The framework for improving air quality monitoring over Indian cities

Indian air quality monitoring guideline is directly adopted from World Health Organization (1977) guidelines without place-based modification. According to Indian air quality guidelines (2003), the location of monitoring sites should be determined from air quality modeling and previous air quality information. If such information is not available, the use of emission densities, wind data, land-use patterns and population information is recommended for prioritizing areas for air quality monitoring. The mixed land-use distribution over Indian cities and randomly distributed sources pose serious challenges, as Indian cities (unlike in other parts of the world) are characterized by a lack of distinct residential, commercial, and industrial regions, so the concept of “homogeneous emissions” (which have guided site monitoring decisions) simply does not apply. In addition, the decision-making data emission and population information, are either not available or outdated for Indian cities. Unlike the cities in Global North, the Indian urban-scape has distinguished features in terms of land use, source and population distribution which has not been addressed in air quality guidelines. We have developed an implementable place-based framework to address the above problem of establishing effective new air quality stations in India and other regions with complex land-use patterns. Four Indian million-plus cities were selected for the present study; Lucknow, Pune, Nashik and Kanpur. We broadly classified air quality monitoring objectives into three; monitoring population exposure, measurements for compliance with the national standards and characterization of sources. Each monitoring station over four cities was evaluated and metadata has been created for each station to identify its monitoring objective for each of the stations. We find that present air quality monitoring networks are highly inadequate in characterizing average population exposure throughout each city, as current stations are predominantly located at the site of pedestrian exposure, and are not representative of the city-wide exposure. Possible new sites for monitoring were identified using night-time light data, satellite-derived PM2.5, existing emission inventories, land-use patterns and other ancillary open-sourced data. Over Lucknow, Pune and Nashik, setting up stations at highly populated areas is recommended to fulfill the knowledge gaps on the average population exposure. Over Kanpur, it was recommended to incorporate stations to measure short-term pollution exposure in traffic and industrial sites. Rapidly developing peri-urban regions were identified using night-time light data and recommendations were provided for setting up monitoring stations in these regions.