Biotic effects on oxygen consumption during weathering: Implications for the second rise of oxygen

Yoshiki Kanzaki, Lee Kump

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The oxygen concentration of the atmosphere likely increased substantially in the late Neoproterozoic. Although several studies have presented compelling geochemical evidence for this stepwise oxygenation, few have addressed the mechanisms behind it. Recently it was hypothesized that the advent of eukaryotic life on land, and the associated increase in soil respiration, led to a transient reduction in the supply of oxygen for rock weathering, temporarily reducing oxidative weathering rates, allowing atmospheric oxygen levels to rise to restore the oxygen supply. To evaluate this hypothesis quantitatively, we developed a simple one-dimensional diffusion-reaction soil model that reduces the many oxygen weathering sinks to one, pyrite, given that it is the dominant sink at low oxygen concentrations. In simulations with no biological respiration, pyrite weathering rates become oxygen independent at an atmospheric oxygen concentration between 10-6× the present-day atmospheric level (PAL) and 1 PAL. On the other hand, when biological respiration is considered, pyrite weathering remains oxygen dependent even at modern oxygen levels. Constrained by modern weathering profiles and soil respiration rates, we find that the atmospheric oxygen level may have increased by up to two orders of magnitude as biotic soil respiration increased. This may be sufficient to explain the second rise in atmospheric oxygen inferred for the Neoproterozoic.

Original languageEnglish (US)
Pages (from-to)611-614
Number of pages4
JournalGeology
Volume45
Issue number7
DOIs
StatePublished - Jul 1 2017

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oxygen consumption
weathering
oxygen
soil respiration
pyrite
weathering rate
effect
respiration
weathering profile
oxygenation

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

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title = "Biotic effects on oxygen consumption during weathering: Implications for the second rise of oxygen",
abstract = "The oxygen concentration of the atmosphere likely increased substantially in the late Neoproterozoic. Although several studies have presented compelling geochemical evidence for this stepwise oxygenation, few have addressed the mechanisms behind it. Recently it was hypothesized that the advent of eukaryotic life on land, and the associated increase in soil respiration, led to a transient reduction in the supply of oxygen for rock weathering, temporarily reducing oxidative weathering rates, allowing atmospheric oxygen levels to rise to restore the oxygen supply. To evaluate this hypothesis quantitatively, we developed a simple one-dimensional diffusion-reaction soil model that reduces the many oxygen weathering sinks to one, pyrite, given that it is the dominant sink at low oxygen concentrations. In simulations with no biological respiration, pyrite weathering rates become oxygen independent at an atmospheric oxygen concentration between 10-6× the present-day atmospheric level (PAL) and 1 PAL. On the other hand, when biological respiration is considered, pyrite weathering remains oxygen dependent even at modern oxygen levels. Constrained by modern weathering profiles and soil respiration rates, we find that the atmospheric oxygen level may have increased by up to two orders of magnitude as biotic soil respiration increased. This may be sufficient to explain the second rise in atmospheric oxygen inferred for the Neoproterozoic.",
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Biotic effects on oxygen consumption during weathering : Implications for the second rise of oxygen. / Kanzaki, Yoshiki; Kump, Lee.

In: Geology, Vol. 45, No. 7, 01.07.2017, p. 611-614.

Research output: Contribution to journalArticle

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