Indirect measurement of oxygen solubility

This paper introduces an experimental methodology for estimating saturation concentrations of oxygen in surface waters and wastewater that employs commonly available analytic techniques (polarographic probe and Winkler titration) for dissolved oxygen (DO) analysis. Because DO analysis techniques can contain significant measurement bias, a protocol intended to minimize the estimate uncertainty is proposed. The protocol's chief attribute is its ability to estimate solubility indirectly, i.e. it avoids the complication of equilibrating samples with the atmosphere and uses measurements with unsaturated water to project a value of solubility. Using this protocol, saturation concentrations in Mississippi River water collected in Minnesota were measured. The ratio of the saturation concentration of Mississippi River water to pure distilled water varied seasonally in 1993 and 1994, with slightly higher ratios in the winter months and lower values in the late summer and fall. The lowest measured ratio was more than 8% below the equivalent clean water value.