Biotic and abiotic processes contributing to the removal of Mn(ll), Co(ll) and Cd(ll) from Pinal Creek, Globe, Arizona

Abstract

Pinal Creek, near Globe, Arizona, has been contaminated by mixing with polluted groundwater caused by copper mining activities over the past century. The focus of this study was to determine the chemical and biological factors that contribute to the removal of heavy metals (e.g. Mn(II), Co(II), and Cd(II)) in the hyporheic zone at Pinal Creek and to determine the stability of the manganese oxides present when exposed to acidic groundwater. Laboratory batch experiment results indicate that the abiotic removal of Mn(II) was small (7 - 29 % ) compared to the biotic removal ( 61 - 99 % ) under conditions similar to those found naturally at Pinal Creek (pH= 7.5, 25 °C, atmospheric oxygen). Co(II) and Cd(II) removal was dominated by abiotic removal processes. Significant amounts of Mn(II) and Cd(II) were released into solution when the pH in batches was lowered to 4, however cobalt was found to be irreversibly bound.