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Biogeochemical cycles -Carbon cycle -Greenhouse effect -Ozone layer -Ozone layer depletion -Characteristics of ozone layer -Effect on future C O N T E N T S

Biogeochemical Cycles:

The cyclic process by which exchange of matters of substances between non living environment and the living organisms occur is called biogeochemical cycle. The most well-known and important biogeochemical cycles, for example, include the carbon cycle, the nitrogen cycle, the oxygen cycle and the water cycle. As biogeochemical cycles describe the movements of substances on the entire globe, the study of these is inherently multidisciplinary .. Biogeochemical Cycles

Biogeochemical cycles:

Biogeochemical cycles Water cycle Nitrogen cycle

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Oxygen cycle Carbon cycle Biogeochemical cycle

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The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, hydrosphere and atmosphere of the Earth. It is one of the most important cycles of the earth and allows for carbon to be recycled and reused throughout the biosphere and all of its organisms. The carbon cycle was initially discovered by Joseph Priestley and Antoine Lavoisier, and popularized by Humphry Davy. It is now usually thought of as including the following major reservoirs of carbon interconnected by pathways of exchange: The atmosphere The terrestrial biosphere, which is usually defined to include fresh water systems and non-living organic material, such as soil carbon. The oceans, including dissolved inorganic carbon and living and non-living marine biota. The sediments including fossil fuels. The Earth's interior, carbon from the Earth's mantle and crust is released to the atmosphere and hydrosphere by volcanoes and geothermal systems C A R B O N C Y C L E

Carbon cycle:

Carbon cycle

Green house effect:

What is green house? Ans:-The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. A representation of the exchanges of energy between the source (the Sun), the Earth's surface, the Earth's atmosphere, and the ultimate sink outer space. The ability of the atmosphere to capture and recycle energy emitted by the Earth surface is the defining characteristic of the greenhouse effect. This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection. Global warming, a recent warming of the Earth's surface and lower atmosphere, is believed to be the result of a strengthening of the greenhouse effect mostly due to human-produced increases in atmospheric greenhouse gases . Green house effect

Do you know???:

In our solar system, Mars, Venus, and the moon Titan also exhibit greenhouse effects. Titan has an anti-greenhouse effect, in that its atmosphere absorbs solar radiation but is relatively transparent to infrared radiation. Pluto also exhibits behavior superficially similar to the anti-greenhouse effect. Do you know???

Ozone layer:

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is damaging to life on Earth. It is mainly located in the lower portion of the stratosphere from approximately 13 to 40 kilometres (8.1 to 25 mi) above Earth, though the thickness varies seasonally and geographically . The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations which continues to operate today . Ozone layer

Characteristics of the Ozone layer:

The ozone layer prevents most harmful UVB wavelengths (280–315 nm) of ultraviolet light (UV light) from passing through the Earth's atmosphere. The thickness of the ozone layer—that is, the total amount of ozone in a column overhead—varies by a large factor worldwide, being in general smaller near the equator and larger towards the poles. It also varies with season, being in general thicker during the spring and thinner during the autumn in the northern hemisphere. The ozone layer is higher in altitude in the tropics, and lower in altitude in the extratropics, especially in the polar regions. Ozone amounts over the continental United States (25°N to 49°N) are highest in the northern spring (April and May). These ozone amounts fall over the course of the summer to their lowest amounts in October, and then rise again over the course of the winter. The total column amount of ozone generally increases as we move from the tropics to higher latitudes in both hemispheres. However, the overall column amounts are greater in the northern hemisphere high latitudes than in the southern hemisphere high latitudes. Characteristics of the Ozone layer

Depletion of ozone layer:

Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere (the ozone layer) since the late 1970s. Seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period is referred as ozone hole. The ozone layer can be depleted by free radical catalysts, including nitric oxide (NO), nitrous oxide (N2O), hydroxyl (OH), atomic chlorine (Cl), and atomic bromine (Br). CFCs and other contributory substances are commonly referred to as ozone-depleting substances ( ODS ). Bans on the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride and trichloroethane are made. It is suspected that a variety of biological consequences such as increases in skin cancer, cataracts, 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. Depletion of ozone layer

Ozone depletion:

Ozone depletion

Effect on future:

Basal and Squamous Cell Carcinomas -The most common forms of skin cancer in humans, basal and squamous cell carcinomas, have been strongly linked to UVB exposure. Malignant Melanoma - Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, being lethal in about 15–20% of the cases diagnosed. Cortical Cataracts - Studies are suggestive of an association between ocular cortical cataracts and UV-B exposure, using crude approximations of exposure and various cataract assessment techniques. Increased Tropospheric Ozone - Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. Effects on crops - An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV light and they would be affected by its increase. Effect on future

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In 1994, the United Nations General Assembly voted to designate the 16th of September as "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987. World Ozone Day

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Thank You

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