Center for Innovation in Engineering and Science Education
Print... | Close   
Is Your Bus Exhausting? Stevens Institute of Technology

 

TEACHERS: Create Your Own Investigation

Objectives
Students will:
  • create and conduct their own investigation
  • collect and analyze ozone and particulate matter data
  • compare student collected data against AIRNow data
  • identify differences between school buses that have and have not been retrofitted

Materials

 

Background:

Depending on available resources, you may use different sampling materials, or use similar materials but pursue differing methodologies. Overall, each investigation will follow the same basic approach outlined below:

  1. Define the sampling objective: Describe the scientific question (hypothesis) the project is addressing. For example, if students are concerned about the pollutant levels near their school, the sampling objective might be:
    • If pollutants are present and measured on the EPA AirNow web site, the EcoBadge OR ACCESS system OR Ozone Detector Badge OR chemical testing paper OR rubber bands OR milkweed will detect the presence of ozone.
    • Due to cool, cloudy, windy weather conditions, and limited sources of NOx, VOCs and PM in the city or town upwind, we predict AQI levels will be low (AQI of 0 - 50).
    • If ozone and particulate matter are present outside, we predict measurements will be higher outside than inside of the school, when the windows are closed and measurements are not taken near copy machines or other potential indoor sources of ozone or particulate matter.
    • If ozone and particulate matter are present outside, we predict measurements will be roughly equal inside and outside of the school, when the windows are closed and measurements are not taken near copy machines or other potential indoor sources of ozone or particulate matter.
    • The NOx, VOCs and PM measurements taken near a school bus that has not been retrofitted will be significantly greater than NOx, VOCs and PM measurements taken near a school bus that has been retrofitted.
  2. List the sampling parameters: In addition to ozone and particulate matter, each group needs to measure or obtain meteorological parameters including: temperature, relative humidity, wind direction and wind speed. If students are using the ACCESS system, meteorological data is measured by the system. Some schools might have on-site weather monitors that can be utilized. Otherwise, weather data can be obtained by accessing the Weather Underground.
  3. Describe the method of data collection: Describe where the sampling equipment will be located, how long you will perform sampling, and whether the measurements (experiment) will be repeated in the same day.
    • Hints: If you are using the Ozone Detector Badge, a group may want to take five 10-minute readings during the class period and then "average" the results. Or, the students could take a measurement once per hour during the school day to see how the levels compare with the readings on the AIRNow web site, if available in your area.

Ozone Information:
Ozone is an odorless, colorless gas composed of three oxygen atoms. It is not usually emitted directly into the air, but at ground level it is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of heat and sunlight. Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOCs that help to form ozone. Other sources of VOCs include household products such as paints, paint strippers, and other solvents; wood preservatives; aerosol sprays; cleansers and disinfectants; moth repellents and air fresheners; stored fuels and automotive products; hobby supplies; dry-cleaned clothing.

VOCs + NOx + Sunlight = Ozone

Sunlight and hot weather can cause ground level ozone to form in harmful concentrations in the air. As a result, it is known as a summertime air pollutant. Many urban areas tend to have high levels of ground level ozone, but even rural areas are subject to increased ozone levels because the wind can carry, or transports, ozone and pollutants that form it hundreds of miles away from their original sources.

Measuring ozone can be tricky and yield unexpected results. For instance, urban areas often have lower levels of ozone than adjoining suburban areas because of "ozone scavenging". Ozone scavenging occurs in locations where higher levels of NOx are found, e.g. urban areas or busy highways, due to emissions. In these areas, emissions containing NOx (Nitrogen oxide), react very quickly with O3 (ozone) to form NO2 (Nitrogen dioxide) and O2 (oxygen).

NOx + O3 -> NO2 + O2

This creates overall lower levels of ozone in the urban areas.

The NOx that does not "scavenge" ozone will continue to drift downwind (about 10 - 40 miles), eventually combine with VOCs and react in the sun to produce ground level ozone creating overall high levels of ground level ozone in the downwind location.

In summary, concentrations of ground level ozone tend to be reduced in urban areas due to ozone scavenging, but during ozone episodes, ozone concentrations can be high in areas 10-40 miles away due to wind transport. All of this may cause the ozone levels you measure to be lower or higher than you might expect.

Further, the EPA created air quality standards that limit the levels of ground level ozone in the air to protect public health. There are two standards; a one hour standard (120 ppb) and an eight hour standard (80 ppb). Every area of the country is eventually expected to meet or be below the standards. If an area does not meet, or "attain" the standard, it is considered a "non-attainment" area, and is subject to many more regulations to help make it an "attainment" area in the future.

Measurements are taken by the EPA to ensure the air quality standards are being met. The measurements you will be doing may not be taken at the same time intervals, or the level of precision as the EPA (or state) measurements. Therefore your measurements cannot be directly compared to the AirNow data, nor will you be able to calculate possible exceedences of the one hour or eight hour standard.

Procedure:

  1. Discuss the type of investigation your group would like to create, such as what materials you will use to measure ozone, what time of day you will perform your investigation, how long you plan to collect data, etc.  
     
  2. Each team is responsible for drafting a description of their investigation which should include:
    • A defined sampling objective (hypothesis).
    • A list of the sampling parameters (ozone and weather).
    • A description of the method of data collection, including the frequency (how often), duration (how long), and location of monitoring (where).
    • A list of materials needed to complete activity.
    • A description of how you plan to analyze the data collected from the investigation.
       
  3. Submit the draft description if the investigation for review by your teacher. You may have to revise the description based on teacher comments.
     
  4. Run the investigation, and collect and analyze data.
     
  5. Access the AIRNow web site and select an animation for an area as close to your location as possible, and that was collected during the same timeframe in which the experiments were run. (Hit the escape key to stop the animation at the specified time).
     
  6. Each group must submit a report on the results of the investigations. The report should include:
    • Hypothesis (sampling objective)
    • Materials used during the investigation
    • Description of the experiment, including how the data was collected and which parameters were sampled.
    • Data
    • Conclusions
       
  7. Compare your data with the data on the AIRNow web site. Where the readings similar? Why or why not?
     
  8. Identify potential sources of NOx and VOCs (precursors of ground level ozone) in your area. Do you have any control over any of the possible sources?
     
  9. Each group will be responsible to create and deliver a 15 minute presentation about the investigation created and the data your group collected. Each presentation should contain the following information:
    • The sampling objective (hypothesis) for the investigation.
    • The sampling parameters used in the investigation.
    • A description of the method of data collection, including the frequency, duration and location of monitoring.
    • Materials used during investigation.
    • A description of how the data was analyzed.
    • How did the data compare with the AIRNow data?
    • A list of possible local sources that were identified by the group and what might be done to reduce emissions.
 

 

Assessment
Each group should create and deliver a 15 minute presentation about the investigation they created and the data collected. Each presentation should contain the following information:

  • The sampling objective (hypothesis) for the investigation.
  • The sampling parameters used in the investigation.
  • A description of the method of data collection, including the frequency, duration and location of monitoring.
  • Materials used during investigation.
  • A description of how the data was analyzed.
  • How did the data compare with the AIRNow data?
  • Possible local sources that were identified by the group and what might be done to reduce emissions.

 

Implementation Tips
If this investigation is attempted outside of "Ozone Season", there may not be data, or ozone, available in your region to support the investigation.  

 


 
 
Copyright all rights reserved 2005. Stevens Institute of Technology.
The Center for Innovation in Engineering and Science Education