Hydrogen Peroxide Formation and Decay in Iron-rich Geothermal Waters: The Relative Roles of Abiotic and Biotic Mechanisms

Abstract Hydrogen peroxide (H2O2) is widely distributed in surface waters where the primary photochemical formation pathway involves the interaction between dissolved organic carbon (DOC) and ultraviolet radiation (UVR). In laboratory studies using iron-rich water from Yellowstone's Chocolate Pots spring, H2O2 formation depended on sample treatment (unfiltered, <0.2 μm filtered, autoclaved) prior to irradiation, suggesting several formation pathways. Similar H2O2 formation in filtered and unfiltered water indicates that it is primarily soluble material that is responsible for H2O2 formation. H2O2 formation with soluble material probably includes only photochemical reactions with DOC and/or metals. Greater H2O2 formation in unfiltered and filtered water than in autoclaved water suggests that the agent(s) involved in H2O2 formation is (are) not stable at high temperatures and pressures and degrade to nonphotoreactive species. Such unstable agents may include DOC and/or dissolved complexes of iron or other m...