OZONE LAYER (Current environmental issue)
Ozone layer, also called ozonosphere, region of the upper atmosphere, between roughly 15 and 35 km (9 and 22 miles) above Earth's surface, containing relatively high concentrations of ozone molecules (O3). It is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. The stratosphere layer contains most of the ozone found in Earth’s atmosphere, and the presence of ozone is the reason for the temperature profile found in the stratosphere. Ozone and oxygen gas both absorb short wave solar radiation of wavelengths less than 290 nano-meters from reaching Earth’s surface, including certain types of ultraviolet (UV) and other forms of radiation that could injure or kill most living things. In the series of reactions that follow, heat is released.
This heat warms the atmosphere in the layer at about 12–27 mi (20–45 km) and gives the stratosphere its characteristic temperature increase with height.
Ozone creation and destruction:
The production of ozone in the stratosphere results primarily from the breaking of the chemical bonds within oxygen molecules (O2) by high-energy solar photons. This process, called photo dissociation, results in the release of single oxygen atoms, which later join with intact oxygen molecules to form ozone. Rising atmospheric oxygen concentrations some two billion years ago allowed ozone to build up in Earth’s atmosphere, a process that gradually led to the formation of the stratosphere. Scientists believe that the formation of the ozone layer played an important role in the development of life on Earth by screening out lethal levels of UVB radiation (ultraviolet radiation with wavelengths between 315 and 280 nano-meters) and thus facilitating the migration of life-forms from the oceans to land.
The amount of ozone in the stratosphere varies naturally throughout the year as a result of chemical processes that create and destroy ozone molecules and as a result of winds and other transport processes that move ozone molecules around the planet. Over the course of several decades, however, human activities substantially altered the ozone layer.
Ozone depletion:
Ozone depletion the global decrease in stratospheric ozone observed since the 1970s, is most pronounced in polar regions, and it is well correlated with the increase of chlorine and bromine in the stratosphere. Those chemicals, once freed by UV radiations from the chlorofluorocarbons (CFC's) and other halo-carbons (carbon-halogen compounds) that contain them, destroy ozone by stripping away single oxygen atoms from ozone molecules. Depletion is so extensive that so-called ozone holes (regions of severely reduced ozone coverage) form over the poles during the onset of
their respective spring seasons. The largest such hole—which has spanned more than 20.7 million square km (8 million square miles) on a consistent basis since 1992—appears annually over Antarctica between September and November.
Causes of Ozone depletion:
Another major cause of large scale ozone depletion is Rocket launches. It has been studied that unregulated rocket launches can result in much more ozone depletion than CFC's. It is estimated that if rocket launches will be let unregulated then it would cause huge ozone loss by the year 2050 than the CFC's have done.
Global warming also leads to ozone layer depletion. Due to global warming and greenhouse effect most of the heat is trapped in troposphere which is the layer below the stratosphere. As we all know ozone is present in stratosphere so heat don’t reaches troposphere and it remain cold as recovery of ozone layer requires maximum sunlight and heat so it leads to depletion of ozone layer.
Effects on Ozone Depletion:
As ozone depletes in the stratosphere, it forms a 'hole' in the layer. This hole enables harmful ultraviolet rays to enter the Earth's atmosphere. Ultraviolet rays of the Sun are associated with a number of health-related, and environmental issues.
Ozone depletion is listed as one of the causes for the declining numbers of amphibian species. Ozone depletion affects many species at every stage of their life cycle. Some of the effects are mentioned below.
UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians, and other marine animals. The most severe effects are decreased reproductive capacity and impaired larval development. Small increases in UVB exposure could result in population reductions for small marine organisms with implications for the whole marine food chain.
Solutions to Ozone Depletion:
