Big Creek Reserve
Procedure for measuring turbidity in water samples.
Materials
LaMotte kit for measuring turbidity in JTU's (Jackson Turbidity
Units)
Kit includes standard turbidity reagent - a kaolin solution, two
graduated cylinders with a black spot in the bottom, and stirring
rod
Cylinder is 22.5 mm diameter and the line is 63mm above the bottom
(25ml), with a second line 126 mm above the bottom (50 ml).
LaMotte Std. Turbid. Rgt. contains <1% kaolin, CAS# 1332-58-7;
>0.1% magnesium nitrate, CAS#10377-60-3; >0.1% preservatives;
Clean filtered water
100 ml vial w/ lid
Thermometer (optional)
Field sample
Collect water sample in 100 ml plastic container w/ lid.
Measure water temperature with thermometer (optional)
Measurement
Fill one cylinder with sample water to lower 25ml line ("sample"
cylinder). Examine black spot by looking down cylinder.
Fill other cylinder with clean water to lower 25ml line ("control"
cylinder).
If spot in sample cylinder is completely obscured,
Dilute by adding clean water to upper 50ml line.
Stir with stirring rod and pour off excess until filled to level
of lower line.
Examine black spot in sample cylinder.
If still obscured, repeat dilution process.
If spot is visible but somewhat obscured, you are ready to measure
using reagent.
Be sure to record the number of dilutions. Each dilution "doubles"
the final JTU value
If spot is somewhat obscured but visible
Add standard standard turbidity (shake vigorously first) reagent
to control cylinder.
The line on the eyedropper is 0.5ml (~10 drops)
Stir with stirring rod.
Compare cylinders by looking down at black spot
If the sample is more obscured than the control, add more reagent
(shake vigorously).
If they match, record the amount of reagent added.
One JTU = 1ml in 250ml clean water, or 0.1 ml in 25ml clean water.
For example, two eyedroppers filled to the line and added to 25ml
clean water equals 10 JTU
If spot is as clearly visible as clean water, record a "0"
Clean-up
Rinse cylinder and put away clean
Save a vial of
sample water, seal tightly, and label.
Keep samples in vial drawer in educational center