Tag: zoology

The noise from the horn and engines of the vehicles results in sound pollution. The use of extensive chemical fertilizers causes accumulation of these chemicals in the soil and leaching into the ground water. The runoff of these chemicals into water causes water pollution. The improper disposal of sewage results in water pollution. The use of CFC-free refrigerator does not cause any air pollution.

The air pollution is basically of two types:
A. Gaseous pollution: Harmful gases given out from variety of sources. 
B. Particulate pollution: Particles such as those of dust, smoke, mining, stone drilling, wearing of rubber tyres of motor vehicles.

 In traffic-congested city air, nitrogen oxides produce brown air or reddish-brown haze. The pollutant that does not get degraded or broken down into the harmless material is a nondegradable pollutant example Benzene Hexachloride (BHC). Anthropogenic pollution is man-made pollution resulting from human activities like burning fossil fuel, deforestation, mining, sewage etc. A primary air pollutant is a pollutant that persists in the environment in the form it is produced example carbon monoxide.

Secondary air pollutants are usually produced photochemically from primary pollutants and are called photochemical oxidants. Secondary air pollutants occur in photochemical smog. Nitrogen oxides, oxygen and ketone bodies combine to form peroxy acyl nitrates or PAN which is a major constituent of photochemical smog. PAN damages chloroplasts, inhibit electron system and spoil enzyme systems controlling cellular metabolism which causes Hill reaction during photosynthesis .

The primary pollutants are directly released from the source like hydrocarbons are released when fossil fuels are burnt and nitrogen oxides are released due to vehicular combustion and also fossil fuel burning. When these primary pollutants react with each other they form a more potent secondary pollutant called the ozone, which is a poisonous gas in the troposphere.

Primary pollutants include ammonia, sulfur dioxide, nitrogen dioxide and carbon monoxide. Secondary pollutants include ground-level ozone, acid rain and nutrient enrichment compounds.

The photochemical smog has the chief constituent of the peroxy-acetyl nitrate (PAN) that are secondary pollutants as they formed by the primary pollutants. These are formed when the hydrocarbon radicals react with the oxygen in the presence of the sunlight. It forms a brown-coloured haze. This also results in the formation of the ground-level ozone. 

• Primary pollutants are the pollutants that are directly released or emitted in the atmosphere. 
• Secondary pollutants are the pollutants which are formed when primary pollutants react with themselves or with other components of atmosphere.

Secondary pollutant is an air pollutant that do not emit directly from the source but forms when primary pollutant reacts in the atmosphere. For example $O _3$ and PAM forms when hydrocarbon reacts with nitrogen oxides in the presence of sunlight, smog forms when industrial or vehicle fumes reacts with sunlight in atmosphere. Thus, the correct answer is 'All of the above'.