This blog post was contributed by Kateryna Lapina, an atmospheric chemist working at the University of Colorado Boulder, Department of Mechanical Engineering. In her work she uses chemical transport models to estimate the negative impacts of ground-level ozone on vegetation, including the loss of major agricultural crops and ozone-sensitive tree species in the U.S.
By Kateryna Lapina
One of the Boulder ozone gardens is located in front of the University of Colorado Museum of Natural History, and the plants in this garden are growing well. Unlike the garden at NCAR’s Mesa Lab main entrance, however, the leaves of the ozone-sensitive plants at CU’s Museum of Natural History show no signs of ozone damage. One reason might be that ozone is lower in this part of Boulder, compared to where NCAR’s Mesa Lab is located. While the Front Range area is generally known for high levels of ozone, it might surprise you to know that ozone levels can vary greatly between locations, even within the same city.
Most ground-level ozone is formed in chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs). While there are some natural sources of these chemicals, they are also released into the air from cars, lawnmowers, power plants, oil and gas operations, and other human-driven activities, and they “cook” in the bright Colorado sunlight to produce ground-level ozone. Because it takes time for the chemicals to “cook” into ozone, most ozone is created some distance away from the pollution source. This explains why the highest ozone levels are found downwind of major pollution sources. In fact, ozone levels tend to be low near pollution sources, like power plants or busy roads. Since CU’s Museum of Natural History is only a hundred feet away from the busy traffic on Broadway Street, plants growing here might not exhibit ozone injury because ozone levels might be low. To learn more about ozone levels at this location, we are installing an ozone monitor at the CU garden this summer.
In addition, ozone levels can vary from year-to-year even at the same location. For example, during the 2014 summer, ozone levels in the Front Range of Colorado were lower than usual because of relatively cool temperatures. This summer, however, ozone levels are high, with a large number of ozone action alerts being issued already. We expect to see many more damaged leaves in our gardens as the season continues.