A Photochemical Study of Manganese Oxides from Pinal Creek, Globe, Arizona

Abstract

Mining activities in the Globe, Arizona area have generated an acidic groundwater plume with a high Mn(II) concentration in an aquifer that feeds the perennial reach of Pinal Creek. As a result of the Mn(II) contamination, manganese oxides coat a majority of the streambed. The focus of this research was on how sunlight effects the manganese redox cycle in a fresh water setting. The major objectives were to determine if the manganese oxides are stable with respect to light or if they can be photochemically reduced, and if light effects the rate of manganese oxide formation. In the experiments performed less than 1% of the manganese present in the oxides was released. The manganese oxides at Pinal Creek appeared to be stable with respect to sunlight. It was not evident from the results of this study that light exposure lowered the rate manganese oxide formation.