National Field Manual
National Field Manual
Alkalinity (determined on a filtered sample) and Acid Neutralizing Capacity (ANC) (determined on a whole-water sample) are measures of the ability of a water sample to neutralize strong acid. Alkalinity and ANC provide information on the suitability of water for uses such as irrigation, determining the efficiency of wastewater processes, determining the presence of contamination by anthropogenic wastes, and maintaining ecosystem health. In addition, alkalinity is used to gain insights on the chemical evolution of an aqueous system. This section of the National Field Manual (NFM) describes the USGS field protocols for alkalinity/ANC determination using either the inflection-point or Gran function plot methods, including calculation of carbonate species, and provides guidance on equipment selection.
Alkalinity and acid neutralizing capacity
Revised by S.A. Rounds
6.6.1 Equipment and supplies
6.6.1.A Maintenance, cleaning, and storage
6.6.2 Calibration and standardization
6.6.3 Collection and processing
Surface water
Ground water
6.6.4 Measurement
6.6.4.A Titration systems and procedures
Digital titrator
Buret titrator
6.6.4.B Inflection point titration method
6.6.4.C Gran-function plot method
6.6.5 Calculations
6.6.5.A Alkalinity or ANC
6.6.5.B Carbonate-speciation equations for samples with pH 
9.2
6.6.5.C Computer-program analysis of titration data
6.6.6 Troubleshooting
6.6.7 Reporting
Selected references
Acknowledgments
Archive: The original report dated 4/98, the 2nd Edition dated 9/2001 (without comments), and the 2nd Edition dated 9/2001 with comment updates (pages 7, 44, 47, 50) have been archived.
Maintainer: Office of Water Quality
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