Seven Things To Do With Wireless CO2
Measuring Carbon Dioxide (CO2) has many applications in the classroom and with the latest advances in technology is easier and more affordable than ever before. Here’s a quick look at some of the cool things you can do with the new Wireless CO2 Sensor!
1. Monitor Air Quality
An engaging way to introduce students to the sensor is to use the “closed” environment that you already have access to - your classroom or lab. This is also a great opportunity to use the data logging capabilities of the sensor. Find a central place in the room to place the sensor, ideally suspended above students heads where they can’t exhale onto the sensor. Place the sensor into logging mode, and collect 8-10 hrs of data (Figure 1a). Depending on the number of students in your room, HVAC, how closed the environment is, you should be able to see fluctuations in the CO2 levels that correspond to the class schedule because all of those students are busy breaking down glucose and producing CO2.
Students can repeat this test in other locations such as the cafeteria, greenhouse, bathrooms, etc. While there are conflicting standards generally a CO2 concentration of <1,000 ppm is desirable and >3,500 ppm people will begin to experience physiological effects. Many modern HVAC systems even have their own sensors that will cycle the air to maintain CO2 levels <1,500 ppm. You can probably tell from the data if your school or lab has one!
2. Investigate Cellular Respiration
With the included sample bottle, students’ can use invertebrates, germinating seeds, or other small organisms to quickly collect respiration data. Variation in environmental factors, like light or temperature, provides easy extensions as well as germination time, species comparisons, body mass, activity level, etc.
Extending this setup, the sensor can be used with bacterial or yeast solutions, and even aquatic species by measuring the gas concentration in the headspace of the container.
While a smaller chamber will yield faster results (gas concentration will change faster) sometimes a bigger chamber is needed to study larger organisms or when modeling ecosystems. This is where the wireless design is particularly helpful, the sensor can easily be placed inside any container along with the organism being studied - without any modifications. If you need to run the sensor for longer than about 18 hrs, connect it to an external USB power pack or power source, and the sensor will continue to log data.
3. Investigate Photosynthesis
To get great photosynthesis data you just need a fresh dark green leaf, the sensor, and the sample bottle. Calibrate the sensor, put the leaf in the bottle, cap it with the sensor, and start data collection! Using the sample bottle and a fresh leaf ensures a quick response with data runs of 5-10 min! Light vs. Dark and wavelength are simple and relevant manipulations for students to conduct. To get the latest tips and tricks for this experiment, check out our blog, "A Biology's Teacher's Take on Photosynthesis with the Wireless CO2 Sensor."
Table 1. Summary of change in rate found from each run of data.
| Test | CO2 Rate (ppm/min) |
|---|---|
| Light (no filter) | -17 |
| Blue Filter | -7 |
| Red Filter | -9 |
| Green Filter | -12 |
| Dark (tinfoil wrapped) | +32 |
And more ideas (than I have time to test): Light intensity, the impact of temperature, herbivory, time of day, herbicide impact, stomata density, C3/C4/CAM plant comparison, CO2 concentration.
4. Measure Carbon Flux in the Field
In some cases, lab experiments aren’t feasible or desirable. It’s easy to take the sensor into the field using a cut bottle, bell jar, or plastic bag to isolate a plant or patch of soil for analysis without disturbing the environment. Firmly press the container into the substrate to create a tight seal and begin collecting data. Students can easily compare different ecosystems to determine if they are a net carbon producer or consumer under conditions. This technique can be repeated in different conditions, times of the day or year to compare results.
This same technique, combined with the concept of measuring a headspace over a liquid to determine the gas exchange, can be used to monitor carbon flux in an aquatic ecosystem. Securing the sensor with a float (or to a fixed object) to protect it creates the airspace needed to measure the carbon dioxide above the water, without damaging the sensor. Collect data for a day to see how a body of water is exchanging carbon with the atmosphere, or collect measurements at different times of the year and compare them as a class to familiarize students with long-term environmental monitoring and larger data sets.
5. Monitor Respiration of Soil Microbes and Decomposers
To streamline the sample collection and measurement of soil samples, students can use a section of PVC to collect a consistent volume of substrate and make the measurement in the same chamber. A 6-8in (15-20cm) section of pipe with an inner diameter of ~1.125" (3cm) can be easily pounded into the ground a specified depth to collect the sample. Seal the end of the pipe with some parafilm or plastic wrap and collect the data.
Data collection can take place in the field or lab and is easily extended for inquiry. Students can treat the samples with pH buffers, water, drying, salt, pesticides, or other chemicals of interest to determine the impact on microbe respiration.
6. Measure Human Respiration
Using a drinking straw and a 1gal (4L) ziplock® bag it's easy to capture human respiration data. Here’s a video comparing breath hold time. This same procedure can be used to test other variables, before and after exercise, time of day, etc.
7. Dissolved CO2 in situ
With the Dissolved CO2 Sleeve students can monitor the concentration of CO2 in an aquatic environment. The Teflon® material is permeable to CO2 molecules but not to water, creating a much smaller headspace around the sensor with better response time. While the CO2 is not dissolved when it is measured this approach has been validated and tracks with other indicators such as pH (Johnson et al 2010). This approach works well in the field and in the lab for photosynthesis and respiration experiments. Below is a picture and some data we collected during beta testing!
Reference:
Johnson, M. S., Billett, M. F., Dinsmore, K. J., Wallin, M. , Dyson, K. E. and Jassal, R. S. (2010), Direct and continuous measurement of dissolved carbon dioxide in freshwater aquatic systems - method and applications. Ecohydrol., 3: 68-78. doi:10.1002/eco.95
