『Abstract
　We have conducted a series of laboratory studies to investigate the generation of ferrous iron and reactive oxygen species when solutions of seawater containing natural organic matter (NOM) and ferric iron are exposed to simulated sunlight. Total ferrous iron and hydrogen peroxide were measured at nanomolar concentrations with high temporal resolution using chemiluminescence-based methods. In all cases, ferrous iron concentrations rapidly peaked at several nanomoles per litre after a few minutes, and then declined over time, while hydrogen peroxide concentrations increased in a non-linear manner. Although concentrations of both species depended on the concentration of NOM, hydrogen peroxide concentrations were only minimally affected by the presence of iron. Increasing the NOM concentration while the total iron concentration was maintained constant led to an increase in the maximum ferrous iron concentrations, suggesting that superoxide-mediated reduction of iron may be a major pathway for ferrous iron formation. This was supported by measurements of superoxide production from irradiation of NOM in the absence of iron and kinetic calculations, as well as as experiment in which superoxide dismutase was added. Further analysis of the data suggested that dissolved oxygen and photo-produced hydrogen peroxide were the primary oxidants of the Fe(II) formed. Thus we propose that superoxide and ferrous iron may be intricately coupled in the system, and that their generation is determined by the supply of NOM available to harvest light and donate electrons.』

1. Introduction
2. Experimental section
　2.1. General
　2.2. Experimental apparatus and procedure
　2.3. Determination of ferrous iron, hydrogen peroxide and superoxide
　2.4. Ferrozine-trapping experiment
3. Results and discussion
　3.1. Photo-generation of ferrous iron and hydrogen peroxide by simulated sunlight
　3.2. Speciation of iron during irradiation
　3.3. Reduction of Fe(III) to Fe(II)
　3.4. Re-oxidation of Fe(II) to Fe(III)
　3.5. Production versus consumption of ferrous iron
4. Conclusions
Acknowledgments
Appendix A. Supplementary data
References

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