Leanne C. Powers

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Hydrogen peroxide (H₂O₂) and its precursor, superoxide (O₂(-)), are well-studied photochemical products that are pivotal in regulating redox transformations of trace metals and organic matter in the surface ocean. In attempts to understand the magnitude of both H₂O₂ and O₂(-) photoproduction on a global scale, we implemented a model to calculate(More)
The composition and photochemical transformations of dissolved organic matter (DOM) in the northern North Pacific Ocean were investigated at the molecular level using ultrahigh resolution mass spectrometry and geochemical tracers. Analyses included vertical profiles and experiments in which deep sea DOM was exposed to sunlight and incubated in the dark. The(More)
Marine Thaumarchaeota were discovered over 20 years ago and although a few isolates from this group are now available for study, we do not yet understand the environmental controls on their growth and distribution. Thaumarchaeotes oxidize ammonia to nitrite, mediating a key step in the global nitrogen cycle, and it is estimated that about 20% of all(More)
Superoxide (O) is a key intermediate in the cycling of organic matter and trace 2 metals in natural waters but production rates are difficult to determine due to low steady-state concentrations, rapid decay rates, and unstable standards. On the other hand, superoxide’s dismutation product, hydrogen peroxide (H2O2), is relatively stable in filtered water.(More)
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