Lead taints garden
The community garden across the street from Epler Hall was nearly destroyed a year ago when Adeline Hall was demolished. Now the 30-year-old garden is mostly recovered, thanks to the loving support of PSU students and mentoring from the facilities and planning department.
But recently, tests of green leafy vegetables from the garden revealed an unsettling surprise: the presence of high levels of lead.
“The garden is right next to the highway,” said Lisa Durden, PSU community garden coordinator. “There’s a pipe that carries storm water run-off from the highway. We think that’s where the contamination came from.”
Durden explained that the storm water would have been contaminated with leaded gas years ago, before the change to unleaded fuel.
“We haven’t been able to come up with any other explanation for the contamination,” she added.
For the community garden, ordinary green veggies proved to be the canary in the coalmine.
In May, overwintered kale, radish tops and broccoli plants were tested for lead content. The plants were taken from the garden’s southwest corner, next to the freeway.
Samples, taken from unwashed plants, showed approximately one microgram/gram (parts per million) of lead for the chard and 0.11 microgram/gram for the broccoli and radish tops.
As a control, samples of California chard from the local Safeway were also analyzed, and showed lead levels below 0.01 microgram/gram – 100 times lower than those of the chard growing in the PSU garden.
Many green vegetables contain a high percentage of calcium, which binds easily with lead. When leafy greens such as kale, chard and spinach start coming up lead-positive, it suggests that the soil is contaminated.
The health risk to an individual depends on age, sex and total exposure. Because of rapidly growing bones and rapid brain development, children and infants are much more susceptible to lead exposure than adults.
Currently, the FDA’s acceptable daily dietary lead intake is six micrograms for children under age six, 25 micrograms for pregnant women and 75 micrograms for other adults. In terms of quantity, this equals about 0.2 ounces of chard per day for a young child and about two ounces for an adult.
How is the community garden responding to the lead problem?
Durden described an upcoming experiment to further characterize the scope of the contamination. Gardeners will plant leafy green vegetables in different spots in the garden this fall, allowing the greens to grow and overwinter. When spring comes, the greens will be harvested and tested for lead content.
Testing has been orchestrated with Dresden Skees-Gregory, PSU sustainability coordinator. The sustainability office, a branch of the facilities and planning department, is providing the lead testing at no charge.
The sustainability office also recently gifted the community garden with $7,000 worth of uncontaminated topsoil. In addition to testing the existing soil for lead, another focus of the project will be planting kale atop different depths of the new topsoil, which has been spread atop the contaminated soil.
The gardeners are uncertain how far the kale’s roots will penetrate. If the new soil layer is thick enough, the roots may not reach the contaminated soil, and thus may not take up any lead.
Durden pointed out that yet another answer is simply not to grow crops that take up lead.
“Some fruits and vegetables, like corn, berries and tomatoes, don’t bind with lead. If a plant doesn’t uptake the lead, eating the plant isn’t harmful,” she explained.
Based on this, it’s possible that the growth of specific crops may be restricted when the next gardening season begins. Skees-Gregory has specifically recommended that kale not be grown in the community garden for consumption.
The part of the garden that is already known to be contaminated – the part closest to the freeway – will be turned into a native plant area, an excellent way of using the land productively but for non-food purposes.
“We’re going for Backyard Garden Certification,” Durden said. “You have to provide food, water and shelter for different animals. We’ll be focusing on pollinators – bees and butterflies.”
Another parcel of vacant land just south of the existing garden belongs to the Oregon Department of Transportation. ODOT has talked about giving the land to PSU. The parcel would allow a significant expansion of the garden space.
“We’re leery,” said Durden. “The land has never been gardened, and since it’s next to the highway, it’s probably contaminated, too.”
If the land is acquired, Durden mentioned a possible brownfield contamination collaborative project with the College of Urban and Public Affairs.
The community garden currently has 70 gardeners. New plots open up in March 2006; priority for reserving a plot goes to students living on campus, with any remaining spaces going to the general student body.
“With all of these projects, the garden is going to be a focus for hands-on sustainability projects,” Durden said.
