APES Lab: Analyzing Vehicles for Particulate Exhaust
Background
Transportation is the single largest source of air pollution in the United States. It is also one of the primary
contributors to global climate change, generating more than 30% of our greenhouse gases. Air pollution
results from several components of a vehicle’s “life-cycle,” including emissions from tailpipes, refueling,
manufacture and disposal. Emissions from an individual car are relatively low when compared to the
smokestack image many people associate with air pollution, but emissions from hundreds of millions of
vehicles add up and are substantial. Driving a car is a typical citizen’s most “polluting” daily activity.
Pollution from cars includes emissions from the combustion process (tailpipe exhaust), and from
evaporation of the fuel itself. Tailpipe exhaust contains many primary pollutants including hydrocarbons,
nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), benzene, sulfur dioxide (SO2),
particulate matter (PM), and Hazardous Air Pollutants. Vehicles also generate secondary pollutants. For
example, smog forms when NOx and hydrocarbons react in sunlight to create ozone. Particulate Matter – in
particular the smallest particulate matter that is 2.5 micrometers or less in diameter – poses particularly
significant risks because it can get deeply imbedded in people lungs, and even into their bloodstream,
causing both respiratory and heart problems.
Clean vehicle and clean fuel technologies – including fuel efficiency, advanced fuels, and new vehicle
designs – can significantly reduce air pollution from our cars and trucks. The White House has issued
several new regulations requiring more stringent fuel and vehicle standards over the past few years.
Materials
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New white tube socks
6 cars or trucks (with difference size engines, made in different years)
Masking tape
Permanent marker
Insulated gloves
Rubber bands
Procedure
1. Record the make, model, engine size, fuel type, year and mileage of each vehicle in Table 1. Assign each
vehicle a number and write that number on a piece of masking tape. Put a number tape on each sock.
2. Make a prediction (write it in first column) as to what each sock will look like after it has been exposed
to the vehicle’s tailpipe emissions for several minutes – which sock will be the dirtiest? Why do you
think this?
3. Do not touch a hot tail pipe! Put a sock over the tail pipe of each vehicle. Make sure the sock has
been pulled up all the way over the pipe. To minimize variability, run all tests when the vehicle has a
cold engine. Make sure the sock is secure. Tape or secure the sock with a rubber band if necessary.
4. Turn on each car and let it idle for 5 minutes, but every 15 sec give the engine a burst of gas for 1 sec.
Turn the engine off and use insulated gloves to remove the sock from the tailpipe.
5. Examine each sock on the outside and carefully turn the sock inside out. Record your findings by
ranking the socks from lightest to darkest in color change. Also indicate how wet or dry each sock is.
1
TABLE 1
# and
prediction
Make
Engine
Fuel
Year
Mileage
Moisture
Color (Describe & Rank)
Questions
1. Record your predictions about which socks will be the dirtiest and which will be the cleanest.
2. Rank your socks from cleanest to dirtiest in Table 1. Rank your socks from driest to wettest. What is
causing the moisture?
3. Discuss your results. Does there seem to be a relationship between pollution and engine size or the type
of fuel used? Does there seem to be a relationship between the amount of pollution a vehicle generates
and the year in which it was manufactured? Did your results match your predictions?
2
4. Table 2 lists the major air pollutants associated with cars and trucks. Please complete the Table and talk
about what each pollutant is and why we should be concerned about it.
5. Every gallon of gas that is burned emits nearly 25 pounds of CO2 and other greenhouse gases into the
atmosphere. About five pounds of that comes from drilling the oil, refining it and delivering it to the gas
stations. The vast majority of the greenhouse gas emissions (more than 19 pounds per gallon) come
right out of the car’s tailpipe. Using your car’s gas mileage (miles/gallon) and the approximate number
of miles you drive each year. Calculate the greenhouse gas emissions that result from your driving in one
year. Assume your car is the “average” and calculate the greenhouse gas emissions released each year
from all 230 million cars in the United States.
6. In March 2013, the White House proposed new regulations to reduce pollution emissions from vehicles.
Briefly summarize when these rules would take effect and what they are designed to do. Do you think
the proposed rules are a good idea? Why or why not?
TABLE 2
Pollutant
What It Is
How It Can Be Harmful
NOx
CO
CO2
Benzene
SO2
PM
3