Dependence of Metal Ion Bioavailability on Biogenic Ligands and Soil Humic SubstancesEPA Grant Number: R825960
Title: Dependence of Metal Ion Bioavailability on Biogenic Ligands and Soil Humic Substances
Investigators: Higashi, Richard M. , Lane, Andrew N. , Fan, Teresa W-M.
Institution: University of California - Davis
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 1998 through December 31, 2001
Project Amount: $345,816
RFA: EPA/DOE/NSF/ONR - Joint Program On Bioremediation (1997) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Description:Organic matter, can strongly affect metal ion binding to soil and sediment. In fact, production of a major form of organic matter - low-molecular weight organic ligands - is the principal mechanism by which plants and microbes acquire metal ions, so that the chemistry of biogenic organic matter is the key to understanding mechanisms of bioavailability for bioremediation purposes.
Thus, the complex interaction between metal ions, biogenic ligands, and humic substances must be understood in order to engineer the proper organisms and conditions for bioremediation of metal ion contamination. We propose to investigate this critically lacking area of knowledge through the following objectives:
i. Determine the sorption behavior of metal ions on isolated humic substances in the presence of
biogenic and synthetic ligands;
ii. Conduct a subset of experiments from (i) as longer-term ageing experiments;
iii. Investigate the properties of isolated humic substances that are involved in (i) and (ii);
iv. Assess the relationship of (i) and (ii) to metal ion bioavailability to vascular plants, including evaluation of soils from a Federal demonstration site (McClellan AFB);
v. Use the findings from (i) thru (iv) to identify key rhizospheric processes that regulate metal bioavailability, additionally incorporating findings from a complementary project on the biochemistry of metal ion ligands in plants/mycorrhizal systems.
Approach:Cadmium, aluminum, and iron metal ion binding to biogenic ligands (ranging from simple organic acids to complex siderophores such as desferrioxamine), ligand binding to isolated humic substances, and the interaction of all three components will be studied using chemical structure and kinetics approaches. The analytical backbone of the project will be techniques from organic chemistry, macromolecular dynamics, and humic structure probes, including multinuclear-multidimensional NMR spectroscopy, fluorescence spectrophotometry, FTIR microspectroscopy, and pyrolysis GCMS.
The investigation will additionally include whole soil experiments utilizing spiked soils as well as soils from a DOD/DOE/EPA National Environmental Technology Test Site, McClellan AFB. Actual metal ion bioavailability will be assessed throughout the study by measuring accumulation in vascular plants: Lemna sp. (duckweed) for aqueous phase experiments and Triticum sp.(wheat) for whole soil assessments.