The Great Oxidation

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Oxygen Content ◽  
Atmospheric Chemistry ◽  
Tipping Point ◽  
Earth’S Atmosphere ◽  
Great Oxidation Event ◽  
Earth's Atmosphere ◽  
Geologic Record

This chapter deals with the “great oxidation event” (GOE), which represents a quantum shift in the oxygen content of the atmosphere. It suggests that the GOE represents the evolution of cyanobacteria. According to the geologic record, the oxygen content of Earth's atmosphere increased dramatically around 2.3 billion years ago. Since cyanobacteria likely evolved much earlier, it does not appear that a well-oxygenated atmosphere is a necessary or immediate consequence of the activities of oxygen-producing organisms. Atmospheric chemistry is a slave to the dynamics of the mantle, as the interior and exterior of the planet are connected in a profound way. Indeed, it took half of Earth's history for the mantle to quiet to point where oxygen could accumulate. This, however, represented a watershed, a tipping point if you will, where the chemistry of Earth's surface was forever altered.

The Mechanisms of Reactions Influencing Atmospheric Ozone

2015 ◽  
Author(s):  
Jack G. Calvert ◽  
John J. Orlando ◽  
William R. Stockwell ◽  
Timothy J. Wallington
Keyword(s):  
Atmospheric Chemistry ◽  
Physical Structure ◽  
Lower Atmosphere ◽  
Atmospheric Ozone ◽  
Earth’S Atmosphere ◽  
Body Of Knowledge ◽  
Earth's Atmosphere ◽  
Essential Resource ◽  
Life On Earth ◽  
Mechanisms Of Reactions

Ozone, an important trace component, is critical to life on Earth and to atmospheric chemistry. The presence of ozone profoundly impacts the physical structure of the atmosphere and meteorology. Ozone is also an important photolytic source for HO radicals, the driving force for most of the chemistry that occurs in the lower atmosphere, is essential to shielding biota, and is the only molecule in the atmosphere that provides protection from UV radiation in the 250-300 nm region. However, recent concerns regarding environmental issues have inspired a need for a greater understanding of ozone, and the effects that it has on the Earth's atmosphere. The Mechanisms of Reactions Influencing Atmospheric Ozone provides an overview of the chemical processes associated with the formation and loss of ozone in the atmosphere, meeting the need for a greater body of knowledge regarding atmospheric chemistry. Renowned atmospheric researcher Jack Calvert and his coauthors discuss the various chemical and physical properties of the earth's atmosphere, the ways in which ozone is formed and destroyed, and the mechanisms of various ozone chemical reactions in the different spheres of the atmosphere. The volume is rich with valuable knowledge and useful descriptions, and will appeal to environmental scientists and engineers alike. A thorough analysis of the processes related to tropospheric ozone, The Mechanisms of Reactions Influencing Atmospheric Ozone is an essential resource for those hoping to combat the continuing and future environmental problems, particularly issues that require a deeper understanding of atmospheric chemistry.

Introduction

1999 ◽  
Author(s):  
Yuk L. Yung ◽  
William B. DeMore
Keyword(s):  
Solar System ◽  
Solar Radiation ◽  
Atmospheric Chemistry ◽  
Past History ◽  
Chemical Change ◽  
Visible Spectrum ◽  
Rate Of Change ◽  
The Sun ◽  
Earth’S Atmosphere ◽  
Earth's Atmosphere

It is usual in the study of planets to consider the Earth first, and then the other planets, so that we can better understand how and why the rest of the solar system is different from us. In this book the order of study will be reversed: we shall first try to understand the solar system, and then we will ask why Earth is unique. We adopt this unconventional approach for two reasons. First, Earth's atmosphere today is the end-point of an evolution that started about 4.6 billion years ago. The pristine materials have all been drastically altered. However, by examining other parts of the solar system that have evolved to a lesser degree, we may deduce what the early Earth might have been like. Second, Earth's atmosphere today is largely determined by the complex biosphere, whose evolution has been intimately coupled to that of the atmosphere. In other words, ours is the only atmosphere in the solar system that supports life, and it is in turn modified by life. Therefore, to appreciate the beauty and the intricacy of our planet, we must start with simpler objects without life. Chemical composition is intimately connected to evolution, which in turn is driven by chemical change. In this book we attempt to provide a coherent basis for understanding the planetary atmospheres, to identify the principal chemical cycles that control their present composition and past history. Figure 1.1 gives an illustration of the intellectual framework in which our field of study is embedded. The unifying theme that connects the planets in the solar system is "origin"; that is, all planets share a common origin about 4.6 billion years ago. The subsequent divergence in the solar system may be partly attributed to evolution, driven primarily by solar radiation. The bulk of solar radiation consists of photons in the visible spectrum with a mean blackbody radiation temperature of 5800 K. The part that is responsible for direct atmospheric chemistry is a tiny portion (less than 1% of the total flux) in the ultraviolet. In addition, the sun emits a steady stream of corpuscular particles, known as the solar wind. While the sun provides the principal source of energy for change, the time rate of change is crucial, and that is where chemical kinetics and chemical cycles play pivotal roles.

The Gaia Hypothesis - Fact or Fancy?

1989 ◽  
Vol 69 (4) ◽  
pp. 759-768
Author(s):  
J.C.A. Craik
Keyword(s):  
Oxygen Content ◽  
Thermodynamic Equilibrium ◽  
Large Scale ◽  
Present Value ◽  
Earth’S Atmosphere ◽  
Gaia Hypothesis ◽  
Earth's Atmosphere ◽  
Scale Properties ◽  
Living Organisms ◽  
Concentric Shell

Many large-scale properties of the biosphere are affected or determined by the activities of living organisms and are maintained at remarkably constant values over long periods. For example, the oxygen content of the atmosphere appears to have been maintained near its present value for hundreds of millions of years, despite the rapid flux of oxygen between production by plants and consumption by animals and decomposing microorganisms. (In this article, I shall use 'biosphere' to denote the whole of the concentric shell of the planet Earth which holds life, and 'biota' to mean all living organisms. Others have sometimes used 'biosphere' to mean the latter.) Lovelock was the first to show clearly how the composition of the Earth's atmosphere, unlike that of Mars or Venus, was held well away from thermodynamic equilibrium by the activities of living organisms (Lovelock, 1983). Other biospheric properties, such as temperature and oceanic pH and salinity, have similarly remained fairly constant despite the existence of large perturbing influences (Lovelock, 1979).

scholarly journals Did Bacterial Enzymes Cap the Oxygen in Early Earth’s Atmosphere?

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Sarah Derouin
Keyword(s):  
Bacterial Enzymes ◽  
Oxygen Levels ◽  
Earth’S Atmosphere ◽  
Great Oxidation Event ◽  
Earth's Atmosphere

A new theory suggests that nitrogenase from cyanobacteria could be the reason oxygen levels remained low after the Great Oxidation Event.

scholarly journals A revised lower estimate of ozone columns during Earth’s oxygenated history

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
G. J. Cooke ◽  
D. R. Marsh ◽  
C. Walsh ◽  
B. Black ◽  
J.-F. Lamarque
Keyword(s):  
Climate Model ◽  
Three Dimensional ◽  
Time Varying ◽  
Geological Evidence ◽  
Earth’S Atmosphere ◽  
Great Oxidation Event ◽  
Climate Simulations ◽  
Order Of Magnitude ◽  
History Of ◽  
Earth's Atmosphere

The history of molecular oxygen (O 2 ) in Earth’s atmosphere is still debated; however, geological evidence supports at least two major episodes where O 2 increased by an order of magnitude or more: the Great Oxidation Event (GOE) and the Neoproterozoic Oxidation Event. O 2 concentrations have likely fluctuated (between 10 −3 and 1.5 times the present atmospheric level) since the GOE ∼2.4 Gyr ago, resulting in a time-varying ozone (O 3 ) layer. Using a three-dimensional chemistry-climate model, we simulate changes in O 3 in Earth’s atmosphere since the GOE and consider the implications for surface habitability, and glaciation during the Mesoproterozoic. We find lower O 3 columns (reduced by up to 4.68 times for a given O 2 level) compared to previous work; hence, higher fluxes of biologically harmful UV radiation would have reached the surface. Reduced O 3 leads to enhanced tropospheric production of the hydroxyl radical (OH) which then substantially reduces the lifetime of methane (CH 4 ). We show that a CH 4 supported greenhouse effect during the Mesoproterozoic is highly unlikely. The reduced O 3 columns we simulate have important implications for astrobiological and terrestrial habitability, demonstrating the relevance of three-dimensional chemistry-climate simulations when assessing paleoclimates and the habitability of faraway worlds.

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