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Contaminant Speciation in Riparian Soils Demonstration
Primary Issue Addressed: Modeling
Secondary Issues Addressed: In situ Treatment; Lead Stabilization
Project Site: University of Idaho
Collaborating Entities: MSE and University of Idaho
Cost Share: University of Idaho
Project Description
The focus of this project is to evaluate phosphorus-lead soil interactions with respect to mineralogical stability. It is an investigation into the reaction processes that take place when phosphate amendments are added to riparian soils containing lead and other solid-phase materials.
Phosphorus has shown excellent potential for the remediation of lead-contaminated soils and reduction of lead bioavailability. However, no existing information correlates the reaction mechanisms of lead in field remediated soils with toxicological studies on waterfowl. This project will serve to fill this gap. In addition, this project will also serve to monitor how the speciation and bioavailability of the other contaminants are affected by phosphorus-based remediation treatments.
The riparian zone of interest in this study will be investigated geochemically using two modeling techniques. Each model will focus on the bulk mineralogy unique to this wetland system and use this information to explore lead mobility and potential sequestration pathways. A thermodynamic database unique for this environmental system will be compiled for use in the models by selecting appropriate equilibrium constants and using them within the models in conjunction with temperature, oxidation-reduction (redox) potential, pH, and major ion data.
Status
The fate of the lead in these remediated soils is continuing to be investigated. Experiments using advanced spectroscopic and microscopic techniques have been conducted. Pourbaix, or Eh-pH, diagrams will be generated, using HSC Chemistry to investigate phase stabilities with varying electron and hydrogen ion activities.
Along with this project, an in-vitro test method for simulation of waterfowl digestive systems has been developed. This technique can now be used to demonstrate the effectiveness of phosphate soil amendments to reduce lead bioavailability, solubility, and leachability through the formation of low-solubility lead compounds. The project final report should be completed in FY05.