Hydrogen peroxide dynamics in an agricultural headwater stream: Evidence for significant nonphotochemical production
Limnol. Oceanogr., 58(6), 2013, 2133-2144 | DOI: 10.4319/lo.2013.58.6.2133
ABSTRACT: Hydrogen peroxide (H2O2) plays key roles in aquatic systems, including metal redox cycling and degradation of organic matter into bioavailable forms. Abiotic photoproduction, via photo-oxidation of chromophoric dissolved organic matter, has generally been assumed to be the most important source of H2O2 to freshwater systems in the daytime. However, the significance of other H2O2 sources has not been previously examined in situ. In this study, isotopically labeled H2O2 (H218O2) was added to in-stream mesocosms exposed to light and dark periods. By measuring total H2O2 and H218O2 in tandem, we inferred absolute rates of H2O2 production and decay, which occurred simultaneously. Abiotic photoproduction rates were measured independently by exposing filtered samples to sunlight. Even in these shallow systems, total production rates greatly exceeded rates of abiotic photoproduction, and other sources of H2O2, most likely biological production, were the dominant control on the H2O2 budget. Thus, H2O2 and its precursor superoxide () may play a greater role in biogeochemical processes, especially in the absence of light, than previously thought.