AIR POLLUTANTS

Subject: Environment

Context : Delhi woke up to high levels of air pollution on Friday as air quality index (AQI) slipped into ‘very poor’ category while some parts of the city saw AQI turn ‘severe’.

Concept:

Besides concentration of particulates (PM 2.5 ,PM 10), the CPCB also monitors gas concentrations, including of nitrogen dioxide (NO2), ammonia (NH3), sulphur dioxide (SO2), carbon monoxide (CO), and ozone (O3).

Major Air Pollutants:

CO:

• By incomplete combustion of carbon based fuels, Automobile exhaust, Cigarette smoke
• Combines with hemoglobin to form carboxy haemoglobin, which is highly stable & reduces oxygen carrying capacity of blood
• Slow our reflexes & make us confused & sleepy

CO2:

• Major greenhouse gas formed by respiration, burning of fuels, decomposition of lime, volcanic eruption.

CFCs:

• Released mainly from air conditioning systems & refrigeration
• Detrimental to Ozone layer present in the stratosphere as CFC + UV >> Cl (Chlorine radicals which causes breakdown of Ozone)

Lead:

• Present in petrol, diesel, lead batteries, paints, hair dye products etc. (Affects children in particular)
• Damages nervous system & cause digestive problems & in some cases causes cancer

O3:

• Formed when NOx particle from vehicle exhaust & volatile Hydrocarbons interact with each other in presence of sunlight

SPM:

• SPMs in air, when breathed in causes lung damage & respiratory problems

SO2:

• Produced from burning coal (60 %), mainly in thermal power plants + Petroleum products + in production of paper & smelting of metals
• Major contributor to smog causing lung diseases

CH4:

• Mainly CH4 burns in fossil fuels + produced by burning of vegetation / rotting

Acid Rain:

• Ph< 5.6 (Rain with oxides of sulphur & nitrogen (SO2 & NO2)) – HNO3 + H2SO4

NOx

• NO3- → Acts as a fertilizer to the soil
• Automobile exhaust produces NO2 which damages plant leaves & retard rate of photosynthesis + also causes red haze & lung irritation

Classical Smog

• Occurs in cool humid climate
• Chemically reducing hence called reducing smog
• Smoke + fog + SO2.