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United States Department of Agriculture

Agricultural Research Service

Title: Solid-State Speciation of Ni and Zn in Contaminated Soils: a Micro Spectroscopic Approach

Authors
item Roberts, Darryl - UNIV DELAWARE, NEWARK, DE
item Senesi, Giorgio - UNIV DELAWARE, NEWARK, DE
item Kukier, Urszula - VA TECH INST, BLACKSBURG
item Chaney, Rufus
item Sparks, Donald - UNIV DELAWARE, NEWARK, DE

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2001
Publication Date: July 24, 2001

Technical Abstract: Soils impacted by Cd, Ni, Pb and Zn have been characterized as having a reduction in the abundance and diversity of soil microorganisms, reduced soil fertility, damaged vegetation, and an increase in susceptibility to erosion. Knowledge of the speciation of soil metals can help one predict their fate, bioavailability, and mobility in soils and would be important in risk assessment and implementing remediation strategies. While sequential extraction procedures and bulk analytical techniques (i.e., X-ray diffraction, thermal analysis) are valuable for characterizing contaminated soils, they may be insensitive to minor phases and they cannot provide spatial variability within a sample. In this study we have employed micro-focused X-ray fluorescence (æ-XRF) spectroscopy and micro-X-ray absorption spectroscopy (æ-XAS) in combination with bulk analysis (XRD and bulk-XAS) to characterize Ni- and Zn-contaminated soils with the goal of elucidating metal speciation on a micro-scale. Zn was present as Zn adsorbed on Fe oxides, and as ZnS, while Ni was present as Ni hydroxide and Ni adsorbed on Fe. The present study shows the utility of combining several analytical techniques to achieve the most accurate and precise speciation of metals in contaminated soils. Identifying certain species was only possible using microscale spectroscopic techniques, a result that can be attributed to their sensitivity to low metal concentrations and good spatial resolution. The results from this study show the utility of micro-focused spectroscopic studies relative to bulk-spectroscopic studies in determining contaminant speciation in soils.

Last Modified: 7/25/2014