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KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

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APPENDIX B<br />

SOP B5.4<br />

Dissolved Oxygen<br />

Probes differ as to specifics of use. Follow the manufacturer‘s instructions to obtain an accurate reading.<br />

The following general steps should be used to measure the dissolved oxygen concentration:<br />

The equipment should be calibrated and its batteries checked in the laboratory before going<br />

to the field.<br />

The probe should be conditioned in a water sample for as long a period as practical before its<br />

use in the field. Long periods of dry storage followed by short periods of use in the field<br />

may result in inaccurate readings.<br />

The instrument should be calibrated in the field before each measurement or group of closely<br />

spaced measurements by placing the probe in a water sample of known dissolved oxygen<br />

concentration (i.e., determined by Winkler method) or in a freshly air-saturated water sample<br />

of known temperature. Dissolved oxygen values for air-saturated water can be determined<br />

by consulting a table listing oxygen solubility as a function of temperature and salinity.<br />

The instrument probe should be immersed in a flow-through cell or directly into the water<br />

column of the well for the most accurate measurement.<br />

Record the dissolved oxygen content and temperature of the sample in a field log book.<br />

Read the dissolved oxygen dial to the nearest 0.1 milligram per liter (mg/L).<br />

Recalibrate the probe when the membrane is replaced, or as needed. Follow the<br />

manufacturer‘s instructions. Duplicate analyses should agree within ± 0.1 mg/L.<br />

Note that although in-situ placement of the probe is preferable, since sample handling is not involved,.<br />

thismay not always be practical. Be sure to record whether the liquid was analyzed in-situ, or if a sample<br />

was taken. If a sample is taken special care should be taken during collection to avoid turbulence, which<br />

can lead to increased oxygen solubility and positive test interference.<br />

Kirtland AFB<br />

SOPs for Field Investigations B-131 April 2004

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