Superoxide radical reactions in the ocean

使用化学发光检测技术测量亚纳摩尔超氧化物(O2-)的新技术的可用性将使科罗拉多矿业学院的一名研究人员能够在非常低的微摩尔水平上进行超氧化物衰变实验，从而首次能够准确测量公开海洋中预期的较慢的超氧化物衰变速率，以及超氧化物与海水成分纳摩尔浓度的反应速率常数。具体而言，这位科学家将涉及以下五个目标：(1)对未改变的海水样品中超氧化物歧化的动力学进行直接观察；(2)如果超氧化物的寿命足够长，则直接测量有阳光照射的海水中超氧化物歧化的稳态浓度；(3)检验关于超氧化物衰变是通过海水成分的催化氧化还原循环进行的假说；(4)检验有关催化衰变速率主要由水中弱络合铜和有色溶解有机物的浓度决定的假说；(5)测量对超氧化物衰变速率和生物地球化学效应，特别是对铁物种的影响非常重要的速率常数。至于更广泛的影响，这项研究不仅将提高我们预测阳光充足的海洋水域中超氧化物的能力，而且还使我们能够更好地评估这种自由基在铁生物地球化学以及其他重要的海洋氧化还原过程中的作用。此外，作为该项目的一部分，一名博士后、一名研究生和一名本科生将得到支持和培训。

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.