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Delhi air pollution: Vehicular emissions biggest internal contributor to pollution levels

Delhi air pollution: The analysis is based on data for every alternate hour from October 24 to November 8. It is sourced from the Decision Support System to determine contribution of different sources to pollution levels in Delhi.

Written by Abhinaya Harigovind | New Delhi |
Updated: November 12, 2021 10:32:29 am
Delhi air pollution, Delhi air quality, Delhi air pollution news, Vehicular emissions, Centre for Science and Environment CSE, DDS Decision Support System, nitrogen dioxide, Delhi newsDelhi air pollution: The contribution of vehicles has been half or more during the study period, the CSE analysis noted. (PTI/File)

Vehicular emissions contribute the highest share to Delhi’s PM 2.5 levels, in terms of local sources of pollution, according to an analysis by the Centre for Science and Environment (CSE).

The analysis is based on data for every alternate hour from October 24 to November 8. It is sourced from the Decision Support System (DSS) developed by the Indian Institute of Tropical Meteorology, Pune, to determine contribution of different sources to pollution levels in Delhi.

The contribution of vehicles has been half or more during the study period, the CSE analysis notes. This figure would be around 50%-53%, said Anumita Roychowdhury, executive director, Research and Advocacy, CSE, who was part of the team that carried out the analysis.

The contribution of household pollution has been 12.5%-13.5%, while that of industry has been 9.9%- 13.7%. The contribution of construction has been 6.7%-7.9%, that of waste burning has stood between 4.6%-4.9%, and the contribution of road dust has been 3.6%-4.1%.

Delhi air pollution, Delhi air quality, Delhi air pollution news, Vehicular emissions, Centre for Science and Environment CSE, DDS Decision Support System, nitrogen dioxide, Delhi news Delhi air pollution: Contributions to PM2.5 levels. Data from the Decision Support System, analysed by CSE.

The CSE analysis of data on the contribution of the surrounding 19 districts to PM 2.5 levels in Delhi from November 2- 6, shows that the contribution of NCR “dominated in the initial phase, going up to 70% to 80%,” but then declined during the smog episode post Diwali, when contribution from local sources dominated.

The contribution of biomass burning from other states also remained low in the pre-Diwali phase but peaked after Diwali. Calm conditions during the smog episode meant the impact of local sources was more with reduced movement from the NCR areas. But transport winds brought in pollutants from biomass burning in other states.The analysis also indicates that nitrogen dioxide levels increase when traffic congestion increases, and travel speed reduces. On November 5, for instance, the NO2 level was close to 70 µg/m3 between 6 pm and 7 pm, up from a figure close to 40 µg/m3, between 2 pm and 3 pm. Peak hours in the evening are usually between 6 pm and 8 pm. The analysis looked at Google Map data for 15 major roads in Delhi and the travel time and speed along these roads.

Roychowdhury said a regional, integrated, multi-sector plan for the NCR and beyond is needed, and this will have to be enforced with a very stringent compliance strategy.

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