A comparison between national air quality index, india and composite air quality index for Ahmedabad, India

Abstract

Ahmedabad is the 5th biggest city and 7th most populated city in India. It is the largest city in Gujarat. The city is spread over a further 450 sq. km. of area. The study report prepared by the World Health organization (WHO) in May 2014 reveals that Ahmedabad is the 9th most air polluted city in the world and 5th most air polluted city in India, based on the concentration of fine particulate matter (PM2.5). In this study, six different ambient air quality monitoring locations are selected in Ahmedabad. A sensor-based continuous ambient air quality monitoring instrument is used to monitor the ambient air quality of selected locations for the summer and winter seasons. The concentration of six pollutants is monitored: respirable suspended particulate matter (PM10), fine particulate matter (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO). The monitoring data shows that in the summer, the average concentration of all the pollutants at all selected locations is within National Ambient Air Quality Standards (NAAQS), 2009. In the winter, gaseous pollutants; an average hourly concentration of O3 and CO; and 24 hrs. the average concentration of SO2 and NO2 are within NAAQS, 2009 at all the selected locations. In the winter, the average concentration of particulate matter (PM10 and PM2.5) are exceeding the standards at four out of six selected locations during monitoring. So, pollutants concentration is more in winter as compared to summer, this may be due to meteorological parameters. The monitoring data also reveals that in Ahmedabad the major responsible pollutants are particulate matters (PM10 and PM2.5) rather than the gaseous pollutants.The monitoring data are used to determine the National Air Quality Index (NAQI), India, and the fuzzy-based Composite Air Quality Index (CAQI). The two indexing systems are compared. In this research article, determination methods of the National Air Quality Index and the Composite Air Quality Index are discussed. The comparison between the two-indexing system reveals that the CAQI estimates more efficiently the pollutants exposure to the population as compared to the NAQI. The CAQI shows the realistic situation, especially when two or more pollutants are exceeding the standards simultaneously. The composite air quality indexing tool is very useful to inform the citizens and to protect human well-being in an urban area. It can be used as a governmental and administrative tool to make abatement strategies and to take effective measures. The wider range of composite air quality indexes proves the superiority over the national air quality index, India.