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Air pollution modelling for Chennai city using GIS as a tool

H. M. G. Charlot
Teaching Research Associate CES
hmgcharlot@yahoo.co.in

M. Kanagaraj
Research Associate
mkanagaraj@yahoo.co.in

R. Narayanan
Research Scholar, DUSD
Anna University, Chennai
sathish1_us@rediffmail.com



Introduction
If the London fog disaster in the early fifties had not killed thousands of people over a short period, few would have bothered about acute pollution disasters. The air that man breathes is polluted by industrial and automobile emission bringing into the atmosphere Suspended particular matter (SPM), Oxides of Sulfur and nitrogen, Carbon monoxide, photochemical oxidants and Hydrocarbons. These pollutants, individually and collectively, have teratogenic, carcinogenic or mutagenic effects and can also cause respiratory ailments, the physiological barriers being ineffective against them.

In the 1980s, the polluted air in the cities could be traced to the chimneys of factories. But by the 1990s it was more than apparent that the major contributor to the haze and the poisons in the air was not factories but automobile cars, buses, trucks, three-wheelers and two-wheelers. For over a decade now, there is no dispute over the fact that more than half the pollution load in our cities is due to automobile exhaust.

In the light of these concerns, there is clearly a need for improved information on levels of traffic-related air pollution. This information is required for a wide range of purposes: to help investigate the relationship involved as inputs to health risk assessment, to assist in establishing and monitoring air quality standards, and to help evaluate and compare transport policies and plans. For all these purposes information is required not only on temporal trends in air pollution but also on geographic variations. GIS based vehicular pollution models are needed to identify pollution hot spots, to define at risk groups, to show changes in spatial patterns of pollution resulting from policy or other interventions and to provide improved estimates of exposure for epidemiological studies.

This paper presents a methodology to develop a GIS based vehicular pollution model using a coordinated approach, taking into consideration of all the parameters influencing vehicle emissions, unlike other conventional approaches which have used GIS as a preprocessing/post processing tool.

Geographic Information Systems
A geographic information system (GIS) is a computer-based information system that enables capture, modeling, manipulation, retrieval, analysis and presentation of geographically referenced data. The rise of GIS technology and its use in a wide range of disciplines provides transportation and air quality modelers with a powerful tool for developing new analysis capability. The organization of data by location allows data from a variety of sources to be easily combined in a uniform framework.

Another important feature of GIS is its ability to bridge the technical gap between the need of analysts and decision-makers for easy understanding of the information. The user friendliness of GIS is a feature that has made GIS one of the most used platforms for planning all over the world. The ability of GIS to answer technical questions also makes GIS an excellent tool. Literature on GIS data structures, applications, and vendor products are substantial.

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