Citation:

Adair*, C J., R T. Wilkin*, M S. McNeil*, AND J T. Wilson*. FIELD MEASUREMENT OF DISSOLVED OXYGEN: A COMPARISON OF TECHNIQUES. Presented at GSA Conference, Reno, NV, 11/13-17/2000.

Description:

The measurement and interpretation of geochemical redox parameters are key components of ground water remedial investigations. Dissolved oxygen (DO) is perhaps the most robust geochemical parameter in redox characterization; however, recent work has indicated a need for proper data review, validation, and verification of geochemical parameters, such as DO, that are routinely collected in the field. The purpose of this study, therefore, was to compare the commonly practiced methods for determining dissolved oxygen concentrations in the field, and develop quality control methods for data verification that can be implemented in the field at the time of sample collection. This study was conducted at four field sites each with different ground water compositions and contaminant types. Comparisons were made using several methods developed for the measurement of DO: Winkler titrimetric method (azide and permanganate modifications), membrane-covered electrode method, indigo carmine colorimetric method and rhodazine D colorimetric method (Chemets). The accuracy of these methods was evaluated in the field by determining DO concentrations of prepared standards using air and O2-N2 gas mixtures. The dissolved oxygen data were compared to the known concentrations to determine the most reliable method(s) for DO determination. We found excellent correlation between Winkler titrations and colorimetric techniques at DO levels from 0 to 5.5 mg/L. Below 1 mg/L DO, the rhodazine D reagent provides accurate and highly reproducible DO values and is not subject to interference with ferrous iron, a common component of low DO ground waters.

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