Romaniello Stephen J.

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Last Name
Romaniello
First Name
Stephen J.
ORCID
0000-0003-1582-6801

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  • Article
    Reconciling evidence of oxidative weathering and atmospheric anoxia on Archean Earth
    (American Association for the Advancement of Science, 2021-09-29) Johnson, Aleisha C. ; Ostrander, Chadlin M. ; Romaniello, Stephen J. ; Reinhard, Christopher T. ; Greaney, Allison T. ; Lyons, Timothy W. ; Anbar, Ariel D.
    Evidence continues to emerge for the production and low-level accumulation of molecular oxygen (O2) at Earth’s surface before the Great Oxidation Event. Quantifying this early O2 has proven difficult. Here, we use the distribution and isotopic composition of molybdenum in the ancient sedimentary record to quantify Archean Mo cycling, which allows us to calculate lower limits for atmospheric O2 partial pressures (PO2) and O2 production fluxes during the Archean. We consider two end-member scenarios. First, if O2 was evenly distributed throughout the atmosphere, then PO2 > 10–6.9 present atmospheric level was required for large periods of time during the Archean eon. Alternatively, if O2 accumulation was instead spatially restricted (e.g., occurring only near the sites of O2 production), then O2 production fluxes >0.01 Tmol O2/year were required. Archean O2 levels were vanishingly low according to our calculations but substantially above those predicted for an abiotic Earth system.
  • Article
    Up in smoke: most aerosolized Fe from biomass burning does not derive from foliage
    (American Geophysical Union, 2023-08-25) Tegler, Logan A. ; Sherry, Alyssa M. ; Herckes, Pierre ; Romaniello, Stephen J. ; Anbar, Ariel D.
    Iron (Fe) is a limiting micronutrient in many marine ecosystems. The lack of sufficient Fe can stunt marine productivity and limit carbon sequestration from the atmosphere to the ocean. Recent studies suggest that biomass burning represents an important Fe source to the marine environment because pyrogenic particles have enhanced solubility after atmospheric processing. We examined foliage representative of four distinct biomes subject to frequent burning events, including boreal/temporal forests, humid tropical, arid tropical, and grassland. We burned these samples in the absence of soil to isolate the Fe from the fine particle (PM2.5) fraction that is derived directly from the burning foliage. We find that <1.5% of the Fe in plant matter is aerosolized throughout the burn in the fine fraction. We estimate that between 2% and 9% of the Fe released from biomass burning can be attributed to the fine fraction of the foliage itself, and <50% from the foliage overall. Most of the Fe aerosolized during biomass burning is accounted for by soil-suspended particles.