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Water: Mercury

Method 1631: Measurement of Mercury in Water; Revision E

Fact Sheet; October 2002

EPA announces a final rule approving revisions to EPA Method 1631 for the determination of low-level mercury in EPA's wastewater program (40 CFR part 136). The newly approved Method 1631, Revision E, is clearer, more responsive to stakeholder needs, and better in laboratory performance.


The U.S. Environmental Protection Agency (EPA) approves analytical methods used to determine chemical components of wastewater. Method 1631 allows determination of mercury at a minimum level of 0.5 ppt (parts-per-trillion). This minimum level supports the measurement of mercury at the lowest water quality criteria (WQC) levels published in the National Toxics Rule and in the Final Water Quality Guidance for the Great Lakes System.

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Method 1631, Revision E

Method 1631, Revision E replaces all previous versions of Method 1631. Revision E includes changes based on recommendations from the laboratory community. These changes improve method performance and increase clarity and method flexibility. This final rule also amends 40 CFR 136.3 (e) Table II to incorporate method revisions on preservation and storage of low-level mercury samples. Revision E retains the clean technique procedures of the previously promulgated Revision C.

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More Information

For further information concerning this final rule, please contact the U.S. EPA Office of Water, Engineering and Analysis Division (4303T), 1200 Pennsylvania Avenue NW, Washington, D.C. 20460.

Federal Register Notice announcing final rule (October 29, 2002).

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