Ambient Air Quality Assessment Using AERMOD for Line Source

Abstract

Air pollution in megacities like Ahmedabad, India, is heavily influenced by vehicular emissions. Quantifying this air pollution is challenging due to the complex interaction of vehicle types, emission standards, traffic patterns, and weather conditions. This study employs AERMOD for line source emission estimation in Ahmedabad, addressing a significant research gap in India. It is among the first of its kind in the region, offering valuable insights for urban pollution control. By adapting AERMOD to local conditions, this work not only contributes to the scientific literature but also provides a scalable model for air quality management in other Indian cities. The air dispersion model is used to predict ground-level concentrations of pollutants (PM, NO2, HC, and CO) emitted by vehicles (line sources) in four identified stretches representing residential, commercial, industrial, and institutional zones of Ahmedabad during the winter season (December 2023 to February 2024). For emission rate estimation, traffic survey data and emission factors from the source apportionment study report by CPCB, India, were used. Other basic model input data, such as GPS coordinates, width, mean sea level, and release height of the stretches, have been gathered, while meteorological data has been acquired from the India Meteorological Department (IMD). The AERMOD results have been compared with government ambient air quality data. The results indicate that the AERMOD-predicted CO concentration is close to the actual measurements, with a slight underprediction. For PM, the model underpredicts the concentration, possibly due to emission sources other than vehicular exhaust, such as road dust, fugitive emissions, construction, and industrial activities. NO2 concentrations are highly overpredicted, whereas HC concentrations align with vehicular traffic trends. Overall, AERMOD appears to be a useful tool for assessing urban air quality, particularly for mobile emission sources.

Keywords: air quality, air pollution, AERMOD, line source, vehicular emission