At a former phosphate fertilizer manufacturing facility, arsenic and lead concentrations are elevated in soils (54, 200and 136, 000 mg/kg) and associated groundwater (> 800 and 100 g/L). In this study, solid phase transformations will be linked to transient changes in aqueous contaminant concentrations.
Monitoring wells were sampled quarterly for three years to evaluate aqueous geochemistry and soil mineralogy was characterized using sequential extractions and x-ray adsorption spectroscopy. These data reveal that aqueous concentrations of lead, arsenic, iron and sulfate fluctuate sinusoidally in response to seasonal and tidal changes in water table elevation. Changes in pH and Eh indicate that these concentrations are responding to redox transitions. Mineralogical data indicates that iron-sulfides oxidize during the spring and reform during periods of sustained reduction. To study potential remedial strategies, mineralogy and aqueous geochemistry were monitored in microcosm studies amended with variable concentrations of Fe (II) and organic matter. These studies mimic episodic saturation of soils and demonstrate that remedial amendments influence mineralogy and contaminant flux to groundwater. Water table modulations effect the long term stabilization achieved by these amendments, suggesting that system hydrology will be the controlling variable in the success of remedy implementation. http://goldschmidt.info/2010/abstracts/abstractViewc2ae.html?abstractId=3490http://goldschmidt.info/2010/abstracts/finalPDFs/A220.pdf