Studying Ozone and Air Quality Deborah Carlisle Steve Schneider

Measuring Ground-level Ozone O3 levels above 120 ppb are considered unhealthy. They can be generated by some electrical equipment or from photochemical reactions with smog: VOC’s + NOX + sunlight  O3 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. Color chart allows for a general

Ozone Levels

Schoenbein Papers Ozone was discovered by C.F. Schoenbein in 1839. 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 O3 high O3 exposure exposure They are relatively easy to make – takes some practice to get an even application of the chemical across the entire filter paper.

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.

Schoenbein Papers Cntrl 80 100 120 140+ Cntrl 50 ppb – jpg 735

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 + H2O + O3  I2 + O2 + K+ I2 + I- + starch  I3- + starch (turns blue) Color chart allows for a general – Strips are inside cardboard with cntrl on the left and 140ppb on right Cntrl 70ppb 100ppb

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. Color chart allows for a general

Outdoor exposure Distribute teacher notes, and have them turn to pg 4 in handout “Use of Test Strips”

Outdoor exposure

http://www.weather.gov/aq/sectors/nemetro.php#tabs http://www.airnow.gov/ Interesting data based on scattered data – based on site BUT local sources are very relevant and use strip to verify certain areas such as bus stops,

Comparing Test Strips

Coloration Why and How?? KI + H2O + O3  I2 + O2 + K+ I2 + I- + starch  I3- + starch (turns blue) Last step : I3- (linear)+ starch (helix) Combination of I3- and helix causes light reflection to be in the blue/violet range of visible spectrum

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 + H2O + O3  I2 + O2 + K+ I2 + I- + starch  I3- + starch (turns blue) Color chart allows for a general – Strips are inside cardboard with cntrl on the left and 140ppb on right Cntrl 70ppb 100ppb

Calibration of Test Strips Green wavelength here – rough idea If G value is below approx. 18 then ppb is greater than 140+

Control vs Exposed

Comparing to color scale

Accurate comparison