• CO(g),, H2S(g), SO2(g), SO3(g), NO(g), NO2(g) and CO2(g) are the inorganic
compounds which change the atmospheric composition. Organic compounds including
hydrocarbons, halo hydrocarbons and particles such as dust and carbon also contribute
to change the composition of the atmosphere./
• Some CO(g) in atmosphere is formed by the oxidation of methane, which is formed
naturally by the anaerobic degradation of organic matter. CO (g) is emitted from all the
incomplete combustion processes including the internal combustion engines of motor
vehicles.
• SO2(g) enters the atmosphere from the combustion of sulphur containing fossil fuels,
volcanic eruption , biological decay of S containing organic matter, reduction of
sulphates and recovery of metals from their sulphides. SO2(g) reacts with oxygen and
forms SO3(g). NO(g) increases the rate of oxidation of atmospheric SO2 (g) in to
SO3(g).
• NOx(g) [NO(g) and NO2(g)] enters the atmosphere from natural processes such as
lightening discharges, and from pollutant sources. The combustion of fossil fuels gives
most of the NOx(g). Much of the NOx(g) entering the atmosphere is from the internal
combustion engines.
• Microbial decay of S containing organic matter and reduction of sulphate ion are the
most common natural sources of H2S.
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• Hydrocarbons are widely used as fuels and enter the atmosphere directly or as byproducts
in the partial combustion of other hydrocarbons. Uncontrolled vehicle exhausts contain
alkanes , alkenes and aromatic hydrocarbons. Methane is produced in large quantities
from the anaerobic decomposition of organic matter submerged in water.
1. Global warming
2. Αcid rain
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