Monitoring pH
pH is a measurement of acidity or
alkalinity and affects many chemical and
biological processes in a water body. pH
measures the hydrogen ions within a
solution. The pH scale ranges from 0-14
and determines whether a solution is
acidic or basic. When monitoring for pH,
a reading between 0 - 6 is considered
acidic and a reading within the range of 9
- 14 is basic. Most aquatic organisms
prefer a neutral pH range of 6.5 - 8.5.
Changes in pH can be caused by a variety
of factors, including: acid rain, mining
activities, and wastewater discharges.
Using pH Test Strips during the 2006 CWA 106 work shop in Prescott, AZ.
Understanding the pH scale: High pH can mean a reduction of the diversity within a stream due
to stress on the physiological systems of most aquatic organisms and a reduction in reproduction.
Low pH can cause toxic conditions for aquatic life by allowing toxic elements and compounds to
become mobile. When monitoring water quality, it would be beneficial to know what aquatic life
exists within the water body of interest and the pH that is preferred by those organisms. Also, it
would be helpful to compare data results to the tribal, state, or federal standards.
Monitoring Equipment: There are a variety
of monitoring devices available to measure pH.
Depending upon monitoring objectives set
forth in an environmental program, the
following equipment options are commonly
used to collect pH data from the field.
Readily available and economically priced:
• pH Test Strips
• pH Kits
Greater precision and higher cost:
• pH Meters
• pH Probes (multi-parameter sondes)
• Contract Laboratories (if necessary)
For additional information:
www.epa.gov/owow/monitoring/volunteer/stream
The Multi-Parameter Sonde shown in the above photograph can
be used to collect pH data
For more information, please contact your CWA Project Officer or Kristin Gullatt, Manager of the Water Division, Tribal Office at (415) 972-3432.
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