Food Crops

• Vegetables absorb relatively small amounts of lead from soil, but lead poisoning poses risks in severely contaminated sites. Root crops such as carrots, and leaf crops such as lettuce, present higher risks of lead poisoning than fruiting vegetables such as beans and tomatoes. Romanian researchers from Alexandru Ioan Cuza University reported that mercury and cadmium negatively affected growth and photosynthetic activity in tomato plants. They also noted that chlorophyll concentrations declined and stems wilted to soil level after exposure to these two heavy metals.
  
  

Rubber Mulch Toxicity

• Dr. Linda Chalker-Scott refutes claims that rubberized mulch poses no toxic threat to the environment. Her research substantiates the presence of metal contaminants in rubber mulch products that have known environmental and medical side effects. She states that it's “abundantly clear from the scientific literature that rubber should not be used as a landscape amendment or mulch.” The problem is with leachates, or materials that release into soil from rubber products as they decompose. When spread as a mulch cover, tire “crumb”–finely shredded tires–decomposes more readily than whole tires discarded in landfills. Decomposition leaches heavy metals into soil for detrimental plant uptake.
  
  

Phytoremediation and Phytoextraction

• At varying levels, dependent on the species, plants can extract or remediate toxins from soil through their root systems. The U.S. Environmental Protection Agency documents numerous cases of using plants to clean sites contaminated with heavy metals. Notably, Rutgers scientists used sunflowers to extract radioactive metals from a contaminated pond at the Chernobyl site. Toxic waste uptake by the sunflowers’ roots didn't adversely affect the plants’ ability to thrive. Similar green technology was used to remove 75 percent of lead concentrations from the soil at a former battery manufacturer’s site in New Jersey.
  
  

Managing Metalliferous Soil

• Home gardeners can prove or dispel worries about heavy-metal concentrations in their gardens by testing soil. University extension offices charge nominal fees for comprehensive soil tests and offer free advice for amending, fertilizing and building healthy soil. Adding organic amendments, including composted leaves and grass clippings, significantly reduces lead concentrations in soil. Organic matter is lead-binding and renders metal unavailable to plants. Reduce food-consumption contamination by siting edible-garden areas away from older buildings that may contain lead-based paints or solvent-saturated soil.