0.15 Rice air curriculum - lesson 5 (teacher): tropospheric ozone

Objective

During Lesson Four, students learned about the “dual” nature of ozone, and in particular stratospheric ozone. Today, students will learn about tropospheric or low-level ozone, which is a very harmful air pollutant. Students will learn about how it is created, and how it affects our health. Students will find ways to learn more about air pollution in their own communities, such as by checking the EPA’s Air Quality Index. These explorations will give students a much better understanding of low-level ozone, which they are measuring each day through the GLOBE protocols. Students will also learn about ways that they can help prevent the creation of ground-level ozone.

With this background knowledge, students will spend the second half of class discussing with other students and with the teacher what they have learned about air pollution, ozone, surface temperature, air temperature, humidity, clouds, and wind direction. Students will be asked to create hypotheses regarding what they think the relationships are between the GLOBE measurements they take every day. For example, do they think that on days that that the air temperature is warmer there will be more ozone measured in the air or vice-versa? Today, students will write down the trends they think they will see in their GLOBE measurement data. By the end of the curriculum, on Day Seven, they can use their data to either refute or support their initial conjectures.

Background information

An air pollutant is any gas or particle in the air that causes harm to living things or the environment. Depending on the type of pollutant, the impacts can include respiratory ailments, cancer, birth defects, heart disease, and damage to the environment. Air pollution has these major effects even though it constitutes only a tiny fraction of air molecules. Most air pollutants have a concentration less than one molecule per million air molecules.

There are many types of air pollution . This lesson focuses on the example of tropospheric ozone (also called “low level ozone”) because it can be measured by students, it has been linked to serious respiratory health effects, and because many cities such as Houston exceed federal standards for tropospheric ozone and must find ways to reduce it.

Power plants, factories, vehicles, and other sources do not directly emit ozone into the air. Instead, tropospheric ozone (also called “low level ozone”) forms when emissions of other gases (specifically, nitrogen oxides (NOx) and hydrocarbons (also known as volatile organic compounds, VOCs)) react in the atmosphere in the presence of heat and sunlight. The actual chemical reactions are very complex, but you can think of it in a simplified form as: