Science Buddies: "Ask an Expert"

I am a ninth grde student doing a science project with the question Is there more bacteria in the canal water before of after rain. I am not sure what to research. The way i am testing the bacteria is by checking the oxygen levels. Please help!

Hi Pipsqueeek,

To test for oxygen levels, you can also test for varyinng bacteria counts by measuring the pH level using litmus paper. You high school chem teacher will have more advanced litmus paper (to get more accurate pH readings) than the common orange strips. The reason why you can do this is because if bacteria go up, they will release a lot of carbon dioxide into the water. When carbon dioxide is dissolved in water, the water becomes acidic through the reaction: CO2 + H2O --> HCO3- + H+. The proton contributes to the acidity of the water.

Hope that helps!

-Sam

In addition to Sam's good ideas, you could also collect water samples from the same place before and after rain in the area. You would need to collect the same amount of water and then add some small amounts to bacterial agar plates. You could then count how many colonies of bacteria on your plates from your sample before and after the rain. Good luck with your experimental design.

Matt Badtke