One means of doing a quick study of particles is to survey a room or building for sources (origins) and sinks (places where they land) of particles. Some examples of particle sources include carpets, paper, clothing, chalk, insulation, and building materials. Sources do not have to be in the room to supply particles.
Particles can be transported from their sources by ventilation systems, breezes, and even people. Particles can attach to clothing at the source and be transported indoors or to other parts of the building as people walk from place to place. The places where particles are deposited are called sinks. For dust, a sink could be a horizontal surface such as a shelf, a video display terminal, or an area that is not often cleaned.
Can you identify the particle sources and sinks in your room or school?
Try collecting particle samples from surfaces that you would like to investigate. These surfaces might include:
- A frequently cleaned surface
- An infrequently cleaned surface
- A video display terminal
- A surface near a video display terminal
- An electronic device that is not a video display terminal
Particles can be lifted from these and other surfaces using clear adhesive tape or a fingerprint lifter. A fingerprint lifter consists of a sheet of transparent acetate with adhesive gel and a thin plastic film that acts as a cover. Tape has the advantage of being fast, cheap, and easily available.
However, you have to be attentive
to avoid contaminating your sample and having the tape actually stick to the
surface from which you are collecting your sample.
clear adhesive tape or
fingerprint lifter (from a fingerprinting kit)
microscope
1 Identify the surfaces where each sample is to be collected. Noting these locations on a map will help you later.
2 Label or otherwise identify the tape or fingerprint lifter that will be used to collect each sample.
3 Collect a sample. Either gently press the tape to the surface or follow these steps to use the fingerprint lifters.
- Remove the thin plastic cover film from the non-adhesive side of the tape on the fingerprint lifter.
- Do not allow the inner side of the cover film to come in contact with any surface. Carefully hold the cover film back so that it is not contaminated.
- Press the adhesive side of the acetate film against the surface to be sampled.
- Carefully remove the acetate sheet from the surface and
carefully replace the cover film.
1 Place the tape or fingerprint lifter under a microscope and bring the particles into focus.
2 Observe the field of view. Count the total number of particles in the field of view.
3 Try to identify some of the particles. Can you guess the sources of the particles?
4 Consider all the samples you collected and their locations. Do you
notice anything interesting? Can you see any patterns? Does a review of all of
your samples help you identify sources of the particles?
Check
http://www.lbl.gov/Education/ELSI/pollution-measure-BC.html