Availability of a newly developed technique for measuring subnanomolar superoxide (O2-) using chemiluminescence detection will allow a researcher at the Colorado School of Mines to conduct superoxide decay experiments at very low micromolar levels, thus allowing, for the first time, accurate measurements of the slower superoxide decay rates expected in open ocean waters and of the rate constants of superoxide reactions with nanomolar concentrations of seawater constituents. Specifically, the scientist will address the following five objectives: (1) carry out direct observations of the kinetics of superoxide decay in unaltered seawater samples; (2) if the lifetime of superoxide is long enough, conduct direct measurement of steady state superoxide concentrations in sunlit seawater; (3) test the hypothesis that superoxide decay proceeds via catalytic redox cycles of seawater constituents; (4) test the hypothesis that the rates of catalytic decay are primarily determined by the water's concentration of weakly complexed copper and chromophoric dissolved organic matter; and (5) measure rate constants important to superoxide decay rates and biogeochemical effects, especially those for iron species.
As regards broader impacts, this study will not only improve our ability to predict superoxide in sunlit marine waters, but also allow us to better assess the role of this radical in iron biogeochemistry, as well as in other important marine redox processes. In addition, one post-doc, one graduate student, and one undergraduate student will be supported and trained as part of this project.
