title: Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans.
abstract: Hydrogen peroxide (H2O2) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H2O2source, yet cannot explain nanomolar H2O2concentrations below the photic zone. Here, we determined the concentration of H2O2in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H2O2measurements in the deep ocean we also re-assessed the contribution of interfering species to 'apparent H2O2', as analysed by the luminol based chemiluminescence technique. Within the vicinity of coastal oxygen minimum zones, accurate measurement of H2O2was not possible due to interference from Fe(II). Offshore, in deep (>1000 m) waters H2O2concentrations ranged from 0.25 ± 0.27 nM (Mediterranean, Balearics-Algeria) to 2.9 ± 2.2 nM (Mediterranean, Corsica-France). Our results indicate that a dark, pelagic H2O2production mechanism must occur throughout the deep ocean. A bacterial source of H2O2is the most likely origin and we show that this source is likely sufficient to account for all of the observed H2O2in the deep ocean.
authors.affiliation: Chemical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hopwood
authors.affiliation: Chemical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany.
authors.forename: Insa
authors.initials: I
authors.lastname: Rapp
authors.affiliation: Chemical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schlosser
authors.affiliation: Chemical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany.
authors.forename: Eric P
authors.initials: EP
authors.lastname: Achterberg