Ozone Depletion Research Today is a free monthly online journal that collates and summarizes the latest research about Ozone Depletion, including details on hole in the ozone layer, causes, effects. | ||||||
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Astrophysical Ionizing Radiation and Earth: A Brief Review and Census of Intermittent Intense Sources.Melott AL, Thomas BC 1 Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas. Abstract Cosmic radiation backgrounds are a constraint on life, and their distribution will affect the Galactic Habitable Zone. Life on Earth has developed in the context of these backgrounds, and characterizing event rates will elaborate the important influences. This in turn can be a base for comparison with other potential life-bearing planets. In this review, we estimate the intensities and rates of occurrence of many kinds of strong radiation bursts by astrophysical entities, ranging from gamma-ray bursts at cosmological distances to the Sun itself. Many of these present potential hazards to the biosphere; on timescales long compared with human history, the probability of an event intense enough to disrupt life on the land surface or in the oceans becomes large. Both photons (e.g., X-rays) and high-energy protons and other nuclei (often called "cosmic rays") constitute hazards. For either species, one of the mechanisms that comes into play even at moderate intensities is the ionization of Earth's atmosphere, which leads through chemical changes (specifically, depletion of stratospheric ozone) to increased ultraviolet B flux from the Sun reaching the surface. UVB is extremely hazardous to most life due to its strong absorption by the genetic material DNA and subsequent breaking of chemical bonds. This often leads to mutation or cell death. It is easily lethal to the microorganisms that lie at the base of the food chain in the ocean. We enumerate the known sources of radiation and characterize their intensities at Earth and rates or upper limits on these quantities. When possible, we estimate a "lethal interval," our best estimate of how often a major extinction-level event is probable given the current state of knowledge; we base these estimates on computed or expected depletion of stratospheric ozone. In general, moderate-level events are dominated by the Sun, but the far more severe infrequent events are probably dominated by gamma-ray bursts and supernovae. We note for the first time that so-called "short-hard" gamma-ray bursts are a substantial threat, comparable in magnitude to supernovae and greater than that of the higher-luminosity long bursts considered in most past work. Given their precursors, short bursts may come with little or no warning. Key Words: Radiation-Gamma-ray burst-Supernova-Solar flare-Ozone depletion-Extinction-Cosmic ray-X-ray. Astrobiology 11, xxx-xxx. Published 6 May 2011 in Astrobiology. Articles on Ozone Depletion published 5 May 2011: Evaluating industrial symbiosis and algae cultivation from a life cycle perspective. Bioresour Technol. A comparative life cycle assessment (LCA) was conducted on 20 scenarios of microalgae cultivation. These scenarios examined the utilization of nutrients and CO(2) from synthetic sources and waste streams as well as the materials used to construct a photobioreactor (PBR). A 0.2-m(3) closed PBR of Chlorella vulgaris at 30%-oil content by weight with the productivity of 25g/m(2)×day was used as a case study. Results of the study show that the utilization of resources from waste streams mainly ... [Abstract] [Full-text] Articles on Ozone Depletion published 4 May 2011: Does simultaneous UV-B exposure enhance the lethal and sub-lethal effects of aquatic hypoxia on developing anuran embryos and larvae? J Comp Physiol B. Recent catastrophic global amphibian declines have been partially linked to increases in UV-B radiation as a consequence of stratospheric ozone depletion. Previous studies have shown that in the presence of other environmental stressors including aquatic pH and temperature and the presence of contaminants or pathogens, the lethal effects of UV-B on amphibian larvae are enhanced due to interactions between the stressors. Little is known about the interactions between UV-B and aquatic hypoxia, a ... [Abstract] [Full-text] Articles on Ozone Depletion published 3 May 2011: UV Photolysis of ClOOCl and the Ozone Hole. Chem Asian J. The photochemistry of the ClO dimer (ClOOCl) plays a central role in the catalytic destruction of polar stratospheric ozone. In spite of decades of intense investigations, some of its laboratory photochemical data had not reached the desired accuracy to allow a reliable simulation of the stratospheric ozone loss until recently. Inevitable impurities in ClOOCl samples have obstructed conventional measurements. In particular, an absorption measurement of ClOOCl in 2007, which gave much lower ... [Abstract] [Full-text] Comparison of Fe(VI) (FeO(4)(2-)) and ozone in inactivating Bacillus subtilis spores. Chemosphere, 83(9): 1228-33. The protozoan parasites such as Cryptosporidiumparvum and Giardialamblia have been recognized as a frequent cause of recent waterborne disease outbreaks because of their strong resistance against chlorine disinfection. In this study, ozone and Fe(VI) (i.e., FeO(4)(2-)) were compared in terms of inactivation efficiency for Bacillus subtilis spores which are commonly utilized as an indicator of protozoan pathogens. Both oxidants highly depended on water pH and temperature in the spore ... [Abstract] [Full-text] Articles on Ozone Depletion published 26 April 2011: Ambipolar and Unipolar PbSe Nanowire Field-Effect Transistors. ACS Nano, 5(4): 3230-6. Wet-chemical methods, under rigorous air-free conditions, were used to synthesize single-crystalline 10 nm diameter PbSe nanowires (NWs), and electric-field, directed assembly was employed to align NW arrays to form the semiconducting channels of field-effect transistors (FETs). Electrical measurements revealed as-aligned NWs in bottom, gold, contact FETs are predominantly p-type ambipolar, consistent with the presentation of small barriers to electron and hole injection for this low band gap ... [Abstract] [Full-text] Articles on Ozone Depletion published 22 April 2011: Impact of Polar Ozone Depletion on Subtropical Precipitation. Science. Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the Southern subtropics in austral summer increases significantly when climate models are integrated with reduced polar ozone concentrations. Furthermore, the ... [Abstract] [Full-text] Growth of soybean at future tropospheric ozone concentrations decreases canopy evapotranspiration and soil water depletion. Environ Pollut, 159(6): 1464-1472. Tropospheric ozone is increasing in many agricultural regions resulting in decreased stomatal conductance and overall biomass of sensitive crop species. These physiological effects of ozone forecast changes in evapotranspiration and thus in the terrestrial hydrological cycle, particularly in intercontinental interiors. Soybean plots were fumigated with ozone to achieve concentrations above ambient levels over five growing seasons in open-air field conditions. Mean season increases in ozone ... [Abstract] [Full-text] Impact of Polar Ozone Depletion on Subtropical Precipitation. Science. Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the Southern subtropics in austral summer increases significantly when climate models are integrated with reduced polar ozone concentrations. Furthermore, the ... [Abstract] [Full-text] © 2004-2011 Ozone Depletion Research Today. All Rights Reserved. |
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