The lack of a comprehensive approach in monitoring air pollution has limited our understanding of a city’s pollution levels and created gaps in the National Clean Air Programme (NCAP) launched to address the deteriorating air quality in 131 cities across the country, researchers from IIT-Delhi and other varsities said with their data showing that India has only 32% of the required number of monitoring stations.
The study titled “Plugging the ambient air monitoring gaps in India’s NCAP airsheds” was published in Atmospheric Environment on Monday. Researchers suggested different factors beyond the existing thumb rules and definitions.
Noting that only 39 of the 131 non-attained cities have completed the source apportionment studies, researchers Sarath Guttikunda, faculty at Transportation Research and Injury Prevention Center, IIT-Delhi; Nishadh Ka and Puja Jawahar from Urban Emissions and Tanushree Ganguly from Council on Energy Environment and Water, New Delhi suggested hybrid monitoring networks.
Data shows that the number of monitoring stations set up across India is grossly inadequate when compared with the recommendations of the guidelines by the Central Pollution Control Board (CPCB). The existing 1321 stations, including manual and continuous monitoring stations, make up for only 32.24% of that number.
The researchers called for establishing an accurate framework to support source apportionment studies and suggested dividing areas into airsheds rather than based on administrative boundaries.
“It is challenging to accurately analyse urban air pollution due to proximity of several cities that are interdependent commercially and economically. Drawing a line based on city administrative boundaries can limit the (polluting) sources..,” the researchers noted.
Citing Delhi’s example where large and medium-scale industrial sources were located outside the city boundary, the study called for monitoring of airsheds. “An airshed is defined as a geographic area where the movement of emissions and pollution is largely influenced by local meteorological conditions and topography and the boundaries are defined in a way to include all the influential sources in the vicinity of the administrative boundary,” the study said, suggesting a continuous air monitoring station per 2-km radius.
Based on the model, India has been divided into 104 airsheds which include 33 cities in the vicinity of the 131 cities which have already been marked as “non-attainment” cities.
Here, data is gathered from 2118 sampling sites to measure and analyse particulate matter pollution. An additional 985 stations for SO2, 977 for NO2 and 509 for carbon are also required, the study suggested.
To a query, the study’s corresponding author Sarath Guttikunda explained that looking at the monitoring needs at the grid level allows monitoring of the hotspots more regularly and closely. “But, it also means that we have to have access to information at the same level. This is one of the reasons why, at this stage we can specify the minimum number for a region, but not necessarily pinpoint where within the region. If the hotspots are pre-determined, then it is a no-brainer to monitor those areas first and must,” he noted.
On the implementation on airshed model, Guttikunda said letting the local academic institutions to take lead could pave the way. “More importantly, the data has to be immediately open for the whole community to use,” he added.
The researchers also batted for a framework for a hybrid monitoring network. Since the capital and operational cost of a reference-grade monitoring network is high, the study suggested a combination of reference-grade monitors and calibrated sensors interspersed to plug the operational gaps and monitor the hyperlocal pollution hotspots within a city.