The effect of substances on dissolved oxygen level

Anna KoAnnie AuTim Kind

Jade Chen

What is the effect of different substances

(elodea, yogurt, dead grass, bar soap, fertilizer)

on the dissolved oxygen level (±0.1 mg/L)

of river water?

DO levels <5.0 mg/L or >110% stressed aquatic life

Waste product of photosynthesis oxygen

Decay = consumes oxygen

Temperature may affect DO levels

We predict that the elodea would be the only

factor to increase the dissolved oxygen level in

water whereas the rest of the variables would

decrease the level of dissolved oxygen.

Independent variable:◦ substance used

Dependent variable:◦ percent change in dissolved oxygen level

Control variables

Dissolved Oxygen Levels (±0.1 mg/L)

Average Change

(±0.6% mg/L)

Calibrated Change

(±0.6% mg/L)

Initial FinalTrial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3

Control 4.0 3.8 -5.0 0.0Elodea 4.3 4.4 4.1 4.0 3.5 3.0 -18.0 -13.0Yogurt 4.3 4.2 4.3 3.5 2.7 3.0 -22.7 -17.7Dead grass

4.2 4.1 4.2 3.5 3.0 3.4 -20.8 -15.8

Bar soap 4.1 4.3 4.0 3.3 2.8 3.0 -26.6 -21.6Fertilizer 4.3 4.2 4.0 3.7 4.3 3.8 -5.6 -0.6

Control

Average Percent Change in DO Levels

0.0

-13.0

-17.7

-15.8

-21.6

-0.6

Elodea Dead grass Bar Soap

Hypothesis – wrong◦ Assumed that elodea will live in river water

All substances decreased DO level

Smallest effect: Fertilizer

Biggest effect: Bar Soap

DO sensor malfunction inaccuracies

Temperature changes (window)

Holes diffusion of gases/evaporation

The effect of river water on elodea

Time = too long

Control temperature

Test other living plants

Control diffusion/evaporation rate

Increase frequency of DO-measurement

Effect on aquatic life

Raise awareness of substances that affect DO levels in water

http://www.state.ky.us/nrepc/water/wcpdo.htm

http://www.fivecreeks.org/monitor/do.html