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| Analytical MethodsUnited States Environmental ProtectionAgencyOffice of Water4303EPA-821-F-98-008April 1998Method 1631: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry
***Summary***

*EPA is proposing in the Federal Register a method that will improve EPA's capability to accurately measure available mercury in water through use of an atomic fluorescence technique. This method is being proposed for approval at 40 CFR part 136 for use in compliance monitoring and for general use.*

**Background**

The U.S. Environmental Protection Agency (EPA) publishes analytical testing methods that are used by industrial and municipal facilities to analyze the chemical and biological components of wastewater, drinking water, sediment, and other environmental samples.  These methods are used for data gathering and compliance monitoring under  the Clean Water Act and the Safe Drinking Water Act.

This proposal would amend the Guidelines Establishing Test Procedures for the Analysis of Pollutants under section 304(h) of the Clean Water Act to augment currently approved mercury test procedures with EPA *Method 1631: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry*.

**Method 1631**

Method 1631 allows determination of mercury at a minimum level (ML) of 0.5 ng/L (parts-per-trillion; ppt), approximately 200 times lower than the level achieved by other mercury methods currently approved at 40 CFR part 136.  Determination of mercury at the lower level is necessary to support measurements at the ambient water quality criteria for mercury published in the National Toxics Rule and in the Final Water Quality Guidance for the Great Lakes System.
***BENEFITS OF METHOD 1631- Allows determination of mercury at 0.5 ng/L; ppt
- Improved accuracy and precision at low levels
- Supports measurements at ambient water quality criteria levels
- Performance based

EPA is offering Method 1631 as an additional testing procedure for compliance monitoring under the National Pollutant Discharge Elimination System; ambient water quality monitoring; development of effluent guidelines;  and general laboratory use.  This rulemaking does not propose to repeal any of the currently approved methods that test for mercury.  Each permitting authority must decide which method is appropriate for its needs.

Method 1631 encourages advances in technology and may reduce  the cost of analysis by permitting the analyst to modify the method to overcome any encountered interferences or lower the cost of measurements, provided that all method equivalency and performance criteria are met. This performance-based approach is consistent with EPA's streamlining proposal (62 FR 14976, March 28, 1997) and the Agency's performance-based measurement system policy (62 FR 52098, October 6, 1997).

**Additional Information and Copies**

For additional information contact Maria Gomez-Taylor at the U.S. Environmental Protection Agency, Office of Water, Engineering and Analysis Division, Mail Code 4303T, 1200 Pennsylvania Avenue NW, Washington, DC 20460; at 202 566-1005; or via E-mail: [email protected].

The *Federal Register* notice contains instructions on how to obtain additional information and how to review the public record for this rulemaking.

Copies of Method 1631 also are available from the U.S. EPA National Center for Environmental Publications and Information (NCEPI), 11029 Kenwood Road, Cincinnati, OH 45242.

 

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