How can I find out the percentage of dissolved oxygen in a water sample?

Answer 1

Once you figure out the ppm or mg/L of oxygen dissolved in the water (using a oxygen meter or DO kit), you have to use a chart to find out the percent of oxygen in the water.

This is because temperature affects how much oxygen is dissolved. 6mg/L of oxygen in a 30 degree water might be considered 80%, but 6 mg/L of oxygen in a 10 degree water it is considerd something like 50%. This is because cold water can hold more oxygen. The saturation point for 5 degree water is like 13 mg/L while saturation point for 30 degree water is 7.5 mg/L

I found a table you can use to determine this. I just googled it very quickly, so you can probably find a better one. I'm sure there is an online calculator somewhere too. How you use it is you determine the amount of dissolved oxygen (mg/L) and the temperature of the water. You draw a straight line that connects these points. Where the line crosses the % saturation line is the % of oxygen in the water.

If you are using an electric oxygen meter, it usually has a thermometer built in so it will automatically calculate the % saturation as well as mg/L (which is the same thing as ppm [parts per million])

When you sample the water, be careful not to agitate the water or get air bubbles in the sample bottle. This will introduce air (oxygen) into the water and affect your results. If you are using a oxygen meter, dip it far enough below the surface.

Answer 2

with just a small water sample im not sure, but in a stream, or lake there is a device that you just dip into the water, and it will tell you the do. Sorry i cant remember the name of it, but i have used it in one of my forestry classes in college. Hope that helps a lil!

Answer 3

With a meter that measures DO.. It is usually in the form of mg/L