RISK ASSESSMENT AND REMEDIATION OF SOIL AND AMENDMENT TRACE ELEMENTS
Title: Phytoextraction of Ni and Cd from Biosolids-Contaminated Soils
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 7, 2007
Publication Date: September 24, 2007
Citation: Chaney, R.L., Broadhurst, C., Green, C.E., Davis, A.P. 2007. Phytoextraction of Ni and Cd from Biosolids-Contaminated Soils. Meeting Abstract.
Before regulations for utilization of biosolids on land were developed, some biosolids had been applied for many years, and some of those contained levels of contaminants which are now recognized as unacceptable for general use cropland. One such site in Fulton Co. IL, involved a biosolid which contained high Cd concentration (>200 mg/kg), and had such a high Cd:Zn ratio that crops could reach high levels of Cd. State regulations required that only feed grain crops be grown, and that the crops were to be analyzed and composition reported to the State before sale. With the imposition of the Clean Water Act, Section 5-3 Rule, the application sites in Fulton Co. were so high in Cd that they exceeded the maximum allowable application for farmland. No further applications were allowed without designation of the sites as surface landfills for biosolids application. Many years later the managers of this land would like to sell the land or convert land use. But with the high Cd levels, and need to maintain high pH to prevent metal phytotoxicity, the land has reduced value.
One alternative would be to phytoextract metals from the soil until land use conversion could be allowed. Dr. Tom Granato asked if it might be possible to phytoextract Ni from the soils in order to help pay for Cd phytoextraction. Phytoextraction Associates, LLC has licensed Cd phytoextraction technologies patented by Chaney, Angle, Li, Reeves and Baker in 2006, and also developed Ni phytomining technology using Alyssum murale. It seems likely that at high pH, Ni phytoextraction could recover enough value above simply growing corn that the land could then be acidified for Cd and Zn phytoextraction using Thlaspi caerulescens. Two high biosolids application soils and one control soil from the Fulton Co. site were adjusted to a range of pH (5.5 to 7.5) and both hyperaccumulator crops grown, as well as Swiss chard as an indicator of soil Cd risk through garden crops. Although Alyssum Ni hyperaccumulation is increased at higher pH, acidification allowed other soil metals to kill the Alyssum, chard and even Thlaspi. Thlaspi thrived on the soil at most pH levels tested.
Results from these experiments will be presented, and estimated costs of phytoextraction for remediation of these soils to allow general land use will be reported.