Presentation on theme: "Studying Ozone and Air Quality"— Presentation transcript:
1 Studying Ozone and Air Quality Deborah CarlisleSteve Schneider
2 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 O3Motor 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
4 Schoenbein PapersOzone 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 high O3exposure exposureThey are relatively easy to make – takes some practice to get an even application of the chemical across the entire filter paper.
5 HistoricallyDespite 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.
7 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 rightCntrl70ppb100ppb
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.Color chart allows for a general
9 Outdoor exposureDistribute teacher notes, and have them turn to pg 4 in handout “Use of Test Strips”
13 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
15 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 rightCntrl70ppb100ppb
16 Calibration of Test Strips Green wavelength here – rough ideaIf G value is below approx. 18 then ppb is greater than 140+