Submitted to: Annual Conference of the US Composting Council
Publication Type: Abstract Only
Publication Acceptance Date: December 7, 2002
Publication Date: January 29, 2003
Many soils have become contaminated by lead use for industries, vehicles and homes. In general, soil Pb comprises greatest risk thru soil/dust ingestion by infants and children, not thru uptake into the edible part of garden foods. To protect young children from adverse health effects of soil Pb, contaminated soils may need to be remediated. The default method is soil removal, but that is expensive, on the order of $1 million per A-ft. Because of the high cost of soil removal/replacement, an alternative method to alleviate risk to highly exposed children has been sought for nearly 20 years. We have tested the use of composts of varied composition because components of the compost can cause inactivation or adsorption of soil-Pb, and improve the vegetative cover. The inactivation is considered an in situ remediation method, and improved cover reduces the physical accessibility of soil. If a child cannot eat the soil, if adults do not drag soil into the home on their shoes and clothes, the risk does not occur. Compost can inactivate soil Pb in two ways: 1) high phosphate in composts promotes formation of chloropyromorphite, a very insoluble Pb compound; or 2) the combination of hydrous Fe oxides and phosphate greatly increase Pb adsorption, reducing bioavailability. Although uncomposted organics can induce similar metal remediation, it is not acceptable to apply such amendments directly in gardens or urban lawns without composting. We have previously reported to USCC on using mixtures of composts and alkaline byproducts to achieve remediation-revegetation of highly metal phytotoxic soils (Zn, Ni, Pb, Cd). Fe additions during composting can reduce the solubility of compost-P and allow application of compost rates needed to attain persistent remediation of a difficult site.