How can you tell that the air you breathe is polluted, when you can’t see the pollution? The answer is planting the ozone-sensitive plants that develop a distinct injury on their leaves in response to ozone pollution. This summer, we (Danica Lombardozzi, NCAR, and Kateryna Lapina, University of Colorado Boulder) planted two ozone gardens to help raise awareness about the ground-level ozone problem in Boulder. The exhibits are located in front of NCAR’s Mesa Lab and at the University of Colorado Museum of Natural History, and both are free to visit. In addition to the respiratory problems it causes in humans, ozone causes a number of negative effects on plants, from reduced crop yield for major agricultural crops such as soybeans and wheat, to reduced amounts of carbon stored in aspen — effects that can be difficult to see. However, the special varietals of milkweed, snap bean, potato and coneflower plants in the ozone gardens were selected because they are “bioindicator” plants, meaning they develop distinct black or brown spots on their leaves when exposed to high levels of ozone for periods of time. The NCAR garden was planted in early June, and a couple of weeks ago Danica observed the first signs of ozone injury on snap beans. Ozone damage on cutleaf coneflower and La Chipper potato plants showed up this weekend. The CU garden was planted three weeks later and Kateryna just noticed some brown spots today that might be early stages of ozone injury. It can be difficult to tell ozone injury in early stages since it can look similar to insect damage. We’ll have to keep checking to see if the leaves develops more symptoms with time (typical of ozone damage), and then we can better tell if the symptoms are caused by ozone damage or something else. Ozone concentrations have been lower this summer than in previous years, and perhaps the injury on plants would have been observed earlier were this a more typical high-ozone summer. We are now waiting to see similar signs of ozone damage on other plants in the gardens.
The first ozone measurements on the roof of NCAR building above the garden showed the ranges from approximately 30 to 100 ppbv (1-minute averages), and typically levels above 40 ppb are considered to be sufficient to induce negative ozone effects on plants. The CU garden is not equipped with monitor, but the SOARS student Brandt Scott took ozone measurements last week to see if the Broadway traffic may reduce ozone levels at the garden location due to reaction with fresh NOx emissions.
The ozone garden project has been a lot of fun for us. Starting the plants in the greenhouse, trips to the Rocky Mountain National Park to collect the native coneflower plant under a special permit, emailing back and forth with scientists and agencies who provided the seeds and advice, creating educational materials – this all kept us busy this summer! Our gardens have already received lots of coverage in media locally as well as nationwide, including a story on NPR. This definitely helped us to get the word out and we are already seeing a steady flow of visitors to the gardens. As the summer progresses we expect to see more ozone-caused injury on the plants and we hope this will help to educate the public on the importance of making our air cleaner.