remaining air not in solution flowed 

 through the retention tank where excess air was 

 vented off. Test water then flowed into the exposure 

 tank, where it became supersaturated when released 



back to normal atmospheric pressure. The degree 

 of supersaturation was controlled by the amount 

 of compressed air added to the water. 



Test animals were either allowed to move 

 about freely in the open tank or were restricted 

 to four net cages (Fig. 1) or to stainless steel wire 

 cages (Nebeker and Lemke, 1968) suspended in the 

 water. Two sizes of wire cages, 7.5 cm in diameter 

 by 12.5 cm high, and 20 cm in diameter by 25 cm 

 high, were used. They were shaped like a standard 

 cylindrical tin can with a screen bottom on the 

 large cage and one set of small cages and a petri 

 dish bottom on the other set of small cages. 



The water in Tank 1 was supersaturated at 

 125% total gas saturation and was used for testing 

 directly and also as a water source for siphoning 

 into other smaller tanks and aquaria holding addi- 

 tional test animals. Water flowing at a rate of 

 9 C/min (Tank 1a - 500 «), and 6.3 fcVmin (Tanks lb, 

 1c, Id - 19 ?) through the siphon lines from Tank 1 

 maintained the smaller tanks at 125%. 



Gas, Chemical, and Data Analyses 



A Weiss saturometer (Fig. 4), modified and 

 adapted as a routine analytical laboratory instru- 

 ment, was used for measuring total dissolved gas 

 pressures in \ the exposure tanks (Table 1). It was 

 calibrated and checked periodically with the Van 

 Slyke Gas Analyzer and the Winkler method for dis- 

 solved oxygen. Several saturometer sensors, gauges, 

 and a mercury manometer were compared periodi- 

 cally to ensure accuracy. The formula: BP + AP 

 - VP/BP x 100 = % saturation, where BP = Barometric 

 Pressure, AP = Saturometer reading, and VP = Water 

 Vapor Pressure, was used to calculate total percent 

 saturation. 



AIRLINE 



AIR ESCAPE VENT 

 / 



WELL 

 WATER 



AIR COMPRESSED i PUM p 



COMPRESSOR GAS AERATION TURBULENCE LOOP 



TANK (AIR+WATER) 



FIG. 3 Diagram of supersaturation generator system. 



52 Nebeker, Stevens, Brett 



EXPOSURE 

 TANK 



