Ultraviolet radiation ozone depletion

J.J. Cullen, P.J. Neale (1994). Ultraviolet radiation, ozone depletion, and marine photosynthesis. Photosyn. Res., 39, 303-320. 

Measurements of ozone (O3) concentrations in the atmosphere are of particular importance. Ozone absorbs strongly in the ultraviolet region and it is this absorption which protects us from a dangerously high dose of ultraviolet radiation from the sun. The vitally important ozone layer lies in the stratosphere and is typically about 10 km thick with a maximum concentration about 25 km above the surface of the earth. Extreme depletion of ozone in a localised part of the atmosphere creates what is known as an ozone hole. 

The other global environmental problem, stratospheric ozone depletion, was less controversial and more imminent. The U.S. Senate Committee Report supporting the Clean Air Act Amendments of 1990 states, Destruction of the ozone layer is caused primarily by the release into the atmosphere of chlorofluorocarbons (CFCs) and similar manufactured substances—persistent chemicals that rise into the stratosphere where they catalyze the destruction of stratospheric ozone. A decrease in stratospheric ozone will allow more ultraviolet (UV) radiation to reach Earth, resulting in increased rates of disease in humans, including increased incidence of skin cancer, cataracts, and, potentially, suppression of the immune system. Increased UV radiation has also been shown to damage crops and marine resources."... 

An important effect of air pollution on the atmosphere is change in spectral transmission. The spectral regions of greatest concern are the ultraviolet and the visible. Changes in ultraviolet radiation have demonstrable adverse effects e.g., a decrease in the stratospheric ozone layer permits harmful UV radiation to penetrate to the surface of the earth. Excessive exposure to UV radiation results in increases in skin cancer and cataracts. The worldwide effort to reduce the release of stratospheric ozone-depleting chemicals such as chlorofluorocarbons is directed toward reducing this increased risk of skin cancer and cataracts for future generations. 

Effect of UV on Productivity of the Southern Ocean. Has ozone depletion over Antarctica affected the productivity of the Southern Ocean There is no easy answer. First, one has to take into account the fact that the drastic decrease of ozone over Antarctica has been reported as recently as 1976, a relatively short time in the evolution of the organisms to develop mechanisms to cope with elevated UV. One of the most vexing problems in studying the effects of UV radiation on productivity, is a dearth of historical data on the level of UV. Without these baselines, normal fluctuations could easily be interpreted as decline in productivity. Second, there is a host of biotic and abiotic factors that play significant roles in governing the productivity of the Southern Ocean (40). Ultraviolet radiation is but one more complicating factor to be considered in an already stressful environment. 

Recently, there have also been some concerns over possible problems related to hydrogen gas leakage as the molecular hydrogen leaks from most containment vessels. It has been hypothesized that if significant amounts of H2 escape to stratosphere, FT free radicals can be formed due to ultraviolet radiation, which in turn can enhance the ozone depletion. However, the effect of these leakage problems may not be significant as the amount of hydrogen that leaks presently is much lower (by a factor of 10-100) than the hypothesized 10-20%. 

Laturnus F, Svensson T, Wiencke C, Oberg G (2004) Ultraviolet radiation affects emission of ozone-depleting substances by marine macroalgae results from a laboratory incubation study. Environ Sci Technol 38 6605-6609... 

Smith RC, Prezelin BB, Baker KS, Bidigare RR, Boucher NP, Coley T, Karentz D, MacIntyre S, Matlick HA, Menzies D, Ondrusek M, Wan Z, Waters KJ (1992) Ozone depletion ultraviolet radiation and phytoplankton biology in Antarctic waters. Science 255 952-959 Sommaruga R, Psenner R (1997) Ultraviolet radiation in a high mountain lake of the Austrian Alps air and underwater measurements. Photochem Photobiol 65 957-963 Swanson AK, Druehl LD (2002) Induction, exudation and the UV protective role of kelp phlorotannins. Aquat Bot 73 241-253... 

Any increase in ultraviolet radiation will exacerbate the danger to herbivores. Ozone depletion by 25% leads to an increase of 50% in ultraviolet B over ambient levels (El-Sayed, 1988). Will livestock be drastically affected if levels rise more in the future Will animals be able to shift to nocturnal activity If not, will large portions of the vegetation be rendered useless for domestic stock and wild species or will animals have to be fed indoors Will humans be affected ... 

F. Sherwood Rowland (1927-) and Mario Molina (1943-) predicted the destruction of stratospheric ozone in 1974. Rowland and Molina theorized that inert CFCs could drift into the stratosphere, where they would be broken down by ultraviolet radiation. Once in the stratosphere, the CFCs would become a source of ozone-depleting chlorine. The destruction of ozone by CFCs can be represented by the following series of reactions ... 

It is clear from the data presented in this chapter that the effects of control strategies developed for CFCs and halons are already measurable. Although loss of stratospheric ozone with accompanying increases in ultraviolet radiation in some locations have clearly occurred, the tropospheric concentrations of CFCs are not increasing nearly as fast as in the past. Indeed, the concentrations of CFC-11 and CFC-113 appear to have peaked and have started to decline. The equivalent effective stratospheric chlorine concentrations are predicted to have peaked about 1997 and to return to levels found around 1980 at about the year 2050 (World Meteorological Organization, 1995). The significance of the 1980 level is that these levels resulted in detectable Antarctic ozone depletion. 

Kerr, J. B and C. T. McElroy, Evidence for Large Upward Trends of Ultraviolet-B Radiation Linked to Ozone Depletion, Science, 262, 1032-1034 (1993). 

Lubin, D and E. H. Jensen, Effects of Clouds and Stratospheric Ozone Depletion on Ultraviolet Radiation Trends, Nature, 377, 710-713 (1995). 

Measured total column ozone has fallen between about 1970 and 1994. Ultraviolet irradiation increases at the surface of the earth due to ozone depletion should peak at about 15% in midlatitudes. The incidence of harmful health effects of UV radiation can be expected to rise, eventually, at midlatitudes. Public health action is still necessary to reduce sun exposure, increase protection against the sun, and develop clear policies on the action that should be taken on early detection and treatment of skin cancers (Armstrong, 1997). 

The health risks associated with ozone depletion will principally be those due to increased ultraviolet-B (UV-B) radiation in the environment, that is, increased damage to the eyes, the immune system, and the skin. Some new risks may also be introduced with the increased use of alternatives to the ozone-depleting substances (ODSs). However, the data are insufficient to develop similar estimates for effects such as immunosuppression and the toxicity of alternatives. 

Booth C.R, and S. Madronich, Radiation amplification factors Improved formulation accounts for large increases in ultraviolet radiation associated with Antarctic ozone depletion, Antartcic Research Series, 62,39-42,1994. 

Kerr, J.B. and C.T. McElroy, Evidence for large upward trends of ultraviolet-B radiation linked to ozone depletion, Science, 262, 1032, 1993. 

Herman, J.R. and McKenzie, R.L. (1999) Ultraviolet radiation at the earth s surface, in WMO Scientific Assessment of Ozone Depletion 1998, Chapter 9. 

The significant depletion of ozone, near-global in extent, which has been observed in recent years has raised concern primarily because of its direct effect of allowing more harmful solar ultraviolet radiation to penetrate to the Earth s surface. However, through its effect on the atmospheric temperature structure, it is possible that the effects of ozone depletion could be far more wide-ranging. 

Chemical kinetics is a subject of crucial environmental and economic importance. In the upper atmosphere, for example, maintenance or depletion of the ozone layer, which protects us from the sun s harmful ultraviolet radiation, depends on the relative rates of reactions that produce and destroy O3 molecules. In the chemical industry, the profitability of the process for the synthesis of ammonia, which is used as a fertilizer, depends on the rate at which gaseous N2 and H2 can be converted to NH3. 

Chlorofluorocarbons (CFCs) are widely used in refrigeration and air conditioning, insulation, and plastic foams. Although nontoxic and nonflammable, they are believed to deplete the ozone layer in the atmosphere which shields the earth from the sun s ultraviolet radiation. While action to control the production and use of CFCs was still being debated, McDonalds s Corporation announced it would no longer use foam food containers produced with the aid of CFC in its fast food outlets. 

Hader, D. P, Effects of enhanced solar ultraviolet radiation on aquatic ecosystems, in UV-B Radiation and Ozone Depletion Effects on Humans, Animals, Plants, Microorganisms, and Materials, Tevini, M., Ed. Lewis Publishers, Boca Raton, FL, 1993, 155. 

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