Posts Tagged ‘Hydro carbons’

Air pollutants: a Discussion

More than 100 substances has been identified which cause air pollution. The important air pollutants are discussed below; they are carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide, sulphur trioxide, nitrogen oxides, organic campounds like hydrocarbons, ketones, aldehydes, flourine compounds, radio active compounds, ozone etc.

Air pollution is a serious problem in the modern time. Largest and most important cause of air pollution is burning of hydrocarbons by motor transport. The degree of air pollution, very from country to country and in a country from place to place. Unplanned urbanization also contributes to air pollution and air quality. Due to air pollution there is steady increase of average global temperature (global warming) and due to global warming serious natural calamities like draught & flood are taking place frequently.

Air pollutants may be in the form of gas, liquid or solid. The combination of smoke and fog is called “smog”.

Other containments of air include lead mercury, benzene, flourides, vinyl chloride etc.

1. Sulphur dioxide: This is one of the several forms of sulphur in air; others are hydrogen sulphide, sulphuric acid and salts of sulphur. This pollutant is produced when sulphur containing fossil fuel is burned, smelting of sulphur & from industries. Sulphur dioxide reacts with water and became sulphuric acid. 80?gm per cubic meter is considered the safe limit.
2. Carbon Monoxide: It is one of the most common air pollutants. It is a product of incomplete combustion (burning) of carbon containing materials, such as motor vehicle, heating facility, industrial process & power plants and industries. 350 to 600 million tones of carbon monoxide is produces every year by human activities mainly industries and automobiles. Some natural source of carbon monoxide producing places has also been identified. Carbon monoxide concentration depends on weather & traffic in cities. During rainy season its concentration is minimum and during winter its concentration is maximum. It also very with petrol powered vehicles in cities and morning & evening rush hours. Its concentration can be seen in blood as carboxy hemoglobin. Its concentration is expressed as 8 hours average concentration.
3. Hydrogen sulphide: In industries hydrogen sulphide is formed when sulphur come into contact with organic material at high temperature. It is produced in coke production plant, waste water treatment plant, wood pulp production unit, oil refining plant industry etc. If humans are exposed to more than 30?g per cubic meter concentration of hydrogen sulphide they suffer mental and neurological problems.
4. Carbon dioxide: It is a normal constituent of air. But when present in very high concentration it can produce adverse effect. It is produced during burning of coal, wood, gas, oil etc. Its concentration is alarmingly increasing and effectively increasing global temperature which is having its effect on climate change.
5. Lead: Man source of lead is lead content of petrol. So, in many countries now started producing unleaded petrol to reduce lead pollution, children & pregnant women are at higher risk of adverse effects of lead pollution due to ineffectiveness of placental barrier to prevent lead from going to fetus in pregnant women.
6. Hydro carbons: Its sources include incineration, combustion of coal, wood and use of petroleum. They take part in chemical reactions that causes photo chemical smog.
7. Ozone: It is one of the strongest oxidizing agents. It is formed by chemical reaction in air. It is combination of 3 (three) oxygen atoms in stead of two in normal oxygen. If excess ozone is present in air it causes oxidation of many materials. In the troposphere layer of atmosphere it is protecting earth from solar radiation by forming an ozone layer.
8. Particulate matters: These are complex mixture of organic and inorganic substances. They are divided in to two groups according to mass and composition. (a) Coarse particles larger than 2.5?m in aerodynamic diameter and (b) Fine particles smaller than 2.5?m in aerodynamic diameter. The fine particles are generally aerosols, combustion particles, organic and metal vapor. Large (coarse) particles are dust from roads, earth, and dust from industry. Respirable particles are emitted from power plants, automobiles, coal burning and incinerators. The sources are concentrated in urban areas. The maximum safe limit of suspended particulate matter (SPM) is 100?g per cubic meter.