Environmental Pollution And Air Pollution

Environmental Chemistry

Environmental chemistry may be defined as the study of the chemical phenomenon in the environment.Environmental chemistry is the study of the sources,reactions,transport,effect and facts of the chemical species in hydrosphere,lithosphere,atmosphere and biosphere.

It is a multi-disciplinary science which includes many vastly different fields such as physics,life sciences,public health,engineering,agriculture,etc.It is important for all chemists to know environmental chemistry so that no or least damage is done to the environment through chemical and related industries.Environmental chemistry helps in the identification of specific pollutants present in the environment.

Environmental Pollution

Environmental pollution may be defined as the unfavourable alteration of the surrounding environment,wholly or largely due to the byproducts of the man's activities,through direct or indirect effects of the changes in the energy patterns,radiation levels,chemical and physical constitution or abundances of the organism.These changes may affect man directly or through water suppliers,agricultural or biological products,physical objects possessions or opportunities for re reation and appreciation of the nature.

Air Pollution

Air refers to the invisible,colourless,odourless and tasteless mass of gases that surround the earth.Life cannot be imagined without air.Air forms nearly 80% of the man's daily intake by weight.An average human being breathes about 22000 times a day inhaling about 16 kg of oxygen.Fresh air consists of 78.0% nitrogen,20.95% oxygen,0.935 argon,0.03% carbondioxide,a number of other gases and water vapour.

Air pollution is basically the presence of the foreign substances in the air.Air pollution may be defined as the imbalance in the quality of the air due to some natural processes or human activities so as to cause the adverse effect on living organisms existing on the earth.The polluted air is undesirable for breathing,for the condition of buildings and monuments exposed to it or for animal and plant life.Physival addition of material that turn the air impure or unclean is the reason for air pollution.

According to WHO,"substances put into the air by the activities of amn into concentration sufficent to cause harmful effect to his health,vegetables,property or to interfere with enjoyment of his property".

In simple words,"Air pollution means to the presence in the outdoor atmosphere of one or more contaminants,such as dust,fumes,gas,mist,odour,smoke or vapour,in quantities,with chaaracteristics and of duration such as to be injurious to human,plant or animal life or to which unreasonably interfere with the comfortable enjoyment of life and property.

Factors which cause air pollution are known as air pollutants,There are four notorious air pollutants.They are oxides of sulphur emitted mainly by power stations and industries,oxides of nitrogen emitted mainly by the power stations,industries and vehicles,oxides of vehicles emitted by vehicles and dust and soot known technically as suspended particulate matter(SPM) resulting from the combustion of fuels.

Air pollutants are categorized into the two groups.They are primary air pollutant and secondary air pollutant.Primary air pollutants are the harmful substances which directly enter into the air due to natural events or man made activities.For example,burning of fossil fuels produces CO and CO₂.

$$2C+O_2 \xrightarrow[]{Δ} 2CO$$

$$C+O_2 \xrightarrow[]{Δ} 2CO_2$$

Secondary air pollutants are also the harmful substancesv which are produced into the airdue to the chemical reaction in between two or more components.For example,primary air pollutant SO₂ combines with aerial oxygen to give SO₃ as the secondary pollutant.

$$2SO_2+O_2 \rightarrow 2SO_3$$

$$SO_3+H_2O \rightarrow H_2SO_4$$

$$2CO+O_2 \rightarrow 2CO_2$$

$$CO_2+H_2O \rightarrow H_2CO_3$$

Air Pollution System

Sources of air pollution

Air becomes polluted by two different ways.They are also known as sources of air pollution.A major sources of air pollution has been particulate and gaseous matter which gets released by burning of fossil fuels such as coal,petroleum,etc.These pollutants have been artificial pollutants and they are emitted in the air by four major fuel burning sources.

i)Automobiles and transportation

They have been regarded as the highest sources of air pollution.They produce nearly \(\frac{2}{3}\) of total CO and \(\frac{1}{2}\) of the total hydro carbons and no found in polluted air.The automobile exhaust also has leaded gas and particularly lead.Carbonmonooxide,oxides of nitrogen,benzopyrene,ethene,etc. are produced due to incomplete combustion of gasoline(petrol,diesel,etc).Lead is also emitted when leaded gasoline is used.

ii)Electrical power plants

Use of coal to generate electrical power plants produces \(\frac{2}{3}\) of total SO₂ found in the air.

iii)Industrial processors

Metallurgical plants and smelters,chemical plants,petroleum refiners,beverage factories,steel plants,sugar factories,brick factories,pulp and paper mills,cotton mills,rubber manufacturing and processing plants,etc. are responsible for \(\frac{1}{5}\) of total air pollution.They release harmful gases like CO,CO₂,SO₂,NO₂,NO,Cl₂,F₂,NH₃,naptha vapour,etc. and particulate matter into the atmosphere.

iv)Heating Plants

Heating plants for homes,domestic burnings of fuels,etc. also contribute significantly to air pollution.

Natural contaminants are also found in air.eg,natural fog,pollen grains,bacteria,dust stroms and products or volcanic eruptions.

References

Poudel, Bhoj Raj Poudel and Dr.Megh Raj. A Text Book Of Inorganic Chemistry. Kathmandu: National Book Centre, 2012.

Sons, John Wiley and. J.D Lee Concise Inorganic Chemistry. 2007.