INDIRECT MEASUREMENT OF OXYGEN SOLUBILITY

This paper introduces an experimental methodology for estimating satur ation concentrations of oxygen in surface waters and wastewater that e mploys commonly available analytic techniques (polarographic probe and Winkler titration) for dissolved oxygen (DO) analysis. Because DO ana lysis techniques can contain significant measurement bias, a protocol intended to minimize the estimate uncertainty is proposed. The protoco l's chief attribute is its ability to estimate solubility indirectly, i.e. it avoids the complication of equilibrating samples with the atmo sphere and uses measurements with unsaturated water to project a value of solubility. Using this protocol, saturation concentrations in Miss issippi River water collected in Minnesota were measured. The ratio of the saturation concentration of Mississippi River water to pure disti lled water varied seasonally in 1993 and 1994, with slightly higher ra tios in the winter months and lower values in the late summer and fall . The lowest measured ratio was more than 8% below the equivalent clea n water value. (C) 1997 Elsevier Science Ltd.