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Studying Ozone and Air Quality Deborah Carlisle Steve Schneider.

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1 Studying Ozone and Air Quality Deborah Carlisle Steve Schneider

2 Measuring Ground-level Ozone O 3 levels above 120 ppb are considered unhealthy. They can be generated by some electrical equipment or from photochemical reactions with smog: VOCs + NO X + sunlight O 3 Motor vehicles are the single largest contributor to ground-level ozone. In this project we are adapting the relatively easy-to-make Schoenbein papers for classroom use, and using ADI to analyze the color changes quantitatively.

3 Ozone Levels

4 Schoenbein Papers Ozone was discovered by C.F. Schoenbein in He developed an ozone-sensitive test paper that was widely used historically, and more recently in classrooms. The standard protocol for using the papers calls for an 8-hour exposure to the air out of direct sunlight. Various studies have shown a dependence on humidity, and there are a variety of recommendations for moistening the strips prior to exposure. Control low O 3 high O 3 exposure exposure

5 Historically Despite the method's early limitations, starting in the mid-1800s, more than 300 stations recorded ozone exposures in countries such as Austria, Australia, Belgium, England, France, Germany, Russia, and the United States.

6 Schoenbein Papers Cntrl

7 100ppb70ppbCntrl How do Ozone Test Strips Work? Ozone is a strong oxidizer. It rapidly reacts with the iodide ion, I - in the KI salt applied to the filter paper: KI + H 2 O + O 3 I 2 + O 2 + K + I 2 + I - + starch I starch (turns blue)

8 Facilitating Classroom Use: 1. We find that strips can be exposed dry, stored, and then dipped into water just before photographing. The exposed strips react with the water to produce a more uniform and consistent color that appears less dependent on humidity. 2. With digital monitoring devices, we are developing a digital color scale that can be used to test ozone levels after exposures of only two hours. 3. We are also testing and developing digital color calibration for commercial ozone-testing papers, although their cost per test may be prohibitive for many schools.

9 Outdoor exposure

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12 Comparing Test Strips

13 Coloration Why and How?? Why and How?? KI + H 2 O + O 3 I 2 + O 2 + K + I 2 + I - + starch I starch (turns blue) Last step : I 3 - (linear)+ starch (helix) Combination of I 3 - and helix causes light reflection to be in the blue/violet range of visible spectrum

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15 100ppb70ppbCntrl How do Ozone Test Strips Work? Ozone is a strong oxidizer. It rapidly reacts with the iodide ion, I - in the KI salt applied to the filter paper: KI + H 2 O + O 3 I 2 + O 2 + K + I 2 + I - + starch I starch (turns blue)

16 Calibration of Test Strips

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18 Control vs Exposed

19 Comparing to color scale

20 Accurate comparison


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