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Counting Air Particulate Matter (page 2)

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Author: Jarred, Grade 7

Hypothesis

I believe that there will be more air particulate matter in the urban areas than in the rural areas. From the background reading I learned that most of the sources of particulate matter come from urban areas. Automobiles and industry are the most common sources of particulate air pollution and there are more of both in urban areas as compared to rural areas.

I also hypothesize that within each area, the three different community types will have different quantities of particulate pollution. The road will have more than the fields, which will have more than the forests (roads > fields > forests). I believe this because there is more activity that produces particulate pollution near a road. In the fields there is air circulation, which will bring in particles but it is not near the sources of pollution. The forest will have the best air quality because the air is still and the tree’s leaves block particles.

Materials

  • 6 or more slides (3in-1in)
  • Permanent marker
  • Ruler
  • 3 sites in an urban area
  • Forest - Millstream Park
  • Field – Millstream Park * Road – Railroad Ave.
  • 3 sites in a rural area
  • Forest – Back yard, Deerfield
  • Field – Back yard, Deerfield
  • Road – Coon Box Rd.
  • Vaseline
  • Dissecting microscope

Procedure

  1. Choose three similar sites in both an urban and rural area: along a major road, grass covered open area, and forest.
  2. Mark two equal areas (1.5 cm x 1.0 cm = 1.5 cm2) on the back of each slide with a permanent marker. Each 1.5 cm2 area constitutes a sample.
  3. Label one section of the slide A the other B. Make sure that all labeling is on the back of the slide, otherwise the sample areas and the labeling may be mistakenly rubbed off.
  4. Give each slide a number 1-6 and have a key for the area and place where the sample will be taken in. For example: #1-urban field, #2-urban road, etc.
  5. On the opposite side you marked on, apply a thin coating of Vaseline. Rub any excess off the slide to make the Vaseline coating even. (When particulate matter lands on the Vaseline it will stick to the slide.)
  6. In the three different areas lay the slide on a flat surface (fallen tree, block of wood, etc.) and in an open area.
  7. Leave the slides out for 24 hours to collect particulate matter.
  8. Record weather conditions for the 24-hour period; high and low temperature, wind velocity.
  9. Record any peculiar activity that may have occurred in the vicinity of a sample during the 24-hour period.
  10. Collect the samples and place them in a covered container so they are not contaminated with additional particulate material as you leave the site.
  11. Carefully, without smearing the Vaseline, take each slide and put them under a dissecting microscope.
  12. Under the microscope count the particulate matter in each of the 1.5 cm2 sample sections and record your observations.
  13. Repeat this procedure a minimum of three times per site.

Discussion

My data show that there is more air pollution particles in the rural areas as compared to the urban areas (Table 1). When all of the samples in all of the communities were averaged together, the total particles for the rural areas averaged 153.40 particles/1.5 cm2 and the urban average was 134.07 particles/1.5 cm2 (Fig. 1). Looking at all the data from each one of the 3 trial taken, in every case the rural areas had a higher number of particles than when compared to the urban areas (Fig. 2). In the three trials the particles in the rural area were 445.5, 459.5, and 475.5 particles/1.5 cm2 and the three urban trials were 348.0, 424.5, and 453.0 particles/1.5 cm2 (Table 1). These findings are completely opposite my hypothesis where I thought that there would be less particulate pollution in the rural areas as compared to the urban areas.

I think that there are several reasons why my experiment produced these results. First, the samples were taken during the period of mid October to mid November. This was the finishing of the corn harvest and during the soybean harvest. Harvesting crops with a combine produces lots of dust and chopped up plants that are blown in the air. I think these particles were what landed on my slides. The urban areas are far enough away from the harvesting that the particles were not blown there. If I had done this test during the summer when there was no harvesting or when farmers are not working their fields, I think I would have different results. I also think that the particles that are produced in urban areas may be too small to be seen with a dissecting microscope. Particles of soot from car and truck exhaust are very small as compared to dust, soil particles, and plant parts that are blown in the air from harvesting.

One other hypothesis I had was that there would be a difference in the particulate air pollution in different types of habitats. My hypothesis was that there would be more particles in near the road and the least amount would be in the woods. I thought the field sites would be somewhere in between. The data for the rural areas (Fig. 3) show that the most particles were collected from the forest site and the least from the road site. This is completely opposite my hypothesis. I this is because the forest slows wind movement and allows particles to settle better than along the road or in a field.

Unlike the rural area, the urban area did agree with my hypothesis that the road would have the most particulate pollution (Fig. 4) when compared to other habitats. But the urban field did show the lowest amount of particles.

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