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USGS personnel collect a water-quality sample on the Missouri River. USGS/Photo by Kelly Brady.
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6.6 Alkalinity and Acid Neutralizing Capacity
Revised By S.A. Rounds
This section of Chapter 6 is available as a pdf file:
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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
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
6.6.4.A Titration systems and procedures
6.6.4.B Inflection point titration method
6.6.4.C Gran-function plot method
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
Section 6.6 Archived Versions: