Notes on Environmental Chemistry: Components of Environment: | Vishal Tiwari

Notes on Environmental Chemistry:

Components of Environment:

Atmosphere: This comprises a blanket of gaseous layer around earth.

Hydrosphere: This comprises about 96% of earth’s surface & includes all sources of water like oceans rivers lakes, glaciers, ground water etc.

Lithosphere: It refers to earth’s solid crust containing the outer mineral cover. It comprises soil, minerals, organic matter etc.

Biosphere: It refers to the domain of living organism in covalent with atmosphere hydrosphere as well as lithosphere.

Environmental Pollution :
Process of contamination of the environment with harmful wastes arising mainly from human activities.

Pollutant: Any substance or species produced either by a natural source or by human activity, which produces adverse effect on the environment.

Contaminant: A substance which does not occurs in nature but is introduced by human activity into the atmosphere affecting its composition.

Source: The site from which the pollution or contaminants originate.

Sink: The material or medium which consumes or interacts with a long lived pollutant is called sink.

Receptor : Anything that is affected by the pollutants.

Threshold limit value (TLV) : This indicates the permissible limit of a pollutant in atmosphere to which a healthy worker is exposed during hours a day or 40 hours a week for life time without any adverse effects. TLV are determined by experimentation on animals, by use of medical knowledge, epidemiology surveys & environmental studies.

Tropospheric pollution or Air pollution:
It is the atmosphere condition in which the presence of certain concentration produce harmful effects on man and his environment. These substances include:

(i) Gases such as oxides of sulphur, CO, oxide of N2 and hydrocarbons

(ii) Particulate matter such as dust, smoke, fumes etc.

(iii) Radioactive material & many others.

Primary pollutants : These are the pollutants which are emitted directly from the sources. Some examples are:

Particulate Matter : Such as ash, smoke, dust, fumes etc.

Inorganic gases : Such as sulphur dioxide, carbon monoxide etc.


Particulate matter:

Soot: produced by incomplete combustion of carbonaceous fossils fuels such as coal, fuel oil, natural gas, wood etc in insufficient supply of oxygen.

Metal particles: These are released by various metal finishing operation. The micro particles of toxic metal & SO2 gas present in the polluted atmosphere get absorbed on the particles rendering them highly toxic.

Metal oxides : They are generated by combustion of fuels containing metallic compounds.

Lead salts: Their source is lead tetraethyl (Pb(C2H5)4) which is added to gasoline to improve its antiknock property. In order to avoid deposition of PbO suitable amounts of C2H4Cl2 & C2H4Br2 are added to gasoline along with Pb(C2H5)4.

Fly ash: It originates from the combustion of high ash fossil. It contains partially burnt particles of the fuels.

Asbestos dust: It originates from industrial units manufacturing asbestos sheets, gaskets ropes etc. Asbestos flowing & asbestos insulations also contribute towards asbestos dust in the atmosphere.

Solid Hydrocarbons: These are emitted from petroleum refineries & comprise of paraffins, olefins & aromatics.

Dust Particulates: Originate from natural, domestic, industrial or agricultural sources. These are thrown into atmosphere by volcanic eruptions, blowing of dust by wind, mining operations etc.

Acid mist : Sulphuric acid mist is produced when SO3 present in the atmosphere comes in contact with moisture. Nitric acid mist is produced when oxides of nitrogen, viz, NO & NO2, undergo the series of reactions in the atmosphere.