The books say super-saturation means 9.00 mg/L DO, but my auditor says it can be less, whos right?
Supersaturation means that the water contains more DO than it SHOULD contain according to physics. According to tablers, the saturation point of oxygen in water at 20°C and 760 mm pressure –which is standard temperature and pressure at sea level– is 9.06 mg/L. So, yes, at sea level and 20°C, anything over 9.06 mg/L represents supersaturation. In Wisconsin, altitudes typically are about 1000 ft above sea level, and standard pressure drops to about 734 mm. Therefore, at 20°C and 734 mm pressure, DO saturation falls to 8.76 mg/L. Under these conditions, DO values greater than 8.76 mg/L represent superaturation. If a lab is warmer than 20°C, the altitude is higher than 1000 feet above sea level, and there is a low pressure system in effect, saturations can be much lower.
