Skip to main content

Oxygen Cycle

It involves the inter- change of oxygen between the elemental form of gaseous O2, contained in a huge reservoir in the atmosphere, and chemically bound O in CO2, H2O, minerals, and organic matter. It is strongly tied with other elemental cycles, particularly the carbon cycle. Elemental oxygen becomes chemically bound by various energy-yielding processes, particularly combustion and metabolic processes in organisms. It is released in photosynthesis. This element readily combines with and oxidizes other species such as carbon in the process of aerobic respiration, or carbon and hydrogen in the combustion of fossil fuels such as methane:

CH4 +  2O2    →   CO2    +  2H2O

Elemental oxygen also oxidizes inorganic substances such as iron(II) in minerals:

4FeO4   +   O2   →    2Fe3O3

A particularly important aspect of the oxygen cycle is stratospheric ozone O3. A relatively small concentration of ozone in the stratosphere, more than 10 km high in the atmosphere, filters out ultraviolet radiation in the wavelength range of 220-330 nm, thus protecting life on the Earth from the highly damaging effects of this radiation. The oxygen cycle is completed by the return of elemental O2 to the atmosphere. The only significant way in which this is done is through photosynthesis mediated by plants.



REACTIONS OF ATMOSPHERIC OXYGEN:


Some of the primary features of the exchange of oxygen among the atmosphere, geosphere, hydro-sphere, biosphere, and anthrosphere are summarized. The oxygen cycle is critically important in atmospheric chemistry, geochemical transformations, and life processes. Oxygen in the troposphere plays a strong role in processes that occur on the Earth's surface. Atmospheric oxygen takes part in energy-producing reactions, such as the burning of fossil fuels:

CH4(in natural gas) +2O2→ CO2+2H2O

Oxygen is returned to the atmosphere through plant photosynthesis:

CO2 + H2O + hv→ {CH2O} + O2

All molecular oxygen now in the atmosphere is thought to have originated through the action of photosynthetic organisms, which shows the importance of photosynthesis in the oxygen balance of the atmosphere. It can be shown that most of the carbon fixed by these photosynthetic processes is dispersed in mineral formations as humic material, only a very small fraction is deposited in fossil fuel beds. Therefore, although combustion of fossil fuels consumes large amounts of O2, there is no danger of running out of atmospheric oxygen.


Comments

Post a Comment

Popular posts from this blog

Relative Atomic Mass

 Hello readers! Hope you will be fine. Our today's topic is relative atomic mass. let's start! It is the average mass of the atoms of that element as compared to1/12th the mass of an atom of carbon-12 isotope. Based on carbon-12 as a standard, the mass of an atom of carbon is 12 units and 1/12th of it comes to be 1 unit. When we compare atomic masses of other elements with atomic masses of carbon-12 atom, they are expressed as relative atomic masses of those elements. The unit of relative atomic mass unit is amu (Atomic mass unit). One atomic mass unit is 1/12th the mass of one atom of carbon-12.  This was the short intro of Relative atomic mass.  See you next with another topic. Thank you!
Post a Comment
Read more

Structure of Atom(Part 5)

 Rutherford's Atomic Model: Rutherford performed 'Gold Foil' experiment to understand how negative and positive charges could coexist in an atom. He bombarded alpha particles on a 0.00004  cm thick gold foil. Alpha particles are emitted by radioactive elements like radium and polonium. These are actually helium nuclei (He2+). They can penetrate through matter to some extent. He observed the effects of α-particles on a photographic plate or a screen coated with zinc sulphide. He proved that the 'plum-pudding' model of the atom was not correct.  Observations made by Rutherford were as follows: i.Almost all the particles passed through the foil un-deflected. ii.Out of 20000 particles, only a few were deflected at fairly large angles and very few bounced back on hitting the gold foil. Results of the experiment: Keeping in view the experiment, Rutherford proposed planetary model for an atom and concluded following results: i.Since most of the particles passed through th
1 comment
Read more

Carbon Cycle

CARBON CYCLE: Carbon circulates through the carbon cycle. It shows that carbon may be pres- ent as gaseous atmospheric CO2 constituting a relatively small but highly significant portion of global carbon. Some of the carbon is dissolved in surface water and groundwater as HCO-3 or molecular CO2 (aq). A very large amount of carbon is present in minerals, particularly magnesium and calcium carbonates such as CaCO3. Photosynthesis fixes inorganic C as biological carbon. represented as (CH2O), which is a constituent of all life molecules. Another fraction of carbon is fixed as petroleum and natural gas, with a much larger amount as hydrocarbonaceous kerogen (the organic matter in oil shale), coal, and lignite. Manufacturing processes are used to convert hydro- carbons to xenobiotic compounds with functional groups containing halogens, oxygen, nitrogen, phosphorus, or sulfur. Although a very small amount of total environmental carbon, these com- pounds are particularly significant because of
Post a Comment
Read more