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The troposphere is the lowest layer of the atmosphere extending from earth surface to tropopause at 10km-18km. About 90% of the total mass resides here and greater part of trace gases burden is found there.
The composition of the atmosphere is predominately determined by
biological processes acting with concert with physical and chemical change.
Though the concentration of the major atmosphere constituents remain
Composition of the troposphere
Major constituents
N2,O2,Ar,CO2
Trace gases
Variable
Sources of trace gases
The majority of the trace gases found in the atmosphere is emitted into the troposphere from the surface and are subject to a complex
For the individual emission of a primary pollutant there are a number
of factors should be taken into account in order to estimate the emission strength, these include the range and type of sources and the spatio-and temporal distribution of the sources. Often these factors are compiled into the so-called emission inventories that combine the rate of emission of various sources with the number and type of each source and the time over which the
generalization of atmosphere
Major species
Concentrations are constantly
Trace species Biological processes
change
Concentrations are changing
Man’s activities
turbulent motion in the atmosphere over large spatial.
Above the mesosphere is a region characterized by a rapid rise in temperature, known as thermosphere. In the thermosphere, the gases, NO2 and O2, are dissociated to a significant extent into atoms so the mean molecular mass of the atmosphere species falls. The pressure is low and thermal energies are significantly departed from the Boltzmann equilibrium. And the top layer of the atmosphere with certain characteristic is ionosphere. Though there are lots of chemistry taking place higher up to the
atmosphere, we may focus in the main on the chemistry of the
troposphere and stratosphere.
Regions of atmosphere
characteristics of dynamical motions of the air are the basis.
Emissions into the atmosphere are often broken down into categories
of anthropogenic(also called “man-made sources) or natural sources also having geogenic sources.
The troposphere is well mixed and its bulk composition is 78%N2,
21%O2,1%Ar, and 0.036%CO2 with varying amounts of water vapor depending on temperature and altitude.
emission occur.
It is worth nothing that there are number of sources that do not occur within the boundary layer, such as lightning production of nitrogen oxides and a range of pollutants emitted from the combustion-taking
of absorbing ultraviolet radiation from the sun, which would
otherwise be harmful to life on the earth.
The stratopause at approximately 50km altitude marks the boundary between the stratosphere and the mesosphere, which extends upwards to the mesopause at approximately 90km altitude. The mesosphere is region of large temperature extremes and strong
regions which are distinguished by different characteristic of
dynamical motions of the air. The lowest region, from the surface of earth to the tropopause at a range of 10km-15km, is termed the troposphere. This region is of active weather systems which determine the climate at the surface of the earth. The lowest of the troposphere is influenced by earth surface on daily basis.
transformation of primary pollutants in the atmosphere are referred to as having secondary sources or being secondary species.
Sources of trace gases
sources
Secondary sources
Chemical physical processes
anthropogenic
Earth surface Primary sources
non surface sources worth nothing
Natural sources
Sources of trace gases
Part 2 Unit 5 Chemistry of the Atmosphere
generalization of atmosphere The thin gaseous envelop that surrounded our planet is integral to the maintenance of life on earth.
troposphere
Determine the climate ,Influenced by earth surface very dominantly
stratosphere
mesosphere thermosphere ionosphere
a quiescent region, have the ozone layer absorbing ultraviolet
series of chemical and physical transformation. Trace species emitted directly into the atmosphere are termed to have
primary sources,e.g.SO2,NO,CO.
Those formed as a products of chemical and/or physical
Above the troposphere lies the stratosphere, a quiescent region of the atmosphere where vertical transport of material is slow and
radiative transfer of energy dominates. In this region lies the ozone layer which has an important property
the same, the concentration of trace species, which are key to many atmosphere processes are changing.
It is apparent that man’s activities are beginning to change the composition of the atmosphere over a range of scales, leading to, for example, increased acid deposition, local and regional ozone episodes, stratospheric ozone loss and potentially climate change.
Strong turbulent motion in large scale Rapid rise in Temperature, NO2,O2 are dissociated into atoms. Gravitation separation, ionization is dominant.
Composition of the troposphere
Increased acid deposition, ozone episodes, ozone loss , climate change
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Regions of atmosphere In order to understand the chemistry of the atmosphere we need to map the different regions of the atmosphere. The atmosphere can be conveniently classified into a number of
