Submitted to: International Symposium on Biogeochemistry of Trace Elements Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2001
Publication Date: July 24, 2001
Soil contamination with Zn and Pb can cause serious environmental problem. Zn can be severely phytotoxic, while Pb presents risk to human health through direct ingestion of contaminated soils or dusts. We have demonstrated use of limestone plus biosolids application to revegetate barren soils to reduce dispersion of contaminants through erosion and to immobilize metals in soil making them less bio-available. Bioavailability of soil metals depends on the chemical form added to soil and the time after addition. In vitro chemical extraction tests (0.1 M HCl, pH 2.2) have been found to correlate well with bioavailability of soil Pb, so we were able to use in vitro tests to evaluate whether soil treatments to achieve effective revegetation of Zn-phytotoxic soil also reduced bioavailability of soil Pb. Soil from the Aberdeen, MD, contaminated by military activities, contained 10,300 mg Pb/kg and was initially pH 6.9. Treatment with NPK, NPK + limestone, or NPK + phosphate gave poor revegetation compared to composted biosolids rich in Fe with or without limestone. Added composted biosolids reduced Pb in tall fescue shoots from 159 to 23 mg/kg dry wt., while bioavailable Pb dropped from 31 to 19% of total soil Pb. Fractional bioavailability of Pb was also tested on long term Pb contaminated farm soils of Silesia, Poland; for soils with over 1000 mg Pb/kg, only 1.3-13.6% (average < 10%) of soil Pb was bioavailable; reduction was lowest in soils high in clay, phosphate, Al, and alkaline pH, but organic matter was not correlated. %-bioavailability was much lower than found with recently Pb-contaminated soils (as high as 80% from recently oxidized PbS. It is possible that normal phosphate fertilization over a long reaction time allowed extensive inactivation of soil Pb.