James W. Moffett1, Oliver C. Zajiriou1
1Chemistry Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
Tóm tắt
18O‐labeled H2O2 and O2 have been used to determine absolute rates and pathways of peroxide formation and decay processes in surface waters of a coastal marine site. Reactions were followed by incubating seawater samples with 18O2 or H218O2 and following the chemical transformation of the isotope label.Decomposition of H218O2 was dominated by biological processes and led to the formation of 18O2 and H218O; the product distribution indicates that 65–80% of the decay was due to catalase with 20–35% due to peroxidase activity. Photochemical oxidation of H218O2 to 18O2 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.