The plants in this Garden tell you when the air is dirty


What if you could look at the plants in your garden in order to learn if the air around you is clean or dirty? At the National Center for Atmospheric Research in Boulder, scientists have planted a garden that does just that. It's called the Ozone Garden, and the plants in that garden react – visibly – when ozone levels are high. You start to see damage on the leaves. A bunch of little black spots," said Danica Lombardozzi, a postdoctoral researcher at NCAR and one of the garden's creators. Ozone at the surface of the earth is an air pollutant that is harmful to people and plants. It is created when certain pollutants, often from combustion, combine, and it can cause breathing problems, especially for children. **Sentinel plants**There are four types of plants in the ozone garden, each selected for their sensitivity to ozone. In the garden, green shoots of milkweed, snap bean, potato and cutleaf coneflower spring from the ground. The coneflower was collected with a special permit from Rocky Mountain National Park, which has experienced ozone levels above national standards, and seen plant damage as a result. "Some plants are going to be more sensitive than other plants," said Lombardozzi, adding that she chose these four because of their sensitivity. What happens when ozone levels are high? The plants breathe in the ozone just like people, and reacts in a way that causes some of the chlorophyll cells in the plant's leaves to die, turning portions of the leaves black. The plants do not typically die, but the damaged leaves fall off and new ones eventually grow back. "It's kind of like the canary in the coal mine", Lombardozzi said.**Visualizing an Invisible Pollutant**Current exposure limits for humans are set by the U.S. Environmental Protection Agency at 75 parts per billion, although the agency is considering lowering this limit. Sensitive plants can start seeing effects at around 40 parts per billion, said Lombardozzi. In the summer, the Front Range often has air quality that is worse than EPA limits, said Kateryna Lapina, a research associate at the University of Colorado Boulder and the other creator of the garden. Lapina, an atmospheric chemist, works on modeling ozone. "With gardens like this the whole idea is to visualize the negative effects of an 'invisible' pollutant, ozone, on living systems, both plants and humans, so everybody can now see and understand it," Lapina said.By Stephanie Paige Ogburn"


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