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Is Your Bus Exhausting? Stevens Institute of Technology


TEACHERS: Transport

Students will:
  • interpret a wind barb
  • access near real time wind data and pollutant animations to track the transport and ultimate destination of pollutants




Each individual breathes nearly 3,400 gallons of air every day. Yet the air is being polluted by human activities like driving cars, burning fossil fuels, and manufacturing chemicals, and natural events such as forest fires. These add gases and particles to the air we breathe and, in high enough concentrations, can have harmful effects on people and the environment. Many air pollutants such as those that form ground level ozone, acid rain, and some toxic compounds remain in the environment for long periods of time and can be transported great distances from their origin.

Since air pollutants do not recognize political boundaries, states and communities cannot independently solve all of their air pollution problems. Resolving air pollution control issues often requires state and local governments to work together to reduce air emissions.

Ozone "precursors," such as NOx emissions, as well as ozone itself, can be carried hundreds of miles from their origins, causing air pollution over wide regions. Although many urban areas have made efforts to control ozone by reducing local NOx and VOCs emissions, incoming ozone transported from other areas also need to be addressed in order to meet the National Ambient Air Quality Standards. High levels of ozone entering some nonattainment areas can make achieving the national ozone standard difficult and costly, unless upwind sources are identified and controlled. If these sources fall within a certain state's boundaries, it can take measures to control them. If, as is often the case, these sources fall beyond the political boundaries of that state, it must work with EPA and other states to reduce air pollution on a regional scale. Often, it is more cost-effective to reduce emissions from upwind sources than to control emissions from smaller businesses in the nonattainment areas being affected downwind.

Some regional strategies for reducing ground-level ozone include:

  • reducing NOx emissions from power plants and industrial combustion sources
  • introducing low-emission cars and trucks
  • burning gasoline reformulated to reduce VOCs, NOx, and other emissions.

Winds blow in different directions and in different speeds at different altitudes. Living on the Earth's surface, we are accustomed to what are known as Surface winds. Surface winds range from 0 - 1,000 feet in altitude (see Online Wind Barb Guide for information about wind barbs). The winds associated with transport occur from 1,000 to 3,000 feet in altitude. The winds we experience at the surface may be moving at a different speed and direction than the winds at the "transport" level. This can create a problem when scientists attempt to track and especially regulate pollution levels.

Although this curriculum concentrates on ground level ozone, its causes and effects, it is important to note that ozone and its precursors are not the only pollutants that are transported by wind.

For example, a number of toxic air pollutants persist in the environment and concentrate in the food web, including toxaphene, a pesticide that is used primarily in the Southern U.S., and have been found in fatty tissues of polar bears and other Arctic animals thousands of miles away from any possible source. Lead and other trace metals have been measured in the air and rainfall at remote locations over the Atlantic and Pacific Oceans, great distances from likely sources. Core samples from peat bogs in the Great Lakes region show deposition of new releases of DDT. Since DDT is used only under special condition in the U.S., this toxic compound may be originating from sources as far away as Mexico or Central America. Fortunately, Mexico has also banned the use and production of DDT.

It is very important that people realize that when it comes to air quality, they have to worry about more than their own neighborhood. Since air pollution does not adhere to boundaries, it is important they we all contribute to the solution, on a local, regional and national level.

In this lesson, students will access wind data at the "transport" level and also access various pollutants' movements across the U.S. as well as other areas on Earth.


  1. Review the wind information below.  Remember that the wind barb points in the direction where the wind is blowing to, as opposed to where the wind is blowing from.
    5 knots
    10 knots
    15 knots
    20 knots

    Example of Wind Barb

    50 knots
    65 knots

    NOTE: The Example Wind Barb above represents a wind that is blowing from the Southeast at 15 knots. Wind speed is often reported in the units of "knots". A "Knot" is a nautical mile per hour.

    • 1 Knot = 1.15 Miles Per Hour (MPH)
    • 1 Knot = 1.9 Kilometers Per Hour (KM/HR)
    • Each short barb represents 5 knots, each long barb 10 knots. A long barb and a short barb is 15 knots, simply by adding the value of each barb together (10 knots + 5 knots = 15 knots. 
    • If you would like more wind barb practice, try this online quiz.
  2. On your Student Worksheet, analyze the wind barbs and determine which way the wind is blowing and how hard the wind is blowing.
    • Wind not only moves air, but also particles and objects that may be in the air. You may have experienced this before if you have dropped a piece of paper outside on a windy day and chased after it as the wind picks up the paper and carries it along.
    • What about the particles you cannot see? Winds can transport particles like NOx, VOCs, ground level ozone and particulates great distances from where they were produced.
  3. Pollutants such as ground level ozone and particulate matter are usually swept along by winds that blow around 3,000 ft above the surface (sea level).  Access the 3,000 ft wind data or the WeatherUnderground or surface wind streamlines and answer the questions on the Student Worksheet.
    • There are times when you can see the pollution in the air, when the air looks brownish-orange, that is called haze. Haze is caused by fine particles that scatter and absorb light. As the number of fine particles increases, more light is absorbed and scattered, resulting in less clarity, color, and visual range.
  4. Think about diesel exhaust and how all of these pollutants may be transported into your area. Now, think about the role of weather in this equation. Has the weather been such that it will effect the level of pollutants in the surrounding air? Combining all of this information, do you think you will be able to see the pollution or haze in the air today in Hartford? Explain.
  5. Check your response. Use NESCAUM's Haze Cam to determine if your hypothesis was correct. Notice the real time information under the image. Is the information similar to what you were expecting? Why or why not?



  • Students should complete the problems on the Student Worksheet.



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The Center for Innovation in Engineering and Science Education