What is ionising radiations?
✅Ionising radiations cause ionisation (one or more electrons are pealed out from the outer shells of an atom) of atoms and molecules of the medium through which they pass.
✅Electromagnetic radiations such as short wavelength ultraviolet radiations (UV), X-rays and gamma rays and energetic particles produced in nuclear processes, electrically charged particles like alpha and beta particles produced in radioactive decay and neutrons produced in nuclear fission, are highly damaging to living organisms.
✅Electrically charged particles produced in the nuclear processes can have sufficient energy to knock electrons out of the atoms or molecules of the medium, thereby producing ions.
✅The ions produced in water molecules, for example, can induce reactions that can break bonds in proteins and other important molecules.
✅An example of this would be when a gamma ray passes through a cell, the water molecules near the DNA might be ionised and the ions might react with the DNA causing it to break.
✅They can also cause chemical changes by breaking the chemical bonds, which can damage living tissues.
✅Short range effects include burns, impaired metabolism, dead tissues and death of the organisms.
✅Long range effects are mutations increased the incidence of tumours and cancer, shortening of life-span and developmental changes.
Smog
✅Smog is a harmful mixture of fog, dust and air pollutants such as nitrogen oxides, volatile organic compounds, etc. which combine with sunlight to form a dense layer of ground-level ozone.
✅Ozone present high in the atmosphere is good, but when nearer to the ground, it can cause irritating health effects.
Smog can be caused by:
✅Large amounts of coal-burning in an area
✅Slash-and-burning of crops (a major source in Delhi)
✅Smog-forming pollutants generate from automobile exhausts, power plants, fireworks, even paint, hairspray, charcoal starter fluid, and plastic popcorn packaging.
Photo chemical smog
also known as summer smog, is a type of smog that is produced when UV light originating from the sun interacts with the oxides of nitrogen present in the atmosphere.
✅This type of smog usually manifests as a brown haze and is most commonly seen in highly populated cities that are placed in relatively warm climates.
✅photochemical smog is most prominently visible during the mornings and afternoons.
particulate matter
✅Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.
✅Particles can be suspended in the air for long periods of time.
✅Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope.
✅Many manmade and natural sources emit PM directly or emit other pollutants that react in the atmosphere to form PM.
✅Photochemical form is formed by a complex series of chemical reactions involving sunlight, oxides of nitrogen, and volatile organic compounds that are present in the atmosphere as a result of air pollution. These reactions often result in the formation of ground level ozone and certain airborne particles. The formation of photochemical smog is closely related to the concentration of primary pollutants in the atmosphere.
✅It is also related to the concentration of secondary pollutants (in some cases).
Sources of PM
✅Sources of fine particles include all types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes.
✅Sources of coarse particles include crushing or grinding operations, and dust from paved or unpaved roads.
✅Other particles may be formed in the air from the chemical change of gases. They are indirectly formed when gases from burning fuels react with sunlight and water vapor. These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.
Evaporation
✅Evaporation is a process by which water is transformed from liquid to gaseous state. Heat is the main cause for evaporation.
✅Movement of air replaces the saturated layer with the unsaturated layer. Hence, the greater the movement of air, the greater is the evaporation.
Factors Affecting Rate of Evaporation
✅Amount of water available.
✅Temperature.
✅Relative humidity.
✅Area of evaporating surface.
✅Wind speed: A high wind speed removes the saturated air from the evaporating surface and replaces it with dry air which favors more evaporation.
✅Whenever there is a combination of high temperature, very low relative humidity and strong winds, the rate of evaporation is exceptionally high. This leads to dehydration of soil to a depth of several inches.
✅Air Pressure: Evaporation is also affected by the atmospheric pressure exerted on the evaporating surface. Lower pressure over open surface of the liquid results in a higher rate of evaporation.
✅Composition of water: Evaporation is inversely proportional to salinity of water.
✅Rate of evaporation is always greater over fresh water than over salt water. [Because of the reduction in the water vapor pressure at the water surface due to salinity.]
