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Water Pollution Science Fair Project

Turbidity and Dissolved Oxygen in River Water

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Turbidity and Dissolved Oxygen in River Water | Science Fair Projects | STEM Projects
Does cloudy water hold more dissolved oxygen or less? Most people assume murky water means poor quality. But turbidity (cloudiness from suspended particles) may have a surprising link to dissolved oxygen. You collect water samples from different spots in a river. For each sample you measure turbidity with a turbidimeter. You measure dissolved oxygen using a chemical titration method. Counting drops of sodium thiosulfate until the yellow color clears tells you the dissolved oxygen level. The results were unexpected. Samples with higher turbidity actually had higher dissolved oxygen. Samples with lower turbidity had lower dissolved oxygen.

Hypothesis

The hypothesis is that the more turbidity levels in water increase, the more dissolved oxygen levels decrease.

Method & Materials

You will find an area of water to test, put a jar beneath the river surface, add dissolved oxygen pillows to the sample, and measure the turbidity levels with a turbidometer.
You will need a turbidometer, bottle with stopper, dissolved oxygen pillows, sodium thiosulfate, protective gloves, nail clippers, boots/hipwaiters, testing tube, and 10 quart jars.

Results

The results of the experiment indicate that higher turbidity levels actually increase the level of dissolved oxygen in water, which is contrary to the hypothesis. This experiment could lead to further exploration of how turbidity affects photosynthesis.

Why do this project?

This science project is interesting because it explores the relationship between two important factors in water quality, turbidity and dissolved oxygen.

Also Consider

Experiment variations to consider include testing different types of water, such as salt water or fresh water, or testing different levels of turbidity.

Full project details

Additional information and source material for this project are available below.

Related video

These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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