what are the causes and effects of ozone depletion?

Answer 1

Ozone depletion is caused by the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years.

Go to the link for more info. There's too much info just to copy and paste....There are health effects, environmental effects, et cetera, et cetera.
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Overview

Ozone is a molecule composed of three oxygen atoms, designated by the chemical symbol O3. Although ozone is found in small amounts at all altitudes in the atmosphere, due to chemical, dynamical, and radiative processes it is not evenly distributed. Approximately 90 percent of all ozone is contained in the region of the atmosphere known as the stratosphere, which lies between 15 and 50 km above the Earth's surface. The region below the stratosphere where our weather takes place is known as the troposphere. The diagram "Vertical Temperature Structure of the Earth's Atmosphere" shows the different layers of the atmosphere and indicates that these layers are defined by whether the temperature is increasing or decreasing with height. The region of the stratosphere that contains higher concentrations of ozone is generally referred to as the ozone layer.
The history of ozone layer research dates back to 1930, when the first theory of how the ozone layer is formed was presented. Kowalok (1993) gives a brief synopsis of important discoveries and events leading to an understanding of stratospheric ozone and the discovery of destructive capabilities of chlorofluorocarbons (CFCs) on ozone in his paper "Common Threads: Research Lessons from Acid Rain, Ozone Depletion, and Global Warming."

Despite its low concentration, ozone plays a critical role in chemical and biological processes by filtering ultraviolet radiation in the 220-320 nm wavelength range (1 nm = 10[-9]m). The region of concern for biological effects is the ultraviolet-B (UV-B) range from 280 to 320 nm. The effectiveness of ozone absorption decreases exponentially as the wavelength of radiation increases. All radiation consisting of wavelengths shorter than 280 nm is absorbed in the upper atmosphere; wavelengths longer than 320 nm are not significantly absorbed by ozone. Therefore, biological systems are vulnerable to wavelengths in the transitional region of 280 to 320 nm due to ozone losses. Lower ozone amounts result in greater amounts of UV-B reaching the surface, which can lead to damaging effects on humans, plants, and animals. Thus, ozone located in the stratosphere is crucial to life on Earth, but ironically, ozone found at the surface of the Earth can be harmful to humans, plants, and animals. For example, high ozone amounts at ground level are known to cause respiratory problems in humans and can lower yields of certain crops. The location of ozone defines whether ozone is beneficial or harmful to humans and the environment.

Natural variations in ozone do occur, but recent levels of ozone loss over the poles and lower latitudes cannot be explained by natural variability alone. Manmade CFC compounds were developed in the early 1930s for a variety of industrial and commercial applications, but it was not until the 1970s that these and other chlorine-containing substances were suspected of having the potential to destroy atmospheric ozone. In 1985 a team of British researchers first reported unusually low ozone levels over Halley Bay, Antarctica, which were caused by chemical reactions with chlorine and nitrogen compounds. Research was initiated that found CFCs to be largely responsible for the anomalously low levels during the polar springtime. This polar ozone depletion at lower stratospheric altitudes is what has been termed the "ozone hole." For example, the "Time Progression of Springtime Ozone Depletion" over the South Pole in 1993 is shown in a diagram provided by D. J. Hofmann of the Climate Monitoring and Diagnostics Laboratory of the National Oceanic and Atmospheric Administration (1994).

The primary concern over ozone depletion is the potential impacts on human health and ecosystems due to increased UV exposure. Increases in skin cancer and cataracts in human populations are expected in a higher UV environment. Lower yields of certain cash crops may result due to increased UV-B stress. Higher UV-B levels in the upper ocean layer may inhibit phytoplankton activities, which can impact the entire marine ecosystem. In addition to direct biological consequences, indirect effects may arise through changes in atmospheric chemistry. Increased UV-B will alter photochemical reaction rates in the lower atmosphere that are important in the production of surface layer ozone and urban smog.

Concern over these potential effects has prompted the international community to enact policies aimed at reducing the production of ozone-depleting chemicals. An important event in the history of international ozone policy was the Montreal Protocol on Substances That Deplete the Ozone Layer (1987), which called for the phaseout and reduction of certain substances over a multiyear time frame. Discoveries of more extensive ozone loss and rapid formulation of replacement substances for chlorine-containing compounds have led to refinements of the original Protocol. Updates set forth at London (1990) and Copenhagen (1992) have called for accelerated phaseout and replacement schedules

Answer 2

The actual cause of ozone depletion rather controversial. There is a major problem with the explanation of chlorofluorocarbons (CFCs) as the cause of ozone depletion. The most pronounced depletion of the ozone layer is over the south pole. However, the vast majority of CFC's are used and released in the northern hemisphere. So, if they were the cause of depletion, then it should be most pronounced at the north pole not the south pole. I have yet to hear and explanation for this fact that I find credible.

Another thing to keep in mind is that ozone is both created and destroyed by sunlight. The thinning of the ozone layer occurs during the winter when there is no sunlight in the polar regions to create new ozone. When the sun comes back in the spring, ozone levels in these regions return to normal.

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Answer 3

The thinning of the ozone layer allows more UV rays from the sun get to the Earth. The ozone layer blocks most of the UV. UV rays can cause skin Cancer to those of us that work or play out side. The ozone 'holes' hover over the north and the south of Earth. If the ozone layer is thinned too much the UV rays might begin to harm plant life. Please note that ozone depletion has nothing to do with Global Warming.

Answer 4

Many think that CFC destroy the ozone over the poles at certain times of the year. They want u to believe that the CFC stroll around the earth but at a particular time they make a mad dash for the poles. The solar winds and the ionized particles are attracted to the poles and as the angle of the earth gets right at the same time each year. the solar wind particles blow a hole in the ozone layer over the poles. The Beta particles blow a hole at the north pole. The alfa particles are attracted to the south pole .

Answer 5

The term ozone depletion is used to describe two distinct but related observations: a slow, steady decline, of about 3% per decade, in the total amount of ozone in the earth's stratosphere during the past twenty years and a much larger, but seasonal, decrease in stratospheric ozone over the earth's polar regions during the same period. (The latter phenomenon is commonly referred to as the "ozone hole".) The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the proximate cause of both trends is believed to be catalytic destruction of ozone by atomic chlorine and bromine. The primary source of these halogen atoms in the stratosphere is photodissociation of Chlorofluorocarbon (CFC) compounds, commonly called freons, and bromofluorocarbon compounds known as Halons, which are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and Halons increased. CFCs, Halons and other contributary substances are commonly referred to as "ODS", or "Ozone Depleting Substances." Since the ozone layer prevents most harmful UVB wavelengths (270–315 nm) of ultraviolet light from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol banning the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride and trichloroethane (also known as methyl chloroform). It is suspected that a variety of biological consequences, including, for example, increases skin cancer, damage to plants, and reduction of plankton populations in the ocean's photic zone, may result from the increased UV exposure due to ozone depletion.

Ozone cycle overview
Ozone creation
Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: Oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing an ultraviolet photon whose wavelength is shorter than 240 nm. This produces two oxygen atoms. The atomic oxygen then combines with O2 to create O3. Ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process which terminates when an oxygen atom "recombines" with an ozone molecule to make 2 O2 molecules. It is theorized that prior to the beginning of the depletion trend, the amount of ozone in the stratosphere was kept roughly constant by a balance between the rates of creation and destruction of ozone molecules by UV light.

Ozone destruction
Chemical factors
Ozone can be destroyed by a number of free radical catalysts, the most important of which are the hydroxyl radical (OH·), the nitric oxide radical (NO·) and atomic chlorine (Cl·) and bromine (Br·). All of these have both natural and anthropogenic (manmade) sources; at the present time, most of the OH· and NO· in the stratosphere is of natural origin, but human activity has dramatically increased the chlorine and bromine. These elements are found in certain stable organic compounds, especially chlorofluorocarbons (CFCs), which may find their way to the stratosphere without being destroyed in the troposphere. Once in the stratosphere, the Cl and Br atoms are liberated from the parent compounds by the action of ultraviolet light, and can destroy ozone molecules in a catalytic cycle. In this cycle, a chlorine atom reacts with an ozone molecule, taking an oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. A free oxygen atom then takes away the oxygen from the ClO, and the final result is an oxygen molecule and a chlorine atom, which then reinitiates the cycle. The chemical shorthand for these reactions are:

Cl + O3 → ClO + O2

ClO + O → Cl + O2

In sum O3 + O → O2 + O2

For this mechanism to operate there must be a source of O atoms, which is primarily the photodissociation of O3.

A single chlorine atom would keep on destroying ozone for up to two years (the time scale for transport back down to the troposphere) were it not for reactions that remove them from this cycle by forming reservoir species such as hydrochloric acid (HCl) and chlorine nitrate (ClONO2. On a per atom basis, bromine is even more efficient than chlorine at destroying ozone, but there is much less bromine in the atmosphere at present. As a result, both chlorine and bromine contribute significantly to the overall ozone depletion.

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