MANHATTAN, Kan. - Spring is in the air and urban gardens are sprouting up all over the country.

"Increasingly, urban agriculture is being done on a community basis, rather than an individual basis," said Kansas State University assistant professor of agronomy, Ganga Hettiarachchi. "There are now more than 18,000 community gardens in the U.S. and Canada," she said, citing American Community Gardening Association data.

Some of those gardens are on once-vacant lots and land where buildings once sat. Such locations are convenient for city-dwellers and make productive use of land that otherwise might be weedy, trash-strewn lots. There is a potential downside, however.

The problem in using properties -- typically called brownfields -- that may have been the site of anything from auto body shops to manufacturing facilities to gas stations, is that the soil on some of those properties can pose health risks if it is contaminated with heavy metals, metalloids or organic compounds, Hettiarachchi said.

She and a team of K-State researchers are working in several states around the country to ensure that growing crops in some urban locales are safe for gardeners and consumers. Other scientists  involved include Sabine Martin, brownfields coordinator and Blase' Leven, associate director, both with the Center for Hazardous Substance Research; Larry Erickson, professor in chemical engineering; Gary Pierzynski, professor and DeAnn Presley, assistant professor, both in agronomy; and Rhonda Janke, associate professor of horticulture. Pierzynski is currently serving as K-State interim dean of the College of Agriculture and director of K-State Research and Extension.

The five-year project began in January, 2009 with guaranteed funding from the Environmental Protection Agency of $750,000 and a possibility of up to $900,000.

Brownfield sites are defined by the EPA as vacant, abandoned property, the reuse of which may be complicated by the presence of a hazardous substance or contaminant, Hettiarachchi said. Examples include vacant residential lots, including those adjacent to industrial facilities and abandoned gas stations.

There may be as many as 1 million brownfields sites in the United States, according to the Department of Housing and Urban Development, which put the number of abandoned industrial sites at 5 million acres.

"Soil quality issues in urban soils include contamination, compaction, stone content, poor drainage and poor soil chemical properties," the scientist said. "Urban soils sometimes contain harmful levels of heavy metals and trace elements, including lead, arsenic, mercury and copper. Contamination may have come from paint, gas or oil, waste incineration, lead pipes or residue from specific industries.

Some brownfield sites also are contaminated with organic compounds, such as chlordane, DDT and PCBs (polychlorinated biphenyls), she said. Chlordane used to be used in homes to control termites and to protect farms, but the EPA banned it in 1988. DDT was an insecticide used at one time to control mosquitoes. It was banned in the United States in 1972. PCB, which was used in electrical transformers and other electrical components, was banned in 1979.

The K-State team is finding, however, that in many cases, steps such as adding nutrient-rich compost and other soil amendments, and adjusting soil pH can alter the soil to the point that it can be used to safely grow food crops.  

The team has analyzed 20 sites in Kansas City, Kan. and Kansas City, Mo., as well as sites in Gary, Ind.; Flagstaff, Ariz.; and Seattle and Tacoma, Wash. Testing is planned on sites in Colorado and Massachusetts in the next few months.

One of the locations is the Washington Wheatley area  -- a neighborhood in Kansas City, Mo. not far from the historic 18th and Vine Jazz District. The area is in the midst of a revitalization effort.

The scientists start at each location by establishing a site history, collecting and screening soil samples. They then recommend best management practices to community gardeners and organizers, which may include adding soil amendments or building raised planting beds.

"We provide continuous monitoring and analysis of the soil and produce raised by the gardeners as well as selected vegetable crops grown by our team on test plots," she said. "We also provide training and technical assistance to participating community organizations throughout the term of the project."

Soils and produce from the site are analyzed by K-State's Department of Agronomy in Manhattan, Kan.

The scientists found no detectable levels of chlordane at the Washington Wheatley site in Kansas City, but they did find detectable levels of DDT and mild to moderately elevated levels of lead.

"Our recommendation for this site was the addition of compost, because soil pH and nutrient concentrations were already at optimal levels" Hettiarachchi said, adding that to eliminate any issues with lead, gardeners were encouraged to wash their hands after working at the site, and to make sure that all produce from that site be thoroughly washed before consumption.

"The concentrations of lead and DDT in the above-ground portions of the vegetables would be very low.  This means the primary way in which humans are exposed to the contaminants would be by direct consumption of soil. This may seem silly since people do not intentionally eat soil but small and important amounts of soil can be ingested in a variety of ways," she said.  

After applying the compost, the team established test plots and grew Swiss chard, sweet potato and tomato plants. Once the plants were grown, the researchers analyzed samples for nutrients and lead. They also compared results using standard kitchen washing and thorough laboratory washing methods.

"DDT levels in the soil were not high enough to be concerned about plant uptake. We found that lead levels in all three plant types were well below the maximum permissible limits, as established by the World Health Organization," Hettiarachchi said.

Adding the compost lowered the lead concentrations in Swiss chard, but had no consistent effect on the sweet potatoes and tomatoes, she said. The level of washing also had no effect on lead concentrations in the produce. The scientists believe that was because lead concentrations in the soil were not high enough to cause significant uptake of lead in the plants.

The researchers have hosted national level webinars and offered technical assistance and guidance for soil contamination issues in gardening soils as an outgrowth of the research.

"Overall, this project will contribute to the use of mildly contaminated brownfield sites in an environmentally, socially and economically beneficial manner," Hettiarachchi said. "It will help in reducing the number of under-utilized brownfields sites that are potentially useable."

SOURCE: K-State.