Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: RISK ASSESSMENT AND REMEDIATION OF SOIL AND AMENDMENT TRACE ELEMENTS Project Number: 1265-12000-037-00
Project Type: Appropriated

Start Date: Apr 03, 2005
End Date: Apr 02, 2010

Objective:
Characterize long term phytoavailability of trace elements in soils amended with swine manure, poultry litter, biosolids, byproducts and composts. Conduct literature review of possible risks from trace elements that have not been evaluated for manure and biosolids and conduct experimental tests needed to provide more complete risk assessments for trace elements in byproducts or contaminated soils. Develop and demonstrate addition of Fe and Mn oxide rich byproducts to manure, biosolids or compost to increase specific metal adsorption capacity and reduce phyto and bio availability of soil accumulated trace elements and phosphate. Develop improved technology for phytoextraction of soil Cd from contaminated soils requiring remediation. Identify methods for bioremediation of munitions contaminated soils using phytoextraction and rumenal biodegradation. Determine if mycorrhizal protein "Glomalin" or soil humic materials give increased metal binding by long term biosolids amended or manured soils and could reduce potential future phytotoxicity of applied metals.

Approach:
Long-term swine manure amended soils will be sampled with cooperators and the phytoavailability of soil Zn and Cu to sensitive plants as a function of pH will be evaluated; all test and control soils will be adjusted to several pH levels and lettuce grown to evaluate soil element phytoavailability. In addition, methods to increase the amorphous Fe and Mn oxides in manure and other soil amendments will be evaluated with known chemical forms and Fe and Mn rich byproducts from industry. After addition of different test byproducts and Fe/Mn sources, the solubility of metals and phosphate will be evaluated and the treated manures mixed with control soils to test the effect of the oxide additions on element phytoavailability to lettuce. Besides changes in the chemisorption of soil/manure metals on Fe and Mn oxides, increased binding by soil organic matter may increase. One soil organic matter formed by microbes from organic amendments is Glomalin; this will be measured in long term manure or biosolids amended soils. Additionally, spectroscopic methods may be used to characterize changes in soil organic matter ability to bind metals. In the case of soil Cd phytoremediation, phytoextraction by Cd hyperaccumulator plant Thlaspi caerulescens will be developed. Diverse genetic types will be evaluated for properties needed in commercial Cd phytoextraction and improved cultivars will be produced by normal plant breeding. Agronomic practices required to maximize annual Cd removal will be field tested with CRADA cooperator. For some Cd contaminated soils, application of Zn and limestone may reduce Cd phytoavailability by preventing upregulation of Zn uptake which increases Cd accumulation even at neutral soil pH. Cooperators will meet to design experimental program to efficiently utilize available funds to further develop bioremediation of TNT using phytoextraction by plants followed by mineralization by rumen microbes. Cooperators will select plant species for testing after review of previous research on plant uptake of TNT; they will identify any soil management conditions which favor TNT uptake into plant shoots rather than immobilization by chemical reactions in the roots. Because preliminary test showed that chemical TNT could be biodegraded by rumen microbes, additional rumen studies should examine TNT that has been absorbed by plant roots and incorporated in plant shoots to validate that plant-TNT can also be biodegraded in the rumen. Chemically pure 14C-TNT will be used in these tests so that the balance of TNT can be quantitatively assessed. Partial degradation products will be identified as appropriate to determine effectiveness of this bioremediation technology.

Last Modified: 8/27/2014
Footer Content Back to Top of Page