Effect of Sulfite Ions on Dissolved Oxygen: A Pollution Investigation
Measuring the concentration of dissolved oxygen in an aqueous environment and analyzing the availability of oxygen in waterways exposed to typical pollutants.
Dissolved Oxygen Sensor (PS-2108)
Lab Summary
Students will measure the concentration of dissolved oxygen in an aqueous environment, both before and after the addition of sodium sulfite, a chemical commonly found in untreated industrial effluent. Students will analyze how sulfites and related chemical compounds affect the availability of oxygen in waterways exposed to typical pollutants.
Sodium sulfite is commonly used industrially, for example in processes such as paper making, dyeing, bleaching, photographic development, and engraving. If runoff from an industrial factory or plant is untreated and effluent is released to the environment, local waterways can be adversely affected. Sulfites and other chemical pollutants, including sulfates, nitrates, ammonia, and heavy metals, produce direct chemical demands on oxygen in the water due to the oxidation-reduction reactions that result. Dissolved oxygen levels lower than 3 parts per million are stressful to most aquatic organisms, and dramatic events like fish kills can result when there is excessive demand on dissolved oxygen in an ecosystem. The overall health of an ecosystem is influenced as well by such factors as pH, temperature, carbonate buffering, water movement, and various populations of organisms all competing for shared resources. Since different aquatic organisms thrive under different environmental conditions, any small change in the complex chemistry of the environment can have far-reaching effects.
Hypothesize: What kinds of redox reactions might be expected when sulfite ions encounter dissolved oxygen? Predict how the concentration of dissolved oxygen will be affected by the addition of sodium sulfite to a sample of aerated water.
Published: January 2002
Downloads
- A Pollution Investigation - PASPORT (42 KB, .zip)
Includes experiment setup, procedures and Datastudio file
- A Pollution Investigation - ScienceWorkshop (42 KB, .zip)
Includes experiment setup, procedures and Datastudio file
Here's What You Need
U.S. Educator prices shown.
Probeware (PASPORT Systems)
Xplorer GLX (PS-2002) - $329
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
PASPORT Dissolved Oxygen Sensor (PS-2108) - $225
The Dissolved Oxygen Sensor provides real-time, aqueous oxygen concentration measurements.
Probeware (ScienceWorkshop Systems)
750 Interface, USB (CI-7650) - $659
The 750 Interface allows students to measure force, temperature, pressure, angular velocity, acceleration, current, & magnetic field with a built-in function generator and oscilloscope mode.
Dissolved Oxygen Sensor (CI-6542) - $269
The Dissolved Oxygen Sensor provides real-time, aqueous dissolved oxygen concentration measurements.
Other Materials
- Distilled or deionized water
- 1 mL of 2-M sodium sulfite solution
- Clamps and lab stand as needed to suspend sensor in solution
- Lab glassware: 600-mL beaker, large and small graduated cylinder (or pipette), stirring rod
- Wash bottles for rinsing sensors
- Optional: magnetic stir bar setup
Additional equipment:
- 2-M sodium sulfite solution (25.2 g Na2SO3 / 100 mL)
- large bottle or aquarium pump to aerate water
- Note: To saturate deionized water with air, fill a clean container one-third full with deionized water, seal it, and shake vigorously for 10 seconds. Alternatively, bubble air through the deionized water for 15 minutes using an aquarium pump.