How does pollution affect dissolved oxygen levels?

Abstract

Even though water is just about everywhere we notice that it has different levels of dissolved oxygen in different places. We used four samples of pond water and added different amounts of potassium nitrate to each. Then we measured the levels of dissolved oxygen in each tube for a 15 minute period. Our work will be able to provide another way to find out the amount of dissolved oxygen. Others will be able to use our work as reference or they may try out the experiment themselves to see if they get different results than us.