Revision History for U.S. Geological Survey Techniques and Methods; Book 9, Handbooks for Water-Resources Investigations;

Section A, National Field Manual for the Collection of Water-Quality Data; Chapter 6.2, Dissolved Oxygen

By U.S. Geological Survey

Dissolved Oxygen

Posted online – first release: 1998, as Techniques of Water-Resources Investigations (TWRI), book 9, chapter A6.2, version 1.0

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Revised: 2006, online as TWRI, book 9, chapter A6.2, version 2.1

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Revised: 2013, online as TWRI, book 9, chapter A6.2, version 3.0

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Revised and reposted October 23, 2020, online as Techniques and Methods (T&M), book 9, chapter A6.2

U.S. Geological Survey, 2020, Dissolved oxygen: U.S. Geological Survey Techniques and Methods, book 9, chap. A6.2, 33 p., https://doi.org/10.3133/tm9A6.2. [Supersedes USGS Techniques of Water-Resources Investigations, book 9, chap. A6.2, version 3.0.]

The personal authors were changed to the agency, U.S. Geological Survey (USGS).

The report series was changed as indicated above.

The layout was changed to match the current style and format of a USGS series report, and the text was set in two columns. A front cover, back cover, title page, and back-of-title page were added and show the following: the change of series (to a T&M), the change in authorship, and a statement that this 2020 release of chapter A6.2 in the T&M series supersedes TWRI, book 9, chapter A6.2, version 3.0.

Substantive changes made in book 9, chapter A6.2, in 2020 are summarized below.

Deleted: 
Section on the iodometric method (Winkler titration) for measuring dissolved-oxygen (DO) concentration was removed.

Procedure change: 
Coverage of amperometric sensors was removed. Optical sensors were designated as the USGS-preferred method for measuring DO concentration.

Section on correcting barometric pressure for altitude was removed and replaced with the requirement to measure the barometric pressure at the altitude of calibration with a National Institute of Standards and Technology-traceable barometer.

Requirement to use spectrophotometric methods to report DO concentrations less than 1.0 milligram per liter (mg/L) was removed. Field instruments can now be used to report DO concentrations less than 1.0 mg/L so long as an instrument-specific rating is developed with spectrophotometric methods.