|of these articles describes the gas mixture air; to other meanings see air (term clarifying).|
Air marks the gas mixture of the terrestrial atmosphere and consists mainly of the two gases nitrogen (78%) and oxygen (21%). Furthermore into comparatively high concentrations come Argon (0.9%) and carbon dioxide (0.03%) forwards. In the natural condition air smell and tasteless is.
The oxygen contained in air is survive necessary for all aerobes land organisms. All animals need it for the respiration. Plants need inair contained carbon dioxide to photosynthesis. For nearly all plants this is only source of carbon.
Table of contents
|gas||formula||Percentage by volume||proportion|
|of main parts of dry air with Normalnull|
|concentration the trace gases|
|carbon dioxide||CO 2||0.038%||0.058%|
|neon||Ne||18.180 ppm||12.67 ppm|
|helium||He||5.240 ppm||0.72 ppm|
|methane||CH 4||1.760 ppm||0.97 ppm|
|krypton||Kr||1.140 ppm||3.30 ppm|
|hydrogen||H 2||~500 ppb||36 ppb|
|dinitrogen oxide||N 2 O||317 ppb||480 ppb|
|xenon||Xe||87 ppb||400 ppb|
|Dichlordifluormethan (CFC-12)||CCl 2 F 2||,535 2200||ppt tri chlorine fluorine methane|
|( CFC-11) ppt||CCl 3 F||226 ppt||1100 ppt|
|Chlordifluormethan (HCFC-22)||CHClF 2||,160 ppt||480 carbon tetrachloride|
|CCl||4 96||ppt ppt||510 ppt|
|Trichlortrifluorethan (CFC-113)||C 2Cl 3F 3||80 ppt||520 ppt|
|methyl chloroform||CH 3 - CCl 3||25 ppt||115 ppt|
|1,1-Dichlor-1-Fluorethan (HCFC-141b)||CCl 2 F-CH 3||17 ppt||70 1-Chlor-1,1-Difluorethan|
|( HCFC-142b) ppt||CClF 2 - CH 3||14 ppt||50 ppt|
|sulfur hexafluoride||SF 6||5 ppt||25 ppt|
|halon 1211||CBrClF 2||4 ppt||25 ppt|
|halon 1301||CBrF 3||,2.5 ppt||13 ppt|
|entire (drying)||5,135 ·10 15 t|
|entire (damp)||5,148 · is shown 10|
15 t the current composition of air at a value of Normalnull in the right table, whereby one differentiates between main parts and trace gases.
as a chemically inertGas is extremely poorly reactive the nitrogen arising in molecular form. In the Stickstoffkreislauf it can be transferred of the nitrogen adjustment only by the processes into connections usable for organisms, which need it for the structure of their amino acids. One designates the contrary processas denitrification. Technically atmospheric nitrogen is used over the Haber-Bosch-process for the fertilizer production. These processes adjust themselves as far as possible and have purely quantitatively only a small effect on the concentration of the nitrogen in the atmosphere.
oxygenthe most important oxidizing agent represents and lends to the today's atmosphere therefore also their oxidizing character. The oxygen is needed among other things for nearly all chemical burn procedures and the biological respiration. It is educated again over photosynthesis, whereby thoseconcerning this in the course of geologic history manufactured quantity for instance the twentyfold of the quantity today available in the atmosphere amounts to. When dipping into larger depths (> 60m) nitrogen in the pressure bottle is replaced by helium. Otherwise can it by in the bloodsolved nitrogen (higher partial pressure) to the depth intoxication come (euphoria, in addition, fear and unconsciousness).
argon is however poorly reactive a comparatively well water-soluble noble gas, as such and without further meaning for chemistry. Owing to his inertness becomesArgon with weld as inert gas used or also because of its relative to air smaller heat conductivity than energy savings medium for window frameworks.
ambient air is not completely drying, therefore this contains zero up to approximately four additionally depending upon air humidityPercent by volume water vapour, the remainder of air divides itself then after the values indicated in the table. The usual values of the steam content vary between a tenth percent by volume at Poland and three percent by volume in the Tropics, with oneAverage value of 1,3% at ground level. They are indicated by different dampness mass.
variability in the time
the concentrations that atmosphere gases are metastable after their character, because even if it itself in the lifetime of humans onlyslightly change, then they should not be confounded therefore with natural constants. This shows up in the development of the terrestrial atmosphere persisting since billions of years, also today not yet finally is and in their course itself the composition of the terrestrial atmosphere several timesfundamentally changed. Only for approximately 350 million years one can thereby of our current atmosphere speak.
The increase of the carbon dioxide content represents the largest current changes of the air composition around approximately 40% since beginning of the industrialization. This is inConnection with the anthropogenen greenhouse effect one the cause for the global heating up. Carbon dioxide formally belongs to that thereby to the trace gases, it becomes as the fifth-most frequent atmosphere gas and due to its meaning for climate and organism however frequently the main partsAir counted.
Larger fluctuations over partly few years and decades are to be registered also with the trace gases, because straight anthropogene emissions can affect their small concentrations with comparatively incompetent output quantities. Likewise volcanic eruptions show frequently a short term influence.
Variability in the area
The indicated concentrations represent global average values and refer to Normalnull, possess however a most extensive validity in the entire Homosphäre, thus into oneHeight of approximately 100 kilometers. Since in different altitudes specific processes of atmosphere chemistry work, there are however also partial substantial deviations. Starting from the Homopause the acceptance of the concentration heavy gases with the height places and thus the relative enrichment of easierGas a general trend. In the high atmosphere therefore hydrogen and helium are proportionately very many more important than at ground level, however the atmospheric pressure and thus the absolute occurrence that are accordingly small gases.
substances of smaller concentration
In addition the following materials in slight traces arise:
- of chlorine oxides
- other nitrogen oxides (apart from N 2 O)
- sulfur dioxide
the biological main meaning of the carbon dioxide lies in its role as a carbon supplier for photosynthesis, why the atmospheric carbon dioxide concentration affects strongly plant growth. By the light-dependent metabolic cycle of the plants, thus the interrelation between Respiration and photosynthesis, can vary the near-surface CO 2 - concentration in the diurnal variation. A nocturnal maximum and accordingly a minimum show up on the day with sufficient ground cover. The same effect comes also in the yearly process to carries, there the non-tropical vegetationpronounced vegetation periods possesses. This entails a maximum in the period in the Northern Hemisphere March until April and a minimum in October or November. Also anthropogene emission cycles can play a role, for example with the using of the heating season with sinkingTemperatures.
As superordinate trend a constant increase of the carbon dioxide in the atmosphere is measured, whereby the concentration in the middle 18. Century with approximately 280 ppmv lay. This corresponds to an increase of approximately 40%, whereby the rates of growth themselves ever furtherincreased and also today still increase. They lie with approximately 1.6 ppmv/a. The sources for this are multilayered, the carbon cycle however lastingly destabilized and to carry over the anthropogenen greenhouse effect for global heating up .
Locally and knows straight close industriellen densely populated areasthe carbon dioxide concentration over the normal values lie also clearly. Values of 400 ppmv are quite frequent thereby. The former Londoner winter smog with 3.000 set up the record ppmv (0.3%).
of ozone values become not in portions, but inthe Dobson unit indicated. Since the values besides on the height (ozone layer, near-surface ozone), as well as on weather conditions, temperature, pollution impact and time depend, and both fast and again disintegrates, is it forms for ozone in above table notlisted.
Carbon monoxide is an invisible combustible poisonous gas, which develops with burns with oxygen deficiency. It blocks oxygen transport in the blood and can in small doses to death lead. Also it damages photosynthesis that Plants. It becomes among other things in autoengines produces, so that exhaust gas without exhaust subsequent treatment is to contain by a catalyst up to 4% Carbon monoxide.
physical dimension of air
| speed of sound|
| atmospheric pressure|
| Sound radiation impedance|
the Gewichtskraft of the air column accelerated by the gravitational pull of the earth produces a static air pressure, with thatrespective measuring point varies. This depends however additionally on thermal (temperature) and dynamic influences (weather conditions). Over a square meter floor space amounts to air mass the air pressure accordingly for instance 10000kg.
The exact definition by Wissenschafter and technicians is somewhat different depending upon field of activity. In the meteorology the air temperature at a value of two meters becomesmeasured, for which the classical, white painted weather little houses in free environment serve.
with the air humidity concerns it the portion of the water vapour of air. It becomes over different damp mass such as steam pressure and dew point as well as relative,absolute and specific humidity quantifies.
In approximation to dry air, with the molecular masses from the respective articles of the individual elements and the appropriate natural constants, air possessesa molecular mass of 28,9634 g/mol.
The refractive index of air amounts to under standard conditions for visible light approximately 1,00029. It depends on pressure, temperature and composition of air, above all however on the air humidity. According to the refractive index changes alsothe speed of light within air.
Specific thermal capacity:
- <math> c_p< /math> = 1.005 kJ/(kg K) = 0.279 KW/H (ton of K) (isobar)
- < math> c_v< /math> = 0.718 kJ/(kg K) = 0.199 KW/H (ton of K) (ISO choir)
air pollution and air pollution control
the air pollutionis the partial aspect of the environmental pollution referred to air. In accordance with the federal immission control law air pollution is a change of the natural composition of air, in particular by smoke, soot, dust, aerosols, steams or Geruchsstoffe. Of special harming lightness are increased ozone values (smog) and sulfur dioxide concentrations (acid rain).
In most industrialized countries the local air pollution decreased/went back in the last decades strongly. At the same time however the output of greenhouse gases continued to increase as carbon dioxide. The local andregional air pollution is however in particular for countries of the third world as well as developing countries like for example Russia or China still another substantial problem.
|Wikiquote: Air - quotations|
|Wiktionary: Air - word origin, synonyms and translations|
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