Impact of Mitigation Strategies on Ambient Air Quality: A WRF-Chem Case Study of Ahmedabad City in Western India

Abstract

Cities all around the world are facing serious challenges due to declining air quality. Ahmedabad, one of India's 131 non-attainment cities, has seen five years in a row of air quality over the National Ambient Air Quality Standards (NAAQS). This study evaluates the effectiveness of various strategies to reduce particulate matter pollution. In particular, it investigates the effects of switching to electric vehicles for 30% of conventional fuel vehicles, converting 30% of industries to natural gas instead of coal, and producing 30% of thermal power using natural gas instead of coal. The WRF-Chem model was employed to simulate Ahmedabad's air quality for two days in May (representing summer) and December (representing winter). The simulations used a 2 km × 2 km gridded emission inventory for 2018, covering all major pollution sources (point, line, and area). Results indicate that this mitigation strategy could reduce particulate emissions by 18%, from 802 to 657 tonnes per day, and lower overall PM₁₀ concentrations by 14%. In May, the northern part of the city near Naroda GIDC (1% of the city area) saw the highest PM₁₀ reduction (36%), while the central-western area (51% of the city area) experienced a minimum reduction of 6%. In December, a 36% reduction was again observed near the 5% area of GIDC Naroda, with reductions as low as 6% in the western and southeastern outskirts (~ 20% area). These findings provide valuable insights for state regulatory agencies to enhance air action plans and meet the targets set by the National Clean Air Program (NCAP).