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Clayton Group Services 1111 REDD 1 1 i; lVDIUVIUM,. 1 •e, 1 _- ' The measurement of physical properties of surface and groundwater in the field is an important indicator of possible contamination and for establishing groundwater stability following groundwater monitoring well development and prior to sampling groundwater. Although the measurements of physical properties can be and often is conducted in the laboratory, the emphasis here is on the field measurement of these properties. Typically, a pH, conductivity, temperature meter is used, and Clayton has such meters. All measurements should be made immediately after the water sample is obtained as some of the water's physical properties change upon being removed from the natural environment. PROCEDURES M 1. Calibration - The pH meter should be calibrated at the beginning of each day using solutions of known pH. Recalibration should be conducted when moving from well to well or at a minimum of every the (10) water samples analyzed. The following procedures should be followed: • Clean the electrodes by rinsing with distilled water and blotting dry; • Place the electrode in a beaker with commercially -prepared buffer solution of known pH which is at or below that expected for the sample. Generally, commercial buffer solutions of pH 4, 7, and 10 are used; • Measure the temperature of the buffer and adjust the temperature compensator of the pH meter; • Calibrate the pH meter to the buffer pH; • Remove the electrodes and rinse with distilled water, blot dry; • Place the electrodes in the second buffer solution, and the pH meter should accurately measure the new buffer pH. If the measurement differs by 0.2 units or more, try a new buffer solution. If the problem persists, consult the pH meter manual.