Risk Assessment and Remediation of Soil and Amendment Trace Elements

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.
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PROGRESS: 2006/10 TO 2007/09<BR>
Progress Report Objectives (from AD-416) 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 (from AD-416) 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. Significant Activities that Support Special Target Populations Objective 1: The utility of ground rubber (contains 1.5% Zn) as a byproduct with potential value as a Zn-fertilizer was assessed in a pot experiment using Lockwood soil. The phytoavailability to spinach and lettuce of applied Zn from rubber compared to Zn sulfate was estimated by plant uptake of the added Zn. A second value of the test was the potential of the added Zn to reduce plant uptake of Cd from this Cd mineralized soil derived from marine shale. Because Zn in the rubber must be released from the rubber before it can be absorbed by the plant roots, rubber-applied Zn was only about 5% as effective as Zn sulfate in increasing Zn. Over time, this Zn should become increasingly plant available, and will be a low cost source of Zn fertilizer value. Added Zn sulfate reduced Cd in spinach by about 40% when 200 mg Zn was added per kg of soil. Alternative soil management practices to further reduce Cd uptake by leafy vegetables are being assessed, and the persistence of the effect of added Zn evaluated. Thus ground rubber appears to be a slow release Zn fertilizer with high purity Zn. Field tests are required to learn the cost effectiveness of using recycled ground rubber in place of virgin Zn in fertilizers. Objective 2: In cooperation with the International Water Management Institute in Bangkok, Thailand, and Phytoextraction Associates LLC, a field trial of Thlaspi caerulescens phytoextraction of Cd was conducted on land contaminated with Cd and Zn by mine waste discharge to irrigation waters. The best genetic lines available at this time were used in the test. Results to be obtained in September, 2007. Objective 3: In previous work, lettuce uptake of stable isotope labeled Cd in soils from long term biosolids utilization field experiments and control soils from the same experiments was assessed. In the lettuce test, the slope of Cd uptake was significantly lower for biosolids amended soil than control soils. The effect of several soil factors in limiting uptake of Cd was assessed by regression analysis, and soil organic matter was found to contribute to the persistent effect of biosolids application which reduced Cd uptake compared to unamended soil which also received the stable isotope applications. Testing of the possible role of glomalin in this organic matter effect on Cd phytoavailability remain to be conducted. Accomplishments Lockwood soil contained natural Cd accumulated to undesired levels in leafy vegetables. In a pot experiment, addition of Zn sulfate at high rates reduced spinach Cd by 40%, but added ground rubber was less effective in reducing Cd uptake because the Zn is only slowly released from the rubber to the soil. Ground rubber appears to be an inexpensive slow release source of high purity Zn fertilizer which could replace use of virgin Zn in fertilizers. An experiment was undertaken to evaluate phytoextraction of metals from soil which had received excessive metals applications from biosolids before present regulations were established. In each case, the effect of soil pH on plant growth and metal accumulation was assessed. The two phytoextraction species, Alyssum murale (Ni) and Thlaspi caerulescens (Cd and Zn) as well as the test leafy vegetable (Swiss chard) had substantially reduced yields at lower pH, but grew well at pH 6.5 and above despite the massive cumulative biosolids metals applications. Analyses of the plants is in progress. TNT feeding test showed that nearly all dietary TNT was reduced and became covalently linked to the diet matrix, greatly reducing the potential for TNT to enter ground water and comprise environmental risk. This confirms a rumen-beaker test conducted earlier that the highly reducing and organic matter rich environment of the rumen is capable of transforming TNT and reducing potential risk from TNT is environmental soils. Technology Transfer Number of Invention Disclosures submitted: 1 Number of Patent Applications filed: 1 Number of U.S. Patents granted: 1 Number of Non-Peer Reviewed Presentations and Proceedings: 5