Theme: The Air We Breathe
Learning and Teaching Activities
Investigation of air particulate levels at various localities
Teaching Tips
This is a simple scientific investigation on examining the air quality of different areas by
examining the particulate matters. This enables students to get the first hand result by
themselves. Do take safety precautions in field work and in handling the sample papers.
Objective: Survey on the particulate matter of different areas and discuss on the results.
Introduction
Total suspended particulates (TSP) are small airborne particles such as dust, fume and smoke.
They are emitted from various sources including power stations, construction activities,
incineration and vehicles.
The fine portions, which are known as the respirable suspended particulates (RSP), are of
greater health concern. As the name implied, the particle sizes are small and usually escape
the barrier set by the nasal hair and pass into the respiratory tract. When they settle in the
respiratory system, respiratory diseases will result. A high level of RSP may cause chronic
and acute effects on human health, particularly the pulmonary function, as they can penetrate
deep into the lungs and cause respiratory problems.
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Students’ Work
In this exercise, 4 – 6 students will form a working group to perform a survey of air quality
by measuring the levels of air particulates at various localities. The list of localities is
depends on interests, e.g. contrast an urban street with a country park path, and contrast a
classroom with the open playground, etc. Take note of the immediate environment of the
locality when investigation.
After collection of the data, students are required to write and submit a report. In the report,
use a precise and concise format to present the data collected, e.g. table or a bar chart. In
addition, try to discuss and propose the possible sources of the air particulates. Finally, try to
comment on the Hong Kong air particulate level.
Procedures of the investigation
1. Smear a layer of Vaseline on cards (15cm x 15 cm). Not leave fingerprints and wastes on
the cards.
2. Place the cards in different districts such as Mong Kok and Wong Tai Sin.
— Find an area that you can place the card for 1 week without disturbance. The side with
Vaseline is placed at the top. Heavy particulate matters are let to settle onto the sheet.
— Do remember to secure the position of the sheet for a long period (1 week) in this
experiment. You might need to carry out a regular inspection.
3. After one week, collect the cards back to school and observe the card using magnifying
glass, the dust is the air particulates. (Density of the dust particles in a sheet reflects the
air particulate levels of the district to some extent. This is a visual interpretation and is a
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kind of semi-quantitative measurement.)
Discussion
In the written report, answer the following questions:
1. Are there any dust/air particulates on the cards? If yes, what are the colors and shapes of them?
2. What is the density of the dust/air particulates on the cards? Please select one of the boxes
below that best describe the density and use as a scale to reflect air quality.
Worst
---------------------- best
Then arrange the results of the localities in an order of bad air quality, find the
“cleanest” one and the “dirtiest” one. Suggest reasons for the high air particulate level in
particular districts.
3. If the distribution of the dust/particulate matter is uneven, what does it imply? How to
compare the different sampling sites?
4. List the possible sources of the dust /air particulates.
5. What are the particle sizes of respirable suspended particulates (RSP)? Are these visible
by a magnifying lens?
6. Comment on the air particulate levels in Hong Kong (with aid of web search). Suggest
possible measurements to improve the situation.
7. State one precaution in carrying out this experiment.
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Suggested Answers (accept alternative and correct answers)
1. Are there any dust/air particulates on the cards? If yes, what are the colors and shapes of them?
Yes, black / brown / gray colors. Of variable shapes.
2. What is the density of the dust/air particulates on the cards? Please select one of the boxes
below that best describe the density and use as a scale to reflect air quality. Then arrange
the results of the localities in an order of bad air quality, find the “cleanest” one and the
“dirtiest” one. Suggest reasons for the high air particulate level in particular districts.
Urban roadside  urban residence area rural roadside  rural residence area
Reasons for high air particulate level: heavy traffic that more air particulates from car
exhaust/ more industrial activities / densely area with more human activities that generate
more air particulates such as construction / Tall buildings with less ventilation or wind
current not strong enough to cause dispersal and thus particulate matters accumulate.
3. If the distribution of the dust/particulate matter is uneven, what does it imply? How to
compare the different sampling areas?
Sources of air pollutants are uneven.
Solution: subdivde the sampling paper into 6 sites. Grade the density in each site according to
pattern shown in Q2 (1, best; 4, worst). Then get a mean density value for the
sampling paper (e.g. the 6 sites have the values: 1, 3, 4, 2, 1, 4. The mean ‘pollution
index’ is: 2.5). Different sampling areas are then compared by their ‘average
pollution indices.
4. List the possible sources of the dust /air particulates.
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Car exhaust, incomplete combustion, electricity generation, industrial activities,
construction, etc.
4. What are the particle sizes of respirable suspended particulates (RSP)? Are these visible
by a magnifying lens?
10 µm or less. Invisible even use magnifying lens.
5. Comment on the air particulate levels in Hong Kong (with aid of web search). Suggest
possible measurements to improve the situation.
Air particulate levels in Hong Kong are generally high, as many cars emit air particulates
and other human activities that produce it.
Possible measurements: all cars install particulate trap / introduce environmental friendly
vehicles such as electric car / monitor the level of air particulates and implement
measures to improve the situation / educate the citizens about the current pollution/ any
reasonable answers.
6. State one precaution in carrying out this experiment.
Do not rock the sheet after collection to avoid shaking off of particulate matters.
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