Hydrogen peroxide (H₂O₂) is an important reactive oxygen species (ROS) in seawater, affecting water quality via participation in metal redox reactions and causing oxidative stress in marine ecosystems. While attempts have been made to better understand H₂O₂ dynamics in seawater, the relative importance of various H₂O₂ sources and losses remains uncertain. We developed a model to estimate photochemical H₂O₂ production rates using remotely sensed ocean color to characterize the ultraviolet (UV) radiation field in surface waters along with published apparent quantum yield (AQY) data for the photochemical formation of H₂O₂. Model inputs included temperature- and wavelength-dependent AQY, modeled solar irradiance, satellite-derived surface seawater temperature and UV optical properties; diffuse attenuation coefficients and dissolved organic matter absorption coefficients were estimated with remote sensing-based algorithms. The final model product, a monthly climatology of depth-resolved H₂O₂ photoproduction rates in the surface mixed layer, yields an integrated global estimate of ~21.1 Tmol yr^-1 for photochemical H₂O₂ production. To evaluate our predictions of H₂O₂ photoproduction in surface waters, we compared modeled rates to measured rates from several stations in the NW Atlantic; comparative differences of 33% or less. This work has important implications for photo-redox reactions in seawater and improves our understanding of the role of solar irradiation on ROS cycling and the overall oxidation state in the oceans.

Primary Presenter: David Kieber, State University of New York, College of Environmental Science and Forestry (djkieber@esf.edu)

Authors:

Yuting Zhu, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA  (yuting.zhu@whoi.edu)

Leanne Powers, Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, NY, USA  (lcpowers@esf.edu)

David Kieber, Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, NY, USA  (djkieber@esf.edu)

William Miller, Department of Marine Sciences, University of Georgia, Athens, GA, USA  (bmiller@uga.edu)