USGS Water-Quality Information
Autonomous underwater vehicle provides high-resolution observations of water quality and much more. Photo (c) Peter Berrini, HDR, Inc., used by permission.
National & Regional Science:
Local Science Features:
Water Quality Data
National Water Information System (NWIS)
NWIS provides current and historical water-quality data.
Today's Water Conditions
Water-Quality Watch provides continuous real-time water-quality measurements.
Water-Quality Web Services
Web services automate the sharing of USGS and USEPA water-quality monitoring data.
For More Data
Additional water-quality data resources are available.
USGS in Your Area
USGS Water Science Centers are located in each state.
6.6 Alkalinity and Acid Neutralizing Capacity
Revised By S.A. Rounds
This section of Chapter 6 is available as a pdf file:
Download a copy of Adobe Acrobat Reader for free.
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: