Investigation of Hydrogen Peroxide Chemistry in Surface Waters of Vineyard Soundwith H2(18)O2 and (18)O2

摘要

O-labeled hydrogen peroxide and O2 have been used determine absolute rates andpathways of peroxide formation and decay processes in surface waters of a coastal marine site. Reactions were followed by incubating seawater samples with O2 or H2O2 and following the chemical transformation of the isotope label. Decomposition of H2O2 was dominated by biological processes and led to the formation of O2 and H2O; the product distribution indicates that 65-80% of the decay was due to catalase with 20-35% due to peroxidase activity. Photochemical oxidation of H2O2 to O2 was also observed. Particle-dependent, light-independent peroxide production was also observed in freshly collected samples, with rates ranging from 0.8 to 2.4 nM h-1. These rates are low relative to photochemical production rates in surface waters, but may be important under conditions of low light intensity. Experiments with a metabolic inhibitor suggest that at least some of this production was biologically mediated. However, there was no evidence for light-dependent biological production.