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Turbidity

Turbidity occurs in most surface waters as the result of suspended clay, silt, finely divided organic and inorganic matter, plankton, and other micro-organisms. In highly turbid waters, the penetration of light is reduced, primary production is less, particulate matter may directly interfere with the respiratory activity of organisms with gills, and the temperature structure may be modified.

Option A. Procedure (Turbidity Tube)

1. Close the drain tube by squeezing the crimp.

2. Fill the transparency tube with the water sample.

3. While looking down through the opening of the tube, partially open the drain crimp and slowly draw off the sample.

4. When the black and white pattern at the base of the transparency tube faintly appears, immediately tighten the crimp and record the level of water remaining via the centimeter rule on the side of the tube.

Option B. Procedure (Vernier Turbidity Sensor)

1. Connect the Turbidity Sensor to the LabQuest interface. The software should automatically identify the sensor.

2. On the meter screen, use the stylus to select Calibrate from the Sensors drop down menu. Select the Channel that contains the Turbidity Sensor.

3. Hit the Calibrate Now button.

4. Obtain the cuvette containing the Turbidity Standard (100 NTU) and gently invert four times to mix any particles that may have settled to the bottom. Do not shake the standard and introduce bubbles.

5. Make sure the cuvette is clean of fingerprints. Insert into the Turbidity Sensor, lining up the mark on the cuvette with the mark on the sensor. Close the lid.

6. Enter 100 into the Reading 1 known value box and then select keep.

7. Fill the blank cuvette to the fill line with distilled water and insert into the Turbidity Sensor, lining up the mark on the cuvette with the mark on the sensor.

8. Enter 0 into the Reading 2 known value box and then select Keep.

9. Empty the distilled water from the blank cuvette and fill with you sample. Be sure the cuvette is clean and free from fingerprints. Insert into Turbidity Sensor, aligning the mark on the cuvette with the mark on the sensor. Record turbidity in NTU.