by Barbara Hoffheins, Todd Minners, Terri McPalmer, and Jon Bell
In 2020, Arlington Regional Master Naturalist (ARMN) volunteers initiated the Ozone Garden with the cooperation and support of Arlington County Parks at Walter Reed Community Center (WRCC) located at 2909 16th St S, Arlington, VA 22204. (The beginnings of this project were reported in an earlier blog piece, “The Ozone Bio-indicator Garden Project: A Cooperative Effort Between ARMN, Arlington County, NASA, and Harvard.”)
The garden is part of the Ozone Bioindicator Garden Network, which is coordinated by the Harvard University and Smithsonian Institution Center for Astrophysics (Smithsonian Astro Observatory), and affiliated with the National Center for Atmospheric Research (sponsored by the National Science Foundation), and the National Aeronautics and Space Administration (NASA). NASA’s TEMPO (Tropospheric Emissions: Monitoring Pollution) mission is to measure air pollutants at high precision across North America with a specially designed instrument scheduled to launch on a satellite in 2022.
The observations of ozone effects on plants in the ozone gardens add to the understanding of ground-based ozone seasonal patterns, distribution, and intensity. Ozone is formed by the interaction of sunlight with carbon monoxide from burning fossil fuels, nitrous oxides, and volatile organic compounds (VOCs). Elevated ozone levels can seriously damage crops and forests and cause respiratory damage or distress in humans and animals. See: USDA Agricultural Research Service report. These and other reasons are why NASA is interested in monitoring and tracking ozone globally.
Ozone enters the leaves from the underside through the stomata and interferes with the photosynthetic process. Ozone damage is typically observed as brown stippling (spots), on the tops of mature leaves, in between and not crossing the veins, and for many plants, not visible on the underside of the leaf. The damage starts with a few spots and can increase to cover and eventually kill the leaf. Insect damage, such as chewing or cutting, and disease effects are visible on both the tops and bottoms of leaves but can be mistaken for ozone damage.
Ozone damage to leaves of sensitive plants can be observed when the ozone level is sufficiently high over a long enough period. This could be a very high level of ozone for as few as two hours or a moderate level for many hours or days. The bean plants in ARMN’s Ozone Garden started showing signs of ozone damage in late summer. To roughly correlate with the visual observations, data was used from the Arlington County air pollution monitor located at Aurora Hills Visitor Center that measures and reports nitrogen oxides, carbon monoxide, and ozone levels on an hourly basis. During the 2021 growing season, there were very few days when the Aurora Hills monitor reported ozone at sustained elevated levels and most of the days were in late July, early August.
ARMN’s Ozone Garden is located on the west side of the WRCC building near a children’s playground. In the spring of 2021, ARMN volunteers constructed three raised beds and planted the following provided by the Smithsonian Astro Observatory:
- Sensitive and tolerant varieties of snap beans (Phaseolus vulgaris): tolerant is var. R-123, sensitive is var S-156.
- Sensitive and tolerant varieties of tobacco (Nicotiana tabacum L.): var. BEL B is tolerant, var. BEL W3 is sensitive.
- Sensitive potato (Solanum tuberosum): var. La Chipper.
- Sensitive milkweed (Asclepias syriaca).
ARMN prepared informational signs in English and Spanish about the garden purpose and ozone effects to inform passersby. The volunteers monitored the garden throughout the season to water, weed, and report observations of the plant leaves. Sometimes visitors to WRCC stopped by to chat with volunteers.
ARMN volunteers learned a lot this season. Although the volunteers collectively have a variety of relevant skills and expertise, monitoring for ozone damage and distinguishing ozone damage from other garden problems were new activities for all. Other issues that needed to be address were insufficient water drainage early in the season, a soil test that indicated excessive alkalinity, and plant leaves that exhibited insect and disease damage. The team also installed rabbit protection for the potato plant after discovering bitten off stems and leaves. The volunteers consulted several sources, including experts from the Virginia Cooperative Extension, the Ozone Bioindicator Garden Network, online scientific publications, the U.S. Environmental Protection Agency (EPA), the U.S. Department of Agriculture (USDA), and NASA brochures.
Recently, the team added some manure where the tobacco had grown, turned over the beds, and planted coneflower and milkweed seeds that need winter weather to trigger germination in the spring in pots that are sunk in the ground. They also tightened up corners of the raised beds that had moved a bit during the summer.
The ARMN Ozone Garden Team has these goals for the 2022 growing season:
- Use the garden to illustrate visually the impacts of ozone pollution on plants.
- Add signs with more detailed photos of each type of plant and instructions for how to find ozone damage and include a QR code on the signs to connect to online educational links.
- Enumerate actions that anyone can take to reduce ozone levels.
- Develop and conduct outreach programs at the garden to educate all ages about air pollution in Arlington and the negative impacts on agriculture and human health.
- Collect data on ozone damage present in the garden and report findings to the National Center for Atmospheric Research.
- Monitor and maintain soil quality for health and consistency across all three garden beds.
The ARMN Ozone Garden team welcomes visitors to the beds at Walter Reed Community Center to see where the project is taking place. As noted above, the beds are located in front of the building on the west side.