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2/18 Air Pollutant Lab

Last updated 7 months ago
8 questions
Introduction
Tiny particles of solid matter swirl about constantly in the air that we breathe. Aside from being an aggravation to the tidy housekeeper, airborne particles clog ventilation and cooling equipment, interfere with the performance of motors and electric components, and intensify health problems from many people. The amount and composition of airborne “dust” varies throughout the year, due partly to environmental factors such as wind and rainfall, human activities such as plowing or harvesting fields, and the life cycles of plants and fungi. The dust particle collectors in this kit assure a standardized method of collecting airborne particulates, either indoors or out. By examining the collectors microscopically, you will probably be able to identify some of the components of the dust collected, and since the particle collectors have grids, you will be able to quantify your results. You can then compare the type and quantity of particulates collected between one site and another or between one time period and another.

The dust that settles on window sills and other surfaces is marvelously heterogeneous. Close examination of individual specks yields clues as to their probable origin. Indoor dust contains large amounts of finely broken up fibers from fabrics of all types, including draperies, carpets, upholstery material, and clothing. Household paper products also shed a substantial amount of fibers. Other sources of airborne particulate matter include pollen from flowing plants; small fragments of tiny, dead insects; residues from tobacco smoke; dander (skin flakes) and fur from house pets and tiny flakes of dead skin from humans; and spores from molds and yeasts that flourish in a dry, crumbly state, particularly during dry weather. Agricultural activity breaks dry soil into fine particles that become windborne, and traffic over unpaved roads has the same effect. Industrial smokestacks, household heating systems (including woodstoves and fireplaces), and automotive exhausts emit variable amounts of fine soot into the air.
Using the Dust Particle Collectors
The adhesive dust particle collectors can be placed at various locations throughout the school and around the school ground to sample particulate fallout. The particle collectors should remain at the collecting sites for 24-72 hours. Write the location, date, and time of day, air temperature, general weather conditions, and wind direction in the space provided on the dust particle collector before you remove the protective backing from the adhesive surface. A fine-point permanent marker works best. Remember later to note the date and time of day at which the collection period is terminated so the total sampling time will be known.

Choose collection sites carefully to minimize the chance of the particle collectors being disturbed by the wind or by curious passersby. Make a list of any features of the collecting area that might release particles of debris into the air. Outdoors, the list might include trees, dirt roads, and patches of lawn. Indoors, the list might include carpet, draperies, clothing, and cleaning supplies such as brooms or dust mops.

To remove the protective backing from the dust particle collector, start at one corner. Handle only the edges. Do not let the adhesive surface come in contact with anything, including your fingers! When returning to the classroom with the dust-laden particle collector at the end of the sampling period, touch only the edges and the non-sticky surface.
Examining the Dust Sample
When view adhesive-side up, the dust particle collector is divided into three zones: white, cross-hatched in 1-mm squares, and transparent. Some small, dark particles such as soot are most easily seen on the white area when viewed through a stereomicroscope; others can be observed best from the transparent side. The actual dimensions of the individual particles can be estimated easily and accurately by viewing them on the 1-mm grid at 20x or 30x magnification.
1

Sketch what you see under your microscope.

1

Can you identify any of the things that you see, such as an insect leg or a hair?

1

Are there any outstanding features, such as unusual colors, shapes, or textures?

1

Are most of the particles filamentous, or string-like, or do they resemble specs of dirt? Thinking back to the collecting site, can you list some objects or structures that may have contributed part of this airborne debris?

1

Would you expect the size of the particles to affect the distance that the particles can travel through the air?

1

What features other than size might influence the distance the particle travels?

1

What statements can you make regarding the “cleanest” and “dirtiest” areas in and around your school?

1

If you were to repeat the experiment at home, where would you expect to find the greatest and the least amounts of dust?