This is a non-biomedical project. Ore mining activities have left a legacy of heavy metal contaminated sites throughout the southwest. Groundwater plumes emanating from these sites incorporate both the aqueous waste from the mining sites and the products of interactions of these wastes with the subsurface media. Understanding of plume aquifer interaction is essential to predicting the composition of the groundwater and the ensuing effects on surface water. Reactions and surface water bodies will determine routes of exposure to population centers which have historically been inhalation and ingestion of contaminated water.
The specific aim of this proposal is to determine the reactions and rate controlling processes of the mobilization of Mn+2 and trace metals (specifically, Cd+2, Zn+2, Pb+2, and Cu+2) due to interactions of an acid mine plume (at low pH and high Fe(II) with Mn+4 containing subsurface media and subsequent Mn+2/Mn+4 chemistry in Pinal Creek, AZ, a state superfund site. To achieve this aim, the project focuses on the redox processes in both the aquifer and the stream that control Mn(III,IV) hydroxide solubility. The project director hypothesizes that trace metal movement in the acid mine plume is controlled by pH and Eh (specifically by manganese/iron Redox cycles). Once Mn (II) laden groundwater reaches the stream, the stream bed materials play a key role in the reoxidation of Mn(II) and surface catalyzed oxidation occurs. As the Mn(IV)is deposited and heavy metals have been adsorbed, total reduction of Mn(IV) releases Mn(II) and any other heavy metals adsorbed on the Mn(IV)solids. They propose to test hypotheses by a combination of laboratory and field studies. Field work will be done in cooperation with the U.S. Geological Survey at Pinal Creek. Analytical work for this project will be done both in the investigators laboratories and through the superfund center analytical core.
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