Air Pollution
Causes of Air Pollution
1. Burning of Fossil Fuels: Sulfur dioxide emitted from the combustion of fossil fuels like coal, petroleum and other factory combustibles is one the major cause of air pollution. Pollution emitting from vehicles including trucks, jeeps, cars, trains, airplanes cause immense amount of pollution. We rely on them to fulfill our daily basic needs of transportation. But, there overuse is killing our environment as dangerous gases are polluting the environment. Carbon Monoxide caused by improper or incomplete combustion and generally emitted from vehicles is another major pollutant along with Nitrogen Oxides, that is produced from both natural and man-made processes.
2. Agricultural activities: Ammonia is a very common by product from agriculture related activities and is one of the most hazardous gases in the atmosphere. Use of insecticides, pesticides and fertilizers in agricultural activities has grown quite a lot. They emit harmful chemicals into the air and can also cause water pollution.
3. Exhaust from factories and industries: Manufacturing industries release large amount of carbon monoxide, hydrocarbons, organic compounds, and chemicals into the air thereby depleting the quality of air. Manufacturing industries can be found at every corner of the earth and there is no area that has not been affected by it. Petroleum refineries also release hydrocarbons and various other chemicals that pollute the air and also cause land pollution.
4. Mining operations: Mining is a process wherein minerals below the earth are extracted using large equipments. During the process dust and chemicals are released in the air causing massive air pollution. This is one of the reason which is responsible for the deteriorating health conditions of workers and nearby residents.
5. Indoor air pollution: Household cleaning products, painting supplies emit toxic chemicals in the air and cause air pollution. Have you ever noticed that once you paint walls of your house, it creates some sort of smell which makes it literally impossible for you to breathe. Suspended particulate matter popular by its acronym SPM, is another cause of pollution. Referring to the particles afloat in the air, SPM is usually caused by dust, combustion etc.
Techniques to measure Air pollution
1. Conventional way of measuring Air pollution :Previously the air pollution monitoring is done via computerized tomography technique which generate a two dimensional map of pollutant concentration. In this system there is a single laser source located at the centre of the area. This laser beam is rotated and directed towards the circumference of the circle. There is a cylindrical mirror so that incident laser beam is reflected in a fan beam over angle across the circle. The beam from the mirrors is the circular region and strikes a set of detectors lie in same plane parallel to the ground. This technique focus on lower transmitted laser energy increasing the range and ability to monitor the area that contains several pollutant sources.
2. Wireless Sensor network for real time monitoring:A distributed infrastructure consists of a wireless sensor network and grid computing technology for air pollution monitoring as well as mining. However, the two layer network architecture and peer to peer e-science grid architecture and distributed data mining algorithms are used in order to collect the data and tiny operating system is used to examine the operation and performance of the wireless sensor network.The various gases like CO2, NO2 are calibrated by using a appropriate calibration technologies and these pre-calibrated sensors are integrated with the wireless sensor using a multi hop data aggregation algorithm. A light weight middleware and web interface in order to view the one pollution data in the form of charts and number. It is also available on the internet. The other parameters like temperature and humidity are also sensed along with the gas concentrations which enable the data analysis through the data fusion techniques this system provide accurate pollutant data .The system in which several monitoring station communicate wirelessly with the backend server using machine to machine communication & each station equipped with the metro logical sensor and gaseous sensor for data logging and wireless communication capabilities. The backend server collects the real time data from station and converts it into the information which is used by the user through the web portals and mobile application.
3. Centralized monitoring: Different sensors are deploying to the different region and each sensor must send their collected information to server so that the end user can easily see the pollution information in the different area. Centralize monitoring ensure the quality, improve the ability and integrity of data. Collected data are uploaded to the cloud dataset so that it can be analyze or viewed for future use
4 .Types of sensor: There are different types of sensors are available for collecting the atmospherically data. Such as Temperature sensor, Humidity sensor, Rain sensor, Gas Sensor etc…different types of gas sensors are available to collect the different gases from the road traffic emission such as CO2 sensor,NO2 sensor, SO2 sensor etc. Wireless sensor network built a node where each node is connected to one sensor. With the additional sensors may help to enhance the network and monitoring the additional pollutants.
Air pollution prevention measures
1. Control by Biofiltration: Biofiltration is a relatively recent air pollution control (APC) technology in which off-gases containing biodegradable volatile organic compounds (VOC) or inorganic air toxics are vented through a biologically active material. The most common style biofilter is just a big box. Some can be as big as a basketball court or as small as one cubic yard. A biofilter’s main function is to bring microorganisms into contact with pollutants contained in an air stream. The box that makes up this biofilter contains a filter material, which is the breeding ground for the microorganisms. The microorganisms live in a thin layer of moisture, the “biofilm”, which surrounds the particles that make up the filter media. During the biofiltration process, the polluted air stream is slowly pumped through the biofilter and the pollutants are absorbed into the filter media. The contaminated gas is diffused in the biofilter and adsorbed onto the biofilm. This gives microorganisms the opportunity to degrade the pollutants and to produce energy and metabolic byproducts in the form of CO2 and H2O.This biological degradation process occurs by oxidation, and can be written as follows: Organic Pollutant + O2 -; CO2 + H2O + Heat + Biomass
2. The impact of Computers upon Air Pollution Research: The electronic computer has a great effect upon air pollution research activities. Some of the ways in which Public Health Service scientists routinely make use of the computer. It is used as a data processor to handle the large volumes of data resulting from continuous air monitoring devices. And it is used to perform the very complex computations involved in various statistical analyses and mathematical model building. In future years computers may be used on a real-time basis to control the sources which emit pollutants to the atmosphere.
3. Control by Gravitational settling chamber:For removal of particles exceeding 50 µm in size from polluted gas streams, gravitational settling chambers.This device consists of huge rectangular chambers. The gas stream polluted with particulates is allowed to enter from one end. The horizontal velocity of the gas stream is kept low (less than 0.3 m/s) in order to give sufficient time for the particles to settle by gravity.The particulates having higher density obey Stoke’s law and settle at the bottom of the chamber from where they are removed ultimately. The several horizontal shelves or trays improve the collection efficiency by shortening the settling path of the particles.
4. Wet Collectors (Scrubbers):In wet collectors or scrubbers, the particulate contaminants are removed from the polluted gas stream by incorporating the particulates into liquid droplets.Common wet scrubbers are:(i) Spray Tower(ii) Venturi Scrubber(iii) Cyclone Scrubber(i) Spray Tower:Water is introduced into a spray tower by means of a spray nozzle. As the polluted gas flows upwards, the particles present collide with the water droplets being sprayed downward from the spray nozzles. Under the influence of gravitational force, the liquid droplets containing the particles settle to the bottom of the spray tower.(ii) Venturi Scrubber:Submicron particles (size 0.5 to 5 µn) associated with smoke and fumes are very effectively removed by the highly efficient Venturi Scrubbers. The polluted gas passes downwards through the throat at the velocity of 60 to 180 m/sec.A coarse water stream is injected upwards into the throat where it gets atomised due to the impact of high velocity of the gas. The liquid droplets collide with the particulates in the polluted gas stream.The particles get entrained in the droplets and fall down to be removed later on. Venturi Scrubbers can also remove soluble gaseous contaminants. Due to the atomisation of water there is proper contact between the liquid and the gas increasing the efficiency of the Venturi Scrubber.To separate the droplets carrying the particulate matter from the gas stream, this gas-liquid mixture in the Venturi Scrubber is then directed into a separation device such as a cyclone separator.(iii) Cyclone Scrubber:The dry cyclone chamber can be converted into a wet cyclone scrubber by inserting high pressure spray nozzles at various places within the dry chamber.The high pressure spray nozzles generate a fine spray that intercepts the small particles in the polluted gas. The centrifugal force throws these particles towards the wall from where they are drained downwards to the bottom of the scrubber.
The relation between Teleworking, traffic and Air Pollution
We know that air pollution is mainly due to traffic congestion. In Urban areas, there is a increase in vehicle emissions which degrades air quality. Number of plans has been implementing to reduce the traffic in Urban areas. This paper tells us about how teleworking, traffic and air pollution are interlinked. And this teleworking method has reduces the traffic volume by 1.9 percent. Main reduction is observed in NO2, CO and PM10,and O2 and SO2. The remark of this paper is teleworking can be a promising tool for urban planning and development, focussing at the traffic volume reduction and Air quality improvement.
Conclusion on Air Polution
Air pollution continues to pose considerable health risk. Global warming make Air pollution and its effects more worse. Reduction of this is one of the greatest strides ot the Environmental protection.
