Soil Testing to Ensure Safe Gardening

Before sowing carrot and kale seeds, many city-dwelling green thumbs may wonder whether the food they will harvest from their urban plots is truly safe to eat.

Soil Kitchen, held on March 16 and 17 in Penn’s Hill College House and University City’s Clark Park, helped gardeners determine if their soil is risk-free. The outreach event, organized by Jane Willenbring, an assistant professor in Penn’s Department of Earth and Environmental Science, provided free soil testing and expert advice.

Participants who brought in a soil sample received information about their yard’s lead, arsenic, and cadmium levels. All three types of metals can be toxic to people who handle or breathe in contaminated soil, as well as those who consume fruits and vegetables grown in contaminated plots.

Lead exposure, for example, is known to cause to brain and nervous system damage and lower IQ in young children. Adults are also vulnerable to high lead levels and may experience cognitive declines, muscle pain, and reproductive problems. Lead contamination is widespread in certain areas of Philadelphia, where older homes have leached lead paint into the surrounding yards.

This was the second year Willenbring presented the Soil Kitchen, an idea she borrowed from an event held during the 2011 National Brownfields Conference in Philadelphia. This year, Willenbring and volunteers tested 155 samples; in one case, the lead concentration was 14 times higher than the level the EPA considers safe.

A portable X-ray fluorescence instrument was used to assess whether the metal content of the soil was high or low. Other tests provided information on the soil texture and pH.

“If we find that people have soil lead, the next obvious question is, ‘What am I supposed to do about that and how is this going to affect me and my children?’” says Willenbring.

Experts were on hand to offer guidance on techniques to remediate residents’ gardens, such as using raised beds and other techniques to avoid contact with contaminated soils.

Text by Katherine Unger Baillie
Photos by Steve Minicola