Mitigation of PM2.5 and Ozone Pollution in Delhi: A Sensitivity Study during the Pre-monsoon period

Ying Chen, Oliver Wild, Edmund Ryan, Saroj Kumar Sahu, Douglas Lowe, Scott Archer-Nicholls, Yu Wang, Gordon McFiggans, Tabish Ansari, Vikas Singh, Ranjeet S. Sokhi, Alex Archibald (+1 others)
2019 Atmospheric Chemistry and Physics Discussions  
<p><strong>Abstract.</strong> Fine particulate matter (PM<sub>2.5</sub>) and surface ozone (O<sub>3</sub>) are major air pollutants in megacities such as Delhi, but the design of suitable mitigation strategies is challenging. Some strategies for reducing PM<sub>2.5</sub> may have the notable side-effect of increasing O<sub>3</sub>. Here, we demonstrate a numerical framework for investigating the impacts of mitigation strategies on both PM<sub>2.5</sub> and O<sub>3</sub> in Delhi. We use
more » ... process emulation to generate a computationally efficient surrogate for a regional air quality model (WRF-Chem). This allows us to perform global sensitivity analysis to identify the major sources of air pollution, and to generate emission-sector based pollutant response surfaces to inform mitigation policy development. Based on more than 100,000 emulation runs during the pre-monsoon period (peak O<sub>3</sub> season), our global sensitivity analysis shows that local traffic emissions from Delhi city region and regional transport of pollutions emitted from the National Capital Region surrounding Delhi (NCR) are dominant factors influencing PM<sub>2.5</sub> and O<sub>3</sub> in Delhi. They together govern the O<sub>3</sub> peak and PM<sub>2.5</sub> concentration during daytime. Regional transport contributes about 80&amp;thinsp;% of the PM<sub>2.5</sub> variation during the night. Reducing traffic emissions in Delhi alone (e.g., by 50&amp;thinsp;%) would reduce PM<sub>2.5</sub> by 15&amp;ndash;20&amp;thinsp;% but lead to a 20&amp;ndash;25&amp;thinsp;% increase in O<sub>3</sub>. However, we show that reducing NCR regional emissions by 25&amp;ndash;30&amp;thinsp;% at the same time would further reduce PM<sub>2.5</sub> by 5&amp;ndash;10&amp;thinsp;% in Delhi and avoid the O<sub>3</sub> increase. This study provides scientific evidence to support the need for joint coordination of controls on local and regional scales to achieve effective reduction on PM<sub>2.5</sub> whilst minimize the risk of O<sub>3</sub> increase in Delhi.</p>
doi:10.5194/acp-2019-618 fatcat:fgyxgp5kofatnfbc5y6jdjtzji