Dissolved oxygen is very important factor to measure when performing water quality tests.This tool demonstrates how to determine O2 concentration in parts per million.
How do your peer results compare with other classes? (Refer to the data table provided with this activity.)
How do your results compare to your classmates' results?
What part of the procedure was most difficult for you to use?
Provided with a LaMotte Test Kit, the learner will determine the dissolved oxygen level in a water sample.
LaMotte Test Kit - This kit is required in order to complete the procedure.
Safety Equipment - Gloves and goggles are required.
The Oklahoma Water Watch produces a Volunteer Monitoring Handbook that would be very helpful. These instructions are from the handbook. There are additional insights in the book.
Rinse both sample bottles twice with distilled or deionized water. Discard this rinse water in the waste container.
Using the sample bottles with the black caps, collect the water samples so that NO air bubbles form or remain in the bottle. Do not introduce air into water sample when adding reagents in steps 3 through 6. After step 6, the DO is "fixed."
Add 8 drops of Manganous Sulfate solution AND 8 drops of Alkaline Potassium Iodide solution to the sample. Make sure the drops fall vertically, straight down into the water sample.
Cap and mix by inverting sample bottle ten times. Brown precipitate will form. Let the precipitate settle below the shoulder of bottle. Invert the bottle once again. Let it settle again. Do not rush this!
Add 8 drops of Sulfuric Acid to the sample.
Cap and mix by inverting the sample. Continue mixing until all solid precipitate dissolves. Only a clear brownish liquid should remain.
Get the large glass tube (your thumb should fit into it, and the lid has a hole). Pour enough "fixed" sample to fill the tube to the white line.
Cap and place aside.
Fill the Tritrator (small syringe) to the 0 mark with Standard Sodium Thiosulfate solution. Gently thump the syringe until NO air bubbles remain on the rubber part of the syringe. There must be no air bubbles at all. Repeat until you get it right!
Insert the titrator into the small hole in the white plastic cap.
Read step 12, then add the Standard Sodium Thiosulfate solution, one drop at a time, making sure to swirl between drops.
STOP adding drops when the color turns from a brownish yellow to a very light yellow (Color Book, BCS #42).
Leaving the titrator in the white plastic cap, remove the cap and place it in a safe place.
Add 8 drops of Starch Solution to the large 20ml test tube with the light yellow water sample.
Re-cap and swirl to mix. The color should now be between a light yellow to a dark blue.
Read step 17, then resume adding single drops, swirling between each drop.
Continue adding drops UNTIL a light sky blue color is reached (Color Book, BCS # 134).
The concentration can now be read off the titrator. Estimate the measurement to the tenths place. The location to read is from the very bottom of the rubber part of the syringe where it comes to a point. The unit is parts per million (ppm) or milligrams of oxygen per liter of pond water. (If the color turned clear instead of light blue, subtract .5mg from your reading.)
Record your measurement in the appropriate location and give to the data manager!! (The attached file is from the Oklahoma Water Resources Board, but can be used to record the dissolved oxygen levels of any body of water. The file also includes ideas about other types of information that could be recorded.)
If time allows, repeat the tests in order to get two readings.
Upload your DO values into the Dissolved Oxygen Levels Data Form.
Look over the attached checklist to see what one needs to do, if a grade is being taken for this activity.
It works better if students work in pairs. If the focus is to determine the stream profile with all parameters, it may be best to have the same students do the same test from site to site, month to month.
Be careful when handling chemicals. The instructions are extensive; hence, it would be better to work in pairs initially.
Please enter a Registration Key to continue.